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Discussion Starter · #1 ·
Where are all the ZZ4 guys at? Im looking to upgrade possibly. From the stamping on my ZZ4, it appears to be aluminum l98 heads stock everything. Center bolt valve covers. Feels like a turd to me power wise and looking to upgrade with bolt ons.
 

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Where are all the ZZ4 guys at? Im looking to upgrade possibly. From the stamping on my ZZ4, it appears to be aluminum l98 heads stock everything. Center bolt valve covers. Feels like a turd to me power wise and looking to upgrade with bolt ons.
Have you spent much time dialing it in? I know someone that had a stock, except for headers, ZZ4 in his 65 El Camino, he ran it with a 700R4 and a mid-3 series gear. It always ran 12.70’s-12.80’s. I’ve also seen guys at the track that couldn’t get ZZ4 equipped cars to run quicker than low-14’s, but that’s more about their lack of tuning and driving skills than the engine itself.

Steve R
 

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The distributor curve sucks. Mine was kinda lame out of the crate, but now I'm running a recurved (ZZ4) HEI, HOTcam, RPM intake, long tube headers, and a 650 holley DP and it pulls hard. Never had it to the track when it was in my Chevelle, but now that it's in my 4000# truck,(89 reg. cab short bed 4x4) it surprises a lot of "fast cars" on the road. It really liked a 750 DP, but mileage really suffered. I'm going to try a 750 AFB next. The HOTcam helped it pull harder in the upper RPM range and didn't give anything up down low. Slight lope, and great vacuum. There are a lot of better cams out there, same with heads, but I say work with what you got and start with recurving the distributor. There's quite a few discussions online about it.
 

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Discussion Starter · #4 ·
Im working on figuring out how to get it tuned properly in another discussion. It really feels like a dog right now but every once in awhile it wakes up for a pull. This morning I was leaving walmarts parking lot and I jumped on it for the hell of it. Ass end swung out a bit. I didnt know where the hell it came from because ive have nothing but issues with it cutting out while accelerating. Maybe its just way off. Transmission is a TH400 Auto 3 speed with 2800 stall. 3.73 gears. As of right now, I cant even get the tires to spin.

ZZ69chevelle. I see your from the Reading area. I moved out of Mt. Penn in 2016 and came down to Delaware. Grew up in Pottstown/Boyertown.
 

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I moved to the Blandon area from Douglassville, so you were pretty close. Wife still works in Boyertown. Where do you have your dist. vacuum advance plugged in? Timed or manifold vacuum? I run mine from a manifold port. Even after recurving my distributor, it used to hesitate with the timed spark vacuum port.
 

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66 El Camino 57 Chevy pickup 2004 Tahoe
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what is your initial timing?
 

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I have a ZZ4, been in it since 1997, stock everything, right about 30K miles on it. Still have the 1967 iron exhaust manifolds. Stock 700R4 that drives beautifully but under WOT, hangs 2nd too long and you have to lift a bit to shift.
I put FiTech GoEFI 600 on it for kicks, runs better, but basically the same as the 600 AFB that was on it. As others said, timing is probably the key, I KNOW mine isn't optimal, I have played with it a bit with vacuum, without (as suggested by the paper that came with the engine) vacuum to ported, to unported… But admittedly, I haven't tried hard. And I probably won't, I will just setup the EFI to do it all without messing with locks/springs/weights.
BUT with what I have, and some stuff in the El Camino, it runs high 14s while being super at daily driving. I have a posi, and what I assume is a 3.0x or 3.2x rear. It does pull like it could do better, maybe 14 flat, but I never wind it out that much over 5K. It has 215/70-14 plain jane tires and actually launches okish. Every time I want to make it run better, I get a daily driver that blows it away, and I figure why bother. I'm concerned that if I up the ante on power, that is when I will start to break things like the transmission (we paid $500 for it in 1997) or the 52 year old rear axle, stuff like that.
 

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Discussion Starter · #8 ·
I moved to the Blandon area from Douglassville, so you were pretty close. Wife still works in Boyertown. Where do you have your dist. vacuum advance plugged in? Timed or manifold vacuum? I run mine from a manifold port. Even after recurving my distributor, it used to hesitate with the timed spark vacuum port.
what is your initial timing?
To be honest with you, I dont even know what your talking about when it comes to vaccum. I understand the concept but have never worked with it before. Ive never even set timing on a motor. Im going to attempt the timing today once I find a gun.
 

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This is the part that everyone questions
"Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º 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"
 

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This is the part that everyone questions
"Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º 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"
That doesn't mean to leave the vacuum advance disconnected permanently.

It means to verify what your total advance is (centrifugal + initial) , you don't want vacuum entering the equation because it doesn't operate at wide-open throttle.

Always connect the vacuum advance to full manifold vacuum - if you want the engine to run cool and get good mileage - and be easy to start.
 

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Here is what I did with my ZZ4 engine years ago, took the cam out and dropped in a LT4 hot cam. Was like night and day performance, not real lopey and the car had great driveability.
 

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Discussion Starter · #13 ·
Here is what I did with my ZZ4 engine years ago, took the cam out and dropped in a LT4 hot cam. Was like night and day performance, not real lopey and the car had great driveability.
You didnt change anything else? Literally just swapped cams?
 

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The Hot Cam and Springs are a great upgrade....but you're not ready for that YET.

Instead, find a local dyno shop that still works on carbs and have your carb AND ignition tuned.

You have a real 350 HP V8 and 3.73 rears gears. You should be shredding tires at will off the line. Either your motor has a fatal injury....or your tune just sucks. Hopefully, it's the latter.
 
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Discussion Starter · #15 ·
The Hot Cam and Springs are a great upgrade....but you're not ready for that YET.

Instead, find a local dyno shop that still works on carbs and have your carb AND ignition tuned.

You have a real 350 HP V8 and 3.73 rears gears. You should be shredding tires at will off the line. Either your motor has a fatal injury....or your tune just sucks. Hopefully, it's the latter.
I have a local restoration shop with a dyno. Will give them a call tomorrow. Going to a car show tomorrow as well. Maybe I will run into someone with more knowledge than me. Shouldnt be a hard task...lol.
 

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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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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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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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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 :thumbsup:
 

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"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/showtopic.php?tid/307406/
 
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