Main girdle-effective designs

[DirtyPrimer]

We went 6.95 at over 200 mph with a 1967 Traditional Pontiac block.
We did this in 1996 using a 1967 2 bolt main thick main web block that we added splayed caps to.  The block was properly machined, the block was stress relieved, the block was properly assembled. Steel rods and Moldex crankshaft.

Engine ran high boost (Turbos), methanol, efi, and a dry sump. 

Lots of Pontiac Guys have blown up similar engines naturally aspirated at much less horsepower. 

We took our time and slowly increased the mph and lowered the et.

Most block/caps develop "fretting" under high HP from the caps moving around.

Most blocks/ caps that are 4 bolt straight designs actually weaken the block.

Most blocks/splayed caps do not need the same sized fasteners on the ends as at the center of the cap.

Personally I think the ideal block would be a skirted block with 2 center bolts and 4 side skirt bolts: 

http://www.mustangandfords.com/techarticles/mdmp_0903_pacific_performance_427ci_engine_build/photo_04.html

Tom Vaught

If I'm not mistaken, that is a very similar design to the current Modular motor block/skirt/main cap design. Seems to be about the strongest way you could build a bottom end. No need for a girdle there.

[junkbrick]

Also, in most cases the strongest parts still break in the hands of weak tuning!  Keep you tuning spot on and the simplest of designs will work surprisingly well...since we are in a turbo forum...detonation or pre-ignition is the killer.

I have ran the Buick V-6 program for years...and the best thing to happen for us has been the girdle.  We can spend $400 on a it, 300 bucks to install it (line boring is a requirement) and we have a block that is almost idiot proof...

almost...but they still break if you are not careful.

From what "I" have seen, the block is pretty strong...but the crank is not.  We put the girdle in place to stabilize and support the crank (we have 1 rod journal for each rod end on the even fire engine..not a really pretty crank design).  Since then, broken cranks are a thing of the past.

I would think a stronger crank vs. a stock crank in the same block will go further on the HP???  All else being equal.

...and Tom V...thanks for all the good reading here!!!  Your wealth of knowledge and desire to educate is very appreciated!

Reed

[BLK98MK8LSC]

Lough engines does A very nice job on BB fords! Maybe they can do the same for a caddy.

[Chevalade]

The girdle in question is already avail, and doesn't need to be custom made and redesigned. The question is if it would be a good working design.

[Boost Engineer]

Post the picture again, the link is no longer valid and I will look at it again.

Tom Vaught

[sean]

Goes over existing caps

[Boost Engineer]

Looks like a Very stiff design. You would need to dowel (2 dowels) the main caps to the girdle to keep the caps from "Fretting" at the girdle surface. You would also want to have dowels at the block to girdle surface in several locations to keep the girdle from shifting around. Ideally the girdle would attach to the block differently from the oil pan (separate fasteners)

Tom Vaught

[El_Diablo]

that would be perfect for a 302 when offered with a matching oil pan..... that thing is pretty sweet

[JGSturbo]

I had that thought once upon a time... except I was going to make it from steel and make the main bearings and girdle ONE piece.
Same design you will find in alot of new engines.   

[RyanMayo]

I had that thought once upon a time... except I was going to make it from steel and make the main bearings and girdle ONE piece.
Same design you will find in alot of new engines.   

I haven't seen any new engines like this, but is there any reason why this wouldn't work?  Seems like, to a point, it would fix the 302's cracking problem,  and should be cheaper than a new block.  I asked a machinist about it one time and he said it wouldn't work, but maybe he was wrong?

[Briansshop]

I'd like to find out some more info on this one: http://www.prcinc.com/development.htm

[Boost Engineer]

I haven't seen any new engines like this, but is there any reason why this wouldn't work?  Seems like, to a point, it would fix the 302's cracking problem,  and should be cheaper than a new block.  I asked a machinist about it one time and he said it wouldn't work, but maybe he was wrong?

