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ZZ4 & ZZ383 - no vacuum advance???? Header size??

 
Old 03-21-2011, 02:31 PM
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Plasticman
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Default ZZ4 & ZZ383 - no vacuum advance???? Header size??

Looking over the specs and info on the ZZ4 and ZZ383 (GM Performance crate engines), I see that neither engine is recommended to have any vacuum advance used.

I can understand part of that with the ZZ383, since it uses "Fast Burn" heads, but still would think a moderate amount of vacuum advance would help idle & cruise efficiency and lower engine temperature.

Any comments, and do any of you with these engines use any vacuum advance?

A another question concerning these 2 engines, what size headers (if any) are you using? Both are rated by using 1-3/4" headers, but I currently have 1-5/8", and have a hard enough time getting at the cylinder head flange bolts. 1-3/4 would be that more difficult, and doubt they would be worth the change (for a street driver). In fact, think the smaller tubes would actually help low / mid end (although neither engine is hurting in the torque department).

Any one do a dyno test on either engine? And what combo do you run?

Plasticman
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Old 03-21-2011, 02:47 PM
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Dennis Beck
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I have the zz383. It has been in my car since '06. I used Patriot ceramic coated shorty center dump headers because they cleared the steering box with no modifications. Then fabricated stainless pipe to my Allen's stainless sideppes.
I have a MSD Pro Billet tach drive distributor with vacum advance and a 6AL box. Runs as cool as the other side of the pillow.
This has been a strong running trouble free combination since I put it in.

Dennis
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Old 03-21-2011, 03:09 PM
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John,

Not sure about the GM crate motors but as you know I have a 383 stroker with vacuum advance. Total advance at only 32 degrees. Original tack drive distributor with Pertronics II. My heads are the Dart Aluminum PRO-1 Platinum. I did not replace the stock 2 1/2" rams horn manifolds but I did port them to match the heads and removed any slag at the collector area. Then it dumps into Allen's 2 1/2" exhaust that was opened up to 3" at the chambers to allow for 1/4" Glass pack done by MasterDave. Great performance and a nice deep exhaust note out the side pipes.

Last edited by Kensmith; 03-21-2011 at 03:12 PM.
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Old 03-21-2011, 03:45 PM
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Are you sure on vac adv? The spec I see on the ZZ383 is just about limiting total advance "with vacuum advance disconnected". Setting total (vs initial) centrifugal advance has been recommended by GM racing for 30+ years. The process is done with vac adv disconnected, then reconnected after setting...

On headers,the length is more important than diameter. When I looked at it with GMPP I recall that no one made set with long enough tubes...

Harry
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Old 03-21-2011, 03:49 PM
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Frankie the Fink
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Uh-oh. Are you joining Big Bill Fleck on the "dark side" ?
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Old 03-21-2011, 03:59 PM
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1 5/8" should be plenty for street exhaust through mufflers.
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Old 03-21-2011, 04:20 PM
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Originally Posted by 66since71 View Post
Are you sure on vac adv? The spec I see on the ZZ383 is just about limiting total advance "with vacuum advance disconnected". Setting total (vs initial) centrifugal advance has been recommended by GM racing for 30+ years. The process is done with vac adv disconnected, then reconnected after setting...

On headers,the length is more important than diameter. When I looked at it with GMPP I recall that no one made set with long enough tubes...

Harry
Harry,

From part of the ZZ383_Engine.pdf:

"The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using the internal centrifugal advance only to achieve the correct timing curve." Note that the ZZ4 spec states essentially the same thing (no vacuum advance).

Yes, I am "very" familiar with setting ignition timing (I have my own Sun Dist. Machine, and know how to use it).

Note that I plan on using my existing Delco points tach drive dist. for a couple of reasons, including the use of my current intake (Offenhauser dual quad with 500 cfm AFB carbs) won't allow a "larger" dist. be used.



Frank,

The dark side beckons............


