Cap walk problems

Sorry if I offended anyone with my post(fastford600). Is a 4 bolt conversion a good upgrade?, sure it is. An aftermarket block is even better yet. Cap walk is not desirable but the chance of it resulting in a completely destroyed engine is pretty low, as long as the tune-up is right on. Cap walk can vary from minor to major and if there is alot of metal transfer you need to upgrade. If it's a small amount it will live.

Greg,

IMHO, you're seeing the combo of two different things. First, is the ARP studs. There are two different styles of stock main bolts, a straight shank and a necked down shank. The stock necked down shank is better than the ARP studs. You'll see more cap walk with the ARP studs than the good stock bolts. Two, you are getting some detonation. It may be mild, but you are getting some. You're running high compression, and you need to add some race gas when driving it on the street, and while at the track, your nitrous tune needs some work.

If you look at the pics about the previously mentioned cap straps, you'll notice fretting between the strap and cap. He was getting detonation, and it is the same exact look your caps have. It doesn't matter if you get a better block, detonation will just break the weakest link.

And again, IMHO,

Dave

Dave,

There may in fact be some detonation. Although there is no evidence of detonation in the combustion chambers.

I wun 110 octane when at the track. Generally run 32 degrees of timing n/a and 27 on the 200 shot. I have spent a year leaning the fuel pressure on the nitrous kit from 9 psi to 7.75 psi. That's when I saw some specks on the plugs, so I went back to 8 psi and all was well.

The N2O comes on at 3000 rpm.

I am not doubting your experience, but I do not see how the ARP studs are weaker than the factory bolts. That just doesn't seem possible.

Greg

will blocks/caps not factory equipped with these stepped down stock bolts accept them?

Greg_P wrote:I am not doubting your experience, but I do not see how the ARP studs are weaker than the factory bolts. That just doesn't seem possible.

A bolt, or stud, has to stretch in order to apply a clamping force on the main cap. It is one thing to get a torque reading by twisting a bolt or stud, but what about the actual clamping force that the bolt or stud is applying? On the ARP stud, the smallest diameter (where is it actually stretching) in the in threads that screw into the block. The rest of the shank is a larger diameter, and while I'm sure it stretches a little, it does not stretch enough to apply the same clamping force that a stock bolt, the good necked down one, applies. Ford engineers designed that bolt. I'm sure they spend way more money designing it than ARP has. There is more than just diameter that makes a bolt "stronger" than other. From what I've heard, ARP can make a reduced shank stud if you request it.

138 wrote:will blocks/caps not factory equipped with these stepped down stock bolts accept them?

Yes. You may have go thru more than one set though to find 10 bolts that will torque correctly to spec.

Hope that helps,

Dave

Bret Powell wrote:Put a good set of aluminum rods in it, ARP studs torqued to about 105-110 w/molly, have it line honed, and STOP already with the lean tunes!

Bret

there is nothing wrong with a lean tune .... its all about timing also , a rich condition will cause more issues then a lean condition

Dave,

Interesting stuff....I'll definitely give the bolts some thought.

Remember, Ford also designed the CJ rod and the D0VE exhaust port, so many times I just don't give that original design argument much merit.

Thanks,

Greg

EDIT:

No disrespect intended, Dave, in fact just the opposite. I appreciate the input.

Greg_P wrote:Dave,

Interesting stuff....I'll definitely give the bolts some thought.

Remember, Ford also designed the CJ rod and the D0VE exhaust port, so many times I just don't give that original design argument about much merit.

Thanks,

Greg

Know what ya mean Greg,All i've heard is if you want it to stay together ya better put the good parts in it,because it's not stock anymore. Then it's (The the OEM parts is just as strong) so,who do you listen to w/o proof.
Dave, i'm not cutting on you it's just that ,like Greg said,Ford hasn't always had the best of idea's through the years
I will run the ARP stuff and be safe.(I hope)

This is interesting re:arp main studs.

The stock Ford bolts have a neck up near the head, not all the way down the shank. How does the neck at the head of the bolt hold the mating surface in place? I am not doubting, just trying to get it straight in my head.

I too thought that the ARP stuff was best, that's why I used it. I could have saved a few bucks!! Is there a way to shim the main cap holes to be tighter to the stud?

