Grade 8 Bolts for Head Bolts
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Camel Trophy
Joined: Aug 2014
Posts: 4,743
Likes: 985
From: Southwestern Virginia
It's not a dumb idea, Rob, it's an ignorant one. That's why I'm asking.
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Camel Trophy
Joined: Aug 2014
Posts: 4,743
Likes: 985
From: Southwestern Virginia
They actually weren't; these engines are from the 60s and were originally designed for traditional head bolts. They had a factory head torque spec of 50-55lbs.
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Camel Trophy
Joined: Aug 2014
Posts: 4,743
Likes: 985
From: Southwestern Virginia
I'm still not convinced it's not worth a try, considering how easy it actually is to do HG on these trucks. I appreciate everyone's insight, but so far I've seen no actual evidence that it wouldn't work. Even if I brought the torque down some, maybe 65 lbs to give it a little more head room for thermal expansion and combustion pressure. *If* I go for it, I'll definitely report back.
Rock Crawling
Joined: Mar 2012
Posts: 377
Likes: 94
they had 5 more bolts per cylinder. To achieve the same clamping force youd need 50% more torque and that puts you back at the almost certain failure range
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Camel Trophy
Joined: Aug 2014
Posts: 4,743
Likes: 985
From: Southwestern Virginia
They did not have five more bolts per cylinder. They had four more bolts per head.
And even that, not all had them. The extra bolts were deemed unnecessary and they went to the 10 bolt pattern which specified 65-70 lbs in 1964 and 70-75 in 1965. That was also with the old school single layer gaskets which didn't seal as well. I'm still betting 65 lbs on the modern multi-layer gaskets would do the trick.
And even that, not all had them. The extra bolts were deemed unnecessary and they went to the 10 bolt pattern which specified 65-70 lbs in 1964 and 70-75 in 1965. That was also with the old school single layer gaskets which didn't seal as well. I'm still betting 65 lbs on the modern multi-layer gaskets would do the trick.
Rock Crawling
Joined: Mar 2012
Posts: 377
Likes: 94
They did not have five more bolts per cylinder. They had four more bolts per head.
And even that, not all had them. The extra bolts were deemed unnecessary and they went to the 10 bolt pattern which specified 65-70 lbs in 1964 and 70-75 in 1965. That was also with the old school single layer gaskets which didn't seal as well. I'm still betting 65 lbs on the modern multi-layer gaskets would do the trick.
And even that, not all had them. The extra bolts were deemed unnecessary and they went to the 10 bolt pattern which specified 65-70 lbs in 1964 and 70-75 in 1965. That was also with the old school single layer gaskets which didn't seal as well. I'm still betting 65 lbs on the modern multi-layer gaskets would do the trick.
I just did some real quick and dirty calcs using advertised torque to get cylinder pressure, average pedestal length at a 1.8, assuming grade 8 proof load of 120ksi, ambient to engine temp delta of 120F, and .2 for bolt torque force equation. 1 bolt out of spec and it'll fail for sure.
DISPLACEMENT # BOLTS FASTENER FT-LBS ENGINE FT-LBS CLAMPING FORCE FASTENER SAFETY FACTOR
3.5 14 55 210 115500 1.2
3.9 14 55 250 115500 1.19
4.6 14 55 300 115500 1.18
3.5 10 65 210 97500 1.06
3.9 10 65 250 97500 1.05
4.6 10 65 300 97500 1.04
TReK
Joined: Jul 2017
Posts: 3,387
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These engines are Not Buick engines.
The Buicks were all cast iron, had a distributor which drove an oil pump, different bolt patterns, etc.
Saying the pos 4.6 is a Buick is no different than calling it a 302, or 350. They are all small block V8s, and that's about all they have in common.
No way would I use grade8 bolts for head bolts, especially on aluminum.
The Buicks were all cast iron, had a distributor which drove an oil pump, different bolt patterns, etc.
Saying the pos 4.6 is a Buick is no different than calling it a 302, or 350. They are all small block V8s, and that's about all they have in common.
No way would I use grade8 bolts for head bolts, especially on aluminum.
