Broken piston(s) SBC

[enkeivette]

I think Glenn guessed it, ring land broke. Another pitson took a bit of a beating but it's still intact. Since I'm poor, I think I'll stick with the SRPs this time around, and just buy 1 or 2 new ones, then upgrade the fuel pump and the rings.

I think I'll be able to reuse this block. What do you guys think? (Look at pic 2) The upper edge of the cylinder is a bit messed up, but it looks like it doesn't extend past the point where the ring slides, so I might just clean it up and run it. The cylinder heads will prob need a once over with the mill, the combustion chamber over each cylinder have evidence of abuse and some metal fragments lodged in the surface, but nothing detrimental. I'll prob get them magnafluxed to make sure there are no cracks.

Remember this before you give me advice. I have less money than you, and I am concerned only with what I NEED to do, not what I SHOULD do.

[enkeivette]

http://i43.tinypic.com/10sbts7.jpg
http://i43.tinypic.com/10p7lmx.jpg
http://i42.tinypic.com/kcz97k.jpg

[Vettezuki]

How much are willing to spend? There's a a shop I like that's local to OC (Anaheim). I'm guessing, but a magnaflux, head touch up, and a couple piston replacements and rebalancing, assuming you do all the dissaseembly work, will be in the $500~ range.

[94cobra69ss396]

Are those forged pistons? If so, that thing had to have been detonating horribly. That's exactly what happened to my stock hypereutectic pistons when I gave the car too much timing. If the mark in the bore isn’t protruding out you should be fine running it. If you can save up the money I would have it checked by a machine shop to see if you could get by with just a hone or if it should be bored but I understand the not having any money thing. You probably won’t need to mill the heads unless you got the car hot and they warped. Check them with a straight edge and see. If they’re not then just clean up the combustion chambers.

[SeanPlunk]

Are those forged pistons? If so, that thing had to have been detonating horribly. That's exactly what happened to my stock hypereutectic pistons when I gave the car too much timing. If the mark in the bore isn’t protruding out you should be fine running it. If you can save up the money I would have it checked by a machine shop to see if you could get by with just a hone or if it should be bored but I understand the not having any money thing. You probably won’t need to mill the heads unless you got the car hot and they warped. Check them with a straight edge and see. If they’re not then just clean up the combustion chambers.

The pistons are indeed forged.

[enkeivette]

Never ever heard detonation. Not saying it didn't denonate, but if it did it wasn't obvious. Timing was at 32 full, 36 is normal for a SBC. Guess I need to pull more. Heads never got hot.

Block is staying in the car, going to clean up the bores with hydrochloric acid to get the aluminum off. No boring, no honing, and possibly no milling. Going old skool. Where's Glenn at? I need some duct tape and some inspiration. :D

Ben, you want me to pay someone else to do the labor? Who did you think you were responding to?

[Vettezuki]

. . .Ben, you want me to pay someone else to do the labor? Who did you think you were responding to?

You gonna mill heads and rebalance the assembly in your garage? I'd like to see that. :smack:

[big_G]

If you get the same EXACT piston (part number) you don't need to re-balance..unless the tops or pads were milled. Also, if you expect the rings to seat you will need to hone the affected cylinders. BTW, I had to do what you're about to do, but only 1 cylinder. (some a-hole dropped a BB down my carb....jealous ex-employee).:mad::mad: BTW, if you're still not using an inter-cooler, detonation is likely the reason. I can't hear any on mine...but reading the spark plugs told me I had occurrences of detonation.

[BRUTAL64]

Never ever heard detonation. Not saying it didn't denonate, but if it did it wasn't obvious. Timing was at 32 full, 36 is normal for a SBC. Guess I need to pull more. Heads never got hot.

Block is staying in the car, going to clean up the bores with hydrochloric acid to get the aluminum off. No boring, no honing, and possibly no milling. Going old skool. Where's Glenn at? I need some duct tape and some inspiration. :D

Ben, you want me to pay someone else to do the labor? Who did you think you were responding to?