Bill

Greg_P wrote:I wun 110 octane when at the track. Generally run 32 degrees of timing n/a and 27 on the 200 shot. I have spent a year leaning the fuel pressure on the nitrous kit from 9 psi to 7.75 psi. That's when I saw some specks on the plugs, so I went back to 8 psi and all was well.

The N2O comes on at 3000 rpm.

I was thinking about this. You're peak torque is probably right around 3000 rpm, which means the engine is generating it's peak cylinder pressure at that point also, and you're hitting it with nitrous and really increasing the cylinder pressure. Have you tried hitting it a little later with the nitrous, while the cylinder pressure n/a is going down? Another way of putting it, if you're developing 650 ft/tq at 3000 rpm, use the nitrous to maintain 650 ft/tq all the way to 6000 rpm, not using the nitrous to get 850 ft/lbs at 3000 rpm.

Greg_P wrote:Remember, Ford also designed the CJ rod and the D0VE exhaust port, so many times I just don't give that original design argument much merit.

The way I see it, a CJ rod can be prepped to take 7000+ rpm with a 1000 gram piston/pin combo in a 460. A DOVE head can be prepped to make 700+ hp n/a. Now while everyone just wants to bolt together parts and go fast, the stock parts can take, and make, a lot of power with the proper machine work and tune. I don't thing the original engineers were ever thinking to put those components under that much stress.

bbf-falcon wrote:so,who do you listen to w/o proof.

There has, years and years ago, individuals who have ran 1500 hp with 2-bolt mains, stock bolts, and cast 460 crankshafts in blown applications already. Albeit, all the parts where prepped, and aluminum rods where used.

Greg,

I've always liked your build. To me, it represents a good solid street motor. Your cam timing is mild, you have high compression, and I'm sure that engine has power right off idle to 6000 rpm. The point will be reached one day when you want to crank it up tighter, go faster in the quarter, or generally you'll want a lot more power everywhere, but for the time being, IMHO, there are better places for you to spend your money to prevent cap walk, than to be sticking in a forged crank and A460 block for the power and ET you're doing right now. Some of the cap walk you seeing might just have come from the couple of bad tunes you had while you're getting your nitrous tune down. In the end, tune is what really determines if the parts you have now will live.

One thing that will definitely help if you use aluminum rods. While you might have to wait until the engine thoughly warms up while using the car on the street, the rods will help to absorb the shock of the nitrous hits at the track.

Hope that helps,

Dave

Just thought I would throw my experience with cap walk in the mix.

My previous engine was a 557 with a Scat cast crank. 2 bolt C8VE block filled to the bottom of the water pump holes. It made around 830 hp NA. No spray ever used. I ran an alky injection deal that was set up on the rich side and ran 31° timing. 12.7:1 compression with flat tops and BT heads. With the safe tune there never was any detonation that I knew of. The engine saw 6800 shift points. I ran it for 6 years and around 1200 1/8 mile passes before the Scat cast crank let go. A rod journal just snapped off. All the bearings looked new.

The engine was freshened ever 2 yrs. There was some cap walk present on #1 and #5. These caps were stock with ARP studs. The center 3 caps were BT/Engine Systems 4 bolt conversion caps. No evidence of cap walk on the 4 bolt caps.

It just proved to me that the 4 bolt caps can/did stop the cap walk, but that studs on the 2 bolt caps did nothing. If you want to stop the cap walk you need to use 4 bolt caps on all 5 with a stock thin web block. (D0VE thick web may be better) Or, invest in an A460 block and don't worry about it.

Some pic of my caps with walk here:
http://my.att.net/p/s/community.dll?ep=331&folderid=89244&groupid=66449&folderview=thumbs&ck=

Mr. Cole,

I was hoping you'd chime in here. Reading about your crank breaking is what set in motion a while back my plan to upgrade to the forged piece in my car.

Greg

Good in put David .

Greg did you get your pm

Yes I did, sorry I haven't replied yet. There are several folks interested in the crank, one since this summer.

If these folks bail on the crank I'll let you know.

This is assuming it'll pass the mag test.

