RedLT4Mike

here is the story....
I've got a 95 TA LT4 heads 222,230 .543.563 on 112 headers
true duals all the bolt ons, BUT I MADE 250RWHP!

It doesnt' stop there...I just got back from the track, and I ran a 14.8@99!!
It is Dynotuned by a pro and he was baffled as to why I wasn't making power
with the engine in a perfect state of tune!

I broke a timing chain last year and my dealership(used car lot) put a new motor in. Is it possible that it could be a 4.3 genII engine from a caprice?
Cause those numbers sound about right for a 4.3 and FARR off of what a 5.7 should make.

I'm really depressed about my situation, and I can't believe this is happening to me.

1 Nasty Bird

look on the side of the block by the knock sensors, if you see "327" its an LT1 block, if its anything else it is not a LT1.

Z95m6

even with the lack of cubes i'm sure you would make more hp than that. Has it ever run good after the new motor? I'm thinking maybe cam is off one tooth, or maybe some valve train damage occured when the chain broke. You need to give us some info about the rebuild. Did they just put in a new block and keep your old heads LT4 heads?

RedLT4Mike

the motor blew when it was bone stock.
all the valvetrain is new...crane 1.6's, crane dual coil springs,
timing chain. and the heads are new too.

Z95m6

Then it has nothing to do with being a 4.3 block. Even if it was a 4.3 block then you would still have over 250rwhp. You have problems somewhere else. Did you log any of the dyno runs?

RedLT4Mike

I don't have any logs of the runs, but I will try and have my tuner send them to me tomorrow.....

Spinner

Fuel pressure?

GreenDemon

If he stuck 5.7 heads on a 4.3 that could cause some compression problems though... even with awesome flow, a big cam, etc., the engien would be making pathetic compression. It's gotta be something serious for such low #s.

DuronClocker

Wouldn't you have been able to tell when you swapped the heads whether it was a 4.3 or 5.7? I don't know much about the 4.3's, but I'm assuming the bores are different. Is this correct?

Shawn 97 Z28 M6

Isn't the 4.3 a V6? I know it's essentially the same stroke and everything as the 5.7 minus 2 cylinders.

Myxtreme1

There is a 4.3 v-8 right? Thats what we are talking about here. I was talking to a friend who owns a salvage yard (connections,lol) and he said the LT1 and 4.3 V8 came in the similar models. I can't remeber all else that he said. You really need to look for the 327 on the side though. If they put in a 4.3 you need to get to a lawyer cause you got screwed.

turbo_Z

They did make a 4.3L "baby" LT1 for Caprices. It looks just like a typical LT1 but shorter stroke and probably smaller bore size too. I dont believe LT4 heads would even bolt up to one of those blocks either but I may be wrong.

Z95m6

I would think that the LT4 heads would bolt up the only problem is the valve's might be to big for the 4.3L bore. I think the 4.3's are very rare. The short block i used for a rebuild came out of a cadilliac and its a 350.

96capricemgr

The L99 4.3l V8 block says 588 on the side where the LT1 says 327. as far as how much power it would make with LT4 stuff one of the Chevy mags. did a build said block mods were needed I am guessing valve to bore clearance issues there. Thing only made 300hp on the dyno, big heads tiny bore meant poor velocity and then shrouded valves. The bore is about 3.875 I think, I have most of one left in my garage but no really accurate way to measure, and the stroke was only 3".
The only heads available for it were iron. It was only available in the Caprice sedans be it 9C1 or civilain(have heard a rumor of ONE wagon with it), all the other b,d-bodies got the LT1.

Red_94Formula

if its a 5.7 it will say it right behind the driver's side head on the block. all 350's have 588 and 327 on them.