Tell me about your 383 Stroker engines

[Jacfourteen]

I'm no engine guru, but thick gaskets are a bad idea.

[djmachinist]

Originally Posted by swb85

DO NOT change to a thicker head gasket, that will make the motor even more prone to detonation. You want to leave the head gasket alone, as it sits you've got a respectable .043" quench distance. You don't want to go any wider. The only way to correctly change static compression is either change pistons or make the combustion chamber in the heads bigger.

You've got a half point more static compression than me so you may need more cam to get your DCR down to pump gas territory, but you've got aluminum heads and 93 pump gas (we only have 91 here).....so you may be able to get away with a little more squeeze than I can.

Ok, I here you guys, scratch the thicker head gasket idea. I had more discussions with G & G about the 10.9 CR problem and Joe told me he would look up the build sheet and get back to me. He did call later and told me my CR calculation sht. I sent him was right except for the deck height which is actually 0.018 in. where I had 0.005 in. (which is what he told me originally).
So the actual Static CR is 9.63 to 1, not 9.9 to 1. He went on to tell me he builds small blocks with this kind of set all the time with no reported pinging problems. He ask me what carb I had which is a "Quick Fuels 680 CFM/Vacuum secondaries". He said that I was running too lean with that carb and a Holly 750 double pumper would fix the Pinging problem and I could set the timing back to 36 deg. instead of the 26 deg. the timing is set at now.

Any comments on the above commentary?

Oh....Also take a shot at what spec build would make a nice sweet street daily driver with AC. Assuming I'm keeping the present Block, crank, rods, the Edelbrock Etec-170 heads and Performer RPM intake manifold......I'm open to changing the pistons, cutting on the Etec heads, & a carb and cam change.
I want it to run on Pump gas even on the hottest summer day with the AC on.
I want this 383 Stroker to have more Pop than the ZZ4 350 I had, but I will give up a few HP for streetabily. Also, what Stactic CR should I shoot for?

Thanks,
Dale

[Super73]

I wrote this before reading your lattest post. But, still a few things to check.



Do you know the intake centerline of the cam?
Do you know if it was installed straight up, retarded or advanced?

Based on the info you provided 10.97 static and the cam having a total of 296* duration at .006 (pulled this off summit), with an intake centerline of 106, your dynamic compression ratio would be right around 8.13.

If it is installed at a 104 icl your DCR would be closer to 8.28.

If at 108icl it would be closer to 7.98.

Now, all of those DCR numbers "should" be pump gas friendly. However, there are a lot of other things that can cause issue which have been mentioned earlier in this thread. Chamber design and quench are two of the big ones imo. Obviously total initial timing could be a culprit at part throttle.

Simple way to see if it is a intake valve timing / dynamic compression ratio issue, change the cam timing with an adjustable timing chain. Obviously this is not going to put the cam in the best spot for power, but, it will tell you if the detonation is directly related to the intake valve closing point (IE dynamic compression). Or if it is possibly a function of timing/head design..

One of the other things that you probably need is what is really happening with air fuel at part throttle? Could an overly lean or rich mixture be causing the detonation? Yes.. This is another thing that should be looked at. AEM makes a guage that is fairly inexpensive that you could put in your truck. Putting it on a dyno is great for WOT, but not as good for part throttle adjustment. It does not simulte "real" driving conditions.

[rblcori7]

Ok guys ive got a few questions for you... im about to start an engine build for my 84 4x4 short bed. and i was wondering what would be my best bet engine wise, Ive got a 4 bolt 350 torn apart sitting in my garage right now that im going to start buying parts for soon.. I want to make around 350whp and 350tq. Should i just keep it a 350 (built up of coarse) or bore it out and build a 383.money is not a huge deal but at the same time it is lol.. any input is much appreciated!!!

[djmachinist]

Ok, the saga continues. The truck is back in the shop this morning. I have decided to back off on a 440 hp engine in the interest of having a nice street daily driver. I'm now shooting for 380hp to 390 hp.
The plan now is G&G machine shop who did the machine work on the ZZ4 block originaly, will port the Etec heads and enlarge the combustion chambers from 64cc to 67 cc. An increase of 3cc. This change results in a CR change from 10.63 to 1, to a CR of 10.22 to 1. The Dynamic CR should come out around 7.460 to 1.

