Installing main cap dowels to help control maincap walk

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Installing main cap dowels to help control maincap walk  Empty Installing main cap dowels to help control maincap walk

Post  manofmerc on February 18th 2014, 7:28 am

I picked up an engine rebuilders magazine AERA I believe it was and there was an artical about putting dowels in a sbc .The author made the statement that after doweling the mains on his sbc circle track engines cap walk was eliminated .I was thinking this could be used to help eliminate main cap walk on our 460s .This isnt like the old 4 bolt 429cj engines pins in the block .This is a hollow dowel that locates in the bolt hole .The machine shop I use doesnt think it would be worth the trouble .And on my next visit to this machine shop I see an A-460 block that has the same dowels on the rear main cap .Now my curosity has really been aroused .I have two d1 blocks one has evidence of cap walk and the on the other it isnt as bad as the first block .I am planing a new build and I am really curious about doweling my d1 block I plan to alin home my block so now is the time .If you all think this is worth while is their a source for these dowels such as the ones on the rear cap on an A-460 block .Doug

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Post  HEMI-HUNTER on February 18th 2014, 9:52 am

im sure you can locate some dowels that will work for your purpose. however, will this be cost effective as compared to a "lets say" 4 blt. conversion. maybe try one block and see what the cost is and if it reduces the cap walk to where it is $$$$$$ worth it. if your getting severe cap walk then you are probley turning your motor pretty high RPM and may want to invest in a A-460 block anyway. if you go with the dowels I would also use a main girdle also witch may stop all the cap walk, but the cost of the dowels plus the girdle and machine work gets you into the 4 blt price range anyway. this has been gone over and over before and really comes down to how much $$$$$$$ do you throw at a 2 blt stock block before you spend enough to justify a aftermarket block? personal I don't think the D1VE block 4 blt. conversion is worth the $$$$$, I would convert a D0VE Block to 4 blt but not a D1. that's just me others have done the D1 conversions and are happy. try the dowels but you gonna spend $500 plus doing it I would guess at todays machine shop prices. then the price to align hone another $300 for a girdle if you want to go that route for extra strength. maybe find a 4 blt CJ block for that kind of money.
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Post  c.evans on February 18th 2014, 10:04 am

To the best of my understanding, Ford uses their small block 1/2" head bolt dowels, for the main cap dowels, in numbers 1 & 5 main caps of the SVO block. So "finding" the dowels should be a no brainer.

Charlie

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Post  norm on February 18th 2014, 9:44 pm

Do dowels help with cap walk? I would think the 4 bolts help more against cap walk and the dowels are more for location.
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Post  manofmerc on February 19th 2014, 6:20 am

Thanks for the responces guys .I already have this d1 block it has been bored and really has served me well.I agree a dove block with 4 bolt conversion would be better I dont have a dove block unfortunatly .And an aftermaket block is out of the budget .I dont know if this dowel installation will prevent or eliminate my cap walk situation .But possibly with installing the dowels I would know if cap walk would be reduced or eliminated the next time I did a teardown .As far as the expense goes the machine shop I use wouldnt charge me no where near the amount it takes to install 4 bolt caps .And I really d1s arent practical to 4 bolt anyway .I have two d1 based 460 cu in engines I have ran for several years .One has evidence of cap walk.The other hardly any .Both were ran in the same car same rpm range (6000-6500).And both had the same tuneup 34-36 degrees timing 11-1 11.5 compression .On my part this is something I want to try after seeing that artical in the AERA magazine somehow I dont think it could hurt and I also am aware it might not HELP any thing either .My machine shop just wants me to install a set of studs .Some engine builders on here are totally against studs so there we go again opening another can of worms .Thanks for the ideas and opinions .Doug

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Post  Paul Kane on February 19th 2014, 1:10 pm

If you are considering doweling a 2-bolt block, then the answer is that doing so will indeed help reduce cap walk since the dowels keep the main caps in place and prevent their mating surfaces from being yanked inward towad the crankshaft main journals.  And so cap walk will be reduced in an engine such as you describe (shy of perhaps 750 hp or so). And 750 hp is about the max I would consider doweling 2-bolt main caps in passenger car block. The irony is that...at 750 hp is the cost and effort really justified in the results?

