I need some 383 stroker help, Please!!!

Ok, here we go. I've got a 94 Z-71 350 that lost oil pressure. Instead of fixing it I decided to build a 383. I bought a crank kit (one piece rear main seal) rods, pistons, all balanced, bored the block .030. I got it in using the stock TBI with a 260 comp cam. It ran good for 15,000 miles and busted the number 5 piston from the top ring groove up about half way around the piston. I then bored it out to .040, built it again with more ring gap, in which it lasted 24 miles and it busted the number 7 piston in the same manner. I had the block cleaned again and went one more time. Now it has busted the number 6 piston. The first two set of pistons were from Power House and the last set was Silv-o-lite. I am running around 9.5 compression on just cheap pump gas. This truck is a daily driver.I have been told that the 350 TBI is not giving the engine enough gas and that is what is causing it. I'm ready to build it one more time if I can just figure out a way to keep it together.

Thanks for any imput,

Kodiak

Sure sounds like its too lean . LT1S10 should be able to help you. Do yourself a favor.Use forged pistons next time and correct the lean condition.

hey Kodiak, is the piston broke off or do it look like it was cut off. if its lean it should look like a cutting torch cut a hole in it or melted it. was you getting into it when it blowed or just riding? :confused:

lt1s10, it is broke. It don't look burned at all. Each time it has broke it has been at normal highway speeds. I have been really easy on it for the first 500 miles each time I have built it. The anti-knock sensor is off the block and my machinest told me that it wasn't needed so I never put another one back in it. Do you think that could have anything to do with it?

Kodiak

Quote:

---

Originally posted by Kodiak
lt1s10, it is broke. It don't look burned at all. Each time it has broke it has been at normal highway speeds. I have been really easy on it for the first 500 miles each time I have built it. The anti-knock sensor is off the block and my machinest told me that it wasn't needed so I never put another one back in it. Do you think that could have anything to do with it?

Kodiak

---

i was hoping you would say burnt, i burnt a lot of pistons and all of them looked burnt so it i knew what it was. if the moter has a anti-knock sensor on it i would hook it up. if it is burning pistons then the knock sensor would retaird the time when it sparked knocked and you wouldnt be having ths conv. can you get a pic. of the piston?

Now, would he be raising the compression ratio or lowering it. I think by increasing the volume of the combustion chamber area he would be lowering compression RATIO, but increasing actual compression values by getting more air into that area due to increased bore and piston. It is harder to see the actual compression without testing it while the engine is running. By broken I would think too tight of ring gap or poor pistons, but by you saying that you are running down the highway normally and they break I would say detonation. The TBI is tuned for a stock 350 and it isn't a very smart fuel injection. By increasing the size and air flow at the same time I think it got too damn dumb. Sorry I really don't like TBI at all. The thing is, check your timing and use some premium or bump up the fuel because at that speed/load likely lower rpms, some throttle tip in possibly, it is quite prone to detonate. The timing is high because you aren't baggin on it and the stock TBI just ain't cutting it I guess. OR maybe it just doesn't like you and it wants to die and be laid to rest??

lt1s10, I can get a pic of each piston on tonight. The first time I built it, I went with the lowest ring gap I could,( the tighter, the longer it is going to last, My thinking). The second time I went with the upper end of the scale. But the third time, I added 30-40% to that and still the same problem.

I know this engine hates me, or loves to eat at my wallet. I've built a dozen engines with out a single problem, but all of them has had a good ol Holly on top.

Kodiak

I would use a Silv-O- lite in a stock 350 only. Not a 383 or a 400.I tried it one time in a boat. Little too much timing, detonation, cheap piston, same results you had .Piston exploded.Use a forged piston and get the TBI figured out before You go through another one. You're out of wiggle room.Buy the pistons first and then have the block bored to the pistons using manufactors piston to wall clearance specs.If that doesnt work can the block and start all over.In the end thats going to be a very expensive 383. Hope the next one works out for you.P.S. Make sure You or the machinist mike each piston and each cylinder wall all the way down.

Quote:

---

Originally posted by Kodiak
lt1s10, I can get a pic of each piston on tonight. The first time I built it, I went with the lowest ring gap I could,( the tighter, the longer it is going to last, My thinking). The second time I went with the upper end of the scale. But the third time, I added 30-40% to that and still the same problem.

I know this engine hates me, or loves to eat at my wallet. I've built a dozen engines with out a single problem, but all of them has had a good ol Holly on top.

