Question About Compression And Heads

Cmc3567 · Nov 16, 2016

I have a 97 4.6 NPI block with all forge internals it's the eagle rotating assembly from mod max with the -17 piston dish and I think it said compression would be 8 7 to1 and wanting to get the pi twisted wedge heads but not sure how much it will bring up the compression I want to run on pump gas this is my daily driver and using a Kenny bell super charger for induction and want as much boost as possible with out blowing the motor does anyone no what the compression will jump to and the most boost I can throw at it thanks in advance

Deleted member 38176 · Nov 18, 2016

8psi max. Your compression is around just under 10:1 8.7? Ummm no. Dont worry about the amount of boost, worry how much power it makes. I wouldn't go over 400rwhp

Cmc3567 · Nov 18, 2016

Should I swap out pistons to drop compression down my goal is 500 to 600 hp what would need to be done to reach that r is it not possible thanks

squeak93 · Nov 18, 2016

Don't worry about the 400 hp rule if you have a forged rotating assembly.

Hell I'm going to run 10.5 and 12psi on a npi block. For how long is the question.

Cmc3567 · Nov 18, 2016

squeak93 said:
Don't worry about the 400 hp rule if you have a forged rotating assembly.

Hell I'm going to run 10.5 and 12psi on a npi block. For how long is the question.

So even with fully forge internals I'll be on borrowed time with 12 to 15 pounds of boost

Cmc3567 · Nov 18, 2016

Cmc3567 said:
So even with fully forge internals I'll be on borrowed time with 12 to 15 pounds of boost

Gearbanger 101 · Nov 18, 2016

Cmc3567 said:
So even with fully forge internals I'll be on borrowed time with 12 to 15 pounds of boost

No, 12-15psi on a forged short block will be fine. Though I doubt you'll make 500hp....let alone 600hp on pump gas with a 2.1L Kenne Bell.

Do you have some sort of goal you're shooting for that you believe requires 5-600hp, or do you just like the way it rolls off your tongue? If you truley are set on those power figures and insist on sticking with the screw compressor, you'd better abandon the 2.1L and go right to the 2.8L race set up. Also, you are aware at those power levels, you're going to have to completely revamp your fuel system and the rest of your drivetrain is going to cry uncle in a hurry, right?

Now....a more realistic goal like 400-450hp will keep you in pump gas ranges, allow you to stick with the 2.1L blower and if you can drive at all, will get good for low-12's/high-11's all day at the track. And with a forged rotating assembly should live a long, long time. FWIW, those power levels with traction will have you going fast enough to bag a new Corvette in a 1/4-mile.

Cmc3567 · Nov 18, 2016

Iit possible to get 5 to 600 hp out of engine will do what I have to to h

Gearbanger 101 said:
No, 12-15psi on a forged short block will be fine. Though I doubt you'll make 500hp....let alone 600hp on pump gas with a 2.1L Kenne Bell.

Do you have some sort of goal you're shooting for that you believe requires 5-600hp, or do you just like the way it rolls off your tongue? If you truley are set on those power figures and insist on sticking with the screw compressor, you'd better abandon the 2.1L and go right to the 2.8L race set up. Also, you are aware at those power levels, you're going to have to completely revamp your fuel system and the rest of your drivetrain is going to cry uncle in a hurry, right?

Now....a more realistic goal like 400-450hp will keep you in pump gas ranges, allow you to stick with the 2.1L blower and if you can drive at all, will get good for low-12's/high-11's all day at the track. And with a forged rotating assembly should live a long, long time. FWIW, those power levels with traction will have you going fast enough to bag a new Corvette in a 1/4-mile.

Cmc3567 · Nov 18, 2016

Cmc3567 said:
Iit possible to get 5 to 600 hp out of engine will do what I have to to h

Don't mind revamping fuel sys and drive train if I go with the other Kenny bell 2.8 will I be able to run pump gas my goal is a 10 second car thanks for the input

Gearbanger 101 · Nov 18, 2016

Cmc3567 said:
If I went with the Kenny bell 2.8 will I be able to run pump gas don't mind revamping fuel sys and drive train already expected that my goal is 10 second in a quarter

It can be done.....but you're going to have to sink a lot of time and money into the suspension too. Count on spending somewhere in the $15K+ range when you're done....and that's assuming you've already got the forged bottom end.

Honestly, if you want to go fast down the track in a 2V, you would probably be better off doing it with a big centrifugal blower. The Screw blowers are awesome on the street, but seem to require a lot more work to get them to go as fast down the track....especially if you're trying to do it with pump gas. A handful of guys have gone 10's in 2V car's with screw chargers....but they're few and far between and have had to spend a lot of money to do so.

You seem like a real novice at this and I get the impression you're only spouting out figures because 10's are the popular number to run. Have you ever been in a 10-second car? How about an 11....or even 12-second car? Not what one of your friends tells you is a 10-second car because "riceworldweekly" says if you do this, that and the other to your Honda, it'll run 10's....but a real, certified 10-second car. It would scare the out of you.

Cmc3567 · Nov 18, 2016

I've had a 12 second fox body before and I no the work that needs to be done to suspension the rear of the car is just about done already have all internals still have to front end to do and I do go to the track rarely most of my races or on the street and the cops love me not new to racing but new to the supercharger world 15 k is in my budget already at almost nine thousand with heads internals and machine work time and money I got

Cmc3567 · Nov 18, 2016

I truly thank you for your insight guess I'll go for 450 seems I'm just about there but I don't have the NPI heads I have a set of trick flow twisted wedge heads haven't gotten the cams yet have the stock pi ones but was wanting something a little more aggressive and recommendations thanks again u was the first guy that broke it down for me and I thank you

Gearbanger 101 · Nov 18, 2016

Like I said.....go with the 2.6L/2.8L if you think you're going to be pushing it beyond 450hp at some point now, or later, but the 2.1L should get you there, or really close on pump gas if you spin it hard enough. Once you get up into the 475+hp range with a 2V GT....think start getting expensive, in a hurry.

In any case, 450hp is still enough to get you into the low-12/high-11 second range.

Cmc3567 · Nov 18, 2016

It definitely has to be pump gas I drive it everyday would be satisfied with 450 so you think The 2.1 would get me there are should I upgrade it my internals are going to be overkill supose to handle up up to 700 hp

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