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Needing new bolts for heads and main caps

Posted By one piece at a time 2 Months Ago
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one piece at a time
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I am needing new bolts for heads and main caps for 292 block. Talking to Ted he said the ARP bolts was overkill. He says get a good grade 8 bolt instead. A 4 year old post on this site indicates that caterpillar Grade 8 were the best to get. Does any one know what the part numbers would be for Cats bolts and washers or What size bolts do I need to ask for as mine are with the block in the machine shop to many miles away to go measure if I can help it. Any info is appreciated. Thanks 
Duane 

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My '55 Merc chassis parts catalog lists the long head bolts as 7/16"-14 X 4 1/16" , qty 10, and 7/16"-14 X 2", qty 10 for the short ones. For the main caps you need 1/2"-13 X 1 3/4", qty 10. I skimmed through the Cat bolt selection online and found some that are close but no exact match. Good luck and let us know how it turns out.
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Thanks That helps. I was told that washers were OK to use as long as they were the same grade as the bolts. 

Duane
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Cool. I'm about to go through the same exercise. I had checked with John Mumert since he lists an ARP head bolt kit but on speaking with him he said ARP has quit making the short ones.
Joe-JDC
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Before ordering these bolts, you had better check the long bolt lengths again.  Four of them are longer than mentioned, and 6 are long.  The 10 short ones are the same length.  Joe-JDC

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Thanks Joe will do . 

Duane
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Joe-JDC (2/26/2021)
Before ordering these bolts, you had better check the long bolt lengths again.  Four of them are longer than mentioned, and 6 are long.  The 10 short ones are the same length.  Joe-JDC


Those specs are from the '55 Merc chassis parts catalog. I realize the long bolts became different lengths in '56, I believe. Don't know if the '56 bolt lengths are backwards compatible with a '55 with '57 heads.
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head bolts 2longones 4and 3/8
3 short longs4and1/8
5 short2and1/8.           measured from end of threads tosholder of head


I used cat grad 8s they are a better than original, but the short bolts are prone to breaking due to the heat cycles memory has it I needed to trim thecshort longs, or you could use some hardened  flat washers. well you are at the cat house the 3/8  grade 8 withe cat hardened flats is the only way to go on exhaust, never come loose in my 292. main cap bolts cant help you  I have a system to give better results having no rear seal aria leaks. a precision plate that presses on the raised dimples of the pandas well as thicker pangasket of denser material. if you ar interested send me your email and will forward pictures(ct1940@shaw.ca
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Just wondering, are the ARP cap screws considered overkill or are too expensive?

GRADE 5 will not suffice for a stock rebuild?

Here's charts if they can help anyone -

http://forums.y-blocksforever.com/uploads/images/42965e6b-bc8d-468b-b343-7667.jpg

http://forums.y-blocksforever.com/uploads/images/e03c1bfc-3c14-44af-bcad-8b70.jpg

http://forums.y-blocksforever.com/uploads/images/7a326776-d261-4604-a6bb-0d12.jpg


W (BY GOD) V - EASTERN PANHANDLE
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Thanks For the chart. It confirms the lengths for me. I didn’t think the 1 3/4 main cap lengths sounded correct. I have been on the Internet researching grade 8 vs ARP bolts and hears my thoughts. Grade 8 bolts have tensile strengths in the 120,000 psi range and cost $2. To $3 maybe $4. ARP bolts are in the $4 to $8 range and are in the 180,000 psi range and up. The harder the bolt the more brittle and more likely to break instead of bend. Harder bolts fatigue faster also according to an article in engine builder . I called John Mummert yesterday he said ARP didn’t stop making the short bolts they were just out of them. He didn’t know when they would be available again. I asked his opinion on grade 8 vs ARP and his response was “ I’ve heard of people doing that “ I found a place on line called Allensfastners.com who sells both ARP brand and other type and grades. There is not an exact match in lengths so either one will require washers and or trimming.

Duane


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