ZZ4 upgrades? - Page 2 - Chevelle Tech
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post #16 of 106 (permalink) Old Sep 6th, 19, 11:09 PM
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re: ZZ4 upgrades?

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Originally Posted by Hotrodder000 View Post
You didnt change anything else? Literally just swapped cams?
Just the cam and the LT4 valve springs. Funny thing was after the cam swap the 1405 Edelbrock was the best carb on that combo but seemed a little soggy on with the ZZ4 cam. On the ZZ4 cam, the 670 Holley seemed better, used it with the new cam but the Eddy would pull to 6500rpm and the Holley was not even close. I did not even try a set of 1.6 rockers and that's supposed to help the LT4 cam even more.
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post #17 of 106 (permalink) Old Sep 6th, 19, 11:26 PM
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re: ZZ4 upgrades?

Hi guys, wanted to share my experience with the zz4. I owned one in my 67 Chevelle. I had a M21 behind it with 4:10 gears. I ran a Holley 670 Street Advenger with the stock intake which is very close to an Edelbrock Performer on it would roast my 235 60 15 rear tires. I would run out of rpm though in the quarter...I would hit 5200 about 30 yards before the stripe. I went to the 275 60 15 rear tires and I could not do rolling burnouts anymore but it still would light them up with a little slip of the clutch. Very fun in the city, stop light to stop light. For a real small small block chevy the motor is stout on the street. You get a little lope when you crank it up and it lopes at idle for like 30 seconds then it smooths out. The heads and cam are built for torque. The runners on the heads are like 160 with a 1.94 valve. The cam is very tiny in it. 256 on the intake and cant remember the exhaust but the @ .050 numbers are like 208/221 for .475/.510 lift on a 112 lsa. The engine block is a one piece rear seal with a factory roller car provision.

A upgrade to the GMPP "hot cam" would get you power up around 375 to 400 horsepower. The hot cam is like 279 on the intake and cant remember the exhaust. The @ .050 numbers are 218/228 or something like that for a lift of .495/.495 on a 112 lsa. The cam runs best if you switch over to the 1.6 rockers for .530 /.530 lift. The heads on this engine are the L98 corvette heads and have self adjusting rockers, so that is the kind of 1.6 rockers you must get...the heads have no guide plates.

Sallee Chevrolet use to campaign these engines with various upgrades from 350 horsepower in stock form to a 430 horse 350 cubic inch small block with a upgrade in the intake to a RPM, hot cam with roller rockers, and a set of the GMPP fast burn heads.

It was later redesigned with the zz5 and zz6. They switched the factory GMPP performer style intake for a single plane and used a upgraded spring package to get the cam to rev to 5500 to 5800. They got 400 horses out of it. They may of switched the L98 heads for a set of Fastburns...not sure on that.

The short block in this engine has hyper -7 flattop pistons with PM rods and a steel crank with windage tray. Compression with the L98 heads are right at 10 to 1. The factory head gasket on the zz4 is like .051 thick and with the piston down in the hole at .025 that gives you a awful quench of .076...which requires 92 or 93 octane. I don't understand that part on GM behalf.

The timing guide that comes with the motor has been posted above and it SUCKS. The timing curve is very lazy and slow. Sallee Chevrolet never ran the vacuum advance on their motors as it would add to much timing at cruise like 56* or 60*….. they recommended to just run the mechanical curve. Sallee says the zz4 ran best at 36* at 3000, which is what I ran. They set timing by setting it 3000 and let the initial fall where it may...which was 18* or 19*.

Here is the deal on the distributor...it sucks....LOL....The mechanical advance is 20* or 22*, cant remember. The vacuum advance adds 20* of timing. The distributor does not stop advancing until 4500 and maybe 5000. This is the same distributor in all the GMPP crate engines.

Here is what I did. First, I took the stock springs out put in a blue and silver spring to get the timing all in under 2700. I then took the distributor apart and measured the slots and figured out how much I would weld the slots up to get a 18* mechanical curve. I then had the distributor stopping its advance at 2700. I never used the vacuum advance while running the stock cam, but you could just figure out how to install a stop so that it would only add 10* so that it would only have 46* of timing at cruise. Im not sure this would work though and I know it would not without a great cooling system.

Later on, I stripped the top half of my motor off. Sold the Performer style intake, stock cam, and L98 heads, rockers, and pushrods. I order a UDHarold roller cam speced at 280/288 and 226/234 @ .050 and which had .530/.530 lift on a 108 lsa. I installed that cam at 104 ICL. I then bought a set of second hand Trick Flow 195 heads for another racer and used the Fel Pro 1094 head gaskets to get my compression up to 10.3. My piston to valve clearance was good. I reused my factory lifters and installed a Edelbrock RPM Air Gap along with a Holley 650 DP. I left the distributor as it was already and got the can to add 12* of timing. So, my timing was 18* for a total of 36* all in by 2700. I ran manifold vacuum and my idle was now 30* and my cruise was at 48* I had a great cooling system, used 93 octane only, and had 2500 cfm dual fan set up and it would run 190 in the Florida heat in the summers. This combo dynoed at 430 horse and 415 torque. I shifted this combo at 6000 and ran through the traps at 6400 at the track and the car was consistent at 12.50's to 12.60's with a decent 60 foot times. Of course, I ran slicks. Later on I added a 125 shot of NOS and it ran a best of 11.7.

