Author Topic: XXO/BVGC '38 Chevy Coupe Build  (Read 1026895 times)

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Offline SPARKY

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2265 on: April 15, 2014, 12:58:44 PM »
Buddy when I talked to Spud about SBCs and Nitro---one of his intresting observations was that he learned the hard way not to mix block and head materials with Nitro---alum heads with alum block cast heads with cast block  other wise he could not keep head gaskets in them
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Offline 38flattie

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2266 on: April 17, 2014, 12:04:55 PM »
Sparky, great talking to you the other day!

We've had issues with head gaskets, and have decided to try and correct the issue after El Mirage.

Currently, we have to run .085" head gaskets, and even with o-rings and receiver grooves, it's hard to get and keep a good seal. We'll be deepening the head chambers .050", so that we can run a .035" head gasket.

Hopefully this gives us the seal we need-if it does, we'll try some hotter tunes!
With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

You can't make a race horse out of a pig. But if you work hard enough at it you can make a mighty fast pig. - Bob Akin

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Offline fordboy628

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2267 on: April 18, 2014, 09:23:36 AM »
Buddy when I talked to Spud about SBCs and Nitro---one of his intresting observations was that he learned the hard way not to mix block and head materials with Nitro---alum heads with alum block cast heads with cast block  other wise he could not keep head gaskets in them

One of the problems with dissimilar materials is the difference in thermal expansion rate.    For instance, an alloy head with a copper head gasket piled on top of an iron block, creates a scenario where all three parts expand & contract at differing rates.     This "creep rate" differential can, if large enough, shear the gasket attachment to the head/block, regardless of the clamp load.    This can be a serious problem, hence the tendency for the "racer's adage":  iron heads with iron blocks, and aluminum heads with aluminum blocks.    It removes one differential of thermal expansion from the equation.

If you are pushing the copper gasket out, even with O-rings & receiver grooves, then either the combustion pressure is too high, OR, the clamp load is not enough, for your application.

Kinda like: "Which eye do you want poked out?"

I realize you are where you are, and may not be able to change much in short order.    Did you ever assess the clamp load via the carbon paper/pressure sensitive film method?    Doing so now may point you in the direction of a quick fix, or at least help you identify the where the real issue is.

Hope this helps.
 :cheers:
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Offline 38flattie

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2268 on: April 18, 2014, 10:16:40 AM »
Thanks for the reply, Mark.

It's a combination of things-clamping force and a gasket to thick for the 0-rings to work properly, I think!

We are not pushing the copper gaskets out, rather the gases start escaping on the block side, at the o-ring receiver groove. We went from dead soft copper to annealed copper, and this seamed to help, but did not cure the problem at high boost and high cylinder poressurs-21lbs and nitro!

Currently, we have to run .085" head gaskets, and even with o-rings and receiver grooves, it's hard to get and keep a good seal. We'll be deepening the head chambers .050", so that we can run a .035" head gasket.
With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

You can't make a race horse out of a pig. But if you work hard enough at it you can make a mighty fast pig. - Bob Akin

http://www.flatcadracing.org/
http://youtu.be/89rVb497_4c

Offline Sumner

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2269 on: April 18, 2014, 12:20:53 PM »
Not sure where you are getting head gaskets from but SCE ( http://scegaskets.com/  )told me they could make me a head gasket for the 4 I'm building for about $150 in design fees and about $150 for each gasket (actually one of those was $130, can't remember which).  I though that was reasonable.  In your case you could split up the design fee amongst all the other 'flat cad' owners  :evil:.

In my case they recommended their composite ICS Titan gaskets with the internal o-ring for up to about 20 lbs. of boost and over that recommended o-ringing the block and going with their Pro Copper that they have in different thicknesses.

Looks like Speed Demon is running them,

Sum

Offline Jack Gifford

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2270 on: April 19, 2014, 12:34:48 AM »
What O-ring wire diameter? Block groove width and depth? Receiver groove width and depth?
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Offline 38flattie

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2271 on: April 19, 2014, 04:57:16 PM »
What O-ring wire diameter? Block groove width and depth? Receiver groove width and depth?

Jack, I think Don or Dale will weigh in with that info later tonight.