Greg

cool deal i didnt know if it was working or not.

Greg_P wrote:Dave,

There may in fact be some detonation. Although there is no evidence of detonation in the combustion chambers.

I wun 110 octane when at the track. Generally run 32 degrees of timing n/a and 27 on the 200 shot. I have spent a year leaning the fuel pressure on the nitrous kit from 9 psi to 7.75 psi. That's when I saw some specks on the plugs, so I went back to 8 psi and all was well.

The N2O comes on at 3000 rpm.

I am not doubting your experience, but I do not see how the ARP studs are weaker than the factory bolts. That just doesn't seem possible.

Greg

Too much timing in my opinion, try 24 degrees. The general rule is 2 deg retard per 50hp of nitrous, always kept me safe to start with. Sometimes I have added 2 degrees more, once I had to pull more(pump gas). Nitrous is very hard on a engine, it comes on very quickly and violently unlike boost. Depending on your compression ratio, better fuel may be needed.

After reading all through this post something is nagging at me. If caps straps are considered (by some) to be help for cap walk, why not a main girdle given that the girdle rests on the main caps exactly as a strap would? i.e. the tops of the caps are machined true and in line with each other so the girdle acts as added strength/support like a cap strap and ties the caps to one another?

That will work fine, it's just none of the comercialy avaliable ones are built like that. That's why they are useless.

A true main girdle, like the old ones Milodon made for the 392 Chrysler Hemis back 45 years ago probably would help. Another company that makes a true main girdle is T/A Performance and they make it for a Buick 430-455. A girdle ties the mains into the oil pan rails and has about .003" preload or crush on the flat of the main caps.

These things nowadays, that they are making for the 429-460 Fords are called "girdles" but they are NOT. They are simply a "halo". Maybe they help some, but I don't think they do much for cap walk.

Uncle Charlie

Erica ran a stock block & crank to the 7's..

https://www.youtube.com/watch?v=2VemwcTaVfY

westsideford wrote:Erica ran a stock block & crank to the 7's..

https://www.youtube.com/watch?v=2VemwcTaVfY

That doesn't mean the main caps weren't walking.
Did you talk to her engine builder to find out ??

David Cole wrote:Just thought I would throw my experience with cap walk in the mix.

My previous engine was a 557 with a Scat cast crank. 2 bolt C8VE block filled to the bottom of the water pump holes. It made around 830 hp NA. No spray ever used. I ran an alky injection deal that was set up on the rich side and ran 31° timing. 12.7:1 compression with flat tops and BT heads. With the safe tune there never was any detonation that I knew of. The engine saw 6800 shift points. I ran it for 6 years and around 1200 1/8 mile passes before the Scat cast crank let go. A rod journal just snapped off. All the bearings looked new.

The engine was freshened ever 2 yrs. There was some cap walk present on #1 and #5. These caps were stock with ARP studs. The center 3 caps were BT/Engine Systems 4 bolt conversion caps. No evidence of cap walk on the 4 bolt caps.

It just proved to me that the 4 bolt caps can/did stop the cap walk, but that studs on the 2 bolt caps did nothing. If you want to stop the cap walk you need to use 4 bolt caps on all 5 with a stock thin web block. (D0VE thick web may be better) Or, invest in an A460 block and don't worry about it.

Some pic of my caps with walk here:
http://my.att.net/p/s/community.dll?ep=331&folderid=89244&groupid=66449&folderview=thumbs&ck=

every engine with c9,d9,or plain d1 blocks we see cap walk above 800 hp no matter the rpm,


-rich

I know the guy that did Erica's engine.....stock FOUR BOLT SCJ block . Because it was said to be 'stock' everyone assumed it was two bolt mains .

Has anyone on here running a blower on a 2 bolt bock at above 800 hp experienced cap walk? I've been told by several blower shops that the big belts dampen out the crank harmonics. So far I have not had any walk at a street low boost setup of around 750 hp or at a highboost set up of 1000+ . I do also run a main girdle. Am I just lucky? As soon as my new engine is finished, I'm going to retire this engine, so I will post some block/cap pics. This is going to be my last 2 bolt motor, I'm seeing too many on the forum having issues, and I don't want to break expensive parts...