I recently picked up a 1972 413 from a motorhome for free and am in the process of rebuilding it using the tall heads and the big waterpump. Ive been able to get a hold of every part except the center row head bolts. Theyre the same bolts as a normal big block mopar but there about an inch longer. I also couldnt find exhaust valve seals, because the exhaust valve diameter is bigger than normal because its sodium filled. Any help will be appreciated.

You could check with ARP directly and probably have a bolt that would work on the head.

Yeah thats what ive been told but i was wondering if anyone knew of a place that had motorhome parts like this. Youd think someone made them at some point right?

Years ago, most likely.

What I'd do is figure out the correct size and then buy new Grade 8 bolts and screw them in. IIRC the head bolts on my 318 were nothing more than Grade 8. The only bolts on the engine that wouldn't be OK for using Grade 8 are the rod bolts.

Don't make this any harder than it is naturally.

R.

A Grade 8 bolt will have six lines or tick marks on the bolt head.

I assume the engine is destined for something with lots of hood clearance or an electric cooling fan?

Ok, i heard grade 8 are bad for head bolts because they dont stretch like a head bolt. And yeah im sticking it in a 68 charger 4 core rad and two fans lol. Anyone have any experience with porting these heads? Theyre 943 casting

You do know those Mopar413industrial and motor home motors where never intended to rev much above 3500 RPM, correct? If not you may want to reconsider which heads to put money into Good luck either way

Yeah im aware of that, but they were also built to run 3500 to 4000 rpm constantly! I know there dog motors but im just using it for low rpm round town driving.

catapiller makes some really nice grade 8 bolts,i used to use them on olds diesels

Some newer vehicles use "torque to yield" head bolts. They permanently stretch on installation by design.

Muscle era MOPARs are not TTY and do not depend on permanent stretch. I don't think a bolt that is harder than original would hurt anything.

"I heard" is usually followed by complete BS, as it is in this case. You now have reason to doubt anything that comes out of that "expert's" mouth.

Fact is, ANY bolt will stretch the same amount with the same load, until it starts to deform, usually by necking down. The reason to use a higher grade bolt is so you can tighten it tighter, providing more clamping force.

If, as I suspect, the head bolts that originally were in the 413 were Grade 8, then ANY grade 8 bolt will substitute perfectly well. And I really don't see why they need replacing in the first place. I've been reusing head bolts and every other kind of bolt for 40+ years, on stock type rebuilds. Actually I have only built one engine on which I replaced head bolts.

Your low compression industrial 413 isn't a high performance engine and I'd reuse head bolts without thinking twice.

As I said above, a Grade 8 bolt will work on any application in your engine EXCEPT for rod bolts, which are a specialized shape anyway.

R.

Really? I didnt know for sure about the grade 8 being different from head bolts, its just what ive heard. If there isnt a difference than thats great because i can get the whole set for around 30 bucks! And i need new head bolts because this motor sat in water for awhile and the bolts have deep pits in the shank and threads

The center head bolts used on Indy 440-1 heads or Edelbrock Victor heads might work. They are typically 3/4 or 1 inch longer than the stock bolts.

Putting a motorhome engine into a '68 Charger is probably a bad idea for several reasons. I assume you don't want to hear that opinion from anyone though. I'm just thinking that when you go to sell the car the potential buyers are going to look at that motorhome engine and knock $5000 off the price.