Kodiak

---

are you cutting your rings to fit? as far a the TBI go if its all hooked up you wouldnt have this problem. the knock senser should have reg. the time, and if it was out of range it should turned on the check engine light. if it was to lean then the o2 sensers skould have warned you. i dont belive it burnt a hole in the piston just ridding down the road. WOT in a 1/4 mile maybe. i hope you can get good pic. i dont know for sure but i think the computer would cut the motor off, if it got that lean. :confused:

I have pics of two pistons in my photo gallery, the third piston is still in the engine. Both pistons have broke in the same manner. I have been filing the rings for each hole and made sure that is the hole they go in. I went with Silv-O-Lite pistons this last time because my machenist said he would stand behind them. I haven't tore the engine down after this third time but I know this is what has happened to them ( spark plug smashed flat). I'm going to try it one more time later this month, and if it don't work this time, I may have a crank for sale. :mad:

Kodiak

Quote:

---

Originally posted by Kodiak
I have pics of two pistons in my photo gallery, the third piston is still in the engine. Both pistons have broke in the same manner. I have been filing the rings for each hole and made sure that is the hole they go in. I went with Silv-O-Lite pistons this last time because my machenist said he would stand behind them. I haven't tore the engine down after this third time but I know this is what has happened to them ( spark plug smashed flat). I'm going to try it one more time later this month, and if it don't work this time, I may have a crank for sale. :mad:

Kodiak

---

i dont see anything that says those pistons ran lean. those pistons are broke. i belive you dont have enough gap in the ring. how much gap do you have in the ring when you check the gap in the block? it dont look like much gap in the ring thats on the piston in the pic. i belive i can make those rings butt each other just mashing them with my hand and that shouldnt be.
i belive the ring is to tight and when it get hot its pulling the top of the piston off. let me know what gap you had and let some others give their opinion. is the machenist gonna stand behind these pistons. i really dont see the heat. :HMMM:

i just went back and looked at the pistons again and you can see carbon still on the top of the piston, dont belive that would be if heat just eat a hole in you piston.

I'm not for real sure what ring gap I put this last time, but it seems like it was around .025 on the top ring. I was going by a truck repair manual the first time and went the lowest I could. That was the piston 5 pic. The second time, I went with the top end specs in the manuel and that is pic 7 with only 24 miles on the new pistons. When I got the Silv-O-Lites, it had a paper in the box that said add 30-40% more ring gap so I went with .025 with still the same results and that is what the machenist figured it up at. After this last time, I pulled the engine (almost a year ago, that is why I don't remember the specs), through it in the shop floor and went with a stock 350. Now I want my power back so it is time again. That 383 sure was a mud slinger. :D

Kodiak

Quote:

---

Originally posted by Kodiak
I'm not for real sure what ring gap I put this last time, but it seems like it was around .025 on the top ring. I was going by a truck repair manual the first time and went the lowest I could. That was the piston 5 pic. The second time, I went with the top end specs in the manuel and that is pic 7 with only 24 miles on the new pistons. When I got the Silv-O-Lites, it had a paper in the box that said add 30-40% more ring gap so I went with .025 with still the same results and that is what the machenist figured it up at. After this last time, I pulled the engine (almost a year ago, that is why I don't remember the specs), through it in the shop floor and went with a stock 350. Now I want my power back so it is time again. That 383 sure was a mud slinger. :D

Kodiak

---

. 025 sounds like a lot. i dont know, let some other people look at them. i still dont belive its lean but i guess it could be. :confused:

From what I saw I'd say those rings killed your pistons. The spot right where the ring ends are is where the piston broke, if you didnt move the ring around then it sure does look suspicious. It seems to look like they butted and busted the top off. 0.025 is quite a bit even with those Silvo-lite. I used them once and ironically my engine was destroyed so I swapped to forged and I didn't look back. Problem with the engine was an exhaust valve seat (hardened because they were old '68 186 castings) came out and shattered on the no. 1 piston and then reverted through the bottom intake runner and dropped another 3 pistons. Ok, back to reality, I assume you are measuring them correctly so whats the deal I wonder. I don't see detonation being a problem from those pistons. Is there something you maybe overlooked, like the other rings, the proper piston fit, deck height. I doubt that you would have overlooked stuff like this on the 3rd time through but I can't really see why this would happen unless the rings were filed incorrectly or with a large variance which would hardly explain why only one piston goes at a time because that could be a time thing too among other things, different heats etc. Are you getting suitable cooling to all the cylinders? Proper cylinder oiling? What type of rings are these? I don't mean to insult I am just brainstorming possibilities.

EDIT: Also, Richard I was thinking of something 'else' the other day when I posted about the compression psi going up but the ratio down. With more air yes the psi would go up, but the ratio would also slightly raise because of the extra volume. However, if the chamber was to decrease by even 1 cc when the cylinder was bored another .010 this could create less ratio than if the bore was .010 less with a one cc smaller chamber. Whatever, its small numbers with small variables and variances, but on the general increasing the bore, while maintaining all other things that determine the ratio, would increase the comp. ratio slightly.

