88305tpiT/A

iTrader: (2)

I am thinking about what motor I want to put in the TA when I get the money saved (a year from now) and figured Id beter start asking questions soon so I have a head start on knowing what I will do.

I was going for 500HP at 7000 Plus RPM from a nascar style bore to stroke ratio. I was thinking about a bowtie or similar block with a 4.125 bore and putting in a nascar crank from musclemotorsports with a 3.335 stroke.
carrilo rods, 240cc runner heads, havent considered pistons yet but almost certainly over 10 to 1 compression for 500HP.
I am still deciding what intake and fuel to use but I am not picky. If fuel injection would work I am game.

The questions I do have are about the cam and valve train.

I talked to a guy at the dyno shop today and he said that an 8000 rpm redline is unrealistic because the valve train would cost so much and wear out so often. I thouhgt that was interesting and so I thought I would put this to you guys to see what you think.

should I bring my RPM goal down and go with a longer stroke?? or could I get away with this kind of rpm?

BTW this would be a total toy car and not my daily driver and would be backed by a manual trans with 3.42s at least in my 3200lb car.

Thanx.
James

five7kid

iTrader: (14)

I'd say forget about HP and RPM numbers and start with a package that is reasonable.

Any 4-speed behind a high-reving engine is going to stress the drivetrain to the breaking point. Figure on a 12-bolt custom rear. Ratio can be decided based on usage and the rest of the package. Figure on suspension mods (tubular LCA's, track arm), some type of aftermarket torque arm (a Spohn with crossmember would be a good idea, since you're going to a non-factory transmission).

Okay, now the rear can handle the power and perhaps get it to the ground. About the engine...

Cubes is where it's at. Forget the NASCAR stuff (cute, but impractical - they are displacement limited, you aren't). Consider a Motown shortblock in the 400+ cube range. You'll probably need an externally balanced flywheel & damper (unless internally balanced is chosen - I believe they offer it).

AFR heads, valve train good for the cam you choose (talk to the "majors", like Comp, Crane, Lunati, for advice). Intake and headers to match the rest of the package.

You can build this to produce 500 HP in the 6000 RPM range. Will probably cost less than trying to put together a package with the used NASCAR pieces.

88305tpiT/A

iTrader: (2)

I agree with your assesment completely. The information about the rear end and suspension is especially usefull as I did not know what I would do about that yet.

I was considering the high rpm motor because I like the idea of it and wondered if the valve train would be semi streetable (i.e. not having to replace the springs every 2000 miles).

I have talked with many people that agree with you (as do I) that cubes is the way to get HP. However I like the idea of rpm for HP because it does seem more challenging, not because it is the cheapest, most reliable, or simplest way to go.

reiterating my questions:

would the valvetrain survive for a reasonable length of time in a non race enviornment on this motor?

is there a cam profile that would give peak HP on this bore stroke combination over 7000RPM while still giving 200+ ft/lbs below 2000RPM?

Thanks for any more Ideas

James

383backinblack

nascar cranks are not designed to run at lower human rpms that people run at on the street, and if they are the stress and crack due to smaller lighter counterweights.

88305tpiT/A

iTrader: (2)

ok... thanks for that input, when I call about the crank Ill ask muscle MS wether theve had any fail from vibratory stress...

anyway I just got DD2k and ran a bunch of combos and I know that the program is supposed to be optimistic and it also does not account for driveability problems related to poor atomization and vacuum but see what you think:

4.125 dart block with 350 mains
3.335 bryant crank
6" carrilo rods
Flat top pistons (havent found - probably custom)
230CC Runner 64 cc chamber dart pro 1 heads
~10.92 Compr ratio with .042 gaskets and zero piston height
Comp 280 AR solid roller 280/280 at .55 lift and 110 LSA with 1.5 RR

I ran this combo with a tunnel ram type of manifold at 1000CFM and got over 350 ft/lbs at 2000 rpm (as good as the TPI I got now) and over 500 HP from 5500 to 7500 RPM.

I was thinking that the holley stealth ram might be a good approximation to this because I have read that the runners support 300CFM and I dont think I will need that much because I am not even hitting the dart heads opitmal flow lift at over .7"

because the valve lift is under .6 and the duration isnt crazy I think that this motor could work for a light street/road race car.

but what do I know....