351 w boss not running like it should

jamesjohner

jamesjohner

New Member
Joined
Apr 9, 2010
Location
Newport, NC
Ok so I've got a 351w with Cleveland v2 heads lifted boss intake, I believe a .492 cam(not exactly sure on the cam), and a 600Cfm edelbrock carb with a point ignition. It's runnin good but I doesn't seem to have the balls that it should have. Any suggestions on what it may be? Timing seems to be accurate until it hits about 4000 rpm then runs like crap.
 
Are the heads and short block stock? If so then you would be better of with a mild cam, dual plane intake and keep the 600. If you have high compression and ported heads and larger valves, yout intake and cam are good and that carb is way to small like haptoad said.

Do you have a vacum or mechanicel advance on the distributor? That cam maybe causing trouble if it's vacum advance.

I've built a few motors. A good balanced "package" works better than throwing "big" cams or intakes on if everything else doesnt match. It will actually hurt preformance in most cases.
 
mbrooks said:
Are the heads and short block stock? If so then you would be better of with a mild cam, dual plane intake and keep the 600. If you have high compression and ported heads and larger valves, yout intake and cam are good and that carb is way to small like haptoad said.
Do you have a vacum or mechanicel advance on the distributor? That cam maybe causing trouble if it's vacum advance.
I've built a few motors. A good balanced "package" works better than throwing "big" cams or intakes on if everything else doesnt match. It will actually hurt preformance in most cases.
Click to expand...

Even if the rotating assembly was stock you have to run custom pistons for the canted valued heads. Your not going to find to many intakes that will work with this application. 492 lift isn't that big of a cam even with the size of stock ports and valves. 4v heads have ports you can almost stick a 12oz drink can in. It's starving for gas.
 
HaPtOAD said:
Even if the rotating assembly was stock you have to run custom pistons for the canted valued heads. Your not going to find to many intakes that will work with this application. 492 lift isn't that big of a cam even with the size of stock ports and valves. 4v heads have ports you can almost stick a 12oz drink can in. It's starving for gas.
Click to expand...
so maybe putting a electric fuel pump on it instead of the stock mechanical one will help out? or are you basically saying that it needs a bigger carb?
 
mbrooks said:
Are the heads and short block stock? If so then you would be better of with a mild cam, dual plane intake and keep the 600. If you have high compression and ported heads and larger valves, yout intake and cam are good and that carb is way to small like haptoad said.
Do you have a vacum or mechanicel advance on the distributor? That cam maybe causing trouble if it's vacum advance.
I've built a few motors. A good balanced "package" works better than throwing "big" cams or intakes on if everything else doesnt match. It will actually hurt preformance in most cases.
Click to expand...
the distributor is vacuum advance. Would you happen to have a guess on how much vacuum its supposed to have?
 
jamesjohner said:
so maybe putting a electric fuel pump on it instead of the stock mechanical one will help out? or are you basically saying that it needs a bigger carb?
Click to expand...

A stock fuel pump should pump enough fuel to the carb, you just don't have the CFMs to keep up with what the motor needs. Yes to the the bigger carb.
 
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