hey guys i know we have gone over this alot
but i would like to see results of APS cars with large CID engines
i saw some on here on a 402 with the base turbos and it look like the power feel off at 5000rpm.
need this info so i can pick the shortblock that will work best for me. im having a hard time picking what i want. ive price all the ones i could use but still need more info.
i want to use the base turbos to there 100%, i dont want to go over the top with cid if they cant hit at least 15psi on a 402. if not its 364 for me
thanks for all the info

 

my 402 did 728rwhp and 789rwtq on 9psi with the standard kit through a stock m6 trans and stock rear with 3.42's. power fell off at about 6200rpms but im using stock L92 heads as well which isnt gonna help my cause. i dont wanna go any higher on boost untill i change out the ducts.

 

do you think the turbos have more in them?
i need to fix my ducts as well.
how do you like those L92?
what cam do you have if you dont mind?

 

i think the turbos do still have more in them...im thinkin with 12-14psi i could see 800rwhp. ill find out eventually.
as for the l92's....730rwhp makes me pretty happy for an $850 investment. they are off the shelf with upgraded springs and retainers. they've worked out pretty well.
my cam is a custom grind from HarrisSpeed...i dont know the exact specs but its something like 23x/24x .6xx/.6xx on a 118lsa. makes for a nice sleeper with hardly any trace of the turbos.

 

A 370 is a nice affordable build as you can stick with stock cam. I love my 408 its fantastic off boost and really spools up the turbos quickly. Of course its a fully built 408.
I think another reason its so good is that went to 9.5 compression. Really don't think lower is necessary on a street car and for sure wouldn't go under 9.0. If it was a track only car than maybe 8.5. The aps standard kit is a good street setup. The turbos are small enough to spool up really quick and that gives you a nice broad powerband.

And as for power how much can we hook up anyway. I already have problems at 7.5psi max. I have nittos on the car now. I might try to get my wheels widened so can run 315 nittos but really don't want to run et street radials as my daily driver tire. So may wind up not going to much past min gate boost which should still be like 750engine hp and 650rwhp. Course hoping my eboost can help ramp in the boost with gear /rpm,but won't get to install and try it now till spring either and they sent me wrong one..60mm not 66mm so have to send it back or sell it off.

Its nice to want the big numbers..like 800rwhp or more but its not so easy to actually use that type of power in real life. I have seen a few higher boost aps dynos with pretty sure 402 or 408s on here somewhere. We already know that that power drop off at much past gate boost is likely the intake tubes sucking shut not the turbos running out of air. The turbos should do 1000 engine hp or so just at lower boost on the 402 or 408. And have seen some dyno maybe try to find it for you of them doing just that.think it was 795 it hit and it could have been gto but think one f body did it too.
Get the intake tubes stented or replaced and then someone can run them up to 15psi or so. I will be happy to dyno mine next year at higher levels but car is sleeping now in garage until spring here.

Course mine is going to be the high end of a 408 build since have the afr225s, fast90/90 and reasaonble cam in there. about 590 lift with the 1.8 yella terras. No lope though from the 121 lsa and only about 210/232 duration specs. Its an easy to tune ,easy to drive cam,no surge. grandma could drive car with it. But works good for me. Didn't want to worry about way high valve spring pressure and have to change out springs every 20,000 miles.

Hopefully will see some more dynos of the aps cars in the next few months.Remember the standard gto system is same turbos as is the c5 standard kit. So you can check on those forums too. Have seen as said a very high dynoing gto setup. And think the gto have no problem with inlet ducts.

 

If i knew what I know now back then I would have done a 370 ci simple easy to build and no need for major up grades. Hell there where boosted 346 running nines.

 

what do you have now?
and the 370 is on my list but im trying to keep the LBS off the car
i might go to 364

 

just wondering - why did u pick the l92 vs the 317? do they flow that much better?

 

i dont know if they outflowed the 317's but i went on the comparison they did with the AFR's awile ago when the l92's first came out. they werent too far off from the afr's except when you get into the really high rpms so i figured they would be decent for a low boost set up...and for $850 bucks i couldnt go wrong. worst case scenerio if they didnt pan out id turn around and sell them on here and go with another type of head.