Yes good points indeed, the 350 picks up 5 ci, the 400 picks up 6 ci and so on. A 383 cannot be a 383 unless the 350 is bored 30 over as well. I checked the comp ratio calculator and that is a good rule of thumb for boring, its close but not so accurate as to actually know it without calculating but it works close enough. Thanks Denny, I'll remember that stuff.

Each time I used Hastings rings. What can I do with the TBI to make it more to the liking of the 383? Every thing about it is still stock, injector, chip. Some one told me to find a 454 injector and put on it and that would fix my problem. I also wonder if it is running lean, if that would heat up the rings too much and that is what is causing my problem. I would love to put a carb on it, but that will lead to transmission modification, so that is not looking good at this point. The block is good and clean so I don't think it has cooling problems. I try to run my engines as cool as possible (160 degree thermastat) and this engine still has the engine oil cooler on it. Will the computer get along with the 260 comp cam with a gear drive? There is all kind of racket under there when it is running.

Kodiak

Kodiak, Just had to read Your post to LT1S10 in his hospital bed.He is anxious to get home to continue his discussions with you. He said he wanted you to put the carburator thoughts out of your mind. You, 1stGenCamaro, and I have all had bad experiences with those pistons and I know several others that have also.Im sure you have something there that you will work out but I am convinced that those pistons are contributing to your problem.I think 1stGenCamaro might agree with me when I once again say , THINK FORGED PISTONS I read all the get well post to Mike under the prayer request thread and he wants everyone to know how much he appreciates them.

I used JE/SRP forged pistons before and man they seemed to be able to take a beating and didn't have any problems with them. These, if I remember correctly, don't need a special file fit ring but I filed mine anyways and haven't had any problems with them. I really don't know what to say about those busted pistons and what is actually causing it though. Hastings rings are quite alright for your intened purpose and shouldn't be blamed. As far as the computer getting along with the cam and gear drive it shouldn't have any problems with the drive and shouldn't be too hard with the TBI either, although I am not sure on that. You did stroke it and add a cam so this (according to my cfm calculator) would increase your cfm needs by roughly 100cfm. I would think the TBI would have enough flow to accomodate that. As well you should hook up the knock sensor just in case.

I have had a thought pop in my mind, those pistons do often require a tighter side clearance than most forged or cast pistons. They don't 'swell' or expand as much when heated. If the bore side clearance was too tight or not tight enough this could cause problems, and since the first motor lasted for quite a while and the second didn't (after you had it rebored etc) this might be somewhat of a problem. I'm not sure if you checked the side clearance and it may not be an issue but like I said, it's just a thought.

riverhorse59, I wish you a speedy recovery. There is no way it will go back together without forged pistons the next time.

1stGenCamaro I didn't check the side clearence at all when building it.

Kodiak

Its not me that's ill.It's LT1S10 thats in the hospital. He was trying to help you.

riverhorse59, sorry about that, guess I misread that post. Best wishes to you lt1s10.

Kodiak

Kodiak, I was just looking at the pictures of your pistons again. Why not send those pictures to Silv-o-lite if thats who made them, don't mention anything about what may or may not have happened to the motor and ask them what happened. Tell them that it has happened more than once,it's getting pretty expensive,AND---ASK them for some help. Professionally and Financially.What can it hurt?

There is your problem!! .025 is not enuff ring gap!! The instructions said 30 percent more! The hypereutectic pistons use a high ring land and it takes all the heat, thus the ring expands a great deal more than a stock type piston.. Enlarge that gap to .035 and you will have no problems.....

riverhorse59 these pistons in the pictures are Powerhouse pistons. One is .030 and the other is .040. The Silv-O-Lites are still in the engine at the time. I was so mad (and broke) that the last time I took it out, it just went in the shop floor where it still is today. I'm going to try to tear it down tomorrow, but I know the Silv-O-Lites are broke also due to a smashed spark plug clue. I'll keep you all posted on the findings.

Great advise from everyone, and thanks so much for all the help.

Kodiak

Ok, here we go again. I got the top end of this engine tore down today and here is what I found. #1 Piston was cracked, #2 piston was fine, #3 piston was busted, #4 piston was busted, #5 piston was busted, #6 piston was busted, #7 piston was cracked, #8 piston was busted. All pistons was busted just as the ones in the pics. One thing I did notice was all pistons was busted or cracked right at the exhaust valves. The pic of the two, I checked and they also was busted at the exhaust valves. I checked the deck height and the pistons clear and do not stick out above the block. I also checked the exhaust valves and the were not hitting the pistons. I don't really think I have a lean mixture problem whereas the top of the pistons were covered with black soot along with the heads. I'm wondering if the timing could be causing a "hot spot" on the pistons and making them weak at that point.