Ken,

Thanks!


And thanks to all for your comments.

John (plasticman)

Last edited by Plasticman; 03-21-2011 at 04:28 PM.
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Old 03-21-2011, 05:18 PM
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I'm running ZZ4 with STOCK distributor (w/Melonized Gear) that I sent to LARS to set up on his SUN Equipment.

I think below was my last settings

ZZ4 as of 5/15/2009
Distributor Can B26/B20 in @ 7 out @ 15
Dwell = 30.0
12 @ 690 RPM Initial (Base)
28 @ 3300 RPM Total (Centrifugal) “ALL IN”
34 @ 750 RPM Vacuum Advance 34-12=22
22 + 34 = 56 MAX Total + Vac
20” Hg @ 700 RPM

BTW...I'm running 2 1/2" Ram Horns w/side exhaust

George

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Old 03-21-2011, 05:41 PM
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66since71
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Plasticman...

It is interesting that they supply the documentation that way. I know the original ZZ development leader very well. He is a big believer in using vacuum advance, so I am really surprised about that comment for th ZZ4. I dont know a lot about Vortec heads, so there may be more story there on the 383. But the engines need some form of load compensation for street driving. if it doesnt come form the ignition timing, then where?

I think there is a way to contact the GMPP staff directly (I think they are just outside Flint Michigan). Maybe a call to them?

Harry

(I saw that you also noticed the supplied distributor for both engines has a vacuum can...)

Scoggin Dickey (sp?) is also a great tech source

Last edited by 66since71; 03-21-2011 at 05:50 PM. Reason: Scoggin Dickey
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Old 03-21-2011, 05:48 PM
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Mine has a 383 with an MSD tach drive distributor with no vacuum advance and the MSD AL6 box. It runs Hooker competition 1 5/8 headers. The 1 3/4 headers interfered with the rack and pinion steering. It has Patriot aftermarket aluminum heads. Car runs great, no pinging on 91 octane. 16 degrees initial at 1000 RPM, I don't know what the total is. I didn't build the engine.

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Old 03-21-2011, 05:57 PM
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Plasticman, My FB385 Service Parts Operations document states ( Set spark timing at 32 dg BTDC at 4000rpm with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32 dg of total advance at WOT. The HEI VACUUM ADVANCE CANISTER SHOULD BE CONNECTED TO A PORTED VACUUM SOURCE ....no vacuum at idle. There is more and I can fax the page to you if it will help. Phil
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Old 03-21-2011, 06:37 PM
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You always set the timing with the vacuum advance disconnected, but then re-connect it afterwards - that's all the spec is referring too. Without it you will be loosing the drivability and efficiency that comes from lots of timing under very light load - which happens a lot with such a light car. I ran a petronics module in my stock tach drive distributor with this motor for 60,000 miles with no problems...

I'd be more worried about how much the headers stick down below the car some full length ones are silly low. I set a friends 65 up with the 383 fast burn and name brand shorties since he wanted to run quiet mufflers anyway - had to grind on the steering box like hell for clearance. Car still runs like a scalded dog, even without the optimum exhaust.

My 64 with a ZZ4, small 2" manifolds, and the factory sidepipes (they only have a 1 5/8" opening in the sleeve between the manifold and the pipes !!) and the car still ran 12.9 at 108mph on 235 radial ta's with a 3:55 rear.

Don't buy any headers that don't have the ball and socket connection on the collector - life is too short to fool with header gaskets....

Last edited by FastEddy; 03-21-2011 at 06:42 PM.
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Old 03-21-2011, 06:48 PM
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Originally Posted by ZYALTR View Post
Plasticman, My FB385 Service Parts Operations document states ( Set spark timing at 32 dg BTDC at 4000rpm with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32 dg of total advance at WOT. The HEI VACUUM ADVANCE CANISTER SHOULD BE CONNECTED TO A PORTED VACUUM SOURCE ....no vacuum at idle. There is more and I can fax the page to you if it will help. Phil
Phil,

I just searched for the FB385 document, and came up with this:
http://www.gmperformanceparts.com/_r...Long_Block.pdf

It is titled: FB385 Engine Long Block Specifications IR 02MY07, and does not have a date.