I am also replacing the Edelbrock cam with a Comp Cams XR269HR Roller cam.

Cam Specs:
Duration @ .050 lift=218/224
Valve lift= 0.495/0.503
Lobe Seperation= 112
Intake Centerline= 108

This cam closes @ 62 deg. ABDC compared to the Edelbrock cam that Closed @ 44 deg. ABDC. This should bleed off some Compression at low speeds. I have attached a Compression Calc and the Cam Spec sheet.

[GMR-PERFORMANCE]

great thread, when I was build my ls 413 for the sand rail I got in touch with a shop in TX. After asking some questions about there CNC head porting and compression vs cam closing point that it did not matter.. Set static compression at 10.9 and run what ever cam as it had no effect on dynamic( he did not know what that was I had to explain it to him) WOW .. We build over a 150 harley engines a year in house all high performance builds. And setting dynamic /static/ compression is very important with a air cooled engine.. The air cooled engines are a bit more testy when it comes to things like this..

[stich626]

why didn't the shop know it was going to be 10.97 to 1 before bolting it together?
part of the eddy heads is the chamber that you are going to have them grind on..
stop!!!!!!!!!!!! think this through..
I'd get new pistons, you can sell the one in there now..
once a grinder hits those heads, good luck selling them, if you change down the road..
if you told the shop you where running 93, they should've stopped before there screwed it together..
change the pistons, in the long run the change will be cheaper than ,having to heads that no one will want, unless you give them away.

[djmachinist]

Originally Posted by stich626

why didn't the shop know it was going to be 10.97 to 1 before bolting it together?
part of the eddy heads is the chamber that you are going to have them grind on..
stop!!!!!!!!!!!! think this through..
I'd get new pistons, you can sell the one in there now..
once a grinder hits those heads, good luck selling them, if you change down the road..
if you told the shop you where running 93, they should've stopped before there screwed it together..
change the pistons, in the long run the change will be cheaper than ,having to heads that no one will want, unless you give them away.

Thanks for the comments, I waited through the week end and took a deep breath before I proceeded,
Yeah, I agree with you about the Dished pistons, that was my first thought.
However after talking to G & G , he assured me he could give these heads a "Street port" job and enlarge the combustion chambers to 67cc without hurting the flow. In fact, he said they would flow better than stock. He does use a flow bench.

I also agree with you they should have known problems would occur with the 10.63 CR, however they tell me they build these kind of engines all the time
with no problems. (I'm not sure I believe that). I do not want a engine pushed to the edge like this. It gets 100 deg. w/ 98% humidity in houston in the summer. If it has pinging problems now in cool weather, whats going to happen in the summer with AC on?

Anyway, moving forward, I did think about this issue of grinding on the heads.
So...I ordered new 12 cc dished pistons from Summit this morning, and I'm leaving the Heads stock. This will give me an CR of 9.8 to 1., which is more inline with conventional wisdom on how high a CR should be used on a Daily driver with AC. Right now I have a 453 HP engine that won't run on pump gas.
Using a 9.8 CR will drop th Hp to 390 to 400 hp + or - a few ponies. Ths should give me a little margin for those hot summer days.

Thanks,
Dale

[POPO1984]

I think you are making a wise decision. with the way things have gone so fare I would be kinda hesitant to let them do some porting on my heads. Anyway hurry up and get that thing done so you can get it on the road and enjoy this nice weather. By the way reading through your build has really made me get back to work on my truck so keep it up man

[Super73]

There is one area that touching the combustion chamber could be benificial.

What bore were the heads designed to run on?
What bore are you running?

If the bore you are running is bigger than the chamber was designed for, opening up the chamber to match the actual bore diameter could result in unshouding the valves and creating more power. Just something to think about since the heads are going to be off.

[GMR-PERFORMANCE]

A static number means nothing really ... You can have a 13.1 engine and run it on pump gas provided that the dynamic number is where it should be and that is based off the cam closing point.

Rule of thumb is keep dynamic under 9.3 for 91 octane fuel, That way you have some room for bad gas etc. I have seen where a shop built something and it had issues they swap in a monster stick to make it run and now you have a engine that is a pig down low and for the street what good is that.

