AZBelvedere

This is my 1st post.

I recently bought a 66 Belvedere with a 360 magnum that has a distinct knock in the motor. I'm trying to figure out exactly what kind of performance I'd have if I rebuilt it. Here is what I know so far:

360 Magnum bored .30 over
dished pistons (don't know compression or brand)
stock spec crank and rods (not sure of brand)
Cam is Hughes roller
duration: 222 intake / 228 exhaust
lift: 510 intake / 510 exhaust
Re-worked cast iron heads 2.02 / 1.70 (don't know cc)
rockers: 1.6 roller
Lifter are quick bleed-off hyd roller
Eldelbrock RPM Airgap / 750 cfm Demon

So far, the top end looks to be in good shape, so I think my problem may be a rod bearing. This car will be used as a street rod cruiser, not a drag car. BTW, this is my first Mopar and my first roller motor rebuild.

Chuck

theomahamoparguy

I will guess about 400 to 425 HP IF (a big if) you get the combination right. This includes maximizing the compression for the gas and then finding the perfect grind cam that wont degrade the compression while running. (this is known as dynamic compression) the cam and piston choices are key players in this equation. The roller cams are more forgiving in terms of streetability because of the rapid rise possible with the roller design.
Of course good quality engine building practices are important too. Try to figure out why the knock is happening and how to prevent it.
This all can take a bit of learning to get right but you have a good source right here. Good luck and most of all enjoy the MOPAR experience.
......it can get addicting...........

AZBelvedere

Is there a way to figure out about what compression the dish pistons produce. I don't have a compression check tool and I already have the top end of the engine apart. Would you know if flat tops be a better choice?

theomahamoparguy

One way to get a rough idea is to do some measuring. Measure how far down in the hole the piston is. then measure the depth of the dish and its diameter. Once you get those measurements, you can determine the cc's of the dish and the cc's above the piston. there are some goob compression ratio calculators on the internet (google). Keith Black has one. Usually the combustion chamber volume for a 360 is about 71cc. (slightly more sometimes)
Figure the gasket height at .039 compressed for fel pro's. now all you need is the stroke (3.58 for a 360) and the bore diameter (4.00, or 4.030 etc.). Enter all this info in the calculator and hit the button. It does all the math. Usually a 360 with dished pistons will be about 9 to 1. (just be glad your not working with a 318. Harder to make compression with a short stroke crank). By the way you dont need a micrometer, you can use feeler gauges and a good straight edge to get the measurements of the dish/deck height.