In the mean time, Poppa Smurf has been busy, changing all of out 1" hoses and clamps over to AN fittings, cleaning up our plumbing even more!
With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

You can't make a race horse out of a pig. But if you work hard enough at it you can make a mighty fast pig. - Bob Akin

http://www.flatcadracing.org/
http://youtu.be/89rVb497_4c

Offline 38flattie

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2272 on: April 19, 2014, 04:59:07 PM »
Poppa Smurf also did our discharge water manifolds!

......AND, the new steel came in for the upgraded chambers on the heads! :evil:

Don also made a new water pump discharge manifold.
« Last Edit: April 19, 2014, 05:17:37 PM by 38flattie »
With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

You can't make a race horse out of a pig. But if you work hard enough at it you can make a mighty fast pig. - Bob Akin

http://www.flatcadracing.org/
http://youtu.be/89rVb497_4c

Offline Roseville Carl

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2273 on: April 20, 2014, 01:13:53 AM »
sure looks better there than on the Dyno!!!
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Offline Milwaukee Midget

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2274 on: April 20, 2014, 12:44:03 PM »
Been away from this one - Recutting the heads in steel?
"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  :roll:

Offline fordboy628

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2275 on: April 21, 2014, 08:13:28 AM »
Thanks for the reply, Mark.

It's a combination of things-clamping force and a gasket to thick for the 0-rings to work properly, I think!

We are not pushing the copper gaskets out, rather the gases start escaping on the block side, at the o-ring receiver groove. We went from dead soft copper to annealed copper, and this seamed to help, but did not cure the problem at high boost and high cylinder poressurs-21lbs and nitro!

Currently, we have to run .085" head gaskets, and even with o-rings and receiver grooves, it's hard to get and keep a good seal. We'll be deepening the head chambers .050", so that we can run a .035" head gasket.

Just went back to page 66 to review photos of the long block with the head studs installed.

Where you "chuffed" the gasket is the area where the gap/span between studs appears to be the largest, AND, there is a water passage there as well, so there is going to be a lot of temperature differential in that area.

Anything you can do to increase the clamp load in this area, (without compromising clamp load elsewhere), is going to help.     I would investigate how altering the stud/nut torque (and/or diameter . . .) on those 2 bolts affects the localized clamp load.     Maybe you are back to the copper-coated thread idea, applied in certain areas.   

I don't have any other ideas for "band-aiding" to help right now, but maybe you can add a bolt/stud there later?    Even a smaller diameter bolt/stud would add clamp load.   (Ala Cosworth DFV or Chevy RO7 . . . )    Maybe a small s/s bolt installed in the water flow area of the "lower head" only?     Maybe move those 2 existing studs closer together some time down the road?     Anything along these lines would, of course, need to be performed at the same location for every cylinder . . . . . .

Sorry, I know these suggestions are expensive and time consuming.

Anybody out there in Land Speed Land, especially Flathead racers, got any good ideas for increasing the localized clamp load?

 :?    :|   :?    :|
Fordboy
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Offline RichFox

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2276 on: April 21, 2014, 10:45:03 AM »
On my OHV Plymouth I plugged all the water holes (dry deck) and skeletonized the gasket  to concentrate clamping where I needed it. Don't know what you could cut out on the Cad though.

Offline Pete1

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2277 on: April 21, 2014, 03:24:00 PM »
"Anybody out there in Land Speed Land, especially Flathead racers, got any good ideas for increasing the localized clamp load?"

I like all of 628's ideas but I like the .035 gasket the best as a temporary fix.

Offline 38flattie

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2278 on: April 22, 2014, 12:53:09 PM »
What O-ring wire diameter? Block groove width and depth? Receiver groove width and depth?

Wire:  .041

Groove Width in Head:  .0395 (interference fit - very important of it won’t stick!)

Groove Depth in Head:  .026

Protrusion:  about .015 proud (wire in the head)

Receiver Groove Width:  .055 to .060 (centered with the head groove)

Receiver Groove Depth:  .012 to .015
With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

You can't make a race horse out of a pig. But if you work hard enough at it you can make a mighty fast pig. - Bob Akin

http://www.flatcadracing.org/
http://youtu.be/89rVb497_4c

Offline Jack Gifford

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Re: XXO/BVGC '38 Chevy Coupe Build
« Reply #2279 on: April 23, 2014, 12:32:29 AM »
Thanks. With those odd-shaped rings/grooves, I assume you did the grooves with a CNC program? With locations referenced to head dowels?
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