[JWA]

I am planning to put a big block stroker motor together and I have a 454 core motor that is a 2 bolt configuration(mk IV) and I am wondering (after I placed my wanted ad) if I should just convert this block to a 4-bolt setup. Plans are for big horse power, may be even a super charger(under hood style

). Is this feasable?

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Jeff ACES#841 TCG#158
68 SS396(454)
68 L78 Project
87 MC SS




[This message has been edited by ACE841 (edited 10-13-99).]

 

[DZAUTO]

JEFF,
It is easy to do, but not necessarily cheap. First you need to find some 4bolt caps. Once upon a time there were tons of old 366BB truck engines available. They ALL had 4bolt caps, and they were usually cheap (sometimes free to $50. for the whole block). But any 4bolt caps will work. A good machine shop can fit them to your block for about $200. When you find some caps be sure to also get the bolts (unless you are going with new studs). I must add that the economics of this conversion vs. finding a 4bolt block is marginal. But I certainly would not discourage you from doing it. The end result will be a plus.

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Tom Parsons

[This message has been edited by DZAUTO (edited 10-13-99).]

 

[68SS396Camaro]

Jeff, I have a truck block thats no good and would be willing to give up the 4bolt caps. But if those are your plans and you have a two bolt block now I would recommend getting splayed main caps. Much stronger than standard 4bolt caps. Of course the caps will cost more but its definately worth it.

 

[Mkrauser]

I would just add, that as long as you properly balance the rotating assemly and don't continuously rev the motor over 7000 RPM your 2 bolt block will be more than adequate.

It is also not as simple as finding any 4 bolt caps and drilling your block. GM main caps are all over the map with tolerances and the way that they register in the block. Some can be align-bored possibly even honed, to fit properly and some can't. This is especially true on the rear main where thrust surfaces are also an issue. If you convert a 2 bolt to a 4 you will probably end up keeping your 2 bolt rear main because it fits so nicely. This is not a problem at all... Talk to your machine shop about splayed VS unsplayed caps. I opted for the standard (nonsplayed) caps for a couple of reasons. Splayed caps "can" stress the main webs and create cracks in the block. For the HP that I was building it wasn't worth the risk...

Check out the Gellner Engineering Billet 4 bolt main cap set. I converted my 477 race motor using these caps 2 years ago and was very pleased with the quality. These things are really nice and have lots of extra material to guarantee a perfect fit. $319 for 4 caps. Phone 216-398-8500. Good luck and I hope this helps a bit...MK

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hometown.aol.com/mkrauser/gmracing/gmracing.htm


70 Chevelle Fathom Blue
70 Malibu Convertible Midnight Regatta Blue

Chicago - Suburbs

 

[L6571SS]

Correct me if I'm wrong here but I don't think on the MK IV blocks you can do the splayed mains, because of the oil galley. I think also that on the Gen V blocks they solved this by moving it up by the cam like in the small blocks.

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JT
71 SS Vortec 355
www.angelfire.com/co/KellyMotorsports

 

[dcarr]

I've had this conversion done a couple of times because I wanted to keep my original block, but also wanted it to be a 4-bolt. Although it really isn't necessary - the 2-bolt setup is strong enough for most street/strip applications.

Anyway, I first bought a set of stock GM 4-bolt caps, but they wouldn't line up properly in my block, and they didn't have enough material to align-bore. So, I got a set of oversize caps from Summers Brothers (or is it "Sommers Brothers" - I can't remember).

Due clearance issues, these large caps could only be used on the three middle bearings, but I suppose that is where you would really need them anyway.


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Dan Carr
[email protected]
Team Chevelle Gold Member #11, ACES #701
Author of the GMC Sprint, El Camino, and '68-'72 SS Authentication pages.
See my GM A-body fleet at:
www.rmi.net/~dcarr/cars/cars.HTM