Power AdderGetting a Supercharger or Turbocharger? Thinking about using Nitrous? All forced induction and N2O topics discussed here.
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OK guys, here's what i have now- 305 tpi, crane 2032 cam, 1.6 crane gold rr's, built tranny with 2400 stall, built rear with 373 gears. headers, no cat, borla catback. SLP runners mild ported plenum. Procharger P1sc. now making about 8pds of boost.
what i want (my question), Im buying an L98 off another member here. I want to build it to make serious power and keep my TPI (further modded of course) Im unsure if i should build a 355 or go 383? either way, it will of course be lighweight forged rotating assembly. Im unsure at this point of what heads to go with, or what cam (maybe keep my crane?) I want this motor to hold 15lbs of boost. and pretty much be able to smoke anything else on the streets light to light. So what should i do guys? 355. 360 alot of boost, or 383 and try to make some boost. Im also leaning toward AFR heads. So, i know many of you have some killer recipes for a build like this, so i need input please. ! more thing. expense dosent matter. I have a toy fund so, im willing to pay for quality parts to go faster than the rest. Thanx..
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You're going to need a larger duration camshaft to keep your dynamic compression ratio down in a 383. You can stick with the 64cc chamber heads if doing a 355 but you'll need dish pistons, if you go 383 I'd look at going with a larger chamber head, again for compression concerns. Less compression and more boost will make better power than more compression and lest boost. When you've decided on the engine size I'd call a cam manufacturer and give them your specs so they can recommend a cam.
__________________ 1988 Trans Am 355. 33,000 original miles.
355ci 10:1, Holley 750DP, Summit Stage 2 intake, AFR 180cc Street Eliminators, Comp Cams XR282 HR10, MAC shorties, Mufflex 4" exhaust, Circle D 3500 stall
Best ET: 12.26@108.44, 1.67 60ft
Best MPH: 12.57@112.5, 2.0 60ft
Thanx for youre help so far guys. But my question is, what would you do if you were me. Build an efficent 355 or TQ monster 383? Ill also be adding a progressive meth or alchy injection to be safer and make more power.
Having once had a 350 supercharged low compression combo with 15lbs of boost, I would stick with the smaller cube engine, _especially_ if you are staying with the TPI-style intake (which at bare minimum I would do a ported aftermarket base, large tube or SLP runners and ported plenum). Reason being, a 383 is going to have more torque. a TPI 383 is going to have an insane amount of torque. a supercharged 383 TPI is not going to hook whatsoever with any decent amount of throttle and unless all you want to do with it is shred tires, it won't be any fun. Also, the 383 is going to make peak power lower in the RPM range, all else being equal. The procharger is going to make more power the higher RPM you go, so you'll get more out of it if you can wind it up higher.
My $.02
__________________ 1988 Trans Am 355. 33,000 original miles.
355ci 10:1, Holley 750DP, Summit Stage 2 intake, AFR 180cc Street Eliminators, Comp Cams XR282 HR10, MAC shorties, Mufflex 4" exhaust, Circle D 3500 stall
Best ET: 12.26@108.44, 1.67 60ft
Best MPH: 12.57@112.5, 2.0 60ft
Ive actually been leaning towards the 355. I also already have SLP runners, ill open them up more, port out the plenum all the way, and do a ported TPIS base. OK, 355, heads and cam reccomendations??? AFR 195's?
would the 210's be too big for TPI, I looked at AFR's website they have too many choices for heads. I dont know which ones would make the most power with boost.
A combo I've seen a lot of guys use with small block forced induction pulling trucks and drag combos is a 377. It's the 3.750 crank from a 383 kit with the stock 4.00 bore of a 350 block. You don't have to invest as much into heads. As long as your heads have decent flow numbers, with forced induction, you don't need as high of an intake lift as a n/a engine. A low boost 355 I built had a .527 intake lift and a .575 exhaust lift so as much exhaust scavanging could happen.
__________________ 91 Z28, L98, NX Dual Stage 100 hp, 200hp system. GMPP heads, Edlebrock Base and Runners, edelbrock headers, UMI LCA's, Panhead bar. On the quest for Low 11's N/A 10's on the bottle.
Last edited by SilentBobZ28; 05-15-2009 at 09:32 AM.
