Need some ZZ4 input...
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Joined: Dec 2005
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From: Martin TN
Need some ZZ4 input...
I recently bought a beat up old 77 Vette for my daily driver.(it's the only vehicle I have that runs/drives right now so when I say daily driver, I mean it.) The PO recently had a new ZZ4 installed. I've never had any dealings with a ZZ4 before but I am pretty disappointed. The car will not even break a tire loose, no matter how hard I try, not even on damp asphalt. I'm sure the 3.08 gears and new 275/60/15 BFG T/A's aren't helping but it should at least do something when I break torque it shouldn't it? So far I've installed a new Edelbrock 750, adjusted the valves, tuned carb, and adjusted the timing. All of these made noticeable improvements but it's still a dog off the line. One thing I'm confused about is when i set the initial advance at 12deg, the total @2000 rpm was only 24deg. I had to turn the initial advance up to 16-18deg to get the total up to 34deg. Is this normal?
Last edited by rellim51; Dec 13, 2009 at 12:46 PM.
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From: Martin TN
It's definitely a ZZ4, I've got the receipt from where he bought it from the dealer. It has headers on it now but they are rusty. I've got a new set of coated Headman's I'm going to install over the holidays. I'm still confused about the timing. At what rpm should the total advance be all in?
Last edited by rellim51; Dec 13, 2009 at 10:37 AM.
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Joined: May 2003
Posts: 3,814
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From: Dearborn Heights Michigan
I put a ZZ4 in my 70 a year ago, autocrossed the car past summer and pleased with the engine.
Have a Holley Street Avenger 670 with larger jets, Headman Headers and run 34* advance with HEI Dist. at 750 RPM idle. All else unchanged.
Can burn rubber at will (3.70 rear) with 255/50/15's.
My set up runs great and the car is very fast.
Have a Holley Street Avenger 670 with larger jets, Headman Headers and run 34* advance with HEI Dist. at 750 RPM idle. All else unchanged.
Can burn rubber at will (3.70 rear) with 255/50/15's.
My set up runs great and the car is very fast.
Burning Brakes
Joined: Dec 2005
Posts: 992
Likes: 56
From: Baldwinsville, NY
Send picture & part number
Hey, Can you get a good picture of the engine and the part number from the receipt?
Saw many ZZ4's at shows this summer, most had cast iron heads and some had procom aluminum heads, those are ZZ4 clones!
Here is the spec. sheet:
http://www.gmperformanceparts.com/En...9712&engCat=sb
Saw many ZZ4's at shows this summer, most had cast iron heads and some had procom aluminum heads, those are ZZ4 clones!
Here is the spec. sheet:
http://www.gmperformanceparts.com/En...9712&engCat=sb
Racer
Joined: Nov 2005
Posts: 409
Likes: 5
From: Orange County CA
I had the iron head version of the ZZ4 engine in my 68 Camaro. It was the 330 Hp Deluxe engine with the Vortec cast iron heads. The car originally had 2:73 gears in it and I was not happy with the performance at all so I went to 3:73 rear end gears and it felt like I added 100 horsepower...totally different car..The car barely turned the rear wheels over with the 2:73, but after I added the 3:73 I could light the tires up from a dead stop without doing a brake torque.Rear end gears will make a huge difference, but freeway driveability will suffer unless you change the trans with an Overdrive.
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Joined: Dec 2005
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From: Martin TN
I would love to run a 700R4 with 3.42 gears but my budget limits the changes for now. For now I'll have to deal with the 3.08's. I'm thinking a little more stall will help off the line acceleration.
Burning Brakes
Joined: Dec 2005
Posts: 992
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From: Baldwinsville, NY
Clear up the timing coment
The spec sheet said 32 @ 4000 RPM with no vacuum.
"Ignition timing: 10 degree BTDC @ 800 rpm 32 degree total @ 4000 rpm with vacuum advance disconnected"
Seems that you have a ZZ4.
I would think that 300+ crank HP would make some tire noise if the timing & carb are working. If you have the old 2 to 1 pipe to a cat and 1 to 2 muffler exhaust, check the cat.
"Ignition timing: 10 degree BTDC @ 800 rpm 32 degree total @ 4000 rpm with vacuum advance disconnected"
Seems that you have a ZZ4.
I would think that 300+ crank HP would make some tire noise if the timing & carb are working. If you have the old 2 to 1 pipe to a cat and 1 to 2 muffler exhaust, check the cat.
Burning Brakes
Joined: Apr 2007
Posts: 1,028
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From: SOUTH ELGIN IL
Dude, I have read up on these ZZ4's because the PO of my car put one in as well. From what I can gather, even though they are advertised at 355hp you will be lucky to get 320 and will most likely be around 300. If i stomp on mine from a stop (TH400, 3.73) I can break the tires loose (255/55/R17) pretty effectively but this motor is just way to tame for me. I added some electric fans this year to fix a cooling issue and picked up a few ponies per my seat of the pants test but it's still a dog. I'm stepping up first chance I get to something that makes at least 400hp. My thought is to keep the short block, sell the heads and replace with some AFR's, an intake and a cam. I'm running a 670 Holley Street Avenger btw.
I have nothing constructive to offer on the timing issue... sorry.
Edit: I forgot, if you can't spin the tires your problem might be with your transmission. Does it shift OK? If it's "soggy" and doesn't shift crisply you might start there. I'm not sure you mentioned what was in there?
I have nothing constructive to offer on the timing issue... sorry.
Edit: I forgot, if you can't spin the tires your problem might be with your transmission. Does it shift OK? If it's "soggy" and doesn't shift crisply you might start there. I'm not sure you mentioned what was in there?
