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Use a main cap girdle w/ plate-style alum. main caps?
#866665
11/29/10 07:13 PM
11/29/10 07:13 PM
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Posts: 15,439
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BradH
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I know the plate-style aluminum main caps like have already been fitted to my 448 block have a questionable reputation for long-term durability ==> cracking. This is supposed to result from the manner in which they're machined (BCR pointed out their lack of radius' at the bottom of where the bolt "tunnels" are cut into the caps). Would adding a main cap girdle in conjunction w/ this style of cap be a benefit? My thought (uneducated on the subject as it may be) is the girdle would help stabilize the caps and reduce flexing that may be a contributor to the cracking problem. Does this sound like a good approach, since I already have the CRE girdle kit? Or are the factors that cause the caps to crack not likely to be alleviated by the addtion of a girdle? NOTE: Photo of caps found in Muscle Motors' online catalog. 
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: BradH]
#866669
12/01/10 02:23 PM
12/01/10 02:23 PM
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Joined: Feb 2007
Posts: 970
Backwater, PA
bwdst6
Bob George Racing #1 Fan
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Bob George Racing #1 Fan
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Posts: 970
Backwater, PA
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The significant loading induced on the block from the crank is in the vertical direction. A main cap girdle does not produce much support in this direction so it doesn’t do much good. But I suppose it won’t hurt either. 
Last edited by bwdst6; 12/01/10 02:25 PM.
This post is available in double vision where drunk.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: bwdst6]
#866670
12/01/10 02:57 PM
12/01/10 02:57 PM
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Joined: Jul 2009
Posts: 413
Norway (old world)
Oyvind Mopar
mopar
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mopar
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Posts: 413
Norway (old world)
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Quote:
The significant loading induced on the block from the crank is in the vertical direction. A main cap girdle does not produce much support in this direction so it doesn’t do much good. But I suppose it won’t hurt either.
These loads are vertical from each cylinderbank, but as they are on 45 degree, I still think the girdle will help. But why not use the design where the girdle is flat on top of the maincap? (Yes, the maincap will be weaker, but it will be supported in some way...). Think I have seen this design from girdle suppliers. I know two thin pieces will flex more than one thick, but maybe the properties of the girdle is keeping the alu cap more in shape and place? Ideally the girdle should have been like a thick beam over the maincap. But, then, maybe the main advantage (cushioning) of the alucap is gone? My 
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: bwdst6]
#866672
12/01/10 03:45 PM
12/01/10 03:45 PM
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Joined: Jan 2003
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BradH
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Quote:
The horizontal component of the 45° from the opposing banks cancel each other out.
I'd expect if you could attach some type of motion / stress detection sensors to the main caps of a running engine that you'd find out they're getting  from a variety of directions.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: Cab_Burge]
#866674
12/01/10 04:09 PM
12/01/10 04:09 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
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Quote:
... it is better to step up and buy a piece(block) that is designed to handle the stresses you want to throw at it, instead of reverse engineering it trying to bandaid it with additional parts like stronger main caps and girdles
Keep in mind that in this case all the parts I'm talking about are already paid for and the block's already been fitted w/ the caps.
Besides, when I tell people I'm sponsored by Johnson & Johnson, I really mean this...
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: bwdst6]
#866677
12/01/10 04:28 PM
12/01/10 04:28 PM
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Joined: Jan 2003
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BradH
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Quote:
Quote:
Keep in mind that in this case all the parts I'm talking about are already paid for and the block's already been fitted w/ the caps.
Besides, when I tell people I'm sponsored by Johnson & Johnson, I really mean this...
So if you’re planning on doing this anyway why did you post this thread?
As I asked at the start of this: "Would adding a main cap girdle in conjunction w/ this style of cap be a benefit? My thought (uneducated on the subject as it may be) is the girdle would help stabilize the caps and reduce flexing that may be a contributor to the cracking problem.
Does this sound like a good approach, since I already have the CRE girdle kit? Or are the factors that cause the caps to crack not likely to be alleviated by the addtion of a girdle?"
Yes, I have the parts. No, I was not already intent on using them together. The girdle was bought for use w/ a stock-cap block I have, too. It's my concerns about the reliability of these particular aluminum caps that have me considering adding the girdle, too.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: BradH]
#866678
12/01/10 04:33 PM
12/01/10 04:33 PM
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Joined: Jan 2003
Posts: 2,933
Finalnd, Perkele
jyrki
master
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master
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Posts: 2,933
Finalnd, Perkele
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How common was the cracking anyway? I have never had that happen, nor have I personally seen it except in the internet. What kind of power are you planing to make?