I am running my 383 at 11.25.1 on pump gas. If you plan everything out it will work, from the engine to tranny to rear gear. Steep gearing and a close ratio box will not load the engine in the same way as cruise style gearing and a auto... that gives me a bit more leeway so to speak.


There is not much to be gain for a street engine to run it up on the edge... other than over heating, ign ping, head aches at the end of the day.. I have owned a full tubbed drag truck that I drove on the street. Nothing but a PIA.. Good for a cruise night here and there nothing more.


Super.. I think I read what you are running but refresh that if you would. Great ET BTW got me by a few tenths on the motor run, I am in the 11.90... traction was a huge issue I tried to run a set of cheater slicks they where of little help at all.

[djmachinist]

Originally Posted by GMR-PERFORMANCE

A static number means nothing really ... You can have a 13.1 engine and run it on pump gas provided that the dynamic number is where it should be and that is based off the cam closing point.

Rule of thumb is keep dynamic under 9.3 for 91 octane fuel, That way you have some room for bad gas etc. I have seen where a shop built something and it had issues they swap in a monster stick to make it run and now you have a engine that is a pig down low and for the street what good is that.

I am running my 383 at 11.25.1 on pump gas. If you plan everything out it will work, from the engine to tranny to rear gear. Steep gearing and a close ratio box will not load the engine in the same way as cruise style gearing and a auto... that gives me a bit more leeway so to speak.


There is not much to be gain for a street engine to run it up on the edge... other than over heating, ign ping, head aches at the end of the day.. I have owned a full tubbed drag truck that I drove on the street. Nothing but a PIA.. Good for a cruise night here and there nothing more.


Super.. I think I read what you are running but refresh that if you would. Great ET BTW got me by a few tenths on the motor run, I am in the 11.90... traction was a huge issue I tried to run a set of cheater slicks they where of little help at all.

I have a question for you..... On the Keith Black website, there online CR calculaton sheet adds 15 deg. to the stated Cam Spec. If a cam closes at 62 deg. ABDC @ 0.050 lift adding the 15 deg. = 77 deg. .....Any thoughts on why the equation is set up this way?

Here's the link to the CR calc. sheet: http://www.kb-silvolite.com/calc.php?action=comp

[Super73]

Every cam lobe is different. Using a set 15* is going to give you false info, period. You need to know real numbers. Where the valve starts moving and where it closes (typically .006 on a hyd cam and normally measured at .020 for a solid, but a solid's total duration will change if you run more/less lash). A small duration high lift cam is going to have less total duration than a low lift big duration cam.

What you use for a follower and where you set lash at if it is a solid makes a difference too.

For instance, my current cam is a solid roller grind but I use a hyd roller on it. Here are the advertised numbers against actual numbers. I know the actual numbers are accurate as I spent 2 hours one night with a solid roller riding the cam, a degree wheel and a dial indicator.

----- Advertised - Actual
.020 --- 273* ----- 298* (.006)
.050 --- 245* ----- 245*

Look at the spread between .050 and .020 for the solid and .006 for the hyd. Solid is 28* / 2 = 14* and the hyd follwer is 53* / 2 = 26.5* That makes a big difference.

My motor is 11.14cr and with the hyd follwer on the cam I have 8.09 dcr.
Put a solid roller on the same cam with .020 lash on it and DCR jumps to 9.01.

So you can understand the change that has to IVC points..

HYD would be 76* ABDC
Solid would be 63.5* ABDC

My point, DO NOT USE RULE OF THUMBS WHEN BUILDING ENGINES... Get all your real specs! Do not guess as it leads to poor results and broken parts!!!

Rant off..

[djmachinist]

Originally Posted by Super73

Every cam lobe is different. Using a set 15* is going to give you false info, period. You need to know real numbers. Where the valve starts moving and where it closes (typically .006 on a hyd cam and normally measured at .020 for a solid, but a solid's total duration will change if you run more/less lash). A small duration high lift cam is going to have less total duration than a low lift big duration cam.

What you use for a follower and where you set lash at if it is a solid makes a difference too.

For instance, my current cam is a solid roller grind but I use a hyd roller on it. Here are the advertised numbers against actual numbers. I know the actual numbers are accurate as I spent 2 hours one night with a solid roller riding the cam, a degree wheel and a dial indicator.

