350 timing with HEI

[bluedog]

Just installed an GM HEI distributor. Plug gap set at .045. What are you guys setting the timing at? I have a stock engine with a Edlebrook 4 bbl. and mainifold. Stock exhaust.

Thanks,

Scott

[bluedog]

Anyone? I thought it was around +8.

[Big D]

I just did the same thing with my 72 , 350 with stock Q-jet and manifold.

It seems to run best around 8 to 10 degrees before TDC. Any more advance and it didn't want to start when the motor was hot. my plugs are also at .045

Installing a HEI made a big difference starting the truck whens it below 30
degrees around here. I'm not sure about performance, It might have jumped the MPG up a couple of points.

[slowboy]

Originally Posted by Big D

I just did the same thing with my 72 , 350 with stock Q-jet and manifold.

It seems to run best around 8 to 10 degrees before TDC. Any more advance and it didn't want to start when the motor was hot. my plugs are also at .045

Installing a HEI made a big difference starting the truck whens it below 30
degrees around here. I'm not sure about performance, It might have jumped the MPG up a couple of points.

sooo...I have my plug gap at .035 ,running R44T plugs and runs rough...is .045 gap what I should have plug gap at with HEI distributor...I also have '72 350 w/ quadrajet...

[KEL]

From what I have read on this site, "YES" gap them at .45

[slowboy]

Guess I will try .045, often wondered, but never knew...wish me luck ! !

[truckdude239]

my points style is 2 before tdc so 8 would be about right can't find it in my repair manual says refer to emission control sticker under hood

[piecesparts]

I run my HEI around 12 to 15 BTDC on my motors. I ahven't had any starting issues, to date. I actually use a timing light that has the advance feature and adjust my timing to 35 degrees TOTAL advance at around 1500 RPM.

[todd99]

Originally Posted by piecesparts

I run my HEI around 12 to 15 BTDC on my motors. I ahven't had any starting issues, to date. I actually use a timing light that has the advance feature and adjust my timing to 35 degrees TOTAL advance at around 1500 RPM.

Whats the advantage of running 12-15 vs say 8?

My plugs are gapped at .040, would it be worth pulling them to increase to .045?

And does elevation factor in?

My goal with my motor is to achieve the best mpg I can.

I have full msd setup with edelbrock manifiold and carb.

[jacobs]

Originally Posted by bluedog

Just installed an GM HEI distributor. Plug gap set at .045. What are you guys setting the timing at? I have a stock engine with a Edlebrook 4 bbl. and mainifold. Stock exhaust.

Thanks,

Scott

HEI won't make any difference in initial timing IF total advance is the same. I just keep advancing the timing until it starts pinging (under full throttle and at about 1000 rpm) and back it off until it's quiet. It's never failed for me in 45 years.

[piecesparts]

To time my engines, I do disconnect the vacuum advance (whether or not the connection is ported). The timing needs to be without a vacuum signal, that way you are getting just the centrifugal timing with no hint of advance. My base timing is a lot higher than the 8 to 10 degrees, though. The 383 stroker gts around 15 MPG on the highway.

I use a Sears adjustable timing light and I set my timing at 35 degrees total advance,. It seems to work best for my needs. I also adjust my carbs with a vacuum gauge to get the most optimim setting on the metering screws.

[NoNeck]

When I first upgraded my 350 Camaro to an HEI back in the late seventies, the suggested gap was 0.060 and 6 degrees BDTC with R44TX spark plugs. The reasoning was that around 1975 when HEI's were first introduced, this was the factory setting.

After burning the tips from my spark plugs, I determined that 0.060 gap was too hot for normal, day to day, stop and go driving. GM must have determined that too, because in 1976 they dropped the 0.060 gap specification to 0.045. This caused a lot of confusion... especially to the shade tree mechanics like me.

After trial and error, I found that a good set of R-45TS plugs, gapped at 0.045, 12 degrees BTDC (8 degrees BTDC for manual trans) worked really well for me.

I always get the best results by using a vacuum gauge to adjust the engine (timing, carb settings) to get the HIGHEST VACUUM setting you can. An internal combustion engine is nothing more than a huge air pump. The more efficiently you move incoming fuel mixture and outgoing spent gases, the better your engine will perform and the better your MPG to boot.

Just an old man... trying to get by.

