[Forrest]

hey guys, I`m wondering what the perf. gain is if I go to 1.60 from a 1.5 (rockers), I have a 455 bored 30 over with small chamb.( 0 decked) about 9.8 comp. 6x heads street strip ported pol. , 2.11 int. and 1.77 ex, ferrea valves, 92 cc( I think, can`t remember, but I`m sure we figured it then to be 9.8 comp.)), w/ trw forged pistons, edel. rpm w/ holley 850 dbl. pump, ultradyne solid (@50 dur. 247 int, 255 ex. gross valve lift 525 int, 540 ex. lobe sep. 108 ,msd 6al , billet dist. , in a 70 gto w/ muncie m20 / 3.73 rear,right now I have 1.5 harl. I had 1.65 harl. after about 500 miles a ex. valve bent (just one), Don`t know if it was caused by too much lift , so I went to 1.5`s, ( put about 1000 miles since, no problem)) . I would like to go to 1.6, but is there going to be that much of a gain. I mostly show the car, and drag it not often ( 3 times a year) not a daily driver, might drive 2 times a week, just to store or shows ect,, ran 110 in the quarter, times sucked ( no slicks) would the 1.6 be beneficial at all?? thanx for your input Forrest

[Forrest]

hey guys, I`m wondering what the perf. gain is if I go to 1.60 from a 1.5 (rockers), I have a 455 bored 30 over with small chamb.( 0 decked) about 9.8 comp. 6x heads street strip ported pol. , 2.11 int. and 1.77 ex, ferrea valves, 92 cc( I think, can`t remember, but I`m sure we figured it then to be 9.8 comp.)), w/ trw forged pistons, edel. rpm w/ holley 850 dbl. pump, ultradyne solid (@50 dur. 247 int, 255 ex. gross valve lift 525 int, 540 ex. lobe sep. 108 ,msd 6al , billet dist. , in a 70 gto w/ muncie m20 / 3.73 rear,right now I have 1.5 harl. I had 1.65 harl. after about 500 miles a ex. valve bent (just one), Don`t know if it was caused by too much lift , so I went to 1.5`s, ( put about 1000 miles since, no problem)) . I would like to go to 1.6, but is there going to be that much of a gain. I mostly show the car, and drag it not often ( 3 times a year) not a daily driver, might drive 2 times a week, just to store or shows ect,, ran 110 in the quarter, times sucked ( no slicks) would the 1.6 be beneficial at all?? thanx for your input Forrest

[Big Injun]

Nice combo. Firstly, I like to get as much lift out of the cam as possible with 1.5 to save on valve train wear. But I too run 1.65 rockers so that I can get near 700 lift on my race motor.

When you had the heads done, did your shop clearance the push rod tubes for a higher ratio rocker? Also, you stated that you mainly show the car. So, if you do not have the clearance for the 1.6s, mainly show the car and don't already own a set, I would go with the 1.5s

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www.PontiacDragDays.com
Dave "Big Injun" Anderson

[Forrest]

thanx Dave, the pushrod guides were clearanced for the 1.65`s, ( thats what I had in there before I went to 1.5`s, I bent that ex. valve w/ the 1.65`s I think, not sure if the 1.65`s caused that or not, !) do you think I will have valve to piston clearance problems with the 1.60`s, and what performance gains are there? any one please resp.! thanx alot for your info Forrest

[jnyeager]

Forrest, it is my personal opinion (having researched your engine combo because it is the one I have) that you won't gain much with the higher ratio rockers. The improvement in breathing will only help if you have the induction to supply it AND your current cam is insufficient. But with this combo, that's not the case. For example, I asked Jim Hand this exact question and he said that with his engine (much like mine and yours) that the 1.5 to 1.65 swap only gained him 1/10th in the quarter. (I hope I recall his answer correctly).
Also, I don't know of anything other than a piston that's going to bend a valve, so I would say that your 1.65 rockers did cause you to hit the valve. Would 1.6s? I can't answer that one.
Good luck with the motor!