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Splayed Mains......

mattthebrat

mattthebrat

Diesel Dork
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Location
Mankato, Minnesota
I haven't seen/heard about alot of guys with the splayed mains.

What is yall's opinion on the splayed mains?
Are they worth the extra cost and work?
Do they replace the need for mains studs, or is it better run both?

Wouldn't a set of the splayed caps essentially weaken the outer edges of the block, because you are angling a hole in close to the side, especially when you have a squirter block?

Is it better to just stick with main studs, and a custom girdle?
 
I don't like splayed mains because:
They take more material away from main webbing that already cracks.
On a 2bolt sbc, they are adding clamping force and distributing it deeper into the block which is why it works well on that setup.
 
They don't weaken the block. They actually tie to a place on the block that has substantially more meat. The majority of the load on the caps side to side is the outside bolt holes, which take a beating on one of these engines. The splayed caps counter that force, part of the reason why the bolts are angled.

I've done two blocks, and my machinist is very confident that we improved the block. Works well on 1000+ HP race engines, engines that wouldn't have survived w/o the caps.

I'm doing these blocks on the side, since all the research on getting one splayed properly has been done on my side. Have some cores to start from too.
 
I have heard splayed mains are awesome. When MaxPF built my engine, he went with a custom girdle and ARP main cap studs.

Here are some pics;

maincapgirdle.jpg


P1010009-ra.jpg


P1010008-ra.jpg


and the blue print for the girdle;

girdle.jpg


and this is what MaxPF says about the girdle;

"For those who have the resources to roll their own, here is the blueprint for the left-side girdle. The right side is simply a mirror image. Also, the print doesn't show it, but the corners on the girdle that sit in the corners on the caps need to be chamfered to clear the radius on the caps. One caveat: the stock pan will NOT fit over this girdle. You will have to radius the front of the girdles (see my pics in previous posts) either have to modify the pan or build a custom pan. I am trying to mod my pan, but it is made of 2 layers of sandwiched metal with (apparently) a coating of some kind between them. It contaminates the welds, and I may not be able to get good clean (and leak-free) welds on it. I will keep everyone updated on my success or failure. If it won't weld cleanly I plan on fabricating a pan from aluminum sheet. The other option is to eliminate the part of the girdle in front of the #2 bulkhead. However, the rear corners still need to be angled (that isn't shown in the prints either, but it is in my pics), and you will still need to figure out how to make the dipstick clear (I plan on simply moving the dipstick tube lower in the pan). No matter what, it is a PITA. I still think it is worth it, though "
 
The only issue I can see with a girdle is theoritcally, the webs can still move, but now they all move forward or backward? Yay or nay?
 
chevydiesel said:
They don't weaken the block. They actually tie to a place on the block that has substantially more meat. The majority of the load on the caps side to side is the outside bolt holes, which take a beating on one of these engines. The splayed caps counter that force, part of the reason why the bolts are angled.

I've done two blocks, and my machinist is very confident that we improved the block. Works well on 1000+ HP race engines, engines that wouldn't have survived w/o the caps.

I'm doing these blocks on the side, since all the research on getting one splayed properly has been done on my side. Have some cores to start from too.
Click to expand...


I am going to go out on a limb here and say that those 1000 HP engines where not 6.5s.):h

Which is my question: I know it works well on purpose built high HP, high RPM race motors, but a 6.5 is different. I am especially concerned about a 506 squirter block, some of them with the 12mm mains already had problems with cracking because there was not enough material. It seems to me that drilling extra holes in that area would just make things worse. Plus you still have the old hole, which even with filler seems like a weak point to me.
 
Yes, those are my CAD drawings for my project :)

With main girdles yes, the main caps could still move back and forth. With mine, it replaces all the caps entirely. Oh and there is 40 main bolts :cool:
 
Yep, those are actually where the original oil pan bolts went, but these will be 10mm ARP studs. The oil pan I'm making will have a new bolt pattern of it's own. I'm going to the machine shop tomorrow BTW.
 
Last edited:
chevydiesel said:
They don't weaken the block. They actually tie to a place on the block that has substantially more meat. The majority of the load on the caps side to side is the outside bolt holes, which take a beating on one of these engines. The splayed caps counter that force, part of the reason why the bolts are angled.

I've done two blocks, and my machinist is very confident that we improved the block. Works well on 1000+ HP race engines, engines that wouldn't have survived w/o the caps.

I'm doing these blocks on the side, since all the research on getting one splayed properly has been done on my side. Have some cores to start from too.
Click to expand...

Any 6.2/6.5 specialist that i have ever researched or talked to say to stay away from splayed mains. Drilling extra holes in webs already prone to cracking can't improve block strength IMO. The best option for increasing the strength of the botom end is a Bedplate. A stud Girdle would be a cheaper option though not as rigid.
 
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