Thread: 325H.P.307 help me with specs.

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1971 307 procomp 2.02 1.60 64cc. howards 465/485 flat tappet cam,KB flat top pistons.wondering about deck hieght and valve clearance.any info would be help.

Possibly the biggest problem will be finding pistons with the proper compression height of ~1.675". Fewer and fewer manufacturers are making pieces for the 3.875" bore block. Have you checked the valve to bore clearance by sitting a head on the block and having a look-see from underneath? You need to be sure the valves will clear the bore. I would not build this combo. I'd find a 4.000" block....matter of fact I'd find myself a rebuildable 350 core to start with, like maybe a Gen I roller motor from a '96 to '00 Chevy truck or van. RPO code L31, badged as 5700 Vortec. Call around and see if you can find a rebuildable L31 short block to use your heads on. Call up the place you got the cam and see if you can exchange it for a L31 hydraulic roller cam when you have all your other parts figured out. It's just a really bad idea anyway, to use a flat tappet cam in today's environment.

The other thing is that you have painted yourself into a corner by purchasing the cam before you know anything about the static compression ratio. The camshaft should be the very last thing you buy for the motor, right after choosing the proper torque converter and rear gear.

Agreed 2.02 intakes on a 3.875 bore block is a bad idea. Even if you notch the top of the bore for valve head clearance the valve is extremely shrouded. Even 1.94s are close and shrouded. If you are locked into the 307 take a look at 305 H.O. heads. You could use something like a Manley Street Flow valve with the necked down stem just above the valve head to gain some flow.

If you are still just building this engine on paper go shopping for pistons first to see if you can get some decent flat tops. Cast would be just fine for a mild street engine. Then calculate your static CR by using the chamber volume and the head gasket volume to determine what deck height you will need to get in the 9-9.25 cr area. After that match the cam to your cruise rpm at highway speed and you will be pretty happy.

Tom

Puttin' Perfume on a Pig...307 Tech?!
This is the info I used putting my 38,000 mile Heinz 57 1968 307 together.
Stock block & guts, w/a stock 327 Crane Cam, late 80's model 305 heads, stock 327 4 barrel intake w/a Quadrajet carb.

HERE's another post that is on the 67-72chevytrucks.com website...joe


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