Blown Street 392 Hemi Bottom End

Discussion of the 331-354-392 HEMIs.

Moderators: TrWaters, 392heminut, scottm

Post Reply
cylontymany
Posts: 21
Joined: Fri Jul 23, 2004 11:35 pm

Blown Street 392 Hemi Bottom End

Post by cylontymany » Sun Nov 26, 2006 5:54 pm

My choices seem to be milling the stock caps and adding a steel strap or dont mill the tops flat and use the new girdle thats available now or use 4 bolt main caps! Lets here it from the boys what shall I do?

johnny5
Posts: 128
Joined: Mon Dec 05, 2005 3:52 pm
Location: St Charles, MO

none of the above

Post by johnny5 » Sun Nov 26, 2006 6:39 pm

The stock caps should hold up for a street motor. If you really think you need more strength, get the Pro-Gram 2-bolt main cap set and use studs. My $0.02

Bailiesdad
Posts: 433
Joined: Sat Dec 01, 2001 6:00 pm
Location: Maryland

Post by Bailiesdad » Mon Nov 27, 2006 11:32 am

I have always used Milodon 3 center 4 bolt splayed main caps and billet front and rear caps. Never had any bottom end problems with that set up up to 1200 hp. I stud every 392 I build.

I also had a set of straight 3 center bolt main caps made and they are on the 3 rd motor. Key is to never cut the block to fit the caps, cut the caps to fit the block.

TrWaters
Posts: 390
Joined: Fri Dec 14, 2001 6:00 pm
Location: Vermont
Contact:

Post by TrWaters » Mon Nov 27, 2006 5:46 pm

There are a few options..... and even more opinions :wink: For a street (non 1200 hp :roll: )motor, stock caps will be fine. But..........

Remember that anything other than using the stock caps with bolts is going to require at the minimum an align hone. Using studs will require an align hone. Using aftermarket caps will require an align bore.

The cap straps are an old school idea. And machining is involved. Would they keep a cap from splitting in the middle? Possible, I suppose. Remember though that the machining is taking away strength from your caps.

The old school 3 cap girdles were designed primarily to strengthen the main bearing webs by tieing the caps and pan rails together. Looking at a stock block, you will notice that there really isnt alot of material in the block webs. ( it is this reason that I have straight 4 bolt caps for the 331 and 354)

As for the new full 5 cap girdles :wink: I think everyone here can guess my opinion. :D

As a note : I really dont recall hearing any horror stories about stock main caps or bolts in a stock or mild street application.
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.

johnny5
Posts: 128
Joined: Mon Dec 05, 2005 3:52 pm
Location: St Charles, MO

Post by johnny5 » Mon Nov 27, 2006 8:07 pm

TrWaters wrote:
As a note : I really dont recall hearing any horror stories about stock main caps or bolts in a stock or mild street application.
My point exactly. Don't fix it if it ain't broken. An interesting point is that today's advancements in camshaft profiles and head porting have really raised the potential output of the early hemis. I think 650hp is the max recommended limit for almost any stock 2-bolt cap. A blown 392 could easily make 750 streetable HP. Hmmm, maybe beefing up the main caps wouldn't be a bad idea after all.

:-?

Bailiesdad
Posts: 433
Joined: Sat Dec 01, 2001 6:00 pm
Location: Maryland

Post by Bailiesdad » Tue Nov 28, 2006 7:29 am

"Remember that anything other than using the stock caps with bolts is going to require at the minimum an align hone. Using studs will require an align hone. Using aftermarket caps will require an align bore."

Tom, add: adding a cap strengthing or reinforcing method.

I have never rebuilt a hemi without align boring or honing the main caps to get the starting point for the rebuild. Upgraded fastners are also automatic.

Anytime any clamping force holding the crank in the block is changed in ANYWAY align boring or honing is mandatory. Even a girdle... :wink:


80-100-150 bucks for a straight perfect crank home is real low cost insurance to get all the measurements exact and keep the rotating parts where they should be, inside the block.... :wink:

TrWaters
Posts: 390
Joined: Fri Dec 14, 2001 6:00 pm
Location: Vermont
Contact:

Post by TrWaters » Tue Nov 28, 2006 9:16 pm

So to answer the original question, I would say ( my opinion) its a question of how much money you want to spend for some peace of mind.

And to clear one thing up..a girdle such as the one that I manufacture will increase rigidity of the bottom end, not clamping force of the main caps. It does not rest on the center of the caps. The caps are torqued the same.....girdle or not. :wink:

Since this is not a post to discuss the good or bad of my particular part, I suggest that the discussion be kept to the original poster's question. I would hate to see yet another topic locked. :roll:
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.

cylontymany
Posts: 21
Joined: Fri Jul 23, 2004 11:35 pm

Post by cylontymany » Tue Nov 28, 2006 10:46 pm

I like the idea of using the program 2 bolt billet caps which would be stronger than the stock ones! Will your girdle work with this set up using studs? Then I can get the best of both worlds! But then this might be over kill too!

budmspeeco
Posts: 133
Joined: Tue Dec 21, 2004 5:35 pm
Location: South Houston, Texas

Blown Street 392 Hemi Bottom End

Post by budmspeeco » Sun Dec 10, 2006 11:06 pm

I think the authority on the subject would be Bob Walker at Hot Heads. He builds and sells a lot of early hemis . Give him a call. Or email. I just had the full set of five of his caps installed on a 392. It now looks indestructible. The 4.400 crank going in it is almost finished at Crankshaft Specialties in Tennessee. I got the rods offset ground to big block 2.200 and then had all the journals hard chromed to std. . For those trying to figure the math the crank was already a 4.250 welded stroker built by CSC over 40 years ago. I don't think there is an "overkill" for any blown engine regardless of its intended use or type. We are all prone to leaning on something even if it was originally a street motor. The basic rule of thumb should be do all you can afford. I sold a lot of little items on eBay to pay for this beauty. I can't wait to put it to use. Buddy
'48 anglia

Bailiesdad
Posts: 433
Joined: Sat Dec 01, 2001 6:00 pm
Location: Maryland

Post by Bailiesdad » Mon Dec 11, 2006 8:28 am

Jr Thompson in CA has probably built more 392 stroker blown motors than just about anyone in history.

He commonly builds 4.750 stroker motors.

Give him a call, he loves Milodon and Velasco.

Post Reply