Recent content by 351tom

I agree with you 100% My aim here is to quantify the possible bearing loads in the aforementioned scenario to point out the folly of such engine modifications. Knowing the torque of the starter motor, I suspect it will depend on on 3 more things; location of spark BTC, cranking speed, & the...

I think the different types of engines we are considering may account for the "different universes". Your earlier comments; indicate you have in mind either stock production engines made since electronic ignitions have been used, or engines that have been upgraded in this regard. This leaves...

Usually marketing rhetoric is used to over state the merits of a product, not to depreciate the integrity of a product, but none the less, I found a third manufacturer (King Engine Bearings) that uses terminology that may be more to your liking. They describe fatigue of the overlay (due to...

From the Clevite Engine Bearing failure analysis guide; For many years, nearly all camshaft bearings were manufactured with a lining of babbitt. Babbitt is a soft slippery material made up primarily of lead and tin and is quite similar to solder. As a bearing surface layer, babbitt...

Yes, shock loads-this seems to bring us back to the original premise; that it's not high compression that requires high torque starters, but rather ignition occurring well befofe top dead center. Back in the 60's & early 70's before electronic ignitions were available, there was no...

A lot of good points made. I found some real world data on a similar size Ford engine I was troubleshooting a while back. Along with the torque characteristics assumptions of 256bits & the observed pressures by Baluncore, I put together the following plot; the cranking speed was 185 rpm so if I...

After seeing those small torque requirement numbers, it's hard to imagine how compression could cause a starter motor to stall. Even using an extreme 14:1 compression ratio, a stock starter could easily handle it; 14:1 deg____x______y______h_____vol___psi_____force___ft. lbs 70 __...

Your responses keep leading me to very high forces being developed. Would it be safe to say that if a stock 90 ft lb starter is not sufficient to crank the engine, then a higher torque starter is not a solution because at 90 ft lbs, the engine is already incurring damage?

Ok, would I be fairly close if I took the distance from 0.5 degrees BTC TO TDC? In this case, the flywheel moves 0.10472" and the piston moves 90 millionths of an inch, so the advantage is 1163.5 and multiplied by the 1377 lbs is 1,602,139 lbs on the rod and 592,507 psi on the rod bearings.

Disregarding the battery, cables , etc, and assuming the cylinder area * pressure at TDC is just enough to load the starter at 90 ft lbs, are my original calculations correct?

Ok, let's try this another way, a stock starter motor on a Chevy 350 has 90 ft lbs of torque. For modified high compression engines, and other hard starting engines, higher torque starters are available in 160,180,200,or even 250 ft lb levels. If an engine needs more than the stock 90 ft lb...

I wasn't limiting the stall to just compression. I think the most common occurrence is due to ignition BTC causing the expanding burning charge to force the piston down while the starter motor is trying to force the piston up. The results of my calculations seem off somewhere however, because...

I am trying to determine rod bearing load when a 90 foot pound torque starter motor stalls. I have drawn the geometry in the picture below. I am figuring using a 10 tooth starter gear & a 153 tooth flywheel, so I calculate 15.3 x 90 ft lbs = 1377 ft lbs torque at the flywheel. So if I consider...