LT1 to LT4 Conversion
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,027
Likes: 2
From: Baltimore MD
St. Jude Donor '08
LT1 to LT4 Conversion
I just found the "GM Performance Parts LT4 Conversion Kits" in my summit book. It claims to take an LT1 to an LT4 and put out over 425HP for only $2300. Ok two questions:
1. Has anyone done this?
2. If the LT4 only put out 330HP how do they get 425+ from this kit?
Thanks in advance,
1. Has anyone done this?
2. If the LT4 only put out 330HP how do they get 425+ from this kit?
Thanks in advance,
Race Director
Joined: Sep 2004
Posts: 13,793
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From: St. Peters MO Sometimes you have to prove yourself by doing alot of killing or alot of dying...
I've wondered that myself... but you do get the hot cam with the kit so that may prove to be the difference maker. Personally if you have an LT1, spend the $$$ in reworking your existing heads. They can flow more air than a stock LT4 head for less $$$, and it gives you the extra funds for additional mods. You can mod an LT1 to put out more power than a stock LT4 easy... and with identical mods, they are pretty equivalent
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
the LT4 did not come with the "hot cam kit" which is what makes the difference in this setup. It was designed to work with the LT4 heads and puts out around 400hp I've herd. If you go to www.gmpartsdirect.com the price is cheaper there.
Its a good kit if you don't want to have to figure out parts that work together. But if you search around I think you your heads ported and a new valve train for around the same price, maybe a little more.
Its a good kit if you don't want to have to figure out parts that work together. But if you search around I think you your heads ported and a new valve train for around the same price, maybe a little more.
Le Mans Master
Joined: Jul 1999
Posts: 8,683
Likes: 6
From: Phoenix AZ
Scoggin Dickey has the LT4 topend and Hotcam kit for $2150, and they also have a kit that includes LT4 CNC heads for $2999. Something to consider. Check them out here;
http://www.sdpc2000.com/catalog/3473...s-and-Kits.htm
http://www.sdpc2000.com/catalog/3473...s-and-Kits.htm
Race Director
Joined: Feb 2003
Posts: 11,672
Likes: 20
From: Lake Wylie SC
One thing they don't tell you and it's a biggie, if you have a 92, you need a new fuel rail assembly which ain't cheap. There is a cross-over on the front of the LT4 intake and the 92 doesn't have the cross-over. I think this should be part of the kit or at least an option. That's why I think upgrading your LT1 heads and going with another aftermarket cam would be best or cost effective anyway.
Safety Car
Joined: Apr 2003
Posts: 3,793
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From: VA
1. Has anyone done this?
2. If the LT4 only put out 330HP how do they get 425+ from this kit?
If you want to know what you would really see with LT4 top end and hotcam, go see what LT4s get with a hotcam:
http://www.grandsportregistry.com/dyno.htm
Safety Car
Joined: Apr 2003
Posts: 3,793
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From: VA
Drifting
Joined: Mar 2004
Posts: 1,522
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Look at the forum sponsor Precision Porting, I know he was letting people send in their LT1 heads for the core and plus a charge they could get LT4 heads. You'd still have to get a LT4 intake, though you should be able to do it through them.
I'd do that, it cost a few more bucks, but make a ton more power!
I'd do that, it cost a few more bucks, but make a ton more power!
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Safety Car
Joined: Sep 2002
Posts: 4,030
Likes: 6
From: Maryland
Originally Posted by pwoolford
I just found the "GM Performance Parts LT4 Conversion Kits" in my summit book. It claims to take an LT1 to an LT4 and put out over 425HP for only $2300. Ok two questions:
1. Has anyone done this?
2. If the LT4 only put out 330HP how do they get 425+ from this kit?
Thanks in advance,
1. Has anyone done this?
2. If the LT4 only put out 330HP how do they get 425+ from this kit?
Thanks in advance,
I don't know of too many that have bought that kit and converted, but there are plenty of LT4's with unported heads and a hot cam. All that kit has is hot cam and heads+ supporting equipment, right? figure 330 rwhp maybe. Maybe 375 hp at the fly, 425 is a BS figure.
As others mentioned, the kit is not the way to go, overpriced for what you get. Just get a cam and port the LT1 heads; add a cat back exhaust. Headers are optional but do add 20-30 ft-lb torque at 4000 rpm.
Drifting
Joined: Aug 2004
Posts: 1,830
Likes: 1
From: atlanta Georgia
Id say get precison porting a call. Get Bob to work on your heads and then get a cam/valvetrain to match it. youd be really happy with that.
i thnik the best you could do on stock lt4 heads and a hot cam would be like 390 chp. but i mean with some tuning who knows. but I think 400 chp would be obtainable with 4.10 gears, lt4 heads,lt4 hot cam kit, Lt headers, all the bolt ons etc...
Nathan got 380 to the wheels with hot cam kit, electirc pump, TEA porting, headers etc..
your friend
Sean
i thnik the best you could do on stock lt4 heads and a hot cam would be like 390 chp. but i mean with some tuning who knows. but I think 400 chp would be obtainable with 4.10 gears, lt4 heads,lt4 hot cam kit, Lt headers, all the bolt ons etc...
Nathan got 380 to the wheels with hot cam kit, electirc pump, TEA porting, headers etc..
your friend
Sean
Last edited by redbullapril23; Mar 18, 2005 at 02:41 PM.
Racer
Joined: Apr 2003
Posts: 342
Likes: 0
From: Kalamazoo MI
I bought the LT4 kit and am getting Bob @ precision porting to do stage 3 work. You have to weigh your budget with your power goals. The best bang for the buck in my opinion is porting LT1 heads. The other end of the spectrum is porting LT4 heads. You can always stage your mods and purchase LT4's now, then get them ported later on. I had the extra cash so I went that route.
Not exactly true. The additional crossover is a later LT1 thing, and not LT4 specific. My 93 lacks the crossover, and I think it wasn't introduced until '95 but not exactly sure. Any LTx fuel rail will bolt up, you just won't have that crossover. As to the actual benefits of the crossover, I don't know, but I am using my old fuel rails.
As to getting 425hp from the kit alone, I would tend to agree that is some kind of gross rating, you might get close at the crank, but definately not 425 to the ground.
Originally Posted by Strick
One thing they don't tell you and it's a biggie, if you have a 92, you need a new fuel rail assembly which ain't cheap. There is a cross-over on the front of the LT4 intake and the 92 doesn't have the cross-over.
As to getting 425hp from the kit alone, I would tend to agree that is some kind of gross rating, you might get close at the crank, but definately not 425 to the ground.
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,027
Likes: 2
From: Baltimore MD
St. Jude Donor '08
I talked to bob today at precision porting and I am probably going to get the stage 3 kit from him with the intake ported to match. He also agreed that 425 was a little misleading. He figured with the stage 3 heads, ported intake, cam and long tube headers I should be around 375-410 at the crank...at least that is what they have seen over and over with customer vehicles.
Thanks for all of the input,
Thanks for all of the input,
