How much cap walk is acceptable ?

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How much cap walk is acceptable ?

Post  nuclearcobra on March 12th 2018, 8:47 am

This is a Dove A block .060 with the A stamp on the front with factory crank , I pulled the caps to check the bearings when i had the pistons out and i see that i have cap walk marks , Just didn't know if a little should be a big alarm or just if you see big marks. I'm going to look for a picture to post and if i can't find it i'll pull a cap and take some pics and post them. Debating on getting it 4 bolted before it go's back together, I was quoted $400 for labor to have it done. The motor isn't wild imo , Its flat top diamonds , SCJ heads unported, flat tappet cam 260-268 637-648 lift , The tune seems to be fine its always consistent , i can run the plugs for a full season 3934's and they still look good , I mix 110 and 93 50/50 , I also wonder if its moving around with that set up or because i sprayed it a handful of times with a 180 shot and it pushed it over the edge. Its a 84 mustang 2760lb , 10' tire and best has been 9.95 on motor with a Hughes motor converter i cant footbrake over 2000 , tried 2500 several times but it
wrinkles the tires sitting there and pushes over the line usually so i stay at 2000 , on spray i ran a 5.96 in the 1/8 at 114mph and 9.71 at 112mph to the 1/4 on that pass because i ran outta gear. I finally have a 5200 nitrous converter from UCC to try this time and wondering if i am pushing my luck with the two bolt factory set up ?
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Re: How much cap walk is acceptable ?

Post  dfree383 on March 12th 2018, 8:51 am

How much compression?

Did you put a dab of antisize in th mating surfaces?
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Re: How much cap walk is acceptable ?

Post  Bill Heard on March 12th 2018, 3:54 pm

$400 doesn't sound to bad to me. I have a friend that has the main caps doweled (that doesn't look right) like the front and rear main caps. Seems to work well.
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Re: How much cap walk is acceptable ?

Post  BBFTorino on March 12th 2018, 11:33 pm

nuclearcobra wrote:This is a Dove A block .060 with the A stamp on the front with factory crank , I pulled the caps to check the bearings when i had the pistons out and i see that i have cap walk marks , Just didn't know if a little should be a big alarm or just if you see big marks. I'm going to look for a picture to post and if i can't find it i'll pull a cap and take some pics and post them. Debating on getting it 4 bolted before it go's back together, I was quoted $400 for labor to have it done. The motor isn't wild imo , Its flat top diamonds , SCJ heads unported, flat tappet cam 260-268 637-648 lift , The tune seems to be fine its always consistent , i can run the plugs for a full season 3934's and they still look good , I mix 110 and 93  50/50 , I also wonder if its moving around with that set up or because i sprayed it a handful of times with a 180 shot and it pushed it over the edge. Its a 84 mustang 2760lb , 10' tire and best has been 9.95 on motor with a Hughes motor converter i cant footbrake over 2000 , tried 2500 several times but it
wrinkles the tires sitting there and pushes over the line usually so i stay at 2000 , on spray i ran a 5.96 in the 1/8 at 114mph and 9.71 at 112mph to the 1/4 on that pass because i ran outta gear. I finally have a 5200 nitrous converter from UCC to try this time and wondering if i am pushing my luck with the two bolt factory set up ?

Your combo is similar to one I ran for a long time. Mine was a D1VE block. I didn't notice any evidence of cap walk from just running on the motor.
But I did have cap walk after a ton of nitrous passes!! It looked like metal transfer between the cap and the block.
Bearings still looked good, just strange marks on the caps & block.

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Re: How much cap walk is acceptable ?

Post  nuclearcobra on March 13th 2018, 1:00 am

Yea that's how mine looked its on both cap and block , and Dave no i didn't have anti seize on them , I've never heard of that before but i'll certainly try it.
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Re: How much cap walk is acceptable ?

Post  dfree383 on March 13th 2018, 10:37 am

Watch your tune and stop mixing the gas, run the strait 110
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Re: How much cap walk is acceptable ?

Post  gt350hr on March 13th 2018, 11:41 am

Cap walk is never acceptable. You need to replace the fasteners too. If the cap moved , the fasteners stretched too. Continued use with cap walk will eventually crack the block up through the cam bearing oil holes.

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Re: How much cap walk is acceptable ?

Post  dfree383 on March 13th 2018, 1:29 pm

gt350hr wrote:   Cap walk is never acceptable. You need to replace the fasteners too. If the cap moved , the fasteners stretched too. Continued use with cap walk will eventually crack the block up through the cam bearing oil holes.

it is what it is, most of them do it to some degree or another with the 2 bolt mains and decent power levels and live fine for a long time.
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Re: How much cap walk is acceptable ?

Post  nuclearcobra on March 13th 2018, 3:25 pm

Wow i didn't think flat tops and scj heads was enough compression for straight 110 , I do run straight 110 when i spray.
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Re: How much cap walk is acceptable ?

Post  nuclearcobra on March 13th 2018, 3:26 pm

Or did you mean straight 110 when i spray because i see i forgot to put that in there in the first post.
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Re: How much cap walk is acceptable ?

Post  dfree383 on March 13th 2018, 4:09 pm

nuclearcobra wrote:Or did you mean straight 110 when i spray because i see i forgot to put that in there in the first post.

