[KingLT1]

Originally Posted by EDFHOBBIES

There was a time when the original LT4 debut in the 90s and boosted cars ran 8.5 to 9.5 like myself with a vortec Trim, then the LS came out they wanted boosted cars to run 10.5 or more shops told customers if you lowered compression to much it would be a dog off the line, And now with the new LT line who knows but I have noticed this, I've seen a lot people do the LT4 blower swap on an LT1 with the LT4 injectors, LT4 pump, Lt4 fuel line, and Aux dsx pump.. Why do they fall short of LT4 numbers.. It's not the lack of fuel, or a different blower.. could it be the compression is more and you can't run as much timing hmmm hmmmm!

And why would shops like LPE use cometic head gaskets on there LT4 builds that are thicker.. Well Brandon told me when I duplicating there 1000 hp build they like to drop compression a tad..

But build how you want! A lot people will tell you you can add meth or E if you need more octane.. For me these cars have plenty of tq, When I start messing with the wifes LT1 I'm getting bigger CC chambers, lower compression pistons, and the cometic head gasket..

The LT1 actually makes more HP per lb of boost up until you reach it's octane wall. The lower compression of the LT4 has a higher ceiling on 93 pump. So once past the LT1 octane wall, the LT4 then starts to make more power because of how much timing needs to be pulled on the LT1 to keep detonation at bay. So if you are stipulating to only using 93 octane then yes lower compression is better for higher horsepower which we already pointed out. LPE says that because they don't mess with E85. My brother just had them build a LT4 with higher compression pistons. 11.1 and E50-60 mix. Always better to make the engine as efficient as possible on motor and run less boost.

[oldman]

agree here

[EDFHOBBIES]

So do I, more compression will make more but not with our fuel systems. It's easier to build around them vs trying to do something on an in adequate fuel system and being dependent on meth

[oldman]

fuel system ain't cheap, but yep, that's the route I took. 11.5 is good upto around 720 ish RWHP on 93 octane, after that I'd go 10.5 or even 10.0 depending on the type of racing. I'm actually at more boost than I wanted 10.5 PSI on a huge (slow turning pulley). The centri likes the 7250 RPM shift. I already tuned it on 93 and E85 or I'd go to an even bigger puller like 4.6 or 4.75 (if they even make one that big). I'd like to keep it at 9 PSI on 11.5 and 93, but maybe I'm paranoid, the car has very little knock retard and probably more a resonance issue anyway. I'll keep an eye on it. Injection window is good and to me that is a huge issue (did a lot of diesel racing).

[Umbriel]

Originally Posted by oldman

fuel system ain't cheap, but yep, that's the route I took. 11.5 is good upto around 720 ish RWHP on 93 octane, after that I'd go 10.5 or even 10.0 depending on the type of racing. I'm actually at more boost than I wanted 10.5 PSI on a huge (slow turning pulley). The centri likes the 7250 RPM shift. I already tuned it on 93 and E85 or I'd go to an even bigger puller like 4.6 or 4.75 (if they even make one that big). I'd like to keep it at 9 PSI on 11.5 and 93, but maybe I'm paranoid, the car has very little knock retard and probably more a resonance issue anyway. I'll keep an eye on it. Injection window is good and to me that is a huge issue (did a lot of diesel racing).

Are you running a Procharger?

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[jCastr25]

How much whp should I expect form a lt1 with forged internals stock compression, complete lt4 fuel system, jms voltage booster, 2” kooks headers, weapon x stage 3 cam, edelbrock 2300, on e50-60?

[EDFHOBBIES]

You should send the 2300 to Brett or greg to be ported you will stretch the fuel system further. Also think about relocating the iat sensor in the blower to a similar place like the maggi.

Wife has the force 2300 my old fuel parts and the DSX on 93 615 and 666 tq.

The octane will be the factor if you stayed stock compression and some iat issues if you dont port the blower or use an ice tank.

[oldman]

Originally Posted by Umbriel

Are you running a Procharger?

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Yep a D1X.... I could not resist the upgrade, a P1X probably would be better for my goals and 11.5 CR.

The D1X with a 3.65 pulley is rated at 1075 engine HP at 7200 RPM (engine), close to the 62000 max impeller / exducer speed.

The P1X is 950 HP at 65,000 rpm so it can take a smaller pulley
My original P1SC (got it second hand in a package) is "only" 825 HP at a max of 65,000 RPM.

So nutshell the P1X would have given me more boost sooner with a smaller pulley and I would still be over the octane limit of 11.5 CR. The D1X gives room to grow if I ever do 10.5... I know then you "need" a FA

[oldman]

Originally Posted by jCastr25

How much whp should I expect form a lt1 with forged internals stock compression, complete lt4 fuel system, jms voltage booster, 2” kooks headers, weapon x stage 3 cam, edelbrock 2300, on e50-60?

This is going to be fuel limited not boost, especially on E60. From my experience, similar engine build LT4 injectors, and LPHPFP (worth about 50 WHRP), and E85 I was at 6.5 ms (or was that 5.5 ms forget now) window max duration at 10.5 PSI. Hence I needed to go to the LP injector.