Plynouth VIP '67 TT IC EFI
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: bwdst6]
#866679
12/01/10 04:40 PM
12/01/10 04:40 PM
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Joined: Feb 2007
Posts: 5,080
organ
maximum entropy
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master
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organ
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i vote USE THE GIRDLE! true, it adds little strength in the vertical plane, but it adds A LOT in the horizontal plane (fore and aft in particular). my raging cap walk stopped with the addition of a run of the mill chenoweth girdle. I BELIEVE! as an added consideration, we're also changing the frequencies that the block resonates at. i talked to a guy from under the bridge who knows a lot about engines, and he said the extended lower portion of bb mopars rings like a bell under certain conditions and at certain rpm. sounds plausible. use it!
for what is the good life if not doing things thoughtfully?
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: jyrki]
#866680
12/01/10 04:43 PM
12/01/10 04:43 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
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I know of three cases where it's happened. Whether that's 5% of the total users or .005%, I can't say. Regardless, IMO that design is "less than ideal" and I'm already financially tied to this particular set. Therefore, I'm looking for ways to reduce the possibility that I'm case #4. And, in my case, a little paranoia goes a long way.  Estimated HP level for engine using this particular block is 650-ish.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: BradH]
#866683
12/02/10 12:49 AM
12/02/10 12:49 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
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Romeo MI
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I dont know if you have had the caps modified yet BUT you could have a machine shop mill it with a radiused end mill about .030 deeper the same diameter to eliminate the stress riser... in my opinion the girdle might help a little but the stress riser is still there and the girdle might chance the frequency/harmonics enough to get it out of the rpm range that you would be running in.... JMO 
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: BradH]
#866684
12/02/10 03:01 AM
12/02/10 03:01 AM
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Joined: Jan 2003
Posts: 1,361
Wild West
M_D
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Wild West
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Due to the nature of the harmonics that I believe would cause cracks in the caps, my guess is a girdle wouldn't provide any help in preventing or prolonging failure due to stress risers in the caps. I believe modifying the cap profile per your drawing would reduce the chances of the caps cracking or at least extend their life, providing the work was properly done. I doubt that modifying the caps would cause a consequential strength loss or a dimensional change to the main bore as it appears the counter-bore leaves very little material and strength left in the remaining web of the cap design pictured.
Whether it is worth it to modify the caps or not is debatable though, imo. If it were me, I probably wouldn't try to modify the caps by spot-facing the counter-bore with a radius, although it would have been better if that were done originally. Now though, even more material that does contribute to strength would need to be removed, and there would be a possible issue of if the resulting flat would be large enough in diameter for the washer to fit correctly.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: MR_P_BODY]
#866685
12/02/10 11:24 AM
12/02/10 11:24 AM
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Joined: Jan 2003
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BradH
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Quote:
... you could have a machine shop mill it with a radiused end mill about .030 deeper the same diameter to eliminate the stress riser...
I think that's basically what Greg at BCR was suggesting on an older thread, too.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: M_D]
#866686
12/02/10 11:27 AM
12/02/10 11:27 AM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
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Quote:
...I believe modifying the cap profile per your drawing would reduce the chances of the caps cracking or at least extend their life, providing the work was properly done... Whether it is worth it to modify the caps or not is debatable though, imo...
So, my  is justified, eh? 
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: BradH]
#866688
12/02/10 09:38 PM
12/02/10 09:38 PM
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Joined: Jan 2003
Posts: 1,361
Wild West
M_D
pro stock
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pro stock
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Quote:
Quote:
...I believe modifying the cap profile per your drawing would reduce the chances of the caps cracking or at least extend their life, providing the work was properly done... Whether it is worth it to modify the caps or not is debatable though, imo...
So, my is justified, eh?
If I was in your boat and could get the work done cheap enough I would probably do it. I didn't know what you might have to pay to get someone to do it, some shops might want almost the cost of a new set of caps to do the work, depending on the shop.
What Greg suggested is about what I had in mind, procedure wise. If you decide to modify them and can't find a local shop you feel comfortable with to do it, you could send them to me and I'll cut them down on one of the machining centers for you. I usually stay away from one of a kind deals since we are geared up for production work, but the setup would be quick and easy in this case.
Last edited by M_D; 12/03/10 03:17 PM.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: M_D]
#866689
12/03/10 11:47 AM
12/03/10 11:47 AM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
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Micha el - I appreciate the offer. I'll check w/ the local machine shops to see how reasonably they'd do the job. Based on what I'd been charged in the past for what I viewed as a fairly simple job (narrowing some rocker arm hold-downs), you may be hearing from me about some work.  EDIT: Name correction...
Last edited by Blew My Budget!; 12/03/10 06:04 PM.