In part, it states that same thing as I mentioned above in post #7, but I copied this directly from the FB385 above:

Set spark timing at 32 before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32 of total advance at wide open throttle (WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to achieve the correct timing curve.

It is actually stated twice in the above doc. Also another doc. titled ZZ4/FB385 says the same thing:

http://www.gmperformanceparts.com/_r...ne_Partial.pdf

Does your FB385 document have a date? I don't have a fax machine that "receives" (ink dried up - again, and I use it so infrequently, I can't keep it from drying out), but appreciate the offer. Can you scan it and send it via email? If the FB385 at one time (or maybe currently) used vac. advance, then the ZZ383 should as well.

Black Magic,

Thanks for your info and specs. We helped WMF62 install a ZZ4 earlier this year in his 62, and this should be of interest to him as well.

Harry,

Yep, think I will end up contacting GMPP and/or SD, but wanted some other input from guys who are actually using these engines (which is what I am getting). As noted, the ZZ4 WMF62 installed came with an HEI with the vacuum can. We only used the melonized dist. gear off it, since he has an Accel dist. to go along with his EFI converted Rochester FI.

Arthur,

Yes, I can see where the 1-3/4 tubes would interfere! Thanks for the info.

Fast Eddy,

I agree on how to set the timing, but the docs mentioned above are pretty specific that the vacuum advance should not be used. I agree with your logic, hence the reason for posting, but wanted real world testaments, and I thank you.

Already been fooling with headers and gaskets (the Vette had them when purchased in 1999), so I plan on using the same ones I have.

Thanks again all,
John (Plasticman)

Last edited by Plasticman; 03-21-2011 at 07:05 PM.
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Old 03-21-2011, 07:04 PM
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Originally Posted by FastEddy View Post
You always set the timing with the vacuum advance disconnected, but then re-connect it afterwards - that's all the spec is referring too. Without it you will be loosing the drivability and efficiency that comes from lots of timing under very light load - which happens a lot with such a light car. I ran a petronics module in my stock tach drive distributor with this motor for 60,000 miles with no problems...

I'd be more worried about how much the headers stick down below the car some full length ones are silly low. I set a friends 65 up with the 383 fast burn and name brand shorties since he wanted to run quiet mufflers anyway - had to grind on the steering box like hell for clearance. Car still runs like a scalded dog, even without the optimum exhaust.

My 64 with a ZZ4, small 2" manifolds, and the factory sidepipes (they only have a 1 5/8" opening in the sleeve between the manifold and the pipes !!) and the car still ran 12.9 at 108mph on 235 radial ta's with a 3:55 rear.

Don't buy any headers that don't have the ball and socket connection on the collector - life is too short to fool with header gaskets....
Dang Fast Eddy...

12's with a stone stock ZZ4? That's movin' right along...

What transmission do you have and what ratio is 1st. gear?

2" Cast Iron Manifolds or headers?

...Stan
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Old 03-21-2011, 07:19 PM
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my previous engine was a 70 LT1 and, with the EFI conversion, running 15* (at 250) initial, the most total advance i could run, using 93 octane, was about 40* (all in by 2200) with an AFR of about 14.9 by 2200. anything more aggressive and it was not a happy camper....

the ZZ4, with the same EFI setup, now is as happy as a clam (not sure how happy that is, but i'm happy...) running 19* (at 200) initial, 52* total (all in by 1800), with an AFR of 14.7 by 1200, using 87 octane. probably have some more room to tinker/tune...

