Packard Forum Index » Post-War (1946-54)

http://cgi.ebay.com/ebaymotors/1954-Packard-Pacific-2-Door-Hardtop-/321056758315?pt=US_Cars_Trucks&hash=item4ac0795a2b

Take a look at the closeup photo of the cylinder head. It's attached with bolts instead of studs and nuts. Since the threads in the block go all the way into the water jacket, I'd think this will cause problems, if not immediately then whenever the bolts are retorqued. Bolts work fine on OHV engines that use a non-compressible steel shim headgasket, but on a L-head? Any one else have thoughts on this?

Strange how a master rebuild shop would do this. The good news is that the bolts can be readily (hopefully) removed and the proper studs installed. It can really be ugly to remove the studs - someone else has done the heavy lifting for the new owner. I agree with you Owen, get rid of the bolts.

I'm trying to recall about some other L-head engines like the Chrysler sixes and the Hudson 232/262/308 family; I think they used bolts so perhaps the head bolt holes in the block were blind holes? Anyone know these details?

I'll call a local Hudson mechanic this morning and ask him about the Hudsons.

Talked to my local Hudson mechanic a few minutes ago. The smaller Hudson engines used studs while the larger ones used bolts. He explained that with studs, the part that goes into the block uses a course thread, and the part with the nut uses a fine thread. This changes the amount of torque. The fine thread requires less torque to seat the head properly. If you switch to bolts, you will need to apply more torque. He also thought that the stud and bolts did go into the water jacket, so you do need to use a good sealer on them to prevent leaks. Please note the only Packard engine he has worked on is mine, which continues to use studs, so he is not positive that the studs on a Packard do go into the water jacket. They do on the Hudsons.

My opinion, buy the car and change out the bolts to studs.

Thanks for the added info. Another question to ask your Hudson mechanic when you have a chance: On the Hudson engines using bolts (as the guy with the 54 Pacific did) that go thru into the water jacket, when you retorque the bolt, how does the thread sealant continue to function since I'd guess the seal would be broken when the bolt turned.

My 1939 Cadillac 60 Special with the 346 L-head V-8 had bolts to fasten the cylinder heads to the block. I did a valve job on it and had one bad bolt hole that needed repairing. I did this with a Helicoil repair kit. The thread size is 7/16"-14. I replaced all the bolts and washers with stainless steel ones and put sealant on the threads that went into the water jackets. According to my Motors Manual the head bolt torque is 70-75 lbs. I would venture that all the 346 V-8s were built this way.

(o{}o)

Something I'd wonder about in future repairs is if the correct studs will now work well or as designed in the block. Since Packard said on introduction the new rolled thread studs were not interchangeable with old cut thread stud equipped engines it's something I've wondered about with Max's replacement studs. Are they cut or rolled and was the block threaded the same thruout?

Don't know about Max's studs but Kanters has both types and you specify when you purchase them, or they ship you based on what was correct for your model.

I'm still not understanding how the thread sealants continue to hold when the bolts are retorqued since that means movement at the threads, wouldn't that disrupt the sealant? I guess it's not an issue, though I don't understand why not.