Reason: Typed the wrong number
A combo I've seen a lot of guys use with small block forced induction pulling trucks and drag combos is a 372. It's the 3.750 crank from a 383 kit with the stock 4.00 bore of a 350 block. You don't have to invest as much into heads. As long as your heads have decent flow numbers, with forced induction, you don't need as high of an intake lift as a n/a engine. A low boost 355 I built had a .527 intake lift and a .575 exhaust lift so as much exhaust scavanging could happen.
372 CI is a stock bore 400 (4.125) with a 350 crank (3.48). 4.125 x 4.125 x .7854 x 3.48 x 8 = 372.
Stock bore 350 with a 3.75 crank = 376 CI. 350 block + 0.030 = 382.66 AKA 383.
Basically a 372 is a stock 350 bored + 0.125. (whick requires a 400 or aftermarket block) I've run them before and the 372 has good flow since the increased bore unshroud's the intake vavle.
My apolligies it's a 377 with a 4 inch bore and a 3.750 crank. I was bored and couldn't sleep so I figured I would help the guy out. The other combo for a medium stroke and small overbore is a 370ci combo. That's a 30 overbore and a 3.625 stroker crank.
Can't really say I'm an expert on the this subject, if your going to run 15lbs of boost thru this engine, say a 350, I think it would be best for the block if you could find one that you dont have to overbore at all, just clean up. GM uses a similar method with its newest forced induction applications... n/a STS 4.6L, supercharged STS-V 4.4L. Just extra security to keep the block from warping couldn't be a bad idea.
I think im stickin with the 355. I just need help on the heads and cam. maybe the internals too.
AFR 195s will do fine. For a cam, I'd call comp and have them spec you out one.
On my old setup I was running a completely stock TPI/heads combo and with the timing way off and no tune I went 12.5@111 mph on 10lbs of boost. The car had 11s, probably mid 11s, in it, had the tuning and timing been sorted out. Unfortunately I nuked the supercharger before I had a chance to get those issues fixed.
__________________ 1988 Trans Am 355. 33,000 original miles.
355ci 10:1, Holley 750DP, Summit Stage 2 intake, AFR 180cc Street Eliminators, Comp Cams XR282 HR10, MAC shorties, Mufflex 4" exhaust, Circle D 3500 stall
Best ET: 12.26@108.44, 1.67 60ft
Best MPH: 12.57@112.5, 2.0 60ft
I agree with the_am_man and that's why I stuck with just a 350 for my build. If you're going with the AFR head, the 195cc would be a better choice since you said it will be mainly a street car and not an all out racecar. The cam you have now may be fine, but that depends on if you want to install a used part in your new engine. For the internals you probably already know to use forged crank, forged h-beam rods, and forged dished pistons to keep the compression ratio down. I used Cat and Speed Pro for my rotating assembly, but I was more budget oriented.
I really just want this car to run in the lows 11's in street trim. Right now my car is g-tech' ing, high 12's with the 305. From similiar builds that i reasearched i should be around 380hp and 400+tq. I want this build to blow those numbers away, or, it wount be worth the motor swap for me. Like i said earlier. I dont want to fear any LSX at a stoplight.
Trust me, if you run 15 lbs of boost through an AFR-headed small block using ported and aftermarket TPI parts you won't have anything to fear from most street cars. Again, using my car for reference, with stock heads and TPI, not near enough timing and running way rich I put down 350 rwhp and 406 rwtq on 8lbs of boost (belt slip). Assuming the numbers you quoted were flywheel hp I already far surpassed those numbers using stock parts and an awful tune with half the boost.
If it is assembled right and tuned properly you will have no problems running low 11s.
__________________ 1988 Trans Am 355. 33,000 original miles.
355ci 10:1, Holley 750DP, Summit Stage 2 intake, AFR 180cc Street Eliminators, Comp Cams XR282 HR10, MAC shorties, Mufflex 4" exhaust, Circle D 3500 stall
Best ET: 12.26@108.44, 1.67 60ft
Best MPH: 12.57@112.5, 2.0 60ft
Thanx for youre help so far guys. But my question is, what would you do if you were me. Build an efficent 355 or TQ monster 383? Ill also be adding a progressive meth or alchy injection to be safer and make more power.