I don’t like mixing fuel it’s safer to just run the strait race gas IMO

Detonation will cause the capwalk too.
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Re: How much cap walk is acceptable ?

Post  Lem Evans on March 13th 2018, 7:10 pm

dfree383 wrote:How much compression?

Did you put a dab of antisize in th mating surfaces?

Are you kidding? My 89 year old grandmother, several decades ago, rubbed BENGAY on her broken hip. Several days later she still had to go to the hospital. Antisize = bengay.

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Re: How much cap walk is acceptable ?

Post  Dave De on March 13th 2018, 8:41 pm

I'll never do that again (2 bolt bottom). I heard this here that you can go upwards of 800 hp without a 4 bolt. For me my 547, 13.5 comp., SCJ head, E85 NA package walked so bad that it was destroying bearings in the half season. The milled surface looked like it was a practice EDM piece.

My 521 10.5 comp., Edel head motor has no cap walk. Same block as the 547 a D9TE.

I think the limit has more to do with compression and stroke. The 547 was not detonating ever.

From my vantage point you are on the edge. I could see how the spray ran over the edge.
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Re: How much cap walk is acceptable ?

Post  dfree383 on March 13th 2018, 9:06 pm

Lem Evans wrote:
dfree383 wrote:How much compression?

Did you put a dab of antisize in th mating surfaces?

Are you kidding? My 89 year old grandmother, several decades ago, rubbed BENGAY on her broken hip. Several days later she still had to go to the hospital. Antisize = bengay.

It helps stop the metal transfer....... postpones the hospital visit
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Re: How much cap walk is acceptable ?

Post  cool40 on March 13th 2018, 10:03 pm

My 526 is a 800+ hp 2 bolt deal and it always has some cap walk. Bearings always look ok so I let'm walk. Cool
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Re: How much cap walk is acceptable ?

Post  BBFTorino on March 14th 2018, 12:16 am

They gotta crawl before they can walk!! Very Happy

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Re: How much cap walk is acceptable ?

Post  DaveMcLain on March 20th 2018, 8:35 pm

On my customer's monster truck engines I have signs of cap walk (A-460 blocks) The engines have all had some from when I freshened them for the first time and it never seems to have changed or gotten any worse.

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Re: How much cap walk is acceptable ?

Post  Frank Merkl on March 20th 2018, 10:45 pm

never have worried about a little metal transfer ! as far as I'm concerned it helps local the caps better! kind of like the new fractured rod cap technique!
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Re: How much cap walk is acceptable ?

Post  away on March 22nd 2018, 10:24 am

cool40 wrote:My 526 is a 800+ hp 2 bolt deal and it always has some cap walk. Bearings always look ok so I let'm walk. Cool

^^^What this guy said. If they walk a little so be it. If they don't something breaks! That is the exact principle that we all go by with the BBF and that is why we do not run main girdles! Clamp everything tight for no cap walk and guess what harmonics goes through the block and crack bang boom!

Also Note: My 532 in my maverick is going on year number 10 this year with all maintenance being the lifters and heads and springs. Never touched the bottom end not even rings!
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Re: How much cap walk is acceptable ?

Post  IDT-572 on March 23rd 2018, 4:01 pm

We have talked about this at length, if the oil clearance is adequate there will be no bearing damage. Also the bolts aren't stretching, maybe bending ever so slightly.

The threaded end of the bolt is loose in the bottom of the cap allowing the cap to move inboard then back out to the register as the bearing and cap are loaded by the crank.

Problem is, that after a period of time the flexing of the cap can eventually crack the cap.

On a race engine, flex gets worse as stroke goes up, cylinder pressure increases, and detonation occurs.

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Re: How much cap walk is acceptable ?

Post  nuclearcobra on March 23rd 2018, 11:52 pm

Thanks to all of you for the input , Very helpful as usual , I wont go any more than the 72-64 jets when i spray and maybe not even that much depending on how much difference a nitrous converter for my combo will make over a used motor converter i bought just to try that certainly wasn't for my combo. Heck if its that much of a improvement i might have to try a nitrous cam next Very Happy , My main goal was to see how fast i could go with a non stroker 460, unported heads and intake using a flat tappet cam , just a basic combo.
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Re: How much cap walk is acceptable ?

Post  Lem Evans on March 24th 2018, 8:18 am

At some point the block can crack also.

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Re: How much cap walk is acceptable ?

Post  dfree383 on March 24th 2018, 8:47 am

Lem Evans wrote:At some point the block can crack also.

Eventually yes agreed, but they seem to last pretty good.
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Re: How much cap walk is acceptable ?

Post  QtrWarrior on March 24th 2018, 9:46 am

dfree383 wrote:
Lem Evans wrote:At some point the block can crack also.

Eventually yes agreed, but they seem to last pretty good.

The only problem is you usually don't know "when " !!
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Re: How much cap walk is acceptable ?

Post  nuclearcobra on March 24th 2018, 8:23 pm

Darn i was all excited now I'm all worried again Laughing , I'll try to take it easy on the ole beast from now on Rolling Eyes Very Happy
I do have the timing at 30 on motor and 23 on the spray.
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