LT4 LT1 to LT4 Conversion

[Grizzly]

Tuna

What was the output of your engine before the change? I guess I'm looking for how much bang we get for our bucks.

 

[Tuna]

Tuna

What was the output of your engine before the change? I guess I'm looking for how much bang we get for our bucks.

I never dyno'ed it before, so I can't give a true answer. However, based on what I've seen other stock LT1's turn out, the improvement is in the 50-60 HP range at the rear wheels. I'm figuring that my original motor was putting maybe 260 at the rear wheels and I saw 306 afterward with only 400 miles on the freshened engine. I'm taking it back to the dyno in a couple of weeks to see how the CORSA exhaust and 3000 miles of break-in have done.

Sorry, but I can't give you a better answer.

 

[Tuna]

Update to my LT1 to LT4 conversion:

In November of last year, my car dyno'ed at 306.2 RWHP and 324.3 T on a Mustang Dyno. This was with the LT4+ upgrade (LT4 heads and intake, LT4 Hot Cam, HD chain, 1.6 roller rockers, latest OptiSpark) installed but running the stock LT1 exhaust, 48mm TB and 24# injectors.

This month I had the CORSA cat back exhaust installed and a new fuel filter. On the same dyno today, the LT4+ cranked out 327.8 RWHP and 347.9 T. I knew it was better but I didn't know how much with the CORSA. Now I do.

Later,

 

[92ghost]

Tuna. Those numbers are outstanding. I'm thinking your right around 395 HP at the crank and about 410 TQ. Your also getting roughly 20 extra HP and 25 TQ from the Corsa's which is more (I think) than they advertise for a stock LT1 which is about 15 extra ponies. (I don't have the numbers in front of me but I believe these are what they advertise)

Because you have 100 extra HP I can see why you have 5 HP more than a stock LT1 with the same exhaust. It leads me to believe that adding go fast parts because of an advertised HP gain may not always be correct, atleast not for all engines, and in fact could be more than what they advertise. Case in point...

Non the less, those are very good numbers you posted. However, it is still shy of the 425 HP mark that they advertise as the proven amount. I think you will get there with Headers and no Cats if my original calculations are close to correct. BTW. what RPM was your peak HP and TQ?

PS. Tuna, you do realize you are the test bed for all us LT1 owners thinking of this mod... Now, hurry and get those coated headers, remove your CATs and get to the dyno for those numbers.

 

[Tuna]

Hi ghost,
I'm not trying to be the test bed but I don't mind.

My next mods will have to wait until next year so I've got to enjoy my new HP the way it is for a while. Then my plan is to add long tube headers, 28# injectors and a 52mm TB. The headers will go on first, then I'll have to do another dyno run.

I'm thinking like you that the headers will probably push my motor up to that 'magic' number of 425 hp at the crank.

And, peak HP was at 5750 and torque was at 4250.

Remember - your results may be different than those obtained by me or the makers of any of the parts I used. (my wife, the attorney, is standing behind me) :L

 

[92ghost]

Tuna. I think you will get to 425 no problem with your next mods. Your peak HP at 5750 will most likely be pushed up when the headers are installed. I doubt you will peak at 6K which in my opinion, anytime you can make that kind of power without reving stratospheric revs your doing good.

 

[92ghost]

There has got to be more people out there who have done this upgrade to their C4 LT1. I'm curious if this kit can be installed on an L98?



Wayne

 

[garycr14]

LT4/L98 Conversion

There has got to be more people out there who have done this upgrade to their C4 LT1. I'm curious if this kit can be installed on an L98?



Wayne

You can not use the same conversion package as the heads on the LT1/LT4
are reverse flow heads, and will not work on the L98. You can find many other opions for the L98 engine. You wont have the same limited parts limitation that us Lt1/4 guy have to deal with.

Good Luck

 

[UB2 SLOW]

I have the same conversion. I also added an extreme duty timeing chain to my set up, 30# injectors, ram air and hooker shorty's(damn emissions). I turn out 344rwhp and 340rwtq. The kit says go with 58mm TB, but that is too big, go with a 52mm.

 

[Tuna]

I have the same conversion. I also added an extreme duty timeing chain to my set up, 30# injectors, ram air and hooker shorty's(damn emissions). I turn out 344rwhp and 340rwtq. The kit says go with 58mm TB, but that is too big, go with a 52mm.

What are you running for fuel pressure on your conversion?

 

[UB2 SLOW]

I have it set at 47psi. I turn 14.7 during normal driving. I drop to 13.1 at WOT.

 

[Tuna]

I have it set at 47psi. I turn 14.7 during normal driving. I drop to 13.1 at WOT.

I need to get my fuel-air ratio checked just to see what mine's doing.

I'm set to 46 psi but with the stock 24# injectors and 48mm TB.

Thanks.

 

[UB2 SLOW]

I also had to add a Walbro 340 fuel pump. I was getting fuel starvation at the track. Driving around town wasnt a problem. I am thinking about upgrading to a 396.

 

[Tuna]

Horse power is addictive!!!

Wish I had the time and money to do more to mine right now.

Maybe next year!

 

[92ghost]

Are there any new LT1 to LT4 conversions out there?

 

[92ghost]

I'm still curious to see if ANY one else has tried this upgrade?

 

[Mad-Mic]

personally i think this kit is over priced and over hyped. all stock LT1's i've seen dyno on a dynojet has been in the 270-280 rwhp range for 60 hp i'd be super PO'ed!

the only way that cam will pull 425 hp at the crank is with FULL bolt on's and your still only pulling roughly 352 rwhp.

with a compentent tuner using LT1 edit you can get around 20 rwhp and with headers your looking at another 20+ rwhp now your at 40+ rwhp. so your telling me cam, heads, and 1.6 rr's only gave you about 40 rwhp? something is fishy here.

if i had an LT1 this is what i would do... aftermarket heads cnc'd, 230/230+ duration at .525+ lift on 1.5 roller rockers with your LT1 intake portmatched and a good dyno tune using LT1 edit. that alone would put you well over 425 at the crank and most likely over 380 rwhp.

for 60 rwhp i'd throw the jug on it and save 1500 bucks

hope i didn't hurt anyones feelings but GM technicians are NOT tuners and more than likely don't even have LT1 edit! all dealership mechanics are is part changers and thats the bottom line.

1 good thing about LTx motors is the more milage you put on them the more HP they make. popular hotrodding did an article on a 93 Z/28 and road tested it for 60k miles and it pulled more HP at 60k miles than it did at 3k miles.

if anyone wants to know more about cam selection call my friend Joe Overton. he knows alittle about LT1's since he has the fastest NA LT1 in the world! not even the fastest NA big cube LS1 can keep up with a lil ole 388 LT1

http://www.lethalefi.com/

 

[garycr14]

I used the AFR heads on mine. Got about 50+ rwhp & rwtq gain. Because I live in Caifornia, I had to be conservetive with the mods, and could not use full headers (used shorties) nor could I go with the hot cam. If I were to do it over I would have changed the cam. I used the 1.6 roller rockers, because the heads are LT4 type, I had to chnge the intake as well, and I agree with tuna, the red intake looks good, but in my case with the torch red car. I think for the same money you could buy a 383 short block from Golen, or another engne builder, have your heads ported, and put out some serious horsepower & torque. If I were to do it again, that is the direction I would look into.