lt1 or lt4... what is the difference

[truespex]

As mentioned in my last post, I'm new to all this, so please, excuse my stupid at times questions... can anyone tell me what the difference is between an lt1 intake and an lt4 intake? Or a website that would haveinfo on this type of thing? Thanks.

[Joe 1320]

The LT4 intake has taller runners to mate up with the LT4 heads. It will not work correctly on LT1 heads.

[Kevin - Blown 95 TA]

In addition to Joe's comments, the LT4 manifold has a lot more material around the ports than the LT1 manifold. This is so it can be opened up more and still have a good sealing surface. There are special GM LT4 intake gaskets for performance applications which are meant to be used with ported manifolds & heads.

[Joe 1320]

Originally posted by Kevin - Blown 95 TA
In addition to Joe's comments, the LT4 manifold has a lot more material around the ports than the LT1 manifold. This is so it can be opened up more and still have a good sealing surface. There are special GM LT4 intake gaskets for performance applications which are meant to be used with ported manifolds & heads.

Um... yeah, what he said. And it's red too.

[DJ Taso]

So, how much would an LT4 conversion cost me? Is there a kit?

[Al 96 Ram Air T/A]

cosrt

Well, a top end conversion is approximately $2300. This gets you a Hot Cam kit, which includes the heads, intake and cam. Now, you need the LT4 timing chain, which is cheap at about $75.00.

However, this still does not make an LT4. In addition to different piston rings, the LT4 had different injectors, exhaust manifolds, PCM c al., and knock module. (I'm sure I'm forgetting something). All in all, an LT1 can be converted to an "almost" LT4, but total cost will be about $3750. After parts, you need programming and exhaust mods. The good thing though is that going the "Hot" route, you can increase you hp by about 75 ponies. And, the best part is you can sell you LT1 take-off parts. While pricy, it's a sure-fire package that makes the whole engine stronger, as it replaces some of the "prone to be a problem" parts (i.e. timing chain & rocker arms). I would also use the Extreme Duty timing cahin, incase your wondering where some of the money was coming from in my $3750 estimate.

While it's almost the same cost as a supercharger, it nets less horsepower. But, keep in my mind, it's a safer way to build power, as it merely maximizes what you already have, without overly taxing the longevity of the engine. The ring lands can and usually do fail with a blower on LT1's. When?? Depends on intercooler, boost, timing, etc. But it can and will usually occur in the 25,000 to 75,000 mile range. (yeah, yeah... I know people will argue that they "know somebody" who has 100K on the motor and it's perfect, but this is not usually the case with high mileage blower motors)
Where as an LT4 build up generally doesn't affect overall life. The good thing is, the LT4 buildup works even better if you decide to mod further, i.e. stroker or blower. The parts are perfectly designed for high power/high revving.

[99WS6TA]

lt4 kit

here is the kit that summit has it says that it could get you 425+ hp. its kinda pricey like everyone else says but not a bad bang for your buck.

if 96-97 model car
http://store.summitracing.com/partde...%2DGMP3287%2D2


if 92-95 model
http://store.summitracing.com/images...pd_2wrrnty.gif

[SteveH37Formula]

Here is a site that has more info on the LT4

http://pws.chartermi.net/~steveher37/LT4/lt4.html

[Injuneer]

One minor point..... although the LT4 heads have raised runner ports (0.100" taller than the LT1 head ports), the LT4 intake has a port opening virtually identical to the LT1 intake. It is the extra "meat" at the top of the LT4 intake that allows it to be heavilly ported to support a really well ported set of LT4 heads. In fact, it MUST be ported to support ported LT4 heads.

And.... the "425HP" number that is so widely quoted by Summit, Pace Parts, etc. is based on an engine dyno test that MORE Performance did in maybe 1998-99. They got 429 SAE corrected flywheel HP. It was reported in one of the Chevy mags at the time, and the article was reprinted in Pontiac Enthusiast in the past year. The article mentions a number of items that were included in the engine dyno test that are not part of the "LT4 Conversion" kit..... larger throttle body, injectors, long tube headers, and "programming". Unfortunately, it later came out that MORE's "programming" was actually done with a $3,000+ aftermarket engine management system. I suspect there were a few more "extras" that were not mentioned in the article.

Not saying you can't get 425HP out of the conversion kit.... only that not all the required parts are included.

The red powder coat is almost worth the extra $$$$