Slant sixers,

I was pulling my head on the '68 Dart yesterday and had never really paid attention to the head bolt thread engagement into the block (never previously had a head bolt or gasket issue). Now that I am going to studs on this engine, and am putting together an aluminum engine (longer head bolts), I got interested... This is all FYI, and please feel free to comment.

Here's what I found.

Iron engine: On my '68 block with '68 head I found that the head bolts (uniformly on this engine) only engage 5/8" (+/- 0.040" or so) of thread into the block. This seems OK to me, at least for most applications, but I had always thought it was 3/4" or more since there is about 1" of thread on the bolt. The new ARP head studs have 3/4" of thread that will all go into the block. Also, note that this head has been milled about 0.080" and this is with an Aussie ACL gasket that was 0.042" compressed. This gives 0.060" less total thickness to the block compared to a stock head/gasket, so we are looking at 9/16" thread engagement on the totally stock setup. Long enough, but not a lot extra.

Aluminum engine: Here, I simply looked at several of the head bolts I pulled from a complete aluminum engine and saw that just under 1" (call it 15/16" +/-0.060"?) engages in the block. I used the remaining grime and rust on the bolts to see what was engaged or not. It appears the iron engine ARP studs could possibly be used on an aluminum engine, with some small sacrifice in engagement. However, I plan to get ARPs specifically designed studs for the alum engine, if they will still make them.

Happy building!

Lou

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Home of Slant6-powered fun machines since 1988

Lou
Really appreciate your enthusiasm! I just bought an aluminum engine to replace the one I had stolen so I am going to be going through this new one soon. Glad you are so busy with helping members on the board. Life is short, it's hard to belive slants have been on the earth 50 plus years and are are as popular as ever! Go Cavs! Just kidding....... Stan

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Hyper_pak

Thanks, Stan! Yep, still Slant 6 crazy... Hey, you helped get me into this mess with that article way back when.

Cheers,

Lou

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Home of Slant6-powered fun machines since 1988

Lou, I would venture to guess that 5/8" engagement will give just as much clamping force as 1", as long as the threads aren't pulling out of the block.

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Official Cookie and Mater Tormentor.

Jan 1989 High Performance Mopar. It's funny how you influence people without knowing it. When I met you for the first time I was very impressed. Heck you remembered stuff I didn't! Now that my colt and wagon are gone, I have to start over again. Don't plan on quitting, still have something to prove. Now the student is the teacher. Keep on doing what you are doing, I have some more to learn, THANKS LOU! Stan

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Hyper_pak

D,

Yep, I'm sure clamping force would be the same, but 5/8" or less could get to the point of possible strippage if I really over torque them, like I usually do. More of an observation... I would worry more with the alum engine holes.

Stan,

Life goes in cycles... I was 17 and had had my '68 Dart for 10 months when that article came out. I still have it... somewhere. Now that same '68 Dart is an EFI, turbo, OD auto frankenstein!

Cheers,

Lou

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Home of Slant6-powered fun machines since 1988

well if you over torque them it wont matter if the bolt engagment is 100ft long...

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1965 Plymouth A/FX 512ci (under construction)
1968 Dodge Dart SL6 14.25 @ 91.5 1.91 60'
1973 Dodge Dart SL6 Stock
Killer Bee's Member Since 09'
http://www.forabodiesonly.com/mopar/sho ... p?t=128702
http://www.youtube.com/user/805moparkid

I "overtorque" everything, and thus (almost) nothing ever loosens up for me. There is a safety factor on factory ratings. I have a feel/idea for how much more a fastener will take before it breaks/strips/plastically deforms.

Call me crazy, but that's how I roll. Never stripped a head bolt...

Lou

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Home of Slant6-powered fun machines since 1988

i agree but there more likely to start to strech then break...

one or two extra lbs wont hurt but have to remember those factory bolts get longer everytime... which means thinner...

but hey! im just a 21 yr old kid! lol if it works it works

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1965 Plymouth A/FX 512ci (under construction)
1968 Dodge Dart SL6 14.25 @ 91.5 1.91 60'
1973 Dodge Dart SL6 Stock
Killer Bee's Member Since 09'
http://www.forabodiesonly.com/mopar/sho ... p?t=128702
http://www.youtube.com/user/805moparkid