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11:1 ford 302 compression

23363 Views 13 Replies 5 Participants Last post by  1968poney
i have a tread about what octane i should use but heres a kicker the whole engine is a stock 1980 block with 1966 289 heads will the compression affect the internals of the engine like the rods crank bearings or pistons heres a list of exact whats in the 302

Stock cam
Stock flat toped pistons with valve reliefs
Stock rods
Stock crank

Engine bore is .030 over
Mains are .010 over
Cam is .010 over

The heads have a chamber of 54.5cc

a bonus the stock 250 289 302 starter doesnt have enough power to get it turning to start but i got it too sounds great but only had it running for a couple of secounds and turned it off. is there any strenght concerns regarding the fact every thing is a stock 1980 302 i believe i dont know if for sure it is fully stock but would it be fine with 11:1 if it is all stock?

Thanks Tom
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In your calculation, did you make an allowance for the valve reliefs. If you didn't, the calculated compression ratio will be higher.

The fact that the starter has a problem turning the engine over makes me wonder if the starter's performance is being affected by a low amperage output from the battery or the wiring isn't heavy enough to deliver the amperage to the starter. The ground wire to the battery's negative post needs to be at least the same size as the positive wire. Is there a good ground connection between the body and the engine? If everything is in order with the starter, it may be that the compression is high or the timing is too far advanced.

You at first mentioned that you had stock pistons then you say that you have the forged pistons. I would be hesitant in using stock cast pistons with a high compression ratio. I hope that you have the forged ones as the cast pistons won't hold up in my opinion.
Another question, did you account for the thickness of the head gasket? Most head gaskets are between .039" and .041" thickness.

I think that I would pull all of the spark plugs to see how the engine turns over. There might be a binding in the rotating assembly.

The old stock starters used an electro magnet system for the field magnets where the newer factory starters and aftermarket performance starters use permenent magnets and reduction gears. If the engine rotates OK without the plugs, try one of the newer small starters. They don't require as much amperage because of the fact that there isn't those electro magnets drawing a load on the battery. It should turn over an engine with high compression.

Watch out for too much timing advance with 93 and high compression and cast pistons. It won't take much to blow a hole through the top of the piston. Are you sure that you want to use your present heads?
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