Since the 351 is causing trouble possible due to some lifters. Our mechanic will have to break it apart to see why compression is low at idle. While it is apart I was thinking of putting in a meaner cam. The current cam is an edelbrock cam 1500-6500 range,Lift @ Valve .496'' Intake/.520'' Exhaust,Duration @ .050'' 224° Intake/234° Exhaust. Would a bigger cam slip right in without having to buy extra parts? Also what cam would you recommend?

the heads i have are some edelbrock rpm. I was also thinking of either porting them or buying some new ones. Would porting make a big difference, or should I just buy some better heads?

 

What is your valve clearance right now?

 

Keith Black #648-KB151.030

351W Performance Piston, .030'' Overbore
Piston Dia.: 4.030''
Piston Top: Flat Top, 2-Valve Reliefs, Neutral
Comp Ratio: 11.5:1 w/55cc Heads, 9.7:1 w/69cc Heads
Rings: 5/64'', 5/64'', 3/16''
Priced Each, Sold as Set
More Details

 

170cc Intake Ports
60cc Combustion Chambers
2.020'' Int/1.600'' Exh Valves
1.460'' Valve Springs, .575'' Max Lift
edelrock rpm heads

 

Spend the money on porting the heads. Your going to get better numbers on working what you already have instead of buying new ones.

 

Without knowing this answer, who knows if you have room for a bigger cam...

 

Your current set up is pretty potent and as you go up from there, you will start to see streetability drop off. The other option is forced induction, but your cr is already pretty high.

The only way to really know is probably more work than you want to do. To know for sure, remove one head and place clay on the valve reliefs. Don't be shy, place about 1/2" x 2" on both reliefs (intake and exhaust) on one cylinder only. Reinstall the head and replace the valve springs with these checking springs: http://store.summitracing.com/partde...5&autoview=sku

These protect the valves and pistons from contact. Rotate the engine 360 degrees. Remove the head and check the clearance based on the impressions left in the clay. If you determine that you can go bigger/longer you will also need to check your rocker geometry and perhaps order different push rods to keep the rocker tip centered over the valve stem. Good luck!

 

I saw a neat trick recently to check valve clearance...2 pieces of teeny tootsie roll candyt instead of clay. Warm them up in your pocket before and leave the wax wrapper on. After removing them, place in freezer for 5-10 minutes to get accurate measurements without deformation. Afterwards, you have a sweet snack.

 

How much money does a good port job run? Does this raise the compression any?

 

No it doesnt raise the compression any. but it really depends on the machine shop doing the porting. The place that did my motor wanted about 800 for head porting. Too steep for me..

I agree with keeping the RPM setup you have. Thats a great streetable motor. What intake and carb are you running? Do you have headers? what size/type of exhaust? You may just need to add a couple of things or a good tune to your carb.. If you are using the Rpm heads and Cam, then you are good. You should run the same intake or the RPM Air Gap for the cooler air/fuel charge.. and probably a 700-750cfm carb. Whats your compression?

What are all the specs of the motor?