It depends on what your overall goals are. For an everyday driver, and if your looking to keep RPM's down below 5500 RPM, while making an abundance of torque, stick with Tuned Port Injection, and go no larger than a 355....
Once you contemplate a 383 or more cubic inches, it really defeats the purpose of running Tuned Port Injection (not that you can't, but it's a waste), and your better off throwing on a Holley Stealth Ram. If you have your heart set on TPI, I wouldn't go any larger than a 355. Methanol cools down the charge very substantially, but depending on how much boost you plan on running, you might not even need it to tell you the truth....
It depends on what your overall goals are. For an everyday driver, and if your looking to keep RPM's down below 5500 RPM, while making an abundance of torque, stick with Tuned Port Injection, and go no larger than a 355....
Once you contemplate a 383 or more cubic inches, it really defeats the purpose of running Tuned Port Injection (not that you can't, but it's a waste), and your better off throwing on a Holley Stealth Ram. If you have your heart set on TPI, I wouldn't go any larger than a 355. Methanol cools down the charge very substantially, but depending on how much boost you plan on running, you might not even need it to tell you the truth....
Thanx steet, thats why i decided to go 355. Now afr 195? what cc? cam?
Thanx steet, thats why i decided to go 355. Now afr 195? what cc? cam?
There are ways to maintain power under the curve w/out sacrificing how much the heads are milled down. I wouldn't go any lower than 72/cc, and with your application, the CC-306 from comp would do extremely well. It's an older grind, yes, but they are awesome up top. Just match the stall accordingly to the cam, and hold on to your hat. The 2400 stall will do fine though if you don't want to go any higher....
right now i have a 2400 stall converter. Should i go maybe 2800-3000? Also considering the 58mmTB.
So far im going 355ci's AFR 195'sw 72cc's, mega ported plenum, megas worked slp's Anyone know what the best forged internals would be, id like to just buy 1 kit.
right now i have a 2400 stall converter. Should i go maybe 2800-3000? Also considering the 58mmTB. So far im going 355ci's AFR 195'sw 72cc's, mega ported plenum, megas worked slp's Anyone know what the best forged internals would be, id like to just buy 1 kit.
Just so you know, every TTA, Grand National and GNX came cast from the factory, and have been running 20+ pounds of psi w/no problem (tuned properly). Forged internals won't hurt of course, but so long as detonation is controlled, it's not needed for lower boost levels, save for maybe peace of mind. The stall really won't matter, because you'll be making boost immediately, with or w/out a load, so foot brake it if you want to go any higher lol....
Ok cool, im not too concerned with the stall, its only gonna see the track maybe a couple times. Does anybody have any real worl HP +TQ #'s with a similar setup? maybe E/T's? After this build ill be pissed if a ZO6 beats me?
i have a similar build currently, 305 .20 over crane 2032 cam, snow methanol injection kit, procharger d1sc 14#'s max on the stock rebuilt shortblock, world products torquer 305 heads 1.6 roller tip rockers, i dyno'd 380hp and 420 ft/lbs to the wheels, last track run i did was a 12.64 at 110mph with a 1.791 60ft
my future engine will be a forged 355 with afr195 heads
Having once had a 350 supercharged low compression combo with 15lbs of boost, I would stick with the smaller cube engine, _especially_ if you are staying with the TPI-style intake (which at bare minimum I would do a ported aftermarket base, large tube or SLP runners and ported plenum). Reason being, a 383 is going to have more torque. a TPI 383 is going to have an insane amount of torque. a supercharged 383 TPI is not going to hook whatsoever with any decent amount of throttle and unless all you want to do with it is shred tires, it won't be any fun. Also, the 383 is going to make peak power lower in the RPM range, all else being equal. The procharger is going to make more power the higher RPM you go, so you'll get more out of it if you can wind it up higher.
My $.02
I totally aggree with him.Torque going to kill your traction in the street.Is easier to control and hook with and engine with less torque similar HP in the street,the track is another story because you can use any tire you want.
So i take most of you would say 355.. Now my mechanic/builder is saying, go for the cubes,383. But i dont think he's taking my intake into consideration.
How much do you guys think i can squeeze out of the 355 with 15pds? I searched and found "AC" 's car making 6-700rwhp thats a 383 tpi with the same snail as i already have?