----- Advertised - Actual
.020 --- 273* ----- 298* (.006)
.050 --- 245* ----- 245*

Look at the spread between .050 and .020 for the solid and .006 for the hyd. Solid is 28* / 2 = 14* and the hyd follwer is 53* / 2 = 26.5* That makes a big difference.

My motor is 11.14cr and with the hyd follwer on the cam I have 8.09 dcr.
Put a solid roller on the same cam with .020 lash on it and DCR jumps to 9.01.

So you can understand the change that has to IVC points..

HYD would be 76* ABDC
Solid would be 63.5* ABDC

My point, DO NOT USE RULE OF THUMBS WHEN BUILDING ENGINES... Get all your real specs! Do not guess as it leads to poor results and broken parts!!!

Rant off..

Good Answer, that is why I ask the question.

Thanks,
Dale

[GMR-PERFORMANCE]

Shaun, if you don't mind me adding to your post ( great info btw) DO not be shocked if you start checking the other lobes on the cam and you find that they are not all the same. Also checking at the cam vs the rocker is the better way to go about it. It can be done at the rocker but unless you move that same rocker you will see change from one to the next.

One other thing I noticed was that when I ran the numbers with the listed items and using the info ont he sheet from Comp I came up with 11.1. now that is using a +5cc dome??? or some programs use a + number as a negative..

I am a engine builder.. I am not a engine assembler.. I check everything where as the other takes things for granted. HD engines, tractors, whatever they are all air pumps nothing more..
Slapping together a 350 with a rv cam and some basic stuff your normal shop should get it right however when you start jigging things around or things dont go right,.. those shops start to feed you BS and really they are guess as they have no clue as to what went wrong or why.. I am not stating that your shops did this as I have no dog in that fight.. I will say that your set up does not make sense.. I run 11.2 on pump gas in the AZ heat and have no issues.

But that falls back on the rule of thumb thing... just like a engine of such size only needs a carb "of this many CFM" Easy to type on a key board, but you read between the lines on who has been there done that and spent the timing testing and tuning parts...

here is some good basic stuff.. ENJOY READING





Dynamic Compression Ratio
Dynamic Compression Ratio (DCR) is an important concept in high performance engines. Determining what the compression ratio is after the intake valve closes provides valuable information about how the engine will perform with a particular cam and octane.

Definition: The Compression Ratio (CR) of an engine is the ratio of the cylinder volume compared to the combustion chamber volume. A cylinder with 10 units of volume (called the sweep volume) and a chamber with a volume of 1 has a 10:1 compression ratio. Static Compression Ratio (SCR) is the ratio most commonly referred to. It is derived from the sweep volume of the cylinder using the full crank stroke (BDC to TDC). Dynamic Compression Ratio, on the other hand, uses the position of the piston at intake valve closing rather than BDC of the crank stroke to determine the sweep volume of the cylinder.

The difference between the two can be substantial. For example, with a cam that closes the intake valve at 70º ABDC, the piston has risen 0.9053" from BDC in a stock rod 350 at the intake closing point. This decreases the sweep volume of the cylinder considerably, reducing the stroke length by almost an inch. Thereby reducing the compression ratio. This is the only difference between calculating the SCR and the DCR. All other values used in calculating the CR are the same. Note that the DCR is always lower than the SCR.

Dynamic compression ratio should not to be confused with cylinder pressure. Cylinder pressures change almost continuously due to many factors including RPM, intake manifold design, head port volume and efficiency, overlap, exhaust design, valve timing, throttle position, and a number of other factors. DCR is derived from measured or calculated values that are the actual dimensions of the engine. Therefore, unless variable cam timing is used, just like the static compression ratio, the Dynamic Compression Ratio, is fixed when the engine is built and never changes during the operation of the engine.

Two important points to remember:

The DCR is always lower than the SCR
The DCR does not change at any time during the operation of the engine

Determining seat timing: Since the early days of the internal combustion gasoline engine, engineers have known that the Otto four stroke engine is compression limited and that the quality of the fuel used determines the CR at which the engine could operate. However, it is not the Static CR but the actual running CR of the engine that is important. Compression of the air/fuel mixture cannot start while the intake valve is open. It may start slightly before the intake valve is fully seated. However, there is no easy way to determine this point so using the advertised duration number provided by the cam manufacture is the next best thing. Most cam grinders use .006" of tappet lift (hydraulic cam), although some use other values, with .004" being a common one. This duration is often referred to as the "seat timing". We will used advertised duration for calculating the DCR.