 

thx for the info. debating the 317 vs l92 issue as well as 370 vs 408. after seeing mightymouse's video with a 364 it looks like a 370 is plenty!!

 

thats good...keep in mind you'll need atleast a 4.00 bore to use the l92's and also a l76 intake aswell...so that may make your decision a little easier on which route to take. only reason i went with a 402 was b/c its a street car and i figured the nice increase in torque with more cubes would make up for any turbo lag i got and since i wasnt lookin to make stupid horsepower with this kit, it would work for me...and so far it has. only down side i think is cost of course.

 

Extra displacement is nice on a street car and off boost and spins up the turbos quicker giving a broader powerband again great on a street car. And you can run less boost and make the same power which can also be nice.

Now its true guys run these hardcore builds on the street and streetable means different things to different people. Some guys like a big turbo and spool up at 5000 and powerband to 7000. I like 3000 to 7000 with spool up staring in the 2thousands range.
Of course YMMV and a 370 is a nice cheap build if you use stock crank, factory type cam and some 317s or whatever heads. And of course those combos can give great 1/4 mile times.

 

im trying find somewere in between
i want a fast spool but i dont want the power to fall off up top
and if its to fast it will just kill tires on the street
so what are we looking at L76 377cid with some l92 heads
how much backpresure is on a 402 with the turbos a say 12psi

 

4xx ci

 

Don't think anyone has measured the backpressure yet. And why so worried about it . We have seen 9s at near 140 with 402 in Jms car. At like 10 or 12psi. Do you need to g much faster than 9s? I sure don't. The bigger engine is better off boost and if it spools too quick well you have same eboost 2 as me. Should be able to ramp up the boost with that.

But cheaper to stay a bit less with ls2 and use the stock crank which is still plenty strong.
So whatever fits in the budget. I think a 427 would have been way too crazy and then could use the upgraded snails But 427 is a nice NA size hardly necessary for sane street cars. Course we are all a bit insane here! LOL

 

how was your 408 off boost was it killing tires or what?
i want to drive across the states if i want to and not kill as much gas.
speed is not what im going for im looking for the best all around engine size to do alot of things.
its not only about the 1/4 mile. i know the larger engine will spool the turbos faster and if i didnt you have said it alot bro LOL.
piston speed is also on my mind and life span of the engine over time.
you know what i mean?

 

Exactly. I don't see many people concerned with gas mileage but I am. I get 25 MPG with my 346 through a t400 9" rear 35 spline axles etc.

there are many factors to making a car fast besides dyno #'s. Another reason I only use ls1's because I have been able to build them for very little money.

 

Well the 408 is very powerful even with zero boost. It is a built 408. Thought the head choice might really hurt bottom but don't seem to much if at all. The 225 on a 346 might but again its a 408.
And a turbo 400 is not a good choice for mileage with no overdrive. I am not building a track car either. Going with 3.54 gears still pretty mellow. Went with a very driveable streetable cam, 9.5 compression,tight stall. My exhaust is only really loud when open the cutout. So you can have both. Going 4l80 because want an overdrive but mileage is not much of a concern I have daily drivers.

A stock crank forged piston and rod ls2 is likely the best choice for you. Don't really need the 402 or 408 or bigger. forged 346 with stock crank if the budget is tight.

 

I hope you won't be too upset if I post my 348 results in here...

Max hp and torque were 532 and 546, respectively on my ~9.2:1 CR 348 with LPE's GT2-3 cam and LPE's CNCed LS6 heads through a 3400 stall and 2.73 gears. The tune was done on EPP's Mustang dyno with 87 octane using just the waste gate springs supplied by APS.



I never scanned my dyno sheets in, instead, created a graph in Excel. I've attached it.

I'd like to have a new engine built, but won't be using a crank with a stroke longer than stock; the 348 put down more than enough torque for me. So I'll go with either a 364, a 375, or a 387.