Not calling into question anyone's statements, but 600+ whp using a P1SC and a tpi intake is a bit hard to swallow. Also, try not to get caught up in dyno numbers. Use them as a tuning tool and reference, nothing more. What really matters is what it's going to do at the track. If you build something similar to what I had but have a good tune, verified 15lbs of boost, quality ported TPI parts and AFR heads (and if you can hook it at the track) you'll have your mid-low 11 sec timeslip.
__________________ 1988 Trans Am 355. 33,000 original miles.
355ci 10:1, Holley 750DP, Summit Stage 2 intake, AFR 180cc Street Eliminators, Comp Cams XR282 HR10, MAC shorties, Mufflex 4" exhaust, Circle D 3500 stall
Best ET: 12.26@108.44, 1.67 60ft
Best MPH: 12.57@112.5, 2.0 60ft
I think i will do the 355, ive keep saying that, But with all the hours of searching i cant find any real HP + TQ #'s or E/T's?? My concern is i want to build a motor that will keep up with all these new 500+HP cars that are coming out of Detriot these days. If i spend 3-5k to build this, i want it to be worth it.
OK, Opinions on Throttle body, should i go 58mm? Im also sending out my plenum to www.corvetteplenum.com Ill be getting the "mega porting" and the SLP runners mega ported. TPIS base. Any other specific recco's for parts from you guys.
I do 12.2's on a bone stock TPI engine with a bunch of nitrous. The dyno sheet means nothing, I crush dyno queens every time I go to the track. This isn't being arrogant either, there is always a guy there with "516hp dyno tuned" that runs slower than me and wants to crawl all over my car to find out what tricks I'm pulling. The torque difference you get between a 383 and a 355 blown is negligible, As has been stated you're choking out the engine with the TPI but with 15psi, good heads, nice cam, you should be fast; VERY fast. I would guess the combo you're wanting to be an 11 second contender with traction. Stick with the lower RPM stall, and don't gear the thing to death, you'll have enough torque to spin 3.23's or the likes. Good luck on the build and remember, the only sheet of paper that matters is the time slip
P.S. I just saw one of the first track outings for the Camaro SS, it went 13.5; I run that N/A.
Anyone else have opinions on this build for me? Or some real world #'s ?
__________________ 1989 Trans Am WS6 LB9, Procharger P1-SC, Crane cam and valvetrain, Freddy Brown 700R4, 2400 TQ converter, Eaton posi 373 gears, SLP runners ported plenum. All MSD ignition and boost box, The whole UMI catalouge for suspension. 24pd injectors, BBK 255lpg FP, Edelbrock shorties, Borla cat back, Ed Wright custom tune. + a WHOLE lot more.
A friend of mine has an 89 corvette with a completely stock TPI intake on a 383, cheap world product iron heads, relatively mild cam and a 67mm single turbo, FAST efi controller, 65# injectors, Walbro in tank pump and running around 20-22 psi. I've driven and ridden in some insanely fast cars but that one was the most frightening one I've driven.
I don't know the exact dyno numbers but I'll get you close: 475 rwhp and around 600 rwtq. If I recall correcly he ran 6.8x or 6.9x in the 1/8 mile the only time he's been to the track with it. The mph was over 100 - not sure of the exact.
Driving that car is what led me to putting a turbo on my tpi.
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1987 Iroc 5.7 - Megasquirt II 3.0, WB O2, 3 Bar, single T70 turbo, 8 psi, Cold AC!
Also just another couple of thoughts. The 383 route certainly works and if I only wanted to be fast, I would go to that. In my case, I want my Iroc to be something I can take on road trips and drive around as much as possible. I'm still getting over 16mpg thrashing on it quite a bit with the stock 350. So my plan is to stick with 350 or 355 cubes and see what 20+ psi does.
Another way to look at it is.. 383 is about 10% more power.. so just run 10% higher boost to make up for it. LOL
__________________
1987 Iroc 5.7 - Megasquirt II 3.0, WB O2, 3 Bar, single T70 turbo, 8 psi, Cold AC!
Thanx man, I went through youre build thread, very nice. Mega Squirt is also something ill be looking into. Tell you the truth im still not sure what route im going yet. leaning more towrds the 383.