Bill

Last edited by wmf62; 03-21-2011 at 10:11 PM.
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Old 03-21-2011, 09:21 PM
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I do not have a document scanner but I can put a copy in the mail to you. I believe I bought this motor in 2006/7 time frame and the info I quote is from the FB 385 specifications I received with it. In the Ignition notes the last sentence is : The HEI distributor supplied with the FB 385 engine has mechanical centrifugal and vacuum spark advance with the following curves."
Mechanical Advance RPM Advance
1100 0 dg
1600 12 dg
2400 16 dg
4600 22 dg

Vacuum Advance Vac (in. Hg) Advance
3.00 " 0 dg
7.50" 20 dg
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Old 03-21-2011, 09:30 PM
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John, I drive to Crystal River every Thursday . I have a conflict this week so I won't be there until a week Thursday but I'd be glad to bring a copy up if you need it. Just let me know. As a note , I've run my FB 385 with mechanical advance since new and just this week a mechanic friend suggested I go to vacuum advance. I've invested in 18" of hose so I'll try it and time it tomorrow if I'm able. Phil
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Old 03-21-2011, 11:14 PM
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Originally Posted by ZYALTR View Post
John, I drive to Crystal River every Thursday . I have a conflict this week so I won't be there until a week Thursday but I'd be glad to bring a copy up if you need it. Just let me know. As a note , I've run my FB 385 with mechanical advance since new and just this week a mechanic friend suggested I go to vacuum advance. I've invested in 18" of hose so I'll try it and time it tomorrow if I'm able. Phil
Phil,

That would be great! I will send you a PM. Thanks for the dist. specs.

It sure would not hurt to try (as long as it does not ping at light loads).

Will try to get wmf62 on over at the same time (his 62 is real interesting to a gear head). Chuck Gongloff is also close by, and probably can get him to come over with one of his Vettes.

John (plasticman)
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Old 03-22-2011, 10:15 AM
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Originally Posted by Stan's Customs View Post
Dang Fast Eddy...

12's with a stone stock ZZ4? That's movin' right along...

What transmission do you have and what ratio is 1st. gear?

2" Cast Iron Manifolds or headers?

...Stan
Cast iron manifolds -you have to chew a little off the top of the manifolds port to match them up to those L98 heads - about 1/8".

I was pretty happy - my first time on a track, and the motor had about 45,000 miles on it by then. It had the wide ratio box at that time, so that would have been around 2:52 maybe?? I forget what first gear they have. It was not the 2:20 box. I ran no spare tire or carrier, and the car weighed in at 2,960 with 1/2 tank on my local scales. 60 foot was 2.03 on that run. oops just remembered, they made me put my hardtop on, so I'm not sure what the car actually weighed on that run.

I was just amazed at the small opening of the sleeve that is between those 2" manifolds and the factory sidepipe - Those manifolds must have gotten pretty hot on my top end runs I added headmans headers later, and it seemed to wake up in the upper R's, but never made it back to the track.

Last edited by FastEddy; 03-22-2011 at 10:23 AM.
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Old 03-22-2011, 10:48 AM
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Originally Posted by FastEddy View Post
Cast iron manifolds -you have to chew a little off the top of the manifolds port to match them up to those L98 heads - about 1/8".

I was pretty happy - my first time on a track, and the motor had about 45,000 miles on it by then. It had the wide ratio box at that time, so that would have been around 2:52 maybe?? I forget what first gear they have. It was not the 2:20 box. I ran no spare tire or carrier, and the car weighed in at 2,960 with 1/2 tank on my local scales. 60 foot was 2.03 on that run. oops just remembered, they made me put my hardtop on, so I'm not sure what the car actually weighed on that run.

I was just amazed at the small opening of the sleeve that is between those 2" manifolds and the factory sidepipe - Those manifolds must have gotten pretty hot on my top end runs I added headmans headers later, and it seemed to wake up in the upper R's, but never made it back to the track.
OK..thanks for the info..

Stan
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