I'm here now. The scratches don't seem deep. If you run your finger nail over them do you feel your finger nail pull at them. If so, then, they are maybe too deep. Just run your finger nail over the scratches and see if they pull. Let me know. Other wise you seem to have a handle on this. If you need me to to check it out, let me know.:drink:
I blew the ring lands out of 4 pistons and never heard a thing. Well, I did hear the engine run funny after that.

[enkeivette]

You gonna mill heads and rebalance the assembly in your garage? I'd like to see that. :smack:

Like I said above I might not mill the heads, and hopefully if I can find the same piston I won't need to rebalance. If it's off, I will just grind on that piston. You can grind on the back of a piston can't you? :leaving:

Big G, you've inspired me, looks like I need to sell the jet skiis and buy a damn intercooler. But I think I'll leave the boost at 10lbs for now.

[Leedom]

BTW, if you're still not using an inter-cooler, detonation is likely the reason. I can't hear any on mine...but reading the spark plugs told me I had occurrences of detonation.

I agree, I think most if not all forced induction set-ups should have an inter-cooler.

[big_G]

You don't need the high-buck ProCharger intercooler. search the internet. I bet the plumbing costs more than the intercooler. BTW, on my last dyno run, we hit >18 lbs. boost and the motor didn't even flinch...lol. Still waiting for my Comp. cam...been on order for over a week...:bang:

[Vettezuki]

I was always under the impression that if you can "hear" detonation, you are into potentially dangerous territory alreayd. Alsmot a case of too late. Ideally you want knock sensors (available for GenI SBCs???) to pick that crap up and pull timing long before you can hear them, especially considering open exhausts and other combustion violence.

[enkeivette]

I couldn't nor have I ever heard detonation, and I do have a knock sensor. But because of my fatty cam it says that I knock as early as 1500rpm under ligth throttle with the sensitivity all the way down. Need to get my Dad to design a circuit to get this thing to work right.

Big G, way ahead of you. Already searching E-Bay.

[big_G]

I couldn't nor have I ever heard detonation, and I do have a knock sensor. But because of my fatty cam it says that I knock as early as 1500rpm under ligth throttle with the sensitivity all the way down. Need to get my Dad to design a circuit to get this thing to work right.

Big G, way ahead of you. Already searching E-Bay.
Make sure you can get CFM flow on the intercooler before you buy. You need at least 1,400. I used to design that chit so many years ago the parts are obsolete. LOL

[enkeivette]

http://photos-e.ak.fbcdn.net/photos-ak-snc1/v4671/39/119/19912599/n19912599_33025124_1356693.jpg

http://photos-f.ak.fbcdn.net/photos-ak-snc1/v4671/39/119/19912599/n19912599_33025125_5993313.jpg

[94cobra69ss396]

http://photos-e.ak.fbcdn.net/photos-ak-snc1/v4671/39/119/19912599/n19912599_33025124_1356693.jpg

http://photos-f.ak.fbcdn.net/photos-ak-snc1/v4671/39/119/19912599/n19912599_33025125_5993313.jpg

You need to pull all the pistons and check them. When mine broke like that I had two other pistons that were cracked between the ring lands that you couldn't see. I'd hate for you to go through all this and have it happen again.

[BRUTAL64]

You need to pull all the pistons and check them. When mine broke like that I had two other pistons that were cracked between the ring lands that you couldn't see. I'd hate for you to go through all this and have it happen again.

Yea, I thought I had only one piston with blown ring lands (that I could see). I pulled the rest and found 3 more. :drink:


You know now that we told you this and you pull the rest--there will not be any more blown pistons. If you don't pull the rest out, you'll have at least 3 more blown pistons. It's a Catch 22.

[enkeivette]

Yea, I thought I had only one piston with blown ring lands (that I could see). I pulled the rest and found 3 more. :drink:


You know now that we told you this and you pull the rest--there will not be any more blown pistons. If you don't pull the rest out, you'll have at least 3 more blown pistons. It's a Catch 22.

Good thing I logged on, was just about to place an order with Summit.

[BRUTAL64]

Good thing I logged on, was just about to place an order with Summit.

Any time you have detonation like this, it can affect bearing crush. You may want to consider changeing all the rod bearings. Just a thought. Hate to see you put this together and then spin a rod bearing.:drink:


If you want to see how detonation effects bearings; take a ball peen hammer (round end) and hit a bearing right in the middle. :drink:

[enkeivette]

Bearings are pretty and wear free, I will reuse them.

Pistons all look okay to me, except for the obvious one and the still questionable one. Here's it is, no cracks from what I can see. I think a tiny piece of the other piston found its way into this cylinder and did a little dance with this piston.

I plan to file down the little blemishes and run it, unless you guys think it's a big mistake.

http://i39.tinypic.com/2lld5w1.jpg

[BRUTAL64]

Not to be a "doom" sayer. You might not see any wear on the bearings. "Crush" is what is effected. Crush is what keeps the bearings from spinning in the rod.


I've seen it before. Broken rings or broke piston- changed- and 2 or 3 months later they spin a bearing. Just want you to know. Your call.:drink:

[enkeivette]

How about the piston? Cool to run it?

[BRUTAL64]

Yes, just smooth it out. NO sharp edges. You may want to take the time to go over all your pistons and smooth all the sharp (even semi-sharp) edges. Anything that the flame front will see.:bigthumbsup:

[BRUTAL64]

Quench--remember our discussion on this?? I think you said it was not a problem with a forced induction engine. Well, a by product of too much quench is detonation.

I know I can be a pain, but I just want you to be aware. I know how much time and money you have in this engine. Really, I'm just watching your back. Honest.:thumbs_up:

[enkeivette]

Maybe you were right about the quench. And I never said quench was not a big deal with blown apps, I said that others have told me this. Others being tech from AFR over the phone. I don't claim to know anything about engine theory.

Just placed a summit order, I ordered two new bearings to meet you half way. :D

[BRUTAL64]

Yes, I remember you stating that you were told by other people that with forced induction you need not worry about quench. I didn't agree, I've always built S/C motors with no more that .045 quench. But, that's just me.
:drink:

As far as the bearings, seems like a fair call.:thumbs_up:

I'll be here at work for 5 hours tomorrow if you have any questions.:drink:

[enkeivette]

Thanks Glenn :beer:

[SeanPlunk]

I'm glad to see the damage isn't too bad. How long until you have her back up and running?

[enkeivette]

I'm glad to see the damage isn't too bad. How long until you have her back up and running?

Took only about 12 hours to pull it all apart, (including 2 hours making a special socket to get to my rear oil pan bolts) should go back together in about another 3 half days. Piston is special order, but I'm sure it'll be waiting for me when I get back from NY next week.

Let's hope these rings make up for that low cylinder pressure and low hp that I've always had a problem with. For those of you who forget my motor pumps out about 135psi while similar setups are in the 180 psi range. Leaky HGs, intake manifold gaskets, and piston rings... need another dyno day.

[94cobra69ss396]

You also need to pull some timing out. I think you said that you were running around 34⁰ full advance which is way too much on a boosted engine running on pump gas. I didn't tune my car but I think the tuner said that full advance was somewhere around 20⁰-22⁰ and I'm only making 8-9psi. Are you using a boost retard ignition box? If not you should. That way you can run more timing at lower boost and still be safe in the higher rpms when it's making more boost.

[enkeivette]

You also need to pull some timing out. I think you said that you were running around 34⁰ full advance which is way too much on a boosted engine running on pump gas. I didn't tune my car but I think the tuner said that full advance was somewhere around 20⁰-22⁰ and I'm only making 8-9psi. Are you using a boost retard ignition box? If not you should. That way you can run more timing at lower boost and still be safe in the higher rpms when it's making more boost.

Way different for a Ford motor, timing on a high performance NA Chevy would be in the 36-40 range. Low for boost would be in the 26-34 range. I will pull it, but not that low.

I was in Autozone yesterday renting some tools and a Firestone mechanic started asking me what I was doing. He went on to recommend that I advance the timing from 34 to 44 to prevent detonation. :leaving: A little bit of knowledge can be dangerous.