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LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Trying to figure out if I have an lt4

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Old 10-22-2017, 04:35 PM
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Trying to figure out if I have an lt4

can someone help me figure out if my engine is an lt4 because the intake is red
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Old 10-22-2017, 05:42 PM
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Re: Trying to figure out if I have an lt4

No. That intake is from a 1993 F-Body LT1 (or 92/93 Corvette) - only year without the diagonal crossover pipe in a slot in the front of the manifold. LT4 was used on 96 Corvettes and a very few 1997 SLP limited edition SS and Firehawks. Somebody painted an LT1 intake red. Factory LT4 intake is powder coated red. And it wouldn't make any sense put an LT1 intake on LT4 heads.

This is the front of an LT4 intake.



The fuel rails on your engine are also unique to the 1993 LT1, with the crossover pipe in the back, and the fluted ridges running down the rails. 94 and newer rails are completely smooth.

Moving to "LT1 Based Engine Tech", since "Drivetrain" forum is for everything behind the engine (clutch, trans, rear axle).

Last edited by Injuneer; 10-23-2017 at 12:56 PM.
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Old 10-31-2017, 05:57 PM
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Re: Trying to figure out if I have an lt4


I just purchased this car from a buddy. unfortunately he lost the build sheet from the guy he got it from. I'm not as well versed with these as I would like to be. Is this an LT4 motor that was swapped in? It is currently in a 1997 z28. Any info you might have would be greatly appreciated.

Thank you
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Old 10-31-2017, 10:06 PM
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Re: Trying to figure out if I have an lt4

Does not look like an LT4. But check for yourself. Try and find the part #'s that differentiate an LT4 from an LT1.

LT1 vs LT4

The intake manifold is definitely NOT an LT4. It would be powder coated red. The fuel lines would connect on the passenger side, not the driver side, since the LT4 was originally a Corvette engine. Yes, there were 100+ 97 Camaros and Firebirds with LT4 engine’s, but no one in there right mind would sell one of those for parts, way too rare. The Corvette did not use the ribbed, stamped steel valve covers like yours. They would be smooth, composite plastic. The Corvette LT4 engines had black plastic injector covers. Check the rocker arms - LT1 are stamped steel, non-roller; LT4 are aluminum, full roller.
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Old 10-31-2017, 10:12 PM
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Re: Trying to figure out if I have an lt4

Couldn’t have been too important to Cmoe827 (Thread Starter). He posted, signed off an hour later, and has not signed back into this site for 9 days. Ho hummmmm.....
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Old 11-01-2017, 06:32 AM
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Re: Trying to figure out if I have an lt4

Thanks injuneer. for me it's going to be a guessing game from start to finished. the heads have aftermarket rollers on them. It also has a cam, headers, and I'm sure other mods. I get to guess and figure it all out.
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Old 11-01-2017, 02:55 PM
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Re: Trying to figure out if I have an lt4

The factory LT4 came with gold anodized Crane Gold 1.6X rockers, as shown in the link.
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Old 01-13-2018, 09:25 PM
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Re: Trying to figure out if I have an lt4

in regards to the original pic, I didn't think '93 cars were mass air? or is my old age finally setting in? of course it's not plugged in, so it could just be there as a pass thru. also, looks like a Caprice motor with that V8 cap on top of the intake plumbing.

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Old 01-14-2018, 02:57 PM
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Re: Trying to figure out if I have an lt4

Engine in the first post appears to be installed in a B-Body, based on the cowl and firewall.

Your mind is fine.... no MAF in 1993.

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Old 01-16-2018, 03:19 PM
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Re: Trying to figure out if I have an lt4

I thought the major difference between the LT1/4 was the top end (heads/rockers/cam)? Unless I am totally out of my mind (always a possibility) the reason for the different intake between the two is the angle that the intake meets the heads. If I remember correctly, the difference with the bottom end was that all of the LT4 engines were blueprinted and had a straight 4 bolt main bearing caps.
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Old 01-16-2018, 05:52 PM
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Re: Trying to figure out if I have an lt4

There are numerous differences, as shown in the link I posted above:

LT1 vs LT4

There is no difference in the angle where the intake meets the heads. The only real difference in a factory LT4 intake is the fact that there is extra metal added to the top (outside) surface of the ports. Oh.... and the red powder coat.

