289 compression woes

[68RustBucket]

i have read and understand the issue of the 289's low compression. i have also determined that it'd be a fun idea to make a peppy little 289 instead of going with a 302, 351, or stroker. so here's what i've learned so far ...

stock heads were 54cc, and provided about 8.75:1 compression. that is relatively low, especially for such heads.

for a significant increase of power (300+hp), aftermarket heads may be required. on this note, 58cc is the smallest combustion chamber i can find on an aftermarket aluminium head. this is going to provide even less compression. 289 heads can be ported a decent amount, but would it be worth it?

I need to know how (including milling options) i can get the compression of my 289 up to around 9:1, if not more, using flat top pistons and aftermarket heads (if deemed necessary). as mentioned before, milling is an option but i'd like other suggestions if there are any. i have a thought on the rest of what the motor will be, so if more info is required just say so. thanks fellas

 

[tylerrocks]

Get pistons built for the CR you are looking for. Milling heads can work but I think (THINK) that you can only get about .5 increase in CR. You could also deck the block.

Tyler

 

[steel1212]

I have the 54 hi po heads on my 302 and I have flat tops giving me about 10.3:1 compression. They have also been ported to give me slightly better flow than gt-40 heads so they aren't to bad and I'm sure I'll get into the 12s N/A with them next year.

 

[silverbluebp]

I built my 289 using stock crank, rods and heads. Alot of thought and research went into the package as a whole. I also wanted it to pass tech specs for any vintage racing clubs across the U.S. By decking the block and milling the heads I ended up with 10.5:1 compression.
If you go to my website, page 2 has the details of what I did.
http://www.cardomain.com/ride/667160

It's a Helluva ride

 

[iskwezm]

my buddies dad built a 10.5:1 289 with AFR's and it made 445 on the dyno,i dont know the rest of the specs,but it sounded wicked

 

[LMan]

what a sweet car, sbbp. Wish mine looked that nice on the track!

 

[68RustBucket]

ok, so what i'm learning is that lots of guys with 289's kept the original heads and worked them pretty good. it seems that my desired compression isn't out of reach at all.

what needs to be done to the original heads to get the most out of them?

what would need to be done to get my desired CR with AFR165's or equivelant?

 

[fasttback]

"stock heads were 54cc, and provided about 8.75:1 compression"

From my understanding the 289 heads w/ 54cc provides roughly 9.3:1 in the 2V Mustangs and 9.8:1 in the 4V 289 Mustangs. The difference was the dished pistons vs flat top.

Years ago (if I can recall correctly), I switched my 289 heads with 351 W 60.4cc heads and calculated roughly 9.0:1 with flat top pistons in a 306 motor.

There are also computer programs that allow you to calculate compression ratios, but you will have to know volumes of everthing (piston +/- cc, head gasket cc, cylinder displacement cc, and combustion chamber cc. etc.).

 

[steel1212]

use THIS it will get you in the ballpark. If you have flat tops add about 5 to the combustion chamber size due to the valve reliefs and it should get you there.

 

[68RustBucket]

thanks a ton fellas. more responses than i expected, which is wonderful. i think i've got all the info i need, just have to make the right decision on heads depending on if i can find a reputable machine shop or not