Still have the motor and still plan on using it in the future!!

I can provide more info on the motor if you need.
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Last edited by Aaron; Sep 6th, 19 at 11:42 PM.
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post #18 of 106 (permalink) Old Sep 7th, 19, 7:59 AM
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re: ZZ4 upgrades?

Quote:
Originally Posted by nashville beth View Post
That doesn't mean to leave the vacuum advance disconnected permanently...
"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"
That is how I read it, seems pretty clear in their intent to me.
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post #19 of 106 (permalink) Old Sep 7th, 19, 8:56 AM
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re: ZZ4 upgrades?

Aaron : Later on, I stripped the top half of my motor off. Sold the Performer style intake, stock cam, and L98 heads, rockers, and pushrods. I order a UDHarold roller cam speced at 280/288 and 226/234 @ .050 and which had .530/.530 lift on a 108 lsa. I installed that cam at 104 ICL. I then bought a set of second hand Trick Flow 195 heads for another racer and used the Fel Pro 1094 head gaskets to get my compression up to 10.3. My piston to valve clearance was good. I reused my factory lifters and installed a Edelbrock RPM Air Gap along with a Holley 650 DP. I left the distributor as it was already and got the can to add 12* of timing. So, my timing was 18* for a total of 36* all in by 2700. I ran manifold vacuum and my idle was now 30* and my cruise was at 48* I had a great cooling system, used 93 octane only, and had 2500 cfm dual fan set up and it would run 190 in the Florida heat in the summers. This combo dynoed at 430 horse and 415 torque. I shifted this combo at 6000 and ran through the traps at 6400 at the track and the car was consistent at 12.50's to 12.60's with a decent 60 foot times. Of course, I ran slicks. Later on I added a 125 shot of NOS and it ran a best of 11.7.

That's how you setup a good advance curve
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post #20 of 106 (permalink) Old Sep 7th, 19, 9:14 AM
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re: ZZ4 upgrades?

Quote:
Originally Posted by Pioneer4x4 View Post
"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"
That is how I read it, seems pretty clear in their intent to me.
You're right. I looked it up - GM did say to leave it disconnected.

Why ? Most agree they did it "to cover their arses" from engine damage caused by people that didn't know how to use vacuum advance.

Here's a good thread on this :

https://www.chevytalk.org/fusionbb/s...hp?tid/307406/
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post #21 of 106 (permalink) Old Sep 7th, 19, 9:38 AM
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re: ZZ4 upgrades?

Quote:
Originally Posted by nashville beth View Post
You're right. I looked it up - GM did say to leave it disconnected.

Why ? Most agree they did it "to cover their arses" from engine damage caused by people that didn't know how to use vacuum advance.

Here's a good thread on this :

https://www.chevytalk.org/fusionbb/s...hp?tid/307406/
And FWIW, I have tried several ways of hooking mine up, no vacuum advance, manifold vacuum, and ported. BUT I haven't spent time checking the amount of advance, or limiting the can any, and I know I should, BUT, I plan to do it all in software anyway with the FiTech…
IF I ever get time to touch it, which it doesn't look like. The performance differences I did notice were slight pinging and mid rpms, with low load (high vacuum) which makes sense, and I do get hard cranking when warm some times. I think that is as much of a reason that GM says not to use vacuum advance, the ZZ4 has enough vacuum while cranking it advances too much to start easily. (Just a W.A.G.)

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post #22 of 106 (permalink) Old Sep 7th, 19, 11:55 AM
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re: ZZ4 upgrades?

Quote:
Originally Posted by Pioneer4x4 View Post
I think that is as much of a reason that GM says not to use vacuum advance, the ZZ4 has enough vacuum while cranking it advances too much to start easily. (Just a W.A.G.)
I don't think so. As the ignition expert was saying in that thread I posted, GM was probably afraid of people adding too much advance.

Vacuum advance is primarily used to add 10-16 degrees at cruise speed to help burn the lean mixtures.

It doesn't come into play when you're starting. It allows you to reduce the initial timing and that makes it easier to crank over when starting.
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post #23 of 106 (permalink) Old Sep 7th, 19, 2:40 PM
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re: ZZ4 upgrades?

I tossed the stock vacuum advance can and went with an aftermarket adjustable one that allowed adjustment for both rate and total travel to limit how much advance is provided. It was cheap and works good. I also changed the advance springs. My current tune is set to get total mechanical all in by 3200. Initial is somewhere around 14°, Total around 34°, and another 12° from Vacuum at full manifold source. This is conservative, but it's in a 4000# truck. I could probably slow it down a hair yet too, but it seems to work just fine. No holes, hesitation, stumbles, or detonation. When the ZZ4 was in my car, I had a few more degrees initial and total, and it was in a little sooner, but the car weighed a lot less and had 4.11's out back.
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post #24 of 106 (permalink) Old Sep 7th, 19, 9:11 PM Thread Starter
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re: ZZ4 upgrades?