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: Monte_Smith]
#866692
12/03/10 06:19 PM
12/03/10 06:19 PM
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Joined: Nov 2003
Posts: 1,279
bcrproducts
super gas
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super gas
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Quote:
While the potential may be there, I myself have never seen a set of those caps cracked at the bolt hole and have installed many sets. I personally am NOT a fan of girdles and would never, under any circumstance, install one..... In this instance, if you are worried about the caps, machining them like your drawing, should be fine.
Monte
With all due respect Monty the caps in question are why BCRproducts started back in about 1992. The caps you see above wer famous for cracking as I broke two sets myself. Now these caps may very well have a radius of some sort at the bottom of the counterbore and they may be fine.
Now you also state that you would never install a girdle under any circumstances??? Again are you speaking from experience or opinion. I would like to hear why you would not. Again we here on Moparts designed together what we feel is the best option for a non aftermarket block utilizing aluminum caps and a tied in girdle. You may have built a few motors in your day but I have sold hundreds of cap sets and hundreds of girdle cap sets and built many of those shortblocks along with Norm at Fortins "see Engine Masters and related articles in Mopar Muscle and Mopar Action". I have a hard time with people saying they can not see the benefit.I do see your point if you are talking about the 1/4 aluminum girdles available online but the one we designed is far different. Yes it may be pricey but then again we all don't have the option of an aftermarket block either. Generally the people that dissagree with a cap and girdle system have never even tried one. I don't recall sending one your way. I have installed a few nirous setups over the years but would never express my expertise on the subject as I just am not an expert on them.
Greg
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Re: Use a main cap girdle w/ plate-style alum. main caps?
[Re: bcrproducts]
#866694
12/04/10 04:36 AM
12/04/10 04:36 AM
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Joined: Nov 2004
Posts: 6,890
North Alabama
Monte_Smith
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Quote:
Quote:
While the potential may be there, I myself have never seen a set of those caps cracked at the bolt hole and have installed many sets. I personally am NOT a fan of girdles and would never, under any circumstance, install one..... In this instance, if you are worried about the caps, machining them like your drawing, should be fine.
Monte
With all due respect Monty the caps in question are why BCRproducts started back in about 1992. The caps you see above wer famous for cracking as I broke two sets myself. Now these caps may very well have a radius of some sort at the bottom of the counterbore and they may be fine.
Now you also state that you would never install a girdle under any circumstances??? Again are you speaking from experience or opinion. I would like to hear why you would not. Again we here on Moparts designed together what we feel is the best option for a non aftermarket block utilizing aluminum caps and a tied in girdle. You may have built a few motors in your day but I have sold hundreds of cap sets and hundreds of girdle cap sets and built many of those shortblocks along with Norm at Fortins "see Engine Masters and related articles in Mopar Muscle and Mopar Action". I have a hard time with people saying they can not see the benefit.I do see your point if you are talking about the 1/4 aluminum girdles available online but the one we designed is far different. Yes it may be pricey but then again we all don't have the option of an aftermarket block either. Generally the people that dissagree with a cap and girdle system have never even tried one. I don't recall sending one your way. I have installed a few nirous setups over the years but would never express my expertise on the subject as I just am not an expert on them.
Greg
All that was just my opinion, nothing more
. I said I never saw any of those caps broken and I have'nt. Thats all I know. Did some break, obviously, I just never saw one. Never broke one on any of my motors, or any motors I ever built and I have built one or two over the years. I made well over 1000hp with some stock block stuff. Never broke a cap, never knocked the main webs out of a block. Maybe I was lucky.
As far as the girdle....no, never tried one and never will. I don't agree with the premise of the girdle, so I won't use it. Whether that is right or wrong, it is my opinion. The main webs are the weak part of the block, not the cap. The girdle attempts to stop cap "bounce", not cap "walk". In my opinion, by clamping the cap tight on the block, with the girdle, you are no longer allowing the cap, to absorb the force and it is transfered, to the web, which is the weak part. A high HP motor, is trying to blow the crank on the ground. I believe in letting the alum cap, absorb some of that force, which takes it off the webs. Same reason I like alum rods. Would you rather beat on your crank with a steel hammer, or an alum hammer. Am I all wrong, maybe, maybe not...but like I said above, I made a bunch of hp with a stock block, alum caps, no girdle and never broke a block. So I am a firm believer, in if something is working, why change it. If you don't agree, thats your opinion and you are entitled to it, same as I am mine.
Monte
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or other non-technical subject matter.
Somtimes, especially now, it is better to step up and buy a piece(block) that is designed to handle the stresses you want to throw at it, instead of reverse engineering it trying to bandaid it with additional parts like stronger main caps and girdles 
