350 (2 bolt) conversion to 383

[gbkwork]

Well,

I just got done pulling a 4000lb. trailer 2000 miles over the weekend only to realize the front of the trailer and my truck's tailgate were covered with oil. So, its time to think about a new engine and tranny.

The engine is pinging constantly (unless I mash on on it and get some additional advance) and occassionally backfires (don't know if its going through the intake or exhaust...it sounds like its in the crankcase).

I have decided to go with a built 700R4 but I am undecided on whether to convert my current engine to an aluminum-headed 383 or just go and buy the GM 350 crate, live with the lack of power until the warranty expires, and forget about it. Pay in mind that the truck needs to tow a 5K lb. boat over the Sierras.

My question is this...assuming all the appropriate clearancing and machine work, will a 2-bolt block handle 450HP / 450 ft/lbs if I upgrade the caps and bolts? Also, do any of you know what a good price is for machining the block for a 383 conversion? I don't mind spending a few hundred dollars more than the $1400 cost of the GM 350 if its going to get me a significantly more powerful engine.

I would prefer to build an engine rather than just buy and install a crate (because I'm a control freak). But, I don't want to spend time on a block that can't handle the power I'm looking for.

Any suggestions?

How mild should I keep the cam & valve train if I plan on re-using my Performer intake and carb?

Also, do any of you have a diagnosis for what went bad in my existing engine (I'm assuming its rings)?

Appreciate all the suggestions.

[phantom dually]

Go with 4 bolt main caps from MILODON. They bolt in at a angle where the block is the strongest.

[gbkwork]

How do the 4-bolts mount? Do you just tap new threads into the block for the two additional bolts?

[cableguy0]

you need to have a machine shop drill and tap to make a 2 bolt block a 4 bolt the holes have to be perfect. and yes a 2 bolt block will easily hold 450hp

[Destructo]

Splayed caps as their called. Stronger than a factory 4 bolt. And can only be installed on an original 2 bolt block. If you want peice of mind you could have some installed. For sure the power could be handled by the splayed caps. You can get 383 kits for a fair price from summit I believe. Go check it out and see if you like what you see.

[bigjimzlll]

It cost me 600 bucks for all of the machine work needed. This included zero decking the block..torque plate bore and hone..clearancing..and balancing

[Mike76251]

Originally posted by gbkwork
How do the 4-bolts mount? Do you just tap new threads into the block for the two additional bolts?

The block will need to be align/bored, align/honed and have the caps registered as those splayed caps have to be fit to the block.

[gbkwork]

Sounds like Big Jim is in my neck of the woods. Any suggestions on a good machine shop in the area?

Also, do you have any suggestions on how mild I should keep the cam and heads if I plan on retaining the Performer carb and intake with the 383? I drive this truck over 15K mi/yr, so it has to be streetable (run A/C, P/S. etc.) and get sane mileage (13 - 15 mpg) with the 700R4.

I would like to go to an aluminum head and am looking at the Performer RPMs (70cc) and Trick Flows (72cc) to keep compression at a reasonable level. Also I am thinking about a hydraulic roller cam setup in the 215 - 230 degree (@.050") range with > .475" of lift.

I appreciate the knowledge.

[bigjimzlll]

Sounds like a good plan so far..I really like the Trick flow heads. The hydraulic roller will cost over 1000.00 before all is said and done. I use 2 machine shops/speed shop . They are both in Anderson. For basic (read cheap but good) then Ken at Keetons is the man. He has to farm out some of the work. My 385's machine work was done at RLP..Randy Liddel Performance..Heres his link http://www.rlpengines.com/index.htm He has a real nice machine shop with a Dyno. I think a cam in the 220-225 @.050 range will work well for what you need. This will give great power from off of idle to 5500rpm. If you call Keetons or RLP tell them Jim Scott sent you..lord knows ive spent a ton with both of them..lol..you can call me at 945-8975

[racedvl]

I would say if you are pulling a trailer all the time. . . 383 is the only way to go.

[71chevylongbed]

I got a Crower 240 cam in my 350. At the rear wheels I'm puttin out 448 pounds of torque at 2200 rpm , 456 pounds at 3300, and it flys up hills!

[gbkwork]

What kind of heads are you running?

[gldevall]

I think the 2 bolt would be strong enough though.

[1FaastC10]

yes the 2 bolt block would be strong enough for a 383 buildup. however, your goals seem a bit confusing. you want 450hp/450tq and milage too? sorry, probably cant have both. for heads you want something in the 180cc range, as they will make good toque. i've heard of a lot of people using Vortec heads as well as S/R Torquers and even AFR 180cc heads for pulling motors. personally, im going to pt together a 383 eventually for my daily driver/work truck (undecided which truck will get it yet, maybe one i dont even have yet) i'm going to use my 96 5.7 block, for its roller cam capability, and a set of Vortec heads. the strong point with the Vortecs is their high torque output, that's what they're designed for. if that's what they're designed for and what you're looking for, i'd go with them. the only downside is that you'll have to buy a new intake. if you're building a motor anyways, you should replace the head bolts, rocker arms, and pivot balls anyways. so there's really no "additional" cost.

[dinnut]

the dude on trucks made a 2 bolt block a 4 bolt. i think it was that show. maybe another one.

[Stroker]

I agree your target of 450 HP for a pulling motor might be a little on the high side. I wouldn't focus on the HP figures much if you need to do heavy towing on grades. Think TORQUE, try to maximize torque at and below your cruising RPM and let the HP fall where it may. You'll definately need the low end torque with the large RPM drop of the 700r4 1-2 shift. If there's anyway you could fit a turbo 400/gearvendor overdrive into the budget I would give it some consideration. It would be the best auto tranny set up I can think of for a durable tow rig. But unfortunatly it carries a steep price tag.

As for the 2 bolt vs 4 bolt question a 2 bolt will most likely get you by but a 4 bolt would be my preference for towing rig. GM used 4 bolts in most of the heavy truck applications there must be a reason. I 'd say the splayed caps are overkill and you should be able to find a good 4 bolt 350 core for less than the machine work to convert to 4 bolt caps.

I agree with 1FaastC10 heads in the 170-180cc range are probably best suited for your use, the dart iron eagle 180 might also be a good choice. Don't get carried away with the compression, cam duration or header size. Choose a good piston and be sure to set ring gaps appropriately for towing.

A few accessories that make sense for a tow rig would include tranny and oil coolers. A oil and tranny temp gages would also be nice. Good luck and happy pulling......Stroker