It is my understanding that LT1 heads do not match up to the LT4 intake, as was already suggested. I wonder if those stamped rockers might be 1.7:1's out of an LS1? Don't know, just wondering.

 

Maybe he didn't want to mess with the stock heads and ported some LT-1 heads and put in the 1.7 LS1 rockers. One of the first things I wanted to see on my LT-4 when I bought it was the cool rockers. Good thing I checked.

 

Those are not LS1 rockers.


LS1 rocker arms.

 

It was definitely a mistake of mine to not check the rockers, but there was enough correct indicators that I didn't even think about it. As far as the intake not matching up to LT1 heads I think that's in reference to the ports not matching up very well; I'm not sure what difference there would be in the bolt pattern?

 

Then he has LT4 heads with stamped steel rockers. Best thing to do is to start checking everything starting with the block and pulling up numbers.

 

The part number he quoted for the heads are not LT4's, they are LT1's.

 

Yup. I never said either was correct. I was quoting the op's first post that the intake part number was correct.

 

Then it does not add up.

 

Could this be part of the recall when the roller rockers went bad on some LT4's. Maybe GM replaced the heads under warranty after theyse actually went bad and just replaced them with the LT1 heads and snuck it past the owner at the time. I would look at any recall type work done on it and see if GM is at fault on a different level than production. There would be records if something like this was the case. I wouldn't put it past some dealers.

 

^I hear ya there. I plan on going to the dealer this week and seeing what I can find as far as records for the car.

 

I suggest you don't go off trying to find some highly unlikely, implausible explanation for what you're seeing. KISS.

There are SIGNIFICANT differences between LT1 and LT4 heads, not just the net build roller rocker arms. CCs of the ports, valves, port heights, springs, etc. Without tearing them down, the casting number will tell you which they are.

What's the VIN on the CAR? The VIN on the dash near the windshield. If the car is a LT4, the VIN of the CAR will tell you if the car even came from the factory with a LT4 engine.

As far as what's below the heads - the block and internals, there are also SIGNIFICANT differences between a LT1 short block and a LT4 short block - crank, pistons, rings, etc.

Based on what I've read, you either have a LT1 engine or LT1 heads on a LT4 short block. I'll put my money on the former. Let us know whar you come up with.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

 

You posted in your first post that the car needed a "crank kit" Assuming you mean crankshaft and bearings, why does it need this? ie. low oil pressures, knock, etc. ?
Again, assuming you do need a crankshaft, why not just pull the motor, either replace it with another, or go through that one and bring it up to specs.
When removing the oil pan you may find it has a 2 bolt main which would more then likely mean that someone replaced the motor with one out of a camaro.
But at any rate, enjoy the car, it still looks like a decent deal at $5500.00 even if the motor needs a crankshaft.

 

To those who asked; Yes, the VIN is correct for an LT4 application.

As far as a crank kit I am referring to crank and rod bearings, and possibly some machining of the crank surfaces (and the necessary undersize bearings of course). The noise it's making sounds like a rod knock to me. I had planned on a full teardown of the engine regardless.

 

Let's get specific. Post the VIN taken from the dash of the car. You can leave the last several digits off if you're concerned about that, but to help eliminate some of this confusion we need to know if the car is VIN Code "P" or "5".

Then we'd need the full casting number taken off the heads.

Once we know that, we can move on to other things hoping to solve this mystery. All this speculation and supposition isn't getting us very far.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day 20 May 2010!!!

 

His car is a 96 six speed equals LT4

From another thread he posted a photo of a 8K tach which says LT4

Would be nice to actually have the VIN, but it ought to confirm LT4

Seems pretty clear the car started out as an LT4....but who knows what is in there now....I am pretty sure it is not what was shipped from the factory

Also a stock LT4 does not have a loping idle of any significance

 

Engines, trannys, and tachs can be changed. I will bet that it is an LT1 from an F body.

Would be nice to know tho.

 

Yes, the 8th digit in the VIN is a 5.

I went to the dealer today to see about getting a VIS run on the car. Since it's older than 10 years, there's nothing they could immediately pull up. They recommended I call GM, so I asked for the number. The parts guy made a couple calls after trying to run a VIS himself, and came to the conslusion that I am up sh*t creek as far as records from GM go. At this point trying to track down previous owners isn't an endeavor I want to venture upon, so I'm just going to pull it apart and work with what I have.

 

I thought we were trying to eliminate all this "he could have changed this part or that part" and get down to concrete stuff.

I changed the dash in my 96 LT1 to a 8K LT4 dash and it looks like it came that way from the factory. Changing to a manual trans isn't out of the question either, so neither of those two are DEFINITIVE proof.

Changing the VIN, however, is a different ball of wax; that's a Federal Offense without going through a boat load of procedures and paper work. So to me, the VIN is the LEAST likely thing that COULD have been changed.

Once we know the VIN is correct, we can move on to the engine.

So where's the casting number off the heads? We don't need to tear 'em apart to see if the exhaust valves are sodium filled or the intake ports are, in fact 195 ccs Vs 170s, just the casting number. Then we can put that one to bed, the heads.

Now the short block: Since they all look the same, one way of telling if it's a LT4 without tearing it apart to see the pistons/rings and crank, is to measure the valve lift. LT1s and LT4s used different lift cams so the valve lift differs. Dial indicator and have at it.

Based on just that I guess we could pretty much have nailed it, but if he's still not satisfied, drop the oil pan and look at the crank's journals. Once the pan is off and if he see's 2 bolt mains, game's up! LT1!

What's the name of the company that tracks accidents and service on cars, "CAR" something or another (CARFAX?)? Maybe it'll show the service records of a possible head or engine change.

However, at some point this becomes excessively time and effort consuming. So OP has to draw the line somewhere. Of course, I don't mind trying to help, but, AT LEAST, he has to cooperate by providing the requested information, otherwise I'm out.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

 

When i checked under the filler cap it was just for fun to see the rockers. I didnt intentionally check to make sure. Just making sure I didn't want to make it sound like I knew what I was doing !!
Is there a part # on the manifold? SOunds to me like the motor may have been damaged. So he reused the manifold and bolted it to a lt1 donor.

I would ask the previous owner what dealer he used ask there for any records.

 

Jake, have you read anything I have posted?