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By 55Monterey - 17 Years Ago
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I am buttoning up the top end rebuild on my '55 292. My question is: Is it absolutely necessary to use original bolts like Mr. Mummert sells or are run of the mill grade 5 or 8 bolts sufficient? Mummerts bolts at $95 + shipping sure seems high. If that's what I absolutely must have then I will buy them but just the thought of putting someone else's kids though college.
And as far as grade, I am stumped there too. The originals have four slash marks on the heads. What grade are those? Seen lots of 5's and 8's but never 4 marks. If the consensus is regular store bought bolts are fine, then what grade? Is the torque specs the same no matter what grade? 55 then 65 then 75.
As an additional FYI, all my long top bolts are 4.0625" and the shorter bottom bolts are 2.125". The 2.125" bolts that go on the bottom have a shoulder on them if that makes a difference too.
Sorry for so many rambling questions, but I want to get this lump buttoned up soon.
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By 56fairlanepost - 17 Years Ago
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Just for information,I checked in the shop manual and there was no suggestion in replacing the head bolts,just to torque them in the proper sequence as you stated,55,65;run til hot and finally 75 and adjust valves as necessary.Now i understand the reason for replacing torque to yeild bolts,but yours are standard grade sae;unless you are building a performance engine,i would just use the original head bolts;I'm sure there may be varying opinions but that is what I would do.jim in the valley
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By 46yblock - 17 Years Ago
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I went through this type of issue recently. Installed the heads with Felpro gaskets and torqued them to 73 ft. lbs in three stages, using original 1964 grade 8 bolts. Came back a week later to remove heads and first bolt was loose, certainly not 73 lbs. So I set the torque wrench, and the bolts had breakaway readings mostly from 55 to 60 lbs. My first thought was that the gaskets had compressed quite a bit during that week (motor was not run). Ted, John and others indicated that it was the bolts that were most likely stretching. I threw the bolts away.
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By speedpro56 - 17 Years Ago
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I'd throw them away too and buy new ones
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By 56fairlanepost - 17 Years Ago
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I was browsing through Mummert's sight and found an interesting tidbit about common mistakes made in reference to head bolts,although the five shorter bolts by the spark plugs are the same length,the ones by the rocker assy are different lengths;the outer edge ones are 1/4" longer and if put in the wrong location will cause a blown head gasket.Now i'm not suggesting you should use the old head bolts,i'm only saying that is what I would do because i had built a number of engines over the years and never had a head bolt failure.If you are uncomfortable with the old bolts then by all means purchase new ones
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By 46yblock - 17 Years Ago
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speedpro56 (9/26/2008)
I'd throw them away too and buy new onesI bought some studs. Yeah overkill but what the heck. I sure do empathize with 55monterey's feelings. My thinking was "grade 8 bolts, cant get much better than that". You think things are ready to go with a final assembly, and another C note pops up.
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By 55Monterey - 17 Years Ago
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Guys, I appreciate all the responses, but my question to you is:
1. Do I need to buy the bolts that Mummert sells?
or
2. Can I use grade 8 bolts as sold in hardware stores?
+++++I am not reusing my 53 year old head bolts+++++
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By charliemccraney - 17 Years Ago
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Grade 8 will be fine. The ones Mummert sells really aren't needed until you're a good bit above stock power levels. Make sure to get the 1/4" longer bolts for the ends of the heads. The alignment dowels are in line with these bolts. About 1/4" of threads is cut out of the block for these dowels. You will have 10 long bolts. 4 should be 1/4" longer than the other 6. Anyone know the lengths?
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By 55Monterey - 17 Years Ago
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THANKS Charlie. All the top (long) bolts that I removed were the same length.4.0625". Why do I need longer ones now?
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By charliemccraney - 17 Years Ago
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It's the way it was originally equipped. The cut for the dowels removes about 1/4" of the threads. The 1/4" extra length gets those threads back for proper engagement.
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By 55Monterey - 17 Years Ago
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My engine has all the same length top head bolts and the engine I got to get the heads off of also had all the same length bolts. Were both of these engines wrong?
I read somewhere about certain years having different bolt lengths than others.
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By 46yblock - 17 Years Ago
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JM says that the late model Y's had the same length long head bolts. Dont know what he means by late model, but the last 2 63-64 292s I have dissassembled both had the two longer bolts on the ends, and both sets were grade 8. All the pre 63 Y's would have had the longer bolts on the end. FYI the ARP head bolts are all the same length on the top row.
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By Hoosier Hurricane - 17 Years Ago
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Monterrey: I believe that '54-'55 Ys had same length long bolts in all upper holes. I believe '56 they changed, and apparently in the last of production they changed again. John
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By 55Monterey - 17 Years Ago
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Thanks Hurricane. James Eickman's book also states that pre '56 Y-Blocks used equal length bolts on the top row. I know that my engine in my '55 Monterey is original and based on the bolt length in my doner engine, it must be pre '56 also.
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