The special case of solid lifter cams. Solid cams are usually speced at an abitrary lift value (often .015" or .020") determined by the designer to be a good approximation of the cam's profile. This lift spec is not always correct for a particular cam. The correct lift point to determine the seat to seat timing of the cam is: Lash / rocker ratio + .004". This accounts for the lash. A cam with a .026" lash (given 1.5 rockers) should be measured at .02133" (.026/1.5+.004= .02133>"). This cam lash, with seat timing speced at .020", is actually a bit smaller than advertised since the valve has yet to actually lift off the seat. How much is the question (.024" lash is the only lash that is correct at .020" with 1.5 rockers). Without knowing the ramp rate, and doing some calculations, or measuring with a degree wheel, it is impossible to know. Again, we have to use the mfg's numbers. Here is some Chevy factory cam help.


Why it matters: A 355 engine with a 9:1 static CR using a 252 cam (110 LSA, 106 ICL) has an intake closing point of 52º ABDC and produces a running CR (DCR) of 7.93. The same 9:1 355 engine with a 292 cam (having an intake closing point of 72º ABDC) has a DCR of 6.87, over a full ratio lower. It appears that most gas engines make the best power with a DCR between 7.5 and 8.5 on 91 or better octane. The larger cam's DCR falls outside this range. It would have markedly less torque at lower RPM primarily due to low cylinder pressures, and a substantial amount of reversion back into the intake track. Higher RPM power would be down also since the engine would not be able to fully utilize the extra A/F mixture provided by the ramming effect of the late intake closing. To bring the 292 cam's DCR up to the 7.5 to 8.5:1 desirable for a street engine, the static CR needs to be raised to around 10:1 to 11.25:1. Race engines, using high octane race gas, can tolerate higher DCR's with 8.8:1 to 9:1 a good DCR to shoot for. The static CR needed to reach 9:1 DCR, for the 292 cam mentioned above, is around 12:1.
This lowering of the compression ratio, due to the late closing of the intake valve, is the primary reason cam manufactures specify a higher static compression ratio for their larger cams: to get the running or dynamic CR into the proper range.


Caveats: Running an engine at the upper limit of the DCR range requires that the engine be well built, with the correct quench distance, and kept cool (170º). Hot intake air and hot coolant are an inducement to detonation. If you anticipate hot conditions, pulling some timing out might be needed. A good cooling system is wise. Staying below 8.25 DCR is probably best for trouble free motoring.

>>Unless you have actually measured the engine (CCed the chambers and pistons in the bores), these calculations are estimations, at best. Treat them as such. The published volumes for heads and pistons can, and do, vary (crankshafts and rods, too). It is best to err on the low side. When contemplating an engine of around 8.4 DCR or higher, measurments are essential, or you could be building another motor.<<


Details: Long duration cams delay the closing of the intake valve and substantially reduce the running compression ratio of an engine compared to the SCR. The cam spec we are interested in to determine the DCR is the intake closing time (or angle) in degrees. This is determined by the duration of the intake lobe, and the installed Intake CenterLine (ICL) (and indirectly by the Lobe Separation Angle (LSA)). Of these, the builder has direct control of the ICL. The others are ground into the camshaft by the grinder (custom grinds are available so the builder could specify the duration and LSA). Changing the ICL changes the DCR. Retarding the cam delays intake closing and decreases the DCR. Advancing the cam causes the intake valve to close earlier (while the pistons is lower in the cylinder, increasing the sweep volume) which increases the DCR. This can be used to manipulate the DCR as well as moving the torque peak up or down the rpm range.

It is necessary to determine the position of the piston at intake valve closing to calculate the DCR. This can be calculated or measured (using a dial indicator and degree wheel). Since compression cannot start until the intake valve is closed, it is necessary to use seat times when calculating the DCR. Using .050" timing will give an incorrect answer since the cylinder is not sealed. At .050" tappet lift, using 1.5 rockers, the valve is still off the seat .075" and .085" with 1.7 rockers. While the flow is nearing zero at this point, compression cannot start until the cylinder is sealed.

