Tim99GT

Ok, So i have been debating for about 2 months on what heads i wanna run on this motor and i think i just made up my mind!
I believe i am going to be ordering a set of TF 38cc heads tomorrow!!

Now, i need yalls help on something.. So when i ordered my MMR 900 s/b like 8 months ago, the rep i was talking to at the time, told me to go with 8.5:1 compression. Well, now i am wishing i would have never ordered it. The more reasearch i do, the more i find out that the car will be a dog without boost at 8.5:1 comp.. (I was a noob then)

Anyway, I think i found my cure. I've been doing some research and have come to the conclusion that i am going to go with the 38cc TF eads. These heads should raise my compression to roughly 9.1:1 comp!!!
This means no more 100 hp mustang driving on the street without boost! It will be less than stock hp #'s none the less, but i dont believe it will be too bad.
So i am excited as hell!! I am going to be placing my order tomorrow and hopefully get them in soon so i can start to assemble this motor.

Anyone running 9-9.5:1 comp??? how does the car feel under normal driving conditions?

Can anyone give a accurate prediction on hp from a 9.1:1 comp withouot boost?

amoosenamedhank

Well that's not that far off the stock compression ratio... but what I'm confused about is why it matters.... Look at it this way... who cares how fast your car is out of boost? And when you do boost, you are in it right away. Typically centrifugal supercharged cars need a little more compression because we have to wait for boost. But you positive displacement guys get it right away. So you can get away with lower compressoin.

Sxynerd

8.5 compression is what anyone with HIGH boost normally runs. Being that you are a KB car the 2.8 should be the perfect blower for it. Now, the the smaller blowers like Centri S trims like mine would barely have enough "Umph" to push it into the high numbers but the T-trim, N2k and the like would be great.

amoosenamedhank

+1 plus with the lower compression you can get away with running more boost on pump gas.

CAMDUP

Common Ford Modular cylinder head combustion chamber sizes
Caution:This is only a guide. You should always confirm your actual combustion chamber volume.
2 valve PI 44 cc ( OEM 1999 and newer)
2 valve NPI 51 cc (OEM 1992 to 1998 )
2 valve PI D.S.S. match port 44 cc (1999 and newer)
2 valve PI D.S.S. Full CNC Port 50cc (1999 and newer)
3 valve Ford Racing CNC ported 50 cc
4 valve Ford Racing CNC ported 52 cc
check out this chart (scroll down)http://www.dssracing.com/ProductDeta...V&Show=ExtInfo

i think 38cc may put your compress. way too high

Tim99GT

Well here's the delima guys:
I will be running right around 18 PSI
Now according to Tim at MPH, he said " We never build motors with 8.5:1 compression" , " we build them with 9.2:1 - 9.3:1"
Now i know i wont be able to make high boost with pump gas with a higher compression ratio, but i will make more hp per PSI at a 9.1:1 vs a 8.5:1.

And as far as the KB goes, Its a big blower. Its either going to be no boost (lets say 8.5:1) making 200 rwhp or in boost making 550rw+.
I just dont know how friendly this would be on the street. Now if i go to say 9.2:1 comp, i will have alittle more hp/tq without boost for normal driving and still be able to pull off 550+ at the wheels WOT.

I'm really confused...
I talked to Tim for a good while today, along with Jim Cushman, and ricky at MMR, and they all agree with bringing the compression back up alittle.

I just dont want to end up with a slug at normal throttle, then when i mash it, it turns to a beast.. if that makes any sense?
IDK...
Tim said that with this blower, and his KB cam/tune, he can get this car to run like stock under normal driving conditions( which is what i want) and turn into a 600rw beast under WOT. This is with the motor being at his normal 9.2:1 build compression.

amoosenamedhank

Well if all of those guys say to do it... I'm going to say go ahead and believe them. Just off of a hunch, they are probably more qualified then myself.

Either, very excited to see your build completed.

Tim99GT

Well according to MMR, the 38cc heads should bring my compression up by .600
so 8.5 + .600 = 9.1:1 compression.
But i am almost positive he told me that the 99's had 42cc heads.. ?
My brain hurts

And if i did the 44cc heads, MMR said that it would lower the compression down to about 8.2:1 - 8.3:1 from 8.5:1.

Tim99GT

ok guys,
A little motor info for you. ( might help in the compression guessing)

MMR 900
-23cc flycut dished pistons
built to 8.5:1 comp
bored .20 over

so this^ + 38cc heads would = what comp?

Mustang_NTriangle

very interesting and you got me thinking about my compression ratio for my setup when I buy my rotating assembly. I have stock heads but a v2 sq.