Most new blocks are the Deep Skirt Block (Like a Ford Modular Engine or a GM LSX type Engine) that use 2 vertical main cap bolts and 2 horizontal cap bolts. Some blocks have 4 vertical main cap bolts and 2 side cap bolts. I think the extra 2 vertical main cap bolts weaken the main webbing, personally.  I still say this is the "Hot Set-up" on a skirted block:

http://www.mustangandfords.com/techarticles/mdmp_0903_pacific_performance_427ci_engine_build/photo_04.html

2 vertical main cap bolts and 4 horizontal cap bolts

Tom Vaught

[JGSturbo]

I haven't seen any new engines like this, but is there any reason why this wouldn't work?  Seems like, to a point, it would fix the 302's cracking problem,  and should be cheaper than a new block.  I asked a machinist about it one time and he said it wouldn't work, but maybe he was wrong?

The 2003-2005 Dodge SRT4 engines have a split block design.
Couldn't find the 2003 Oct. SCC mag article   One forum has it BUT their a pay site now? WTF.

Any thoughts on having a complete skirt/main cap assembly casted for the SBF?
If it could be done in the $600-$750 range with the short pan?

It would need to be completely line bored/honed but its could bridge the gap between a stock block and a $2K+ aftermarket.
I have a garden gnome 302 sitting here for a base....

[nealysa]

It won't fix the stock 302 block form cracking in the lifter valley since the metal is still thin and weak at that point.

[JGSturbo]

Example?

The examples shown earlier in this thread same to extend the fail point of various blocks, so why should the stock 302 be an exception??

All of the force in an engine is on the main caps, a lower half block will distribute the force to the outer cylinder walls and away from the lifter valley.

[Boost Engineer]

JGSTURBO,

Take some time to read up on the thrust forces acting on the cylinder walls. Primarily the
Major Thrust Surface vs the Minor Thrust Surface of a V-8 Cylinder block.

Tom Vaught

[JGSturbo]

Found some articles about major vs. minor thrust.... interesting.

When I look inside the light weight 302 casting I see a lack of structure attaching the main bearings to rest of the block. By re-enforcing this structure it should transfer SOME of the major thrust to the minor areas ?

[RyanMayo]

Most new blocks are the Deep Skirt Block (Like a Ford Modular Engine or a GM LSX type Engine) that use 2 vertical main cap bolts and 2 horizontal cap bolts. Some blocks have 4 vertical main cap bolts and 2 side cap bolts. I think the extra 2 vertical main cap bolts weaken the main webbing, personally.  I still say this is the "Hot Set-up" on a skirted block:

http://www.mustangandfords.com/techarticles/mdmp_0903_pacific_performance_427ci_engine_build/photo_04.html

2 vertical main cap bolts and 4 horizontal cap bolts

Tom Vaught

That block definitely looks the part.

Let me ask you this Tom, in most applications do you think it's really necessary to build them that meaty?  It seems the splayed-bolt setup has proven strong enough for just about anything short of Top Fuel, so I'm curious why the OEMs really see a need to go to the deep-skirt, cross-bolted design.

...Off to Google major vs. minor thrust surface...

[RyanMayo]

The 2003-2005 Dodge SRT4 engines have a split block design.
Couldn't find the 2003 Oct. SCC mag article   One forum has it BUT their a pay site now? WTF.

Any thoughts on having a complete skirt/main cap assembly casted for the SBF?
If it could be done in the $600-$750 range with the short pan?

It would need to be completely line bored/honed but its could bridge the gap between a stock block and a $2K+ aftermarket.
I have a garden gnome 302 sitting here for a base....

Did not know that about the SRT 4.  Good stuff.

[Boost Engineer]

That block definitely looks the part.

Let me ask you this Tom, in most applications do you think it's really necessary to build them that meaty?  It seems the splayed-bolt setup has proven strong enough for just about anything short of Top Fuel, so I'm curious why the OEMs really see a need to go to the deep-skirt, cross-bolted design.

...Off to Google major vs. minor thrust surface...

The Jaguar Block is aluminum and uses a girdle, as does the Mazda I-4 Turbo engine.
The Ford 406 and 427 used cross bolted mains early on with cast-iron blocks. The Hemi Chrysler followed suit.  Quote: "there's no doubt the 426 'Hemi'and RB block in general had a stronger bottom end- one well kept secret seems to be, the fuelers using 392's required a girdle across the mains and oil pan rails, otherwise the bottom of the engine would blow out and drop the crank and main caps- that was rectified with the low skirt cross bolt design of the RB/B engine"

Tom Vaught