Another factor that influences DCR is rod length. It's length determines the piston location at intake closing, different rod lengths change the DCR. Longer rods position the piston slightly higher in the cylinder at intake closing. This decreases the DCR, possibility necessitating a different cam profile than a shorter rod would require. However, the effect is slight and might only be a major factor if the rod is substantially different than stock. Still it needs to be taken into account when calculating the DCR.


Calculating DCR: Calculating the DCR requires some basic information and several calculations. First off, the remaining stroke after the intake closes must be determined. This takes three inputs: intake valve closing point, rod length, and the actual crank stroke, plus a little trig. Here are the formulas:

Variables used:

RD = Rod horizontal Displacement in inches
ICA = advertised Intake Closing timing (Angle) in degrees ABDC
RR = Rod Distance in inches below crank CL
RL = Rod Length
PR1 = Piston Rise from RR in inches on crank CL.
PR2 = Piston Rise from crank CL
ST = STroke
1/2ST = one half the STroke
DST = Dynamic STroke length to use for DCR calcs
What's going on: First we need to find some of the above variables. We need to calculate RD and RR. Then, using these number, we find PR1 and PR2. Finally, we plug these number into a formula to find the Dynamic Stroke (DST).
Calcs:

RD = 1/2ST * (sine ICA)
RR = 1/2ST * (cosine ICA)
PR1 = sq root of ((RL*RL) - (RD*RD))
PR2 = PR1 - RR
DST = ST - ((PR2 + 1/2ST) - RL)
This result is what I call the Dynamic Stroke (DST), the distance remaining to TDC after the intake valve closes. This is the critical dimension needed to determine the Dynamic Compression Ratio. After calculating the DST, this dimension is used in place of the crankshaft stroke length for calculating the DCR. Most any CR calculator will work. Just enter the DST as the stroke and the result is the Dynamic CR. Of course, the more accurate the entries are the more accurate the results will be.
Using this information: DCR is only a tool, among others, that a builder has available. It is not the "end all" in cam or CR selection. However, the information provided is very useful for helping to match a cam to an engine or an engine to a cam. It is still necessary to match all the components in an engine and chassis for the best performance possible. Pairing a 305º cam with milled 882 heads just won't cut it even if the DCR is correct. The heads will never support the RPM capabilities of the cam.

A good approach when building an engine is to determine the duration and LSA needed for the desired RPM range. Once this is know, manipulate the chamber size and piston valve reliefs (and sometimes the cam advance) to provide a DCR around 8.2:1. Now that the correct piston volume and chamber size is know, enter the actual crankshaft stroke in your CR calculator to see what static CR to build to. Often the needed SCR is higher that you would expect. Note: The quench distance (piston/head clearance) should always be set between .035" and .045" with the lower limit giving the best performance and detonation resistance.

Alternatively, with the SCR known, manipulate the cam specs until a desirable DCR is found. When the best intake closing time is derived, look for a cam with that intake closing timing, that provides the other attributes desired (LSA and duration). Often times the best cam is smaller than one might expect. Sometimes a CR change is needed to run a cam with the desired attributes.

The information given here should be used as a guideline only. There are no hard and fast rules. It is up to you, the engine builder, to determine the correct build of your engine. And remember, unless accurate measurements are taken, these calculations are approximations.

AGAIN THIS IS BASE LINE STUFF AND IF YOU INPUT INCORRECT INFO YOU WILL GET INCORRECT INFO.

[djmachinist]

GMR-Performance,

Wow, Thats quite a commentary. Good info.

The Piston volume stated is a flat top with 2 valve reliefs listed as +5 cc by the manufactor. The KB Spreadsheet use's a + to add volume. Since I posted the CR Calc, I found out that the Deck height was wrong at 0.005 which did add up to a CR of 11.0 to 1. The actual deck height is 0.018, giving a static CR of 10.63 to 1.

The Edelbrock # 2204 used had an Intake closing of 44 deg. ABDC which accounted for a DCR of over 9.0 to 1.... From what I understand, This was the Culprit that caused my pinging problem if all other factors were ok.

The latest changes to the heads (Pocket Porting & Blending) will enlarge the the Combution Chambers from 64cc to 66cc according to the machine shop.

