Hey guys,

Does anyone know how much mechanical advance is typically built into a stock HEI distributor? It's from a 79 Z28 if it makes a difference. Just curious. I'm gonna be firing up my new motor for the first time this weekend and was curious. I figure 10 degrees BTDC initial is probably just fine for my break in period, then I'll go to the track and dial things in better.

Thanks,
Joe

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79' Z28 4-spd- built 355, TRW flattops, WP SportsmanII heads, Crane Energizer 284/284 duration .480"/.480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :)

I can't say exact factual numbers but be aware you could find as much as 35 or more degrees of mechanical in that dist. Also the vacuum advance canister may have more than 20 degrees in it!! '79 was prime smog motor time which meant very low initial setting, lots of vacuum advance and not exactly what you may want for your mill!! The HEI that was in my car was cranking out over 40 degs total with about 6 or 8 initial!!

With a new mill I'd find a shop with a dist machine and someone that can use it (it's becoming a lost art with all the aftermarket out there) Have them dial it in for you. Shouldn't be more than a half hr on the clock... Well worth it!!

WOW! I never would have expected something like that. I figured it'd have less advance in it if anything. Guess it's time to get a new distributor... http://www.camaros.net/forum/frown.gif

Thanks.

-Joe

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79' Z28 4-spd- built 355, TRW flattops, WP SportsmanII heads, Crane Energizer 284/284 duration .480"/.480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :)

How did they get away with so much timing and no detonation? Did the lower compression allow for more timing? This really is baffling me...

-Joe

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79' Z28 4-spd- built 355, TRW flattops, WP SportsmanII heads, Crane Energizer 284/284 duration .480"/.480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :)

I believe the '79 L48 350 in a vette was about 195hp with a 4bbl carb, compression was very low. I would think the avg 350 in '79 made 165-170hp...

You'll spend less and get great results with a re-curve.

...Dennis

[This message has been edited by DjD (edited 10-11-2001).]

Well, I was sorta already planning on a new distributor anyways, just not for about another month. Anyhow, I just bit the bullet and ordered a Summit Racing HEI. At $150 it's the cheapest thing out there, and I've used some of summit's other products and they were nice quality stuff.

-Joe

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79' Z28 4-spd- built 355, TRW flattops, WP SportsmanII heads, Crane Energizer 284/284 duration .480"/.480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :)

FYI-
On the point distributors the rotation direction and degrees of mech advance are stamped on the underside of the breaker cam or pole piece on mag pulse distributors.

The HEI may have this stamping too.
The only way to be sure is to actually check it. The advance weight system on these distributors is not as good as the non HEI distributors were. The weights bind up and have too little weight, aftermarket weights fit poorly and can freeze up the advance limiting it. The mag pulse retards the spark at higher RPM's, so that throws it off too.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

I found what David is saying about the HEI mechanical advance to be exacty true - too little weight and sticky operation. Something that helps though - try using the heavier aftermarket weights (your Summit HEI probably already has them) and polish both sides until they are glassy smooth (I used Mother's mag rim polish). It seemed to help mine operate a lot better. You should have around 22 degrees mechanical advance - I set at 12 initial for a total of 34 (then the vac advance adds about 10 more at cruise speeds).

By the way - never put any kind oil on the mechanical advance, it will gum up the whole works. Don't ask how I know http://www.camaros.net/forum/biggrin.gif

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68 Camaro, 383 small block with TH350 trans. 12.2's and never trailered.

[This message has been edited by Eric68 (edited 10-12-2001).]

I assume that the Summit unit is built with these shortcomings in mind, but I appreciate the heads up.

LOL Eric.

-Joe

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79' Z28 4-spd- built 355, TRW flattops, WP SportsmanII heads, Crane Energizer 284/284 duration .480"/.480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :)