Main Caps VS Block Girdle
- Thread starter yipekiya
- Start date
turboman38
It costs money to go fast
- Joined
- Aug 1, 2001
IMO you don't need a girdle unless you are running in the 10's every weekend. If you are racing that often and that fast you should be running a stage motor.
I put the two center steel maincaps on my motor for strength. It keeps the crank from walking if you start to detonate the motor. My car should be running low to mid 11's after I get the heads and intercooler in it.
Just my 2 cents
I put the two center steel maincaps on my motor for strength. It keeps the crank from walking if you start to detonate the motor. My car should be running low to mid 11's after I get the heads and intercooler in it.
Just my 2 cents
REDS HOT AIR
Buick Tweaker
- Joined
- May 24, 2001
my oppinion differs but not everyone will say the same...
to me caps arent worth it since all i've seen blow the crank out the main caps didnt break the block did..
so i've got mine out now and putting a girdle on it..
to me caps arent worth it since all i've seen blow the crank out the main caps didnt break the block did..
so i've got mine out now and putting a girdle on it..
One thing to consider in the girdle vs. main caps debate is that the installation of aftermarket main caps requires align-honing the block. This can introduce slack in the timing chain, and in a high performance application (using a double roller-type chain) the tensioner cannot be used to take up the slack. I could be wrong but I don't believe custom-length timing sets are available for our engines.
We've used both the girdle and caps (see sig) but have no evidence favoring one method of block strengthening over the other.
We've used both the girdle and caps (see sig) but have no evidence favoring one method of block strengthening over the other.
This is my opinion only OK?
Girdle - mill material off the back of the cap (at the point of highest stress) and then place a back up against it. If the cap was keyed with the girdle, I'd be more of a believer but I don't think as far as cap strength, it is better.
It will help to keep your mains in the block from moving if that's a problem. I think this could be a problem if your crank is flexing causing some deflection in the force vector trying to push the caps around. Iron has some ductility though so it wouldn't immediately crack and fail. Harry Hruska once told me the saw the crank whipping, the mains didn't fail. The motor had steel caps. Oil leaks suck.
Caps - they're steel and bigger. That's good.
Ideally, a girdle that left the back of the cap alone but merely tied the mains to the pan rail might be good.
EDIT:
I'd like to see any failure mode information on a failed bottom end. I'd bet the caps and webbing were failed at that point if the failure was caused by one or the other. Not oiling but stress.
If the webbing pulls out of the block, a girdle will do little to prevent the crank axis from drooping under the pressure. Any movement over a thou will kill the crank. A half inch of steel isn't much to help but I'm certain it will provide some relief. Steel main caps will also provide relief.
BTW, my car has been running mid to low tens for 2 years now and the only thing happening is a possibly widening thrust bearing clearance.
I have a +.005 timing chain at home that is 7 position indexable. A +.010 is also available. Timing slack with the line bored block was zero with this set. I use a billet roller cam with a double roller timing set AND a tensioner. Pump pickup was clean after a year of running and the tensioner showed normal wear.
My only failure has been a thrust bearing. I put steel caps on after that - so far, so good...
Girdle - mill material off the back of the cap (at the point of highest stress) and then place a back up against it. If the cap was keyed with the girdle, I'd be more of a believer but I don't think as far as cap strength, it is better.
It will help to keep your mains in the block from moving if that's a problem. I think this could be a problem if your crank is flexing causing some deflection in the force vector trying to push the caps around. Iron has some ductility though so it wouldn't immediately crack and fail. Harry Hruska once told me the saw the crank whipping, the mains didn't fail. The motor had steel caps. Oil leaks suck.
Caps - they're steel and bigger. That's good.
Ideally, a girdle that left the back of the cap alone but merely tied the mains to the pan rail might be good.
EDIT:
I'd like to see any failure mode information on a failed bottom end. I'd bet the caps and webbing were failed at that point if the failure was caused by one or the other. Not oiling but stress.
If the webbing pulls out of the block, a girdle will do little to prevent the crank axis from drooping under the pressure. Any movement over a thou will kill the crank. A half inch of steel isn't much to help but I'm certain it will provide some relief. Steel main caps will also provide relief.
BTW, my car has been running mid to low tens for 2 years now and the only thing happening is a possibly widening thrust bearing clearance.
I have a +.005 timing chain at home that is 7 position indexable. A +.010 is also available. Timing slack with the line bored block was zero with this set. I use a billet roller cam with a double roller timing set AND a tensioner. Pump pickup was clean after a year of running and the tensioner showed normal wear.
My only failure has been a thrust bearing. I put steel caps on after that - so far, so good...
Rob, I,ve built a couple of 3.8's with the steel caps for friends, both cars are runing low 11,s at 120 mph. One is 3640 lbs with driver the other is 3850 lbs with driver, so far so good. (fingers crossed) I would like to do another 3.8 with a girdle but I feel to do it right would involve a lot of work. ( torque the caps to the block with contersunk cap screws them mill the caps and pan rail togeather) I had a friend whos girtled block had the caps milled flat and the shims were used to level things out, that motor lasted only a few miles, of course I don't know if other issues may have helped cause the rapid bearing failure.
9secvsix
9secvsix
Yes, Precision doesn't believe they help. There isn't any way anybody is going to tell me that a girdle doesn't HELP. In your theorys above, I do agree with 99.9% BUT you cannot discredit the girdle, will prevent a significant amount of stress on the cap and webbing. As far as pinning the cap to the girdle, I don't see a need for it as the main studs are locked down to the girdle and that takes stress off the stud, which will help the fastener hold the cap down under high HP applications. The cap fits TIGHTLEY in the block so how can it move? The bottom line is when you only have 2 bolts holding a cap down, and you subject those 2 bolts alone under a certain amount of force, they WILL stretch a certain amount and allow the cap to move. The iron caps do not break first, they distort. I would go with the girdle first and leave the stock caps. BUT I stress only if you intend on pushing it to the max(mid to low 10's). I'd go with steel centers anything above that and just run good gas when you are beating on it. Factor in the oil leaks associated with the girdle, that's why I say one or the other depending on HP levels.
Yes, you can run low 10's with caps alone, but I can't see why when the girdle option is available now.
Flame suit on
REDS HOT AIR
Buick Tweaker
- Joined
- May 24, 2001
someone actually believes something from them people
btw: turbine wheels cant fail either
http://gnttype.org/techarea/pictureguides/blocks/DOTC.html
heres a blown out bottom end...notice center mains are still in place ...also notice that the rear main is still bolted to the block
other words caps are fine block gave up ...only way to strenthen it up is girdle
btw: turbine wheels cant fail either
http://gnttype.org/techarea/pictureguides/blocks/DOTC.html
heres a blown out bottom end...notice center mains are still in place ...also notice that the rear main is still bolted to the block
other words caps are fine block gave up ...only way to strenthen it up is girdle
One comment about possibly "weakening the stock caps by milling them down": very little material is removed... just enough to even them up with the oil pan rail. Then you go and bolt an inch slab of steel on top of that.
Why mill the caps and rail all at one time? Using thin shims at each cap is how you achieve the proper preload, then have the assembly align honed while bolted together, if that was the concern there.
As far as leaks, mine leaked like a seive... BUT, I used the wrong type of gasket and no sealer around the studs. I actually succeeded in stopping half of the leaks by using the Right Stuff sealer from under the car in a "jerry rigging" situation! Reassembly will be done properly, and I am convinced it won't leak... nearly as much!
As far as my thrust beaing failure goes, I am convinced that it was my own fault upon assembly. Several years ago when I put that short block together, I didn't even know you were supposed to "set" it! Doh!
Why mill the caps and rail all at one time? Using thin shims at each cap is how you achieve the proper preload, then have the assembly align honed while bolted together, if that was the concern there.
As far as leaks, mine leaked like a seive... BUT, I used the wrong type of gasket and no sealer around the studs. I actually succeeded in stopping half of the leaks by using the Right Stuff sealer from under the car in a "jerry rigging" situation! Reassembly will be done properly, and I am convinced it won't leak... nearly as much!
As far as my thrust beaing failure goes, I am convinced that it was my own fault upon assembly. Several years ago when I put that short block together, I didn't even know you were supposed to "set" it! Doh!
Intercooler
New Member
- Joined
- May 24, 2001
Why we are on the subject, where are my studs??? I leave tomorrow and can't get a return e-mail from you but you are on here. E-mail me please.Originally posted by REDS HOT AIR
someone actually believes something from them people
btw: turbine wheels cant fail either
http://gnttype.org/techarea/pictureguides/blocks/DOTC.html
heres a blown out bottom end...notice center mains are still in place ...also notice that the rear main is still bolted to the block
other words caps are fine block gave up ...only way to strenthen it up is girdle
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