This will lower my static CR to 10.33 to 1....I also have changed the Cam to Comp Roller # XR-269-HR that has a Intake closing of 62 deg. ABDC. A full 18 deg. later than the Edelbrock cam. This should give me a DCR of around 8.5 to 1.

I hope this cures my pinging problem.

Thanks for the info,
Dale

[POPO1984]

Good info

[GMR-PERFORMANCE]

That should work, Just understand that someone else may run your set up with a different ratio trans and steeper rear gear and never have a issue. There is much more to it than meets the eye. Myself am a firm believer in a engine dyno tune and break it from the builder. IF there is a issue most times it will be found in the dyno cell. At that point you have the builder on the spot and it will need to be fixed. Many shops that have a in house dyno will never make that mistake as they reall have a minds eye view of what is going on.

We tune in house on a chassis dyno and I was shocked at many things that should or should not work. If only goes to show that many things that are read online are more hear say than anything else. I call them keyboard engine builders..

That does not mean that you can just throw what ever at a engine and it will work... Putting in the R&D time with the engine kits and then tuning them , and running them on the street in heat, poor gas, stop and go traffic will be the final test and of course the legal 1/4 mile run he he ..

[Super73]

I like this DCR calculator. Use tab 4 (DCR Manual Calculator). Pianoprdigy from LS1tech created this back in 2005 and it's the only one I use now.

Reason I like it? Gives you .006/.050/.200 valve events as well Overlap and DCR. It also let you put in more info about your set up than most..

http://73-ls1.com/pianoprodigy_ve_calculator.xls

[GMR-PERFORMANCE]

no workie

[Super73]

Try it now.. Saved it a long time ago and rehosted it.

[djmachinist]

Ok....I picked up the truck Saturday. The Machine shop performed a "Steet pocket" port job. The Combustion chambers CC'd at 65cc up from the original 64cc chambers. The deck and Flat top piston were left alone. The big change was replacing the Edelbrock cam with a Comp Cams roller design that is a little milder grind overall and has a 18 deg. later intake closing than the Edelbrock cam had. The Static CR came down from 10.63 to 10.44. The DCR came dowm fron 9.3 to 8.45..

The good news is the engine is running great. Nice Idle, Verry good throttle responce, good low and mid range power and will rev to about 6000 rpm. And No "Pinging". The Static CR is still a little to high for my comfort level, however the Pinging seems to be gone.

Dale

[GMR-PERFORMANCE]

DId they also swap to a thicker head gasket?

[djmachinist]

Originally Posted by GMR-PERFORMANCE

DId they also swap to a thicker head gasket?

No, a Fel-Pro .041 thick head gasket was used. I have attached the CR/DCR calc.

Dale

[Super73]

Glad it's running better..


Did they give you a grind number or tell you what comp cam they put in it?
Did you go with that XR269?

I'm also very curious where the original DCR number of 9.3 came from. Here is a link to Summits web page with the spec for the edelbrock 2204 cam you had in it. http://www.summitracing.com/parts/EDL-2204/ It has a total al 296* of duration. With a higher 11-1 CR this is what the DCR would look like based on different intake center lines.

102 ICL = 8.46dcr
104 ICL = 8.31dcr
106 ICL = 8.16dcr
108 ICL = 8.01dcr

I can almost garuntee the cam was not installed on a 102 icl, but even if it was DCR was never higher than 8.46. For it to have been 9.3dcr with 11-1 CR your intake would have had to closed at 57* ABDC. In order to do that, a cam with 296* total duration would have had to been installed at an intake center of 89*. No timing set goes that far.

My point, you were never at 9.3dcr..

Now for the new set up. If you went with the Comp cams XR269HR you mentioned earlier in the thread, even with less SCR you DCR is higher if installed on the 108 icl it is advertised on.

106 ICL = 8.65dcr
108 ICL = 8.52dcr (installed straight up with the 108icl)
110 ICL = 8.40dcr

Now with that, I hate to be the one that says I told you so, but I believe in the begining of this thread, I advised you to assemble the motor yourself and actually check everything out. Who knows what else is not right in that motor. Hopefully nothing else is wrong with it, but it makes you wonder. I would even wonder if the parts they told you are in it are really in it. Guess you will never know for sure.