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

 

One question why do you want to run the engine up that high to create power. It would have no torque and would be lazy on the street.

 

I dont think it would be too bad down around 2-3K but I really dont know why you couldent get at least 200ft-lbs at 1500 while making peak torque above 4500 or higher.
in my eyes that would be as streetable as I would need for the cruising and racing I might do with it. its not like I would drive this thing to work. just take it to the strip once in awhile and road race on weekends.

is it so unrealistic to think that I could get usable torque below 2000 rpm while still getting peak HP above 7000?

 

I would definitely use a solid roller cam for that setup. Probably a comp cams XR292R. Build it with good springs and some good roller rockers like comp Pro Magnums.

 

Actually now that i think about it, that would be a cool setup. That is if you could afford all of the top dollar components that would be needed.

 

I like the Idea too...

BTW I am looking up your cam selection but the dialup is kinda sloooowwww..

{edit}

ok I was thinking alittle more duration like 265 and WAY more lift like .650 or so.

to get out of the box 240cc heads to flow well at 7000 I think you would need at least .600 lift and over 260 degrees of duration at .500

but I am not experienced at picking cams.

 

I ran that setup through DD2000 and cam up with more than 500 hp form 5500rpm to 9000rpm.

I used:
Dart Pro 1 230cc runners
Comp XR292R
Race headers
900cfm carb

 

oh cool you have DD ...

dude I have lots of specs for parts -- could you run them for me?

 

Sure name some setups.

 

im not sure what specs you need but the cam choice you made seemed to give HP that was a little high in the rpm range than what I had in mind.

how about something with a little less duration and more overlap angle like 112 Degrees??

and where was the torque peak and what kind of torque did it make under 3K??

 

Rpm HP TQ

2000 110 288
2500 164 345
3000 211 369
3500 265 397

Peak TQ 496 @5500
HP 587 @7000

 

wow that sounds great!!

why dont you try this setup...

same short block

pro topline 242cc alum heads

and a cam with 112LSA 250/255 at .500 lift with .600 total

and a smaller carb like 850

 

I changed to a XR274R and get much better lower end torque without much lose in peak power.

553 HP @ 6500 rpms
504 TQ @ 5000

 

so let me get this straight you have to pick from a list of existing grinds that DD gives you??

 

I don't have a head flow file or the Pro Lightning 242's. But i do know that you don't need a head even close to that big to make 500 hp. I think it would be way over-board. The Pro Lightning 200's can support more thatn 550hp.

 

No i can enter custom specs. But these are good cams. If i knew the head flow numbers for the pro lightning 242's i could make a file for them, and use them in dd2000.

 

ok then the dart heads are definately fine for this setup but I would like to know what a little more lift and LSA would do to flatten out the torque band and get HP peak back up to 7000 while giving the 200 ftlbs at 2000. I guess this would be a custom grind but if you can find a similar cam DD it.

 

or maybe go with 1.65-1.7 roler rockers

 

i tired used the cam specs you gave assuming a roller cam and got. Using same setup as before only changing cam.

578 HP @6500
501 TQ @5000

A smaller carb does nothing at all, maybe 5hp.

 

hmm well thanks a bunch for the info.
this really is encouraging news on the streetability of this setup but I still have to figure out how long the valvesprings would last.
and I think just from the couple of minutes spent on picking cams that I could find a grind that would make HP peak at 7K and 200ftlbs at 2K.

maybe the XR280R with .600 of total lift.....
or better yet the 300AR spec--> 300/300 adv. 255/255 @ .500 .575 max 110LSA

 

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....

 

One thing to remember is I think DD2k is off on tq figures. I seen an article in a magazine on this once.

Also another thing to remember is DD2k doesn't at all figure in cfm of a carb being too big. So in theory I could make a 305 with 1000cfm carb and it would work fine on the program... while that is way to much for a irl motor. They figure the carb you pick will run perfectly on that motor.

Also if you read the tutorial, like 136 pages long... not much of us have that much time... but anyways they say you don't make any difference in tq with longer rods such as 6.0 instead of 5.7 inch rod... just another thing

I called into Comp Cams about getting a cam for my new motor:
383
4340 forged and balanced assembly
trw flat tops 10.7:1 comp
210cc AFR Race Ready 2.08 and 1.60 valve heads
victor jr intake with 2 inch HVH spacer and a 750 demon on top

They said would probably need xr274r but I'm thinking about calling back in and seeing if xr280r will work better. With 1.6 rockers that gives me a .608 int and .614 exh lifts.

I think a 3k stall would work fine on the street. I'm running a 9 1/2 inch 2400 stall right now with my peanut cam and 3.27 gears in a daily driver right now.

 

yea that all makes sense.

I have a while to go before I build this motor anyway so I will probably end up getting several tens of opinions on it before I spend the first dollar.