need help from Mopar guru's

Ken Haase · 04-12-2017, 11:24 AM

Guys, thanks for the replies so far. My experience is with other brands so I have no first hand experience with B/RB Mopars. Bigfoot, my initial reaction was along the lines of your thoughts.
JMan, and Steve, he's using good H-beam steel rods and 4340 stroker crank in an OEM 400 block with a girdle, but it's not filled. I'm somewhat familiar with the co-efficient of linear expansion for different metals, and these clearances would not be a problem in my limited experience.
If I'm understanding this correctly, this issue is related to a lack of sufficient block rigidity? With 17 head bolts, I'm a little surprised that there would be a gasket clampling problem. And, I'm still unclear how there was not a problem with the 451". He's using the same block and it had no girdle at that time. But it was 10.5 instead of 12.5 CR.
I will suggest he think about the thicker gasket. Thanks again.

ss3011 · 04-12-2017, 12:01 PM

My 455 stocker Pontiac has a 0 deck and a .030" head gasket . It runs to 6200 rpm and usually imprints the piston numbers on the quench area of the combustion chamber . Bottom line is you need more than .030" , especially if the rpm is higher .

Everett Vassar · 04-14-2017, 08:33 PM

Cometic will make any thickness you want. I'm thinking .042 clearance is what you would shoot for maybe .038 we had this problem on a 440 years ago. We had the block decked for the old TRW dome pistons not knowing they had changed the pin loc

Everett Vassar · 04-14-2017, 08:40 PM

Cometic will make any thickness you want. I'm thinking .042 clearance is what you would shoot for maybe .038 we had this problem on a 440 years ago. We had the block decked for the old TRW dome pistons not knowing they had changed the pin loc at some point. Wound up with a nice set of Ross pistons still out of the hole, we had to order Cometics about .065 thick. We had no head gasket issues,but the pushrods would not stay in it. We didn't run that motor very long, just looking back and wondering if raising the head off the block that far was making the push rods too short?

Ken Haase · 04-15-2017, 02:15 AM

He's going with .051 Cometics. Thanks to all for the help, and especially to a long-time former Mopar S/S'er for the initial warning. Saved my friend a lot of grief and $'s.

04-12-2017, 11:24 AM	#1
Ken Haase Member Join Date: Mar 2007 Posts: 233 Likes: 0 Liked 1 Time in 1 Post	Re: need help from Mopar guru's Guys, thanks for the replies so far. My experience is with other brands so I have no first hand experience with B/RB Mopars. Bigfoot, my initial reaction was along the lines of your thoughts. JMan, and Steve, he's using good H-beam steel rods and 4340 stroker crank in an OEM 400 block with a girdle, but it's not filled. I'm somewhat familiar with the co-efficient of linear expansion for different metals, and these clearances would not be a problem in my limited experience. If I'm understanding this correctly, this issue is related to a lack of sufficient block rigidity? With 17 head bolts, I'm a little surprised that there would be a gasket clampling problem. And, I'm still unclear how there was not a problem with the 451". He's using the same block and it had no girdle at that time. But it was 10.5 instead of 12.5 CR. I will suggest he think about the thicker gasket. Thanks again.

04-12-2017, 12:01 PM	#2
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 910 Likes: 70 Liked 239 Times in 114 Posts	Re: need help from Mopar guru's My 455 stocker Pontiac has a 0 deck and a .030" head gasket . It runs to 6200 rpm and usually imprints the piston numbers on the quench area of the combustion chamber . Bottom line is you need more than .030" , especially if the rpm is higher .

04-14-2017, 08:33 PM	#3
Everett Vassar Member Join Date: Jun 2004 Location: Kennedale,Tx Posts: 227 Likes: 0 Liked 2 Times in 2 Posts	Re: need help from Mopar guru's Cometic will make any thickness you want. I'm thinking .042 clearance is what you would shoot for maybe .038 we had this problem on a 440 years ago. We had the block decked for the old TRW dome pistons not knowing they had changed the pin loc

04-14-2017, 08:40 PM	#4
Everett Vassar Member Join Date: Jun 2004 Location: Kennedale,Tx Posts: 227 Likes: 0 Liked 2 Times in 2 Posts	Re: need help from Mopar guru's Cometic will make any thickness you want. I'm thinking .042 clearance is what you would shoot for maybe .038 we had this problem on a 440 years ago. We had the block decked for the old TRW dome pistons not knowing they had changed the pin loc at some point. Wound up with a nice set of Ross pistons still out of the hole, we had to order Cometics about .065 thick. We had no head gasket issues,but the pushrods would not stay in it. We didn't run that motor very long, just looking back and wondering if raising the head off the block that far was making the push rods too short?

04-15-2017, 02:15 AM	#5
Ken Haase Member Join Date: Mar 2007 Posts: 233 Likes: 0 Liked 1 Time in 1 Post	Re: need help from Mopar guru's He's going with .051 Cometics. Thanks to all for the help, and especially to a long-time former Mopar S/S'er for the initial warning. Saved my friend a lot of grief and $'s.