[techg8]

My 79 trans am is running strong after this past winter's re ring and Edelbrock cam/intake job.

I have improved the exhaust with headers and the Pypes RacePro 2.5" X kit - which I LOVE by the way

Now I would like some advise on the HEI timing curve.

Currently with stock springs,
18 degrees initial
17 degrees mechanical in by ~2250rpm
17 degrees of vacuum advance

I am familiar with the concept of advancing as far as I can until just before pinging sets in under load, but would like to hear from people running 403s as to what this engine "likes" for performance timing. Are the stock settings as good as it gets? Can improvements be had by recurving?

What kind of timing curve have you used, what worked what didnt?? initial? mechanical? vacuum?

thanks for any tips. Recurving my HEI is the last performance mod I will be doing to my TA, and I hope to squeeze a little more response and power out of an already great engine.

[Grand73Am]

Which Edelbrock cam did you use? Just wondering since I just got the #3712 performer cam to put in my 403 soon.

[techg8]

same. 3712 cam and lifter kit

The engine runs great, no complaints at all. But if theres more to be had by working on the timing curve then I want it.

[Grand73Am]

Hope you get some good advice about the timing.

Good to hear about the performer camshaft. I just wanted something a step up from stock that wouldn't require having to change my factory stock valve train setup. I got the recommended new springs and timing gear and chain.
I notice the instructions say it may be necessary to change the pushrods though. Of course I'll check their travel, but were you able to keep the original pushrods or did you have to change yours? Thanks.

[techg8]

I think I just cleaned up the original ones and reused them

[techg8]

Well I have had a chance to tinker with my timing a littl ebit and here are the results:

first I bumped the initial setting up 4 degrees to 22. This was an improvement at WOT but the engine didnt seem to like it at idle (manifold vacuum advance). Not so much of an improvement part throttle around town etc....

So I pulled the vacuum can and opened up the "slot" a bit, adding about 10 degrees vac advance. The engine did not like this at idle on Manifold vacuum, so I teed into the egr ported vacuum line - this was the ticket.

The engine idles at 750 rpm 22degrees and smells, sounds and idles great!

just off idle the vacuum advance kicks in and really has enhanced the response of the car to throttle.

WOT runs are a blast, simply put.

I run 3.08 gears so around town I am not way up in the rpms. I am typically cruising at 1500-1750 when the vac advance is all the way in.

My one concern is how this setup will fare on the hiway for extended driving. Lets say I am at freeway speed, maybe 2500 rpm with mechanical advance all the way in and high vacuum cruise....66 degrees is a lot of timing. I wonder if it wont run overly hot or have some other issue. Time will tell.....

[techg8]

The TA is really running well.

Here is a burnout vid just for fun.....

https://www.youtube.com/watch?v=zvwzlhqYPdE

I just LOVE how mellow the pypes Race Pro system is at idle, and how it sounds great at WOT rpms! One of my best purchases for the car!

[Grand73Am]

I like it!

[bs78ta]

A rolling burnout would be a better indicator of the power band. Hell a Yugo can do a burnout if you powerbrake it.

[techg8]

Originally Posted by bs78ta

A rolling burnout would be a better indicator of the power band. Hell a Yugo can do a burnout if you powerbrake it.

So would a dyno sheet, but It seems like you missed the point.

Its just for fun my man - not trying to prove anything about my combo.

[Greg Reid]

Originally Posted by techg8

Currently with stock springs,
18 degrees initial
17 degrees mechanical in by ~2250rpm
17 degrees of vacuum advance
...I bumped the initial setting up 4 degrees to 22...

So you are running +40 degrees or so advance at 2250 without vacuum? Don't know much about Olds engines...actually nothing....but that sounds like a lot. Or is that with vacuum applied?
If the car likes it, I'm not knocking it, just curious.

[techg8]

Originally Posted by Greg Reid

So you are running +40 degrees or so advance at 2250 without vacuum? Don't know much about Olds engines...actually nothing....but that sounds like a lot. Or is that with vacuum applied?
If the car likes it, I'm not knocking it, just curious.

yes. right about 40 degrees without vacuum adv around 2250

the numbers spook me a bit too, but the engine does really like it.

It reminds me a lot of the 86 Olds 307 I ran with the CCC system in a Gbody. TONS of timing advance.

[Greg Reid]

Very interesting.

[77 TRASHCAN]

Originally Posted by Greg Reid

So you are running +40 degrees or so advance at 2250 without vacuum? Don't know much about Olds engines...actually nothing....but that sounds like a lot. Or is that with vacuum applied?
If the car likes it, I'm not knocking it, just curious.

Every engine is different. I have a 70 350 Pontiac in my car right now. Performed a simple rebuild. Stock pistons, honed w/ ball hone, new rings, 066 cam. I have 44 degrees total in it, never ever has pinged. The 70 350 is listed @ 8.8:1, I'm sure it is not...LOL. In the preparation, I polished all sharp edges off piston tops, and chambers. Went to a lot of detail, for an essential re-ring build. I guess the details helped, it runs good. I'm going to check the static compression, thinking about retarding the cam phasing, maybe pickup some cyl pressure, and performance...,maybe I am plotting a couple larger cube builds, the 350 is O.K., just not a 400 or 455...

[Greg Reid]

True..every one likes what it likes. I've never personally had one that liked it quite that far advanced.