Took the car to a show today. Ran like absolute crap most of the time. Wont idle in gear, bogs on accel, just plain runs like crap. Wont even break the tires loose from a dead stop. Finding a shop on monday to take a look. I dont have enough knowledge. Now im mad. lol.

If it's not broken, let's fix it till it is.
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post #25 of 106 (permalink) Old Sep 7th, 19, 9:32 PM
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re: ZZ4 upgrades?

Quote:
Originally Posted by Hotrodder000 View Post
Took the car to a show today. Ran like absolute crap most of the time. Wont idle in gear, bogs on accel, just plain runs like crap. Wont even break the tires loose from a dead stop. Finding a shop on monday to take a look. I dont have enough knowledge. Now im mad. lol.
PM me and I will tell you what to do to a 1405 Eddy carb so it will work on the street right.
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post #26 of 106 (permalink) Old Sep 7th, 19, 9:49 PM
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re: ZZ4 upgrades?

Quote:
Originally Posted by Hotrodder000 View Post
Took the car to a show today. Ran like absolute crap most of the time. Wont idle in gear, bogs on accel, just plain runs like crap. Wont even break the tires loose from a dead stop. Finding a shop on monday to take a look. I dont have enough knowledge. Now im mad. lol.
That’s probably a good idea at this point.

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post #27 of 106 (permalink) Old Sep 7th, 19, 10:21 PM
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re: ZZ4 upgrades?

Quote:
Originally Posted by Hotrodder000 View Post
Took the car to a show today. Ran like absolute crap most of the time. Wont idle in gear, bogs on accel, just plain runs like crap. Wont even break the tires loose from a dead stop. Finding a shop on monday to take a look. I dont have enough knowledge. Now im mad. lol.
You need to find an old timer who knows how to set up the timing on an old car.

The car show would have been a great place to find help.
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post #28 of 106 (permalink) Old Sep 8th, 19, 12:17 PM
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re: ZZ4 upgrades?

x2 its worth it youll really be surprised how much better/stronger it can be despite what your dailys do. Dont just leave it due to time/not knowing etc. Looking back I did that with a few that I gave up hope on far as making power..that was a mistake.
The wideband is a great idea....It can take a car that "runs fine" and make it waaay better.
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post #29 of 106 (permalink) Old Sep 8th, 19, 1:24 PM
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re: ZZ4 upgrades?

Well, I wrote the changes needed to get the stock ZZ distributors working correctly, but not many seem to care, they use all sorts of idiocy from top tuners and dyno experts to make it even worse. IF those mods are not done, the engine will never wake up, no matter what you do to it.

Now, distributor,

Weights 41, center 375 stock parts are FINE, the springs are the problem. This package gives 22 crankshaft degrees of mechanical advance timing. But, because GMPP set all the specs on a dyno, they left the distributor on PORTED vacuum, dead wrong for that engine. What that did was give the engine no light to no load timing help, and create a second acceleration advance curve. To compensate for the second curve, the mechanical was set up with garage door springs, starting the curve at 1,300 or so RP's, and limiting the curve way past 5,500 RPM's, way too allow for real world performance.

Fix, speed up the mechanical curve, use springs toat start at 850/900 RPM's, limit at 3,000 RPM's AND SET THE VACUUM ADVANCE UP CORRECTLY TO USE FULL MANIFOLD VACUUM, NOT PORTED. Doing so will give that engine the acceleration advance curve it wants.

Vacuum advance: either use a Crane 99619-1 stand alone degrees stop plate, or a home made degrees stop plate to limit the degrees the 69120 vacuum advance has (full FREE instructions, with pics available at [email protected]) to limit the vacuum advance to give 10 degrees of timing. Then, along with the 11/12 initial timing the ZZ has, add the vacuum advance degrees to FULL MANIFOLD VACUUM sourcing to get 21/22 IDLE degrees of timing.

Fix whatever else in the carb that was messed up with the ported vacuum stupidity, and go forth.

YES, a different duration cam will require different timing specs, but, with the Crane stop plate installed, they are easily arrived at.

But, nope, nobody here knows anything about stuff like timing, fat and skinny block engines, tuning, carbs, we are all dummies, and drones.
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post #30 of 106 (permalink) Old Sep 8th, 19, 8:39 PM Thread Starter
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re: ZZ4 upgrades?

Quote:
Originally Posted by nashville beth View Post
You need to find an old timer who knows how to set up the timing on an old car.

The car show would have been a great place to find help.
Not really. All of these shows around here 2010 and newer corvettes with people who want to sit in chairs in the shade. I went to a show a few weeks ago and a bunch of crappy pick up trucks showed up with the fronts lifted and the rears lowered. Piece of junk hondas as well that were lowered to the ground...I was so ashamed to be there.
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If it's not broken, let's fix it till it is.
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