My knowledgeable Pontiac buddy is telling me that they changed the keyway position on cranks a few degrees in the early 70's to affect the cam timing for emissions purposes. Therefore, most aftermarket timing chains are set up for the later cranks so cam timing will be off when used on 60's cranks. Does this sound plausible?
Doesn't sound right to me but its always a good idea to check a cam timing when you install it anyway just to be sure it was ground properly and it's installed where you want it.
Here's my issue: I bought a a 428 from a friend that was supposed to be a screamer. The timing chain was shot so I replaced it. I'm running the motor now and it seems to have no top end and my friend is telling me the the timing chain story.
Here's my issue: I bought a a 428 from a friend that was supposed to be a screamer. The timing chain was shot so I replaced it. I'm running the motor now and it seems to have no top end and my friend is telling me the the timing chain story.
If the heads and shortblock are good, sounds like the cam may be too small. Do you know what cam you have ?
A 428 would need at least 220 dur @ .050 lift, in order to make much power above 5000rpm. Mid 220's would make little more upper end power. And, 230 would make even more. Probably don't need to go any bigger than an 041 clone. I like to use Rhoads lifters with these 041 clones.
If you don't like Rhoads lifters, Howards has a version with less adv duration, which will work better, with reg type lifters. Should make a good 428 cam.
My knowledgeable Pontiac buddy is telling me that they changed the keyway position on cranks a few degrees in the early 70's to affect the cam timing for emissions purposes. Therefore, most aftermarket timing chains are set up for the later cranks so cam timing will be off when used on 60's cranks. Does this sound plausible?
That's what I thought too. But I thought I'd throw it out to this group and see what would come of it. I have a few old timing chain sets. I might try to compare 60's vs mid 70's to see how the keyways line up
Think about it If the keyways in cranks were different, there would have to be different timing covers or balancers as well because the timing marks would be off.
To quickly verify this, just check top dead center at the timing mark.
I used Rhodes lifters and the one thing they leave DONT tell you is how much noise they make. Then try to ask how the 60 lb HV oil pump verses a stock or 80 lb SD oil pump affects bleed down rates and you will get no answers... Or 30 weight oil verses 20-50. The car ran good, the noise for me was unacceptable.