flathead head bolt torque foot lbs

5

52fordv8

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so when i put my heads back on my 52 ford flathead engine . it says to do them 65-70 foot lbs ?????? is that to much or is it wise to back off from that any or ???? and it says to put sealer on all the bolt threads ?? i baught permatext non hardening stuff . its made for gaskets and etc usees. just asking . before i begain
 
I agree...55# is plenty and re-torque often. I keep doing it until they (head bolts) quit moving. Also make sure you have a good torque wrench. A borrowed wrench from Auto Zone wouldn't be a good choice for me...
 
ok mr walt and el rat in my oppion i thought that 65-70 foot lbs was awhfull high in my thought to put on them . . and for the torque wrech i have a kobalt handle setting pop stop . i figured that is a good one its a 1/2 drive .
 
how about when re-torqueing disturbing the thread sealer if it is used to stop water running up the bolts as mine will be ? , cheers jim .
 
37coop, Keep in mind the Permatex is non-hardening so it's flexible and still sticks after movement.
 
Interesting day, this may be an appropriate place to show some test results my son called me about today on a "junk" Flathead block. The block is cracked everywhere!

He torqued up ALL 24 holes on the pass side with a SBC outer main cap bolt for a 4 B.M. block and a spacer below. It is the equivalent of a good grade 8 bolt, possibly a 140,000# fastener (I'm not certain where G.M. rates their pieces). Used 30W race oil as lube for test!

Went to 90# on EVERY hole including the 2 with the vertical cracks from the water holes. Did not "hurt" a single thread OR hole!

Not a single issue, done it twice, like when we mount the block plate for honing, except used the 90# number on purpose.

If he has it available on Tuesday still, I will get him to "break-one" intentionally, either the bolt or the block threads! He said he felt they would take past the 100# number?? Only his guess, he stopped at that point.

(Add) I'm sure some here have access to "junk" blocks, maybe give it a try! I've NEVER lost a single bolt hole in ANY Flathead during mounting the block plate using 65# torque, never.

Thanks, Gary in N.Y.

P.S. Two items, these had conventional 7/16-14 H-3 taps run through them first, and second, before he finished, I had him take 2 separate holes to 100#, he did and still no problem! The bolt here in the photo has 90# as taken, torque wrench is brand new, purchased 2 weeks ago!
 

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The reason I limit the torque to 45 ft/lbs has nothing to do with the strength of the blocck threads or the bolts. It's the deck, it's very thin in spots and very thick in spots. like between the cylinders and over the exhast ports. So overtorqing the block puts an uneven stress in areas. So I torque the block evemly from the weakest sopt. Read JWL's book.
 
I use a torque wrench but I often torque by 'feel' according to the stud or bolt size. Going beyond about 45-50 ft-lbs for a fine-thread 7/16" stud just feels like it's too much. So I usually check and re-torque often to the same 45-50 lbs till the numbers stabilize. Same goes for some axle nuts that are specified to 200 ft lbs --- I usually go to 150-175 ft lbs max and then re-check after running a while.

Jack E/NJ
 
Shouldn't there be to torque ratings.One for the fine thread when using studs and one for the course thread when using bolts as in later engines to achieve the same clamp down pressure on the heads.Geoff.
 
GOSFAST said:
Interesting day, this may be an appropriate place to show some test results my son called me about today on a "junk" Flathead block. The block is cracked everywhere!

He torqued up ALL 24 holes on the pass side with a SBC outer main cap bolt for a 4 B.M. block and a spacer below. It is the equivalent of a good grade 8 bolt, possibly a 140,000# fastener (I'm not certain where G.M. rates their pieces). Used 30W race oil as lube for test!

Went to 90# on EVERY hole including the 2 with the vertical cracks from the water holes. Did not "hurt" a single thread OR hole!

Not a single issue, done it twice, like when we mount the block plate for honing, except used the 90# number on purpose.

If he has it available on Tuesday still, I will get him to "break-one" intentionally, either the bolt or the block threads! He said he felt they would take past the 100# number?? Only his guess, he stopped at that point.

(Add) I'm sure some here have access to "junk" blocks, maybe give it a try! I've NEVER lost a single bolt hole in ANY Flathead during mounting the block plate using 65# torque, never.

Thanks, Gary in N.Y.

P.S. Two items, these had conventional 7/16-14 H-3 taps run through them first, and second, before he finished, I had him take 2 separate holes to 100#, he did and still no problem! The bolt here in the photo has 90# as taken, torque wrench is brand new, purchased 2 weeks ago!
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Hi Gary; I'm not sure of your point here. Per an old post here bolts should break at around 110 ft lbs. Also with high torque the deck will be stressed, more so at the thinner areas, and an engine running at temperature and firing the compressed A/F could run into some very serious trouble. Minimum torque 45 ft lbs or so, as Ron said, that gives a proper seal would be best. Good luck, Craig.
 
Craig CT said:
Hi Gary; I'm not sure of your point here. Per an old post here bolts should break at around 110 ft lbs. Also with high torque the deck will be stressed, more so at the thinner areas, and an engine running at temperature and firing the compressed A/F could run into some very serious trouble. Minimum torque 45 ft lbs or so, as Ron said, that gives a proper seal would be best. Good luck, Craig.
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Hi Craig, I'm not questioning anyone's methods of ***'y here or even the casting integrity, but I've gotten a few requests back here asking "at what point would the threads pull/strip or the fastener break!

This is the sole purpose of what I posted!

Let me add another dimension to this area, you build a unit for a customer (no fire-up/dyno involved), deliver it fully ***'d, and completely painted. Stock head bolts and cast iron heads.

With that scenario how does the owner go forward with any 2 or 3 times retorquing on the freshly painted surfaces (bolts) without making a "mess" so to speak, just curious here. Remember, not everyone building these is doing the install/fire-up? I have a 284" going to N.C. hopefully in a couple weeks, no dyno, fully painted. Customer already questioned this very procedure.

For me this is a non-issue, but I'm curious about others out there doing these Flatheads??

Thanks, Gary in N.Y.

P.S. I'm a believer (up to a point and this is a separate issue with me) about retorquing heads/studs, but having the dyno solves this issue for us. We can test/retorque, remove, then paint!

Double P.S. You all have a good holiday, am away, be back Tuesday!
 
19Fordy said:
37coop, Keep in mind the Permatex is non-hardening so it's flexible and still sticks after movement.
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thanks , I,m not sure we sell permatex over here(u.k) , I assume Loctite thread seal is the same , cheers jim.
 
With my NOS 81A motor the heads went on and I never retorqued them. 20000 miles later I had the heads off and back on- no retorque, no issues. Rebuilt an 8BA and blew a head gasket during the second run. I only cured subseqent blown head gaskets on this engine by retorquing after every heat cycle until there was no further head bolt movement - I'd need to dig out my notes and check, but it took at least 6 heat cycles.
 
I disagree, the clamping forcw us the same weather aluminum or cast iron, Using 45 ft/lbs abs a torque it may take more heat cycles to stabilize the head bolts. You can do as you please, just about everything you do to a flathead works.
 
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