Poor Running zz383 Help Needed

[kryptik]

Hello everyone,

I have a zz383 engine with an edelbrock air-gap manifold, tri-y 1-5/8" headers into 2-1/2" pipes. I am using a tko600 trans and 3.50 rear gears.

The engine and carburetor (quickfuel 680 VS with Wilson tapered spacer AND 4-hole phenolic spacer) were involved in a very serious front-end accident. I've recently installed and fired up the engine/carb in a new camaro. The engine seems ok; good oil pressure, no leaks, sounds great cruising at 2500-3000rpm.

As far as the carb...the idle is stable but very rough, the low end torque is gone (the engine will stumble and run rough when getting into 1st or if I'm in any gear below ~2300 rpm especially in 5th), and it also has a rough shaky Wide Open Throttle.

This is not the engine that I put 14,000 miles on before the accident. I tore it down to the shortblock and did not notice any internal damage. So, I am suspecting the carb because the choke mechanism appears damaged in that the fast idle does not work.

I also suspect a vacuum leak because when chasing the threads for the intake manifold, the tap chewed up the two manifold bolt holes before I noticed anything (rear passenger corner). The bolts still threaded in but they could be shaken when in the hole. Perhaps they are not properly retaining the manifold??

Last question...I'm thinking of replacing the carb...I loved the 680cfm vac secondary quickfuel but maybe stepping up to the new 735vs would be better for this engine (some people say 680 is too small but I found that it was great for the street driving I do) Or a different carb altogether?


Sorry for the wordiness guys but it's a complicated situation. Thanks a lot for any help.

Matt

[72elco]

i dont know if this helps but I am running a 750 speed demon and she runs great (single plane intake) Was just dynoed at 365to the rear wheels. I havent really paid attention to gas mileage but if I keep my foot out of it around town I imagine I am in the 13-16 range (700r4)

[kryptik]

I've had the engine for 14,000 miles before the accident and it ran amazing with a dual plane and 680cfm carb so I must be something that was damaged or not installed properly.

[Pro Stock]

Hello everyone,

I have a zz383 engine with an edelbrock air-gap manifold, tri-y 1-5/8" headers into 2-1/2" pipes. I am using a tko600 trans and 3.50 rear gears.

The engine and carburetor (quickfuel 680 VS with Wilson tapered spacer AND 4-hole phenolic spacer) were involved in a very serious front-end accident. I've recently installed and fired up the engine/carb in a new camaro. The engine seems ok; good oil pressure, no leaks, sounds great cruising at 2500-3000rpm.

As far as the carb...the idle is stable but very rough, the low end torque is gone (the engine will stumble and run rough when getting into 1st or if I'm in any gear below ~2300 rpm especially in 5th), and it also has a rough shaky Wide Open Throttle.

This is not the engine that I put 14,000 miles on before the accident. I tore it down to the shortblock and did not notice any internal damage. So, I am suspecting the carb because the choke mechanism appears damaged in that the fast idle does not work.

I also suspect a vacuum leak because when chasing the threads for the intake manifold, the tap chewed up the two manifold bolt holes before I noticed anything (rear passenger corner). The bolts still threaded in but they could be shaken when in the hole. Perhaps they are not properly retaining the manifold??

Last question...I'm thinking of replacing the carb...I loved the 680cfm vac secondary quickfuel but maybe stepping up to the new 735vs would be better for this engine (some people say 680 is too small but I found that it was great for the street driving I do) Or a different carb altogether?


Sorry for the wordiness guys but it's a complicated situation. Thanks a lot for any help.

Matt

Matt, I already replied to your other thread but reading this thread made me wonder why you haven't sent your carb back to see if it can be repaired, also the Demon carb mentioned in this thread is another great choice, we run one on our ZZ383 dyno mule all of the time and it works well and makes more power top to bottom than our 675.

[kryptik]

Found the problem...the engine was in a serious collision...i had a microcrack in the #5 exhaust lifter which caused it to split and pop out of the lifter socket. Assuming the cam and block MAY be damaged. Today's my birthday...what a great birthday gift haha :-P.

Anyways...I used a Demon carb before and it always gave me trouble...not saying it's a bad carb, just that I prefer the quickfuel.