BBC 454 PTV ISSUES with AFR heads
11-15-2010, 11:45 AM
#1
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BBC 454 PTV ISSUES with AFR heads Hi all,
I have PTV issue with BBC 454 and AFR heads. I checked using solid lifters and pistons hits the intake valve....
Please tell me what is wrong..can't figure what it is
I have eagle rotating assembly
4.00 crank
6.135 rods
22.00 CC dome pistons with two valve reliefs
Heads are afr 325 with 119cc chamber.
cam is 250/256 0.588/0.593 flat tappet tried smaller cam still hits same way.
Tried to advance and retard the cam with no changes.
PR's are 9.350\8.380
Please guide me.
I have PTV issue with BBC 454 and AFR heads. I checked using solid lifters and pistons hits the intake valve....
Please tell me what is wrong..can't figure what it is
I have eagle rotating assembly
4.00 crank
6.135 rods
22.00 CC dome pistons with two valve reliefs
Heads are afr 325 with 119cc chamber.
cam is 250/256 0.588/0.593 flat tappet tried smaller cam still hits same way.
Tried to advance and retard the cam with no changes.
PR's are 9.350\8.380
Please guide me.
11-15-2010, 02:27 PM
#2
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Is the side of the valve hitting the side of the valve recess in the piston? The valves in those heads must be bigger than 2.19" diameter. Maybe they aren't in the stock location either? I can't see that low of lift (for a big block) causing issues IF the valve reliefs in the piston are wide enough for the valves. I have similar lift and duration in my 489 with 20cc domes and the heads have been milled a bunch. My valves are only 2.19/1.88...I have over .100" on the intakes and exhausts.
11-15-2010, 03:12 PM
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I'm also at a loss here. It only hits the valve relief boundaries.
I think my problem is from the heads because with this cam valve will reach end of the valve relief.
Also what got me confused is the issue comes with intake valve which is having less duration and lift while having plenty of clearance at exhaust side not evern touching the clay.
May be I should fly cut?
I think my problem is from the heads because with this cam valve will reach end of the valve relief.
Also what got me confused is the issue comes with intake valve which is having less duration and lift while having plenty of clearance at exhaust side not evern touching the clay.
May be I should fly cut?
11-16-2010, 01:14 AM
#4
If the AFR heads valves are larger than the 2.19" GM rectangle port head valves, they wont fit into the pockets on top of the piston. You can have the pistons valve reliefs machined to a larger radius to fit. Also I would want to have at least .080" PTV clearance.