The extra metal allows the manifold to be opened up to match the 0.100" taller raised runner intake ports in the head. Unfortunately, GM either ran out of money or ran out of interest in the LT4 project, and never bothered to enlarge the manifold ports to match the taller head ports. If you plan to use an LT4 intake with LT4 heads in any sort of performance application, the intake manifold runners need to be opened up.

But other than that difficult to even see difference, the LT4 intake is identical to the 94-97 LT1 intake manifold. The extra metal at the top of the intake ports prevents the LT4 manifold from being bolted to the LT1 heads, because the extra metal interferes with the valve cover rail on the LT1 heads. Can be modified, but there is no reason to put an LT4 intake on LT1 heads. I have the LT4 intake and LT4 heads, ported by CNC Cylinder Heads in Florida.

Bottom end has minor differences, but all the Corvette LT1 and LT4s engine use the same 4-bolt main block. As far as "blueprinting", I was always under the impression that was done by SLP for the small number of LT4's they put in the 1997 SS and Firehawk.

Other bottom end differces - LT4 crank has undercut and rolled fillets. Timing chain is a single roller with steel sprockets, rather than powder metal. Pistons have smaller valve reliefs, and use a "positive twist" top ring to reduce ring flutter, to control blowby.
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Old 01-17-2018, 12:11 PM
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Re: Trying to figure out if I have an lt4

Originally Posted by Injuneer View Post
There are numerous differences, as shown in the link I posted above:

LT1 vs LT4

There is no difference in the angle where the intake meets the heads. The only real difference in a factory LT4 intake is the fact that there is extra metal added to the top (outside) surface of the ports. Oh.... and the red powder coat.

The extra metal allows the manifold to be opened up to match the 0.100" taller raised runner intake ports in the head. Unfortunately, GM either ran out of money or ran out of interest in the LT4 project, and never bothered to enlarge the manifold ports to match the taller head ports. If you plan to use an LT4 intake with LT4 heads in any sort of performance application, the intake manifold runners need to be opened up.

But other than that difficult to even see difference, the LT4 intake is identical to the 94-97 LT1 intake manifold. The extra metal at the top of the intake ports prevents the LT4 manifold from being bolted to the LT1 heads, because the extra metal interferes with the valve cover rail on the LT1 heads. Can be modified, but there is no reason to put an LT4 intake on LT1 heads. I have the LT4 intake and LT4 heads, ported by CNC Cylinder Heads in Florida.

Bottom end has minor differences, but all the Corvette LT1 and LT4s engine use the same 4-bolt main block. As far as "blueprinting", I was always under the impression that was done by SLP for the small number of LT4's they put in the 1997 SS and Firehawk.

Other bottom end differces - LT4 crank has undercut and rolled fillets. Timing chain is a single roller with steel sprockets, rather than powder metal. Pistons have smaller valve reliefs, and use a "positive twist" top ring to reduce ring flutter, to control blowby.
I know on the Camaro side, there were 109 LT4 versions produced in 1997. 100 white with orange stripes, and 9 Hendrick Motor Sports versions, same color scheme. There were 61 Hendrick Motor Sports SS cars that were silver with black stripes that had LT1 engines. I'm completely ignorant about the Pontiac side of the house.

Strange about the mains. When I heard about the difference in blocks, I hunted a few junk yards in Colorado and only found 2 bolt mains on Corvettes. These were all 1995/6 if my memory serves me. I ended up having the machine shop that built my 383 install splayed caps, which I wish I would have known about before spending time at the junk yards.

I also have the LT4 conversion, which I purchased through a dealership online; I don't recall the site. I custom ordered just the heads and intake rather than the set, then ported and polished the heads with a local shop in Denver. Who knows how good the work was though, because the shop never provided flow numbers (not good from my current knowledge). The intake was match ported and polished, and opened to 58mm at the TB. For the rest of the build I added 7/16 studs, CC beehive springs, CC Pro Mag 1.6 rockers and guide plates to the heads and used GM's heavy duty LT1/4 timing set.
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Old 01-17-2018, 12:41 PM
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Re: Trying to figure out if I have an lt4

I also found this searching for speed parts: To identify an LT4 from an LT1, the LT4 VIN number has the eighth digit as a "5" and the LT1 has it as a "P."
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