NoNeck

[slowboy]

have my timing set at 10 deg btdc...plugs gapped at .045

idles smooth, but no throttle response...just makes a lot of loud noise from 'Cherry Bombs'...sounds like it's hauling ass, but is just creeping

also, transmission goes through all 3 gears in about as many seconds when starting from dead stand still [normal driving]

all suggestions appreciated

[mwmeador38]

Your vacuum advance is ruptured.

[tim21391]

we set my buddys 350 with msd ignition at 8+ then 32 total

[70 shorty]

Total advance is what you really should be worried about, not initial timing. My 350 in my Vette is set at 36 degrees at about 2400.

[slowboy]

I've never heard of 'total advance' until these post...I don't have any idea how to set this...
but really need to learn

do I set 'total' the same way...but...just have idle up to 2400 rpm...and then instead of 8-10...go to 36 degrees...and does this require a special timing light, or can I use the old one I have

also...would this fix my transmission changing gears so quickly problem

Thanks for advice

[piecesparts]

You will need a timing light that can set the advance. Sears sells a really good one for a nice price.

Your tranny shifting issues are aligned to the setting of your TV cable.

[slowboy]

Thanks Frank, but...

Not sure what you mean by 'TV' cable.

I had wife sit in truck and hold gas pedal all the way to floor
while I tried setting what I call 'detent' cable, is this the same as 'TV' cable? While pedal was to floor, I unhooked clip, and hooked it back.

Seems to have made it worse though.

If you will, please add a little more detail.

Thanks again,

Keith

[piecesparts]

THe detent cable on TH350s or the TV cable on later model trucks with 700R4s is the cable that connects to the throttle linkage. If you look close, there is an adjustment to that cable. there is a slide piece that is made to click-stop out to the right spot , when you hold the pedal to the floor. That adjustment is at the point where the cable mounts to the bracket just behind the carburetor. On older trannys it is a half-moon shaped button on the plastic housing that you push in and then push the cable slide into the housing. after you do that, then do the pedal to the floor and see if it clicks out to the right spot for your tranny shift. On later models it is the same principal, but the design is not a haof-moon shaped plunger. Just look for it. This adjustment stages in your shift point or "Kickdown" for the tranny,.

[Indyuke]

On Turbo 350's the detent cable is only for kickdown or downshift. Actual shift points are controlled by a governor and by vacuum signal from engine manifold. This gives a direct indication of engine load for the trans to go by.

[slowboy]

Ok...plugs = .045
timing = 16deg BTDC [seems to run best there, starts fine hot...not starting too good cold...don't have rod and manifold coil spring cover for auto choke on Quadrajet...need info on setting choke to get best results without these 2 parts until I can find them somewhere]
transmission doing better...previous owner liked to go fast [top end] and changed rearend gears...not sure what's in it...but pretty sure this would affect transmission's gear changing...?...am I right or wrong...

all suggestions appreciated

[Indyuke]

Changing the rear gears would change shift feel... higher gearing the truck would shift at lower speeds. It wouldn't really change when the trans shifts common to engine rpm. That would stay the same.

If you went with higher rear gearing, the trans would tend to shift at lower vehicle speeds and lower engine load, but generally same rpm. Lower rear gearing the opposite would generally be true.

[slowboy]

I guess tranny is doing right.
Thanks

Still can't find the 'sweet-spot' for the timing though.

Just put the 'remanufactured' Quadrajet on it. Starting to wonder
if it is tuned right.

Sometimes it's hard to get by trying to do things that I can't pay
someone to do anymore.
Being disabled and unable to work sux.
Although I have learned a lot having to do things myself.
Being 54 and trying to learn new things is 'C-H-A-L-L-E-N-G-I-N-G'.
"WOO-HOO"...LOL ! !

[LONGHAIR]

You really should have started a new post, rather than hi-jacking a 5 year old one.....but at this point, I guess it doesn't matter.

The main thing to note here is that the statement "I just installed an GM HEI distributor", means very little. There are at least a dozen different variations of calibration. Just because they all "look" the same and they all "fit", does not mean that they will "act" the same.....because they will not.
You really need to know where the advance curve is tuned to....and be willing to adjust it. For some reason, many guys think that they can pull out the points distributor, drop in the HEI, and they get all of the advantages "automatically".
It's just not that easy, unless you go to the trouble to have your "new" distributor calibrated to match the old one before you install it.
Most of the stock HEIs are set-up to run with ported vacuum...and you don't want that.