Last edited by Dantana; Dec 14, 2009 at 12:39 PM.
Drifting
Joined: May 2005
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From: Somers CT
I have a ZZ4 and also was disappointed with the performance but yours sounds especially down. I've spent allot of time messing with the timing on mine because the distributer that comes with it wants to give too much advance. What you found at 24 deg is not enough.........you need 36 deg. total advance (no vac) so if you're at 34 you're pretty close.
The problem you'll most likely find (if you have the GM dist. and nobody has fooled with the springs or internals) is that when you advance the timing to get 36deg (no vac) total advance at 3000rpm, that your advance at idle or part throttle is too much; it may even ping slightly. I've changed several different vac cans and could never get it just right. I finally bought a Crane recurve kit, changed the springs and installed the advance stop in the kit to limit the advance and it performs fine now.
Read the Stickey at the top of the page on Timing, it might help you better understand it all. Also take a look at the springs inside the dist. They should be stainless steel, if they have a color tint they've most likely have been changed.
The problem you'll most likely find (if you have the GM dist. and nobody has fooled with the springs or internals) is that when you advance the timing to get 36deg (no vac) total advance at 3000rpm, that your advance at idle or part throttle is too much; it may even ping slightly. I've changed several different vac cans and could never get it just right. I finally bought a Crane recurve kit, changed the springs and installed the advance stop in the kit to limit the advance and it performs fine now.
Read the Stickey at the top of the page on Timing, it might help you better understand it all. Also take a look at the springs inside the dist. They should be stainless steel, if they have a color tint they've most likely have been changed.
Last edited by TopGunn; Dec 14, 2009 at 12:42 PM.
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From: Obscurity's Armpit
I installed a ZZ3 (only 10 hp less than ZZ4) in my '80 several years ago. Overall, I was disappointed with it. I had opted for the Twisted Wedge heads that the dealer was offering and I had installed headers, a high-flow cat and other performance items. The car had 3.08 gears and a brand new TH350. I bought Lars' timing kit and had my carb modified and I never got above 251 hp and 308 tq at the rear wheels.
One theory I heard at the time is that every "joint" (ie 2 knuckles per half-shaft) creates more frictional losses.
IMHO, a 100 hp drop from the flywheel (advertised hp) to rear wheels is unacceptable.
YMMV
One theory I heard at the time is that every "joint" (ie 2 knuckles per half-shaft) creates more frictional losses.
IMHO, a 100 hp drop from the flywheel (advertised hp) to rear wheels is unacceptable.
YMMV
Racer
Joined: Apr 2006
Posts: 429
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From: Marietta Georgia
The "power T" sticker on the rear window is like dragging around a boat anchor. . .
I felt the same way about my 'ZZZ' (the grand daddy to the ZZ4) when I bought my car from the PO. Sounds like your timing is about right - make sure that your carb is properly tuned up and make sure that your transmission is crisp. I know that the ZZZ testing is done with a Holley 750cfm, but I actually started with a bigger carb and a 2,800 stall tq converter and had no trouble breaking the tires loose. I had to upgrade the ignition (MSD distributor and 6AL box) to feed the new carb, but it all made a difference in the "seat of the pants" dept.
I felt the same way about my 'ZZZ' (the grand daddy to the ZZ4) when I bought my car from the PO. Sounds like your timing is about right - make sure that your carb is properly tuned up and make sure that your transmission is crisp. I know that the ZZZ testing is done with a Holley 750cfm, but I actually started with a bigger carb and a 2,800 stall tq converter and had no trouble breaking the tires loose. I had to upgrade the ignition (MSD distributor and 6AL box) to feed the new carb, but it all made a difference in the "seat of the pants" dept.
Racer
Joined: Feb 2004
Posts: 360
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From: Meridian, MS
as far as powerbreaking, i have 450 hp and it wont power break. you have 4 wheel disk brakes. they are pretty effective, but you should be able to just stomp it and get a little squeal. My 78 stock l-48 would make a little noise from a dead stop. but as others here stay, sounds like you need to recurve your distributor. my gm 383 came with a balancer that had 60 degrees of timing marks on it. so i took the advance weight springs off, started the car and set the car for total timing. 34 degrees with the vortec heads. then i put the springs on to control when the advance comes in. i am not even sure where my initial timing is set. i just made sure that it was not pinging on acceleration.
Racer
Joined: Feb 2004
Posts: 360
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From: Meridian, MS
i juste re read your post....seems you have the total 34...my reacted too quickly, a little bit of a stall converter might help. a buddy of mine had a 350/350 horse motor with a 300 stall in a montecarlo, he could smoke the tires across the parking lot no problem 
Racer
Joined: Nov 2007
Posts: 350
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From: coon rapids mn
corvettes are a different animal when it comes to doing Smokey burnouts! the near 50/50 weight bias they way the suspension works! my vette will barley squawk the tires from a dead stop but i still beets a friends 454 chevelle! you want to wake that zz4 up change the cam! i had one in my Malibu that weighed 3500 pounds with me in it and it would run high 12's in the 1/4 @102-104 mph with just a cam change
Racer
Joined: May 2003
Posts: 375
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From: LaSalle ON
I had a ZZ3 with the heads ported, roller rockers and 1 5/8" headers through a crummy 2" exhaust and had no problems breaking the rear tires loose with a 3.31 rear end. My friend has a ZZ4 with Dart Conquest heads on it in his '74 and ran 12.90's with a 3.73 rear end & BFG drag radials.