I have a 1969 396 in which I changed the original distributor and coil with a used GM HEI I had laying on the shelf, don't know much about it.

The car seems to run strong. It has a mild hydrulic cam w/ rollers, holley 750 single pump w/vacume secondaires, 049 heads just re-done, Turbo-400.

My question is, is there anything I can do to quicken the throttle response? I heard of lightening up on the spings in the distributor would help this, never did that so I don't know.

Also just before It shifts at WOT it seems to miss just a little bit and I 'm leaning torwards the Stock HEI as the cause.
What kind of ignition are you guys running? Happy with them?
I don't race this car, but would love to get quicker carb response and get rid of that missing situation.

Any help,tips or suggestions will be apprecated.

Thanks Guys.

Yup it's true.

First things first though.
In stock form the HEI has a grotesk amount of shaft play that makes your timing vary.
Remove the distributor and shim the shaft play down to .020.
Next go get yourself a curve kit.Throw the advance cam and weights in the kit away.

Get a dial back timing light,disconnect the vacuum advance,slowly rev the engine to a point where the timing stops, this might be as high as 4500 rpm, set your total timing at 34-36 degrees.If the advance seems like it starts to retard stop.You need to get a different set of advance weights and an advance cam.Don't use the ones in the kit.They are junk.Rob them off another HEI.

A little experimenting is in order.
When I bought one years ago I quickly added the two lightest springs.It was not good.Ping ping ping.
I added one medium spring,ping ping ping.
I added the second medium spring,better.
I added one stock spring with the medium and that was the best for me.

As for the popping, read this post
http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=4;t=017400
and if it keeps doing it or you are not happy with the results do a search.I am sure you will find something.Keep checking back.

Careful, some HEI have an enormous amount of timing, mehcanical advance. You might be feeling WAY TOO MUCH advance. I've seen them with nearly 40 degrees of mehcanical advance which is way too much for a mild performance motor. Many HEIs were designed to be used with 8:1 compression smog motors.

I suspect this is the case with yours OR the module needs to be replaced.

Yes this is true about the high mechanical advance in some units.If you end up with 34-36 degrees total and under 10 degrees initial you need a different set of advance weights and a new advance cam.

Some distributor modules will give you intermitent problems.
Not all of them just die with no warning like most people will tell you.I have experianced the old now it works/now it doesn't myself.

Do you think it best to buy an aftermarket MSD, mallory, or some other HEI better suited for my setup? If so any suggestions?

Thanks for the response guys

Also what are these things (boxes) I see designed to delivery multipe sparks per power stroke???

That is the MSD you speak of.Multipal Spark Discharge.

Give us your engines build combiation with the stall speed and rear gears.

Sorry for the late response, I've been away.

The engine is a 1969 396/375 Hp L-78 W/stock pistons and standard bore.
Heads are 049 open chamber w/new seats a 219-188 valves.
Stock intake.
Holley 750 single pump vac sec.

Cam is a hydraulic crane, part # 134242, says on card advertised duration 286/296.
No AC. Turbo 400 trans, Stall speed unknown. And i'm picking up an open 12 bolt this weekend :D

So any idea as to what differential and gearing would best suit me I'd love to hear them cause I never had a posi before(remember I don't race the car.......much ;) ). Right now the car has the original open 10 bolt(ratio unknown) in it and pushes 2500 RPM @55 MPH.
Would like to get that RPM down just a little I think, does that seem high for cruising?


Still missing a little @ WOT......


Thanks for any advice

well i think you may have about a 3.42 gear ratio based on the 2500 rpms at 55 and using a common tire height of 26 inches(70 mph would be 3100 rpms)......2500 rpms for cruising is not bad thats pretty good unless you want to go faster like 70 mph or so then a set of 3.08 gears will be at about 2800 rpms for that speed(2200 rpms at 55 mph).....unless you do alot of highway driving i would stick to the gear ratio you have now.....

your engine would be very responsive with as much inital lead you can give it.......i would set you intial lead at about 18 degrees and set it for 36 total...........

the hei you have maybe giving to much total timming causing the miss, i have had it before and that was the problem . i would bet your timming is in the 50's right now......

i do my own dist. but i go farther into them then the normal person does i set each one up to just the engine it will run.......i weld the mechanical advance slot up to limit the total timming.

the stock weights are a great piece you just need the springs from a recurve kit......

there is alot of time involved to get it perfect........

if your not into spending alot of time to do this then i would say have one built just for you from one of the dist. companys.......

for me its easy to do then to explain