KWIL

I took my car for dyno tuning yesterday.

Good news- only cost me $50.00 for three runs, including tuning. They used a wideband O2 and optimized the A/F, and re-jetted my carb. The car is running better now (it was pig-rich).

Bad news- max horsepower was 200 at the rear wheels, torque around 280. The guy who tuned it said he wanted to re-curve the dist., but could not because the dist. hold down bolt seemed to be seized and he did not want to risk it breaking off. Also, he told me the carb was not a good choice for my engine because the metering block did not allow for a jet change needed because the mixture leaned out at the top-end (I am paraphrasing because I dont completely understand carb terminology.)

Worst of all, he told me that he is sure I do not have a ZZ4 engine. He said he believed it was the predecessor to the ZZ4 which produced about 300 HP. He based this conclusion on the dyno runs and the bolt pattern on my valve covers (he said the ZZ4 bolts were on the perimeter of the covers vs. the middle)

I have included a link to an engine pic- its the only one I have right now. Can anyone tell if this is a ZZ4?
http://www.villagephotos.com/pubbrow...elected=504476

Assuming it is, where is the missing 100 HP? I know my sidepipes are very restrictive, and could probably use a better carb... but 100??


:(

Brettmc

Bad timing will eat up ponies. Plus you're gonna have losses thru the driveline. An auto tranny will soak up about 20%, a manual maybe 15%. A mechanical fan can eat up as much as 15hp.

Brett :thumbs:

honaker

I can't vouch for the engine, however, this month edision of Car Craft has an article on drive line loss and they break down where the ponies go. An automatic can soak up to 20% and depending on howconverter an pump, maybe more. A manual soaks up about 15% but depending on over drive and a few other things, it can go up more. Also the rear end will soak up A few horses, mech fan, water pump, power steering, alternator also suck a few off the top. Belive it or not, wheel balance and drive shaft balance will soak up a pony. Not much but it adds to the over all loss.

All in all, it's about average to lose around a 100 horses from the crank to the road.

KWIL

I expected a HP drop through the driveline of about 20% (from what I have read). If thats the case, 20% of 200 is 40. So that would be about 240 hp from an engine thats rated at 355 HP. I know that other factors will eat up HP. But that much :eek: ?

Brettmc

Check the timing curve...I'll bet that's where most of em are getting loose.

Brett :thumbs:

Twin_Turbo

The zz4 engine uses the revised D port L98 alu heads with screw in studs and a rslightly evised combustion chamber (small quench area under the spark plug), those use center bolt style valve covers. The part number is 10088113

As for the carb, what are you running and yes, the hooker sidemount headers with the original muffler inserts are REALLY restrictive

75Rag

I can vouch for the timing and restrictive exhaust bit. I have a stock L-48, all that's been done is true dual exhaust and a Lars re-curve kit. She put down 203 rwhp ..... not bad for a motor that was 165 flywheel when produced!


[Modified by 75Rag, 11:25 AM 9/23/2003]

zwede

The ZZ4 is rated at SAE Gross so that means it has 355hp at the flywheel with no accessories (no PS, no waterpump, etc). SAE Gross also allows open dyno headers, carb & ignition tweaks and cool intake air and coolant. As installed in a car I wouldn't expect more than 300-315 hp at the flywheel (this would be SAE Net). Then you loose about 20-25% before you get to the wheels (TH400 I would expect 25%. TH350 20% if you're lucky). Knock off drivetrain and your expected range is 225-252 at the wheels.

Between your timing curve and the restrictive exhaust I think it will be easy to find the missing 30-40 rwhp.

So my thinking here is you do have a ZZ4 and it is basically healthy.

KWIL

twin turbo,

I have tried to ID the carb before, but the numbers I see on it dont correspond to any part #s I could find. I know its a Holley 800CFM.

Im not using the Hooker sidepipe setup. I have shorty headers, and the JEGS dynomax (old school) sidepipes. I do plan to lose the muffler inserts and possibly go open, or try the JCL inserts- they seem a little pricey though.

BSeery

My ZZ4 with stock carb and exhaust dyno'ed out at 217 HP at the rear wheels.
To check for sure, on the passenger side of the engine, on the block right in front of the cylinder head will be a pad where the part number is stamped. it should start or end in ZZ4, I don't remember which.

Sigforty

Here are some pics of my ZZ4 it does have center bolt valve cover bolts.

Twin_Turbo

The # should be on the choke tower, and an 800cfm carb is way too big

Matt Gruber

hype is an American tradition. :lol:
A real horse, in the 1/4 mile puts out 10 HP, so really you have the power of 20 horses.
see dyno tips in sig/profile :nopity

AGVI

You have about 300hp... :nopity

You should be saying 'I have 300hp!' :party:

It's just a number for your ego...enjoy your car, don't worry about numbers :cheers:

79VetteMike

Do you have aluminum or iron heads?

KWIL

79 Vette Mike- They are aluminum.
I dont have anything stamped in the area that was described above, but there is a sticker in that area with a serial # that ends in ZZ4. I did a CF search and found this- http://forums.corvetteforum.com/zero...184528#3184528

It looks just like VetteNut72's sticker.
So I guess it is an older ZZ4.

"You have about 300hp...
You should be saying 'I have 300hp!'
It's just a number for your ego...enjoy your car, don't worry about numbers"

AGVI, I do enjoy my car, and I am not really worried about numbers, but I brought it to the dyno tune shop because it did not seem as fast as it should/ could be with a ZZ4. Not for my ego, but because I want the car to go faster.

GrandSportC3

Those numbers are appropriate for late model cars with lightweight driveshaft etc... For C3 Vettes - It's closer to 20 - 25 % with MT and 25 - 30% with AT...
Especially the TH400 eats up a lot of HP...

Brettmc

Say it aint so!!! :cry :cry :cry

Brett :(

GrandSportC3

On my '69 - I had a engine that was dynoed at 430 flywheel HP..
The car had a TH400 tranny and I dynoed at around 300 RWHP...
On my '68 with MT - I'm losing approx. 20% through the drivetrain..
After installing carbon fiber driveshaft and halfshafts - I hope to be able to reduce the drivetrain loss..

69 N.O.X. RATT

I know of two dyno confirmned big power big blocks in which case both motors were motor and chassis dyno'd and the turbo 400 ate up 35% of the motor dyno's power

Big block #1 540 in. 690 motor hp, 460 hp chassis dyno
Big block #2 555 in. 940 motor hp, 617 hp chassis dyno

The turbo 400 is strong but very "Heavy"