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By 46yblock - 14 Years Ago
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A friend has suggested I get some ARP main bolts for my 322 in progress. Looked at JM's site and the ARP bolts require drilling and tapping of the 312 block for high performance use of the ARPs. So my 312 has been fully machined awaiting my assembly. Dont want to take it back to the shop, and am thinking... no racing, mild cam, balanced assembley, absolute peak rpm of 5500, that doesnt qualify as high performance use, does it? Feedback appreciated.
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By PF Arcand - 14 Years Ago
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Mike: How about just going with stk replacement new bolts? In any case be very carefull with the torque applied to the 312 blocks mains. Do not use the early factory 1956 torque figures originally published.
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By Speedbump - 14 Years Ago
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Those things lived for years, even with superchargers, with the stock bolts. I wouldn't even bother with new ones unless the old ones have been overtorqued or abused as in a spun main bearing, etc. Throw your money at something else, that bottom end was a pretty good design.
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By John Mummert - 14 Years Ago
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I would guess that 40-60% of all 312 blocks have cracks at the main cap bolt holes. IMO these cracks were caused by a combination of bolts that were too short, reduced material around the bolt hole and in some cases over torquing. I have seen stand blocks that were cracked.
This is why the bolts we supply are longer than original. Bare in mind that Ford drilled and tapped all blocks deeper and used longer bolts beginning with the 1959 B9AE blocks. Why did they do that?
Mike, if your block survived this long it will probably be okay but the longer bolts are an insurance policy.
re: New stock main cap bolts. I don't know of a source for them.
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By 46yblock - 14 Years Ago
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Thanks guys. The new absolute top rpm is going to be dropped by 500  .
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By 46yblock - 14 Years Ago
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OK, I am sold. Will be ordering some new ARP bolts this week.
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By NoShortcuts - 14 Years Ago
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One of the things that I've come away with from Ted Eaton's entries, is that dynometer tests are usually done starting above (?) 2500 rpm, because starting at lower rpm excessively loads the engine (including main bearings). The higher rpm staring point is a frustration for those of us that are stop-and-go, off-idle to road speed, generally below 4000 rpm applications. Applying Ted's info., low speed street operation of our engines may be harder on the engine's lower end than 4,000 to 5,500 rpm operation.
Adding to what John Mummert stated, Ford went to drilling the y-block main cap bolt holes deeper with the 1959 B9AE blocks and correspondingly using longer bolts. In a production/ manufacturing situation, that is a significant production change and the expense of doing this was no whim on the part of some engineer. The change had to come out of what was being reported from the field related to engine problems and from the Ford authorized engine rebuilders. Yes, the engine went into production in 1953, but as the horsepower output went up, the miles traveled added up, time went by, the rebuilding process came into play. There's ALWAYS a time lag for lesson's learned with any product...
Think of the pennies Ford saved by eliminating the y-block oil drip trough for the timing chain, the counter weight for the camshaft fuel pump eccentric, and the metal trays from under the rockerarm shafts in (?) 1957. For the automobile companies, everything is cost driven. "-Don't do it IF you don't feel that you have to do so. BUT, remember, your [i]REPUTATION is at stake, too." [/i]
Regards,
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By bird55 - 14 Years Ago
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my 2cents. I used ARP Studs, not bolts. Insurance for insurance. And I like the thought of evening out the torque load on the stud. more money 'a course.
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