high performance heads on 289

[calpolymustang]

has anyone put aftermarket heads on a 289 with 2-barrel pistons (9.3:1)? im looking into 1.90 int and 1.60 ex (i like the numbers on the AFR 165s), but im worried about piston clearance with my cam. i would really like to add full-roller 1.7 rockers, but that would bump my cam lift to .519". maybe i should stay with 1.6 since the 1.90 intake will be more likely to hit than the stock valve

please let me know, and if you could, state your cam lift and valve size
thanks

 

[D.Hearne]

You shouldn't have any piston clearance issues even with a .519 lift. I'd be more concerned about dropping the already low comp ratio from 9.3 to 1 to any thing lower with the typically larger chambers that the aftermarket heads have. Try to get a set with 58 cc chambers, then have them milled to get them closer to the 289's 53-54 cc chambers.You really need to bump the ratio up with aluminum heads,not reduce it.

 

[rbohm]

with the 1.90 intake valves, you should have plenty of clearance untill you get over .500 lift. and D's right, get the smallest chambers you can when ordering the heads.

 

[calpolymustang]

AFR said they'd machine them to 54cc

 

[D.Hearne]

Most of the time, it's not the actual lift that gets the piston close to the valve, it's the duration or timing on the lobes in relation to the piston's arrival at TDC on the exhaust stroke. Usually a higher lift is accompanied by a longer duration especially in a flat-tappet cam.