SteveP

I have a ZZ4 350/355 hp crate engine that I'm having some difficulty with. It's in a 69 Chevy 1/2 ton truck with a 700r4 trans and 3:40 positraction rear. Timing is set at 10 degrees. I've had 3 different carbs, (re-jetted Edelbrock 1406, 750 Holley jetted 2 sizes up and currently have a stock 770 Holley Street Avenger). Problem is, I can't stop it from pinging, (pre-ignition). Also, the thing is weak, seems like the 355 hp is over-rated. I'm using high test fuel (Exxon, Shell, etc.) Any suggestions would be appreciated.

86 IROC

iTrader: (14)

What height tires? What converter? Those engines are really at home in a 3500lb or lighter car, your truck is at least 500lbs heavier than that. I would recurve the distributor for the heavier vehicle. It seems like it could use a lot more gear as well. JMHO...

blubyou02

iTrader: (1)

Are you sure the vacuum advance is working fully,what about the centrifigual
weights are they sticking,what type of springs are on the weights.

SteveP

Thanks for the replies.

The tires are 28". The converter is standard stall, (about 1800). The frame is a 1969 1/2 ton shortened approx. a foot with a 1951 GMC panel truck on top of it and all the parts are stock crate engine including the distributor. Do you think I need to step up from the 3:40 rear?

The vacuum advance is working fully, don't know about the weights or springs assuming since it's a brand new GM distributor less than 1 year old that it should be functioning as advertised.

86 IROC

iTrader: (14)

They like gears, we ran 4.10's in a friend's car with 28" tall tires. Think about it, you have 3.40 gears, 26" tire is the std. variable... you have 28's, you've just cut your effective gear in an already heavy vehicle.

Both cars I had experience with that had ZZ4's ran 12.90's right out of the crate with some fine tuning. Both on a 28" tall tire w/ 4.10's and a 3000-3500 stall. One had a 700R4, the other was a TH400.

I think the advance curve could use some tweaking, and maybe a little more gear like 3.73's with a slightly looser converter. Should help move that brick along a little better while keeping road manners.

SteveP

Thanks for the help and we like the way you put words together. Refering to my heap as a "brick" got lots of laughs. Thanks again.

86 IROC

iTrader: (14)

NP, to me... anything over 3500lbs is a "brick." lol It sound slike a neat project, when you posted panel truck - I instantly thought... "Gravedigger!"

ZONES89RS

iTrader: (25)

Hmmm, still shouldnt be pre igniting, bump the timing back a couple degrees at a time till it goes away and see what happens.

84MonteSS

iTrader: (2)

What's the total timing? My motor liked it best around 36. It shouldn't be knocking at all on 93 octane with only 10deg initial. 3.40 gears + 28" tires+ 1800 converter isn't helping anything in the acceleration department. It's not that weak when set up right...with only 3.42 gears, 3400 converter and 26" tires (raceweight 3500) I went 12.80's.

3rdgentug

iTrader: (23)

your zz4 is probly like mine we put in out 48 chevy
it was just a turd

it ran horribly til with less then 1000 miles it went, something on the bottom end jusst failed horribly.
took it to a chevy dealership locally that put in a new crank, new bearings, and shaved both heads.
while it was down we put in a very slightly larger cam, i wish i could remember the specs and 1.6 rr
it was a night n day differece to say the least

726.0chevelle

iTrader: (17)

if your talking about pinging in overdrive thats always prob when running decent compression overdrive and carbs. i believe that msd makes a kit that will back the timing off when in od