And conversely, doweling the 2-bolt main caps of the standard passenger car block so as to make the block useful for super-high power levels is the wrong way to go as well.  In such engines with passenger car blocks you want to let the parts move around.  Pinning the 2-bolt main caps in place (in a super-high hp engine) will induce a greater load on the main caps in the area where they are not pinned in place and thereby be more likely to make them fail.

In other words, in high hp engines with passenger car blocks you need to learn to accept cap walk as part of the program. "Main cap walk" is not the same as "main cap failure."  Main cap walk is simply an artifact of a high horsepower engine program that uses the passenger car block.

Paul

P.S.: In regards to letting things move around: you are better off with the OEM main bolts. The aftermarket studs are "too much fastener" for such a program and bring with them similar (if not identical) problems.
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Post  the Coug on February 19th 2014, 3:37 pm

why not just clip the caps flat on the you and put a 3/4 or 1 inch thick bar across the top of the cap, that will fix cap walk and probably be cheaper in the long run

Just have the caps cut flat and have a bar machined to lay on top and run bolts thru or stud it.

what some people do not understand is it is the center of the cap bowing out that creates the cap walking, a Girdle does nothing to address this it still has a gap in between the girdle and the Cap, so in essence all you have is an emptier wallet and more weight in the engine....
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Post  manofmerc on February 20th 2014, 7:31 am

My engine isnt a super high performance .It is a bracket race engine runs 6.90 -7.10 in a 3400 pound car .Again since i plan on having my spare block alin honed I just want to do all the improvements I can while it is at the machine shop .And this is an experment for me .Like previously stated If after installing these dowels on my next teardown there isnt any evidence of maincap walk problem solved !And maybe guys with d1-d9 blocks have an alternative to dove blocks and a-460 Since I saw this being done to the sbc in the aera magazine I have wanted to post this and so glad I did .Maybe we can all learn something about our 460 based engines from this post .Thanks for the responces and I hope more are to come

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Post  the Coug on February 20th 2014, 3:12 pm

my conclusion it will not work, reasons

#1 the weak dowel is not long enough to substantially support any side movement

#2 with the short dowel being split down the side it will wobble and be very susceptible to movement, making the dowel loose as it gets flexed

#3 it is doing nothing to stop or control the flex in the cap it's self, which I see as a waste of money

now if you work to control the cap flex then you are working at fixing the problem, this is like putting a bandaid on cut artery. might slow the bleeding down but will still bleed.
This is why I said to strap it, that is at least working to fix the flex in the top of the cap.....


have a nice day
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Post  jm on February 20th 2014, 5:35 pm

I think what randy (the coug) says about the strap idea would be the best idea. but if you could do both, it would be neat to see. I always wanted to try the dowel thing my self. I wish greg would chime in and tell us how his 545 in his torino is doing with the strap conversion he performed on his bottom end. Smile 

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Post  manofmerc on February 21st 2014, 8:40 am

 Coug the dowels I saw on the a-460 block werent split like head dowels and the ones on the sbc in the AERA magazine werent either .The ones I saw appeared to be really good quality steel .Before I would consider this I would have to look at the sbf head dowels before installing those .If you all will go over Pauls post about doing this dowel install read this .He states installing dowels will help prevent the cap from squeezing in .Not exactly what he said but you get the point .Just read his post he makes his case much better than I .Thanks for everyones responces a lot of good and interesting ideas .Maybe I am trying to put lipstick on a pig but its my pig .Doug

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Post  466cj on February 22nd 2014, 12:49 am

manofmerc wrote: Maybe I am trying to put lipstick on a pig but its my pig .Doug

Pins or dowels are for locating a cap. I'd say you nailed it on the head with your above statement!

What Randy posted is good advice, that or get a good 4 bolt main block. Cap walk is about surface area and clamping force. If you cannot provide an increase in that then making the cap stronger is next best and even on a 4 bolt you still need a stong cap that don't flex. Cap walk is just one thing to be concerned with.

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