Kodiak

Quote:

---

Originally posted by Kodiak
Ok, here we go again. I got the top end of this engine tore down today and here is what I found. #1 Piston was cracked, #2 piston was fine, #3 piston was busted, #4 piston was busted, #5 piston was busted, #6 piston was busted, #7 piston was cracked, #8 piston was busted. All pistons was busted just as the ones in the pics. One thing I did notice was all pistons was busted or cracked right at the exhaust valves. The pic of the two, I checked and they also was busted at the exhaust valves. I checked the deck height and the pistons clear and do not stick out above the block. I also checked the exhaust valves and the were not hitting the pistons. I don't really think I have a lean mixture problem whereas the top of the pistons were covered with black soot along with the heads. I'm wondering if the timing could be causing a "hot spot" on the pistons and making them weak at that point.

Kodiak

---

kodiak i don't see how you're gonna have soot at one place and a hot spot at another on the same piston if its heat doing the damage. if youve got that much heat , you should be able to see it. The top of the piston ant that big. is the cracked pistons cracked towards the front of the motor or to the rear of the motor? Something is jerking the top of those pistons off. why the exhaust valve? i don't see anything hitting the top of the piston. looks like the top of the pistons are being pulled up and for that to happen the piston would have to be rocking back and forth or cocking some how. also on the heat thing if it was heat it should show some damage down the side of the piston where the piston broke. It would try to go down passed the ring before it would burn a hole in the piston, don't see any damage on the sides. how about if the block was bored at the wrong angle, couldn't that put a drag on one side of the piston? Its been done before. are you sure that the ring is not loose in the in the ring grove? some things to look at and think about. :confused:

I got some more pics up, but they wasn't as good as I would liked for them to be ( my camera died). See what ya think. I got another block (4 bolt main)to start all over again, so pour it on me.

Kodiak

Quote:

---

Originally posted by Kodiak
I got some more pics up, but they wasn't as good as I would liked for them to be ( my camera died). See what ya think. I got another block (4 bolt main)to start all over again, so pour it on me.

Kodiak

---

when you cut the ring gap did you check the gap with the ring off of the piston and pushed down into the block on every ring and on ea. dif cylender. how many pistons are broke where the ring butts togother? i see a few. did it have good power when it ran?

Quote:

---

Originally posted by lt1s10
when you cut the ring gap did you check the gap with the ring off of the piston and pushed down into the block on every ring and on ea. dif cylender. how many pistons are broke where the ring butts togother? i see a few. did it have good power when it ran?

---

Every ring was filed for each hole off the piston pushed down square. I think there is three pistons that are broke at the ring gap, two that is not and the two that are cracked, are not at the ring gap. When it was running, it ran like a scalded dog. It never let out a puff of smoke or steam the whole time. Some of the clean spots is where a mechanic came down and looked at it and cleaned just a few spots on it to look at the surface but not all you pointed out DennyW. And yes that is the ring you see in the one pic.

This next block will be bored to each piston, and I'm going to stand over him to make sure it is. What should be the piston to wall clearance? This was the engine that had .025 ring gap, what should I go with next time with forged pistons?

Kodiak

Quote:

---

Originally posted by Kodiak
Every ring was filed for each hole off the piston pushed down square. I think there is three pistons that are broke at the ring gap, two that is not and the two that are cracked, are not at the ring gap. When it was running, it ran like a scalded dog. It never let out a puff of smoke or steam the whole time. Some of the clean spots is where a mechanic came down and looked at it and cleaned just a few spots on it to look at the surface but not all you pointed out DennyW. And yes that is the ring you see in the one pic.

This next block will be bored to each piston, and I'm going to stand over him to make sure it is. What should be the piston to wall clearance? This was the engine that had .025 ring gap, what should I go with next time with forged pistons?

Kodiak

---

i really dont know kodiak, i fill like you have a block, piston, rings, bore fit problem. you need to clean the heads up, but i dont see any water eating the top of the piston up. JMO- get a block ready, stright bore and the right clearances, good set of forged pistons, good set of rings (buy them cut) get everything fitted with the right clearances and assemble with care.

check the air filter, fuel filter, and fuel pump pressure before you start it up. put the knock senser back on. check close for vac. leakes. a new chip wouldnt hurt but most of them only work at WOT. it should not take but a small amount of fuel to ride down the rd. at 50 mph. so i dont belive its lean. let us know whats going on :cool:

everybody has their opinion but this is...
ball park... pistons clearance- 0.0007-0.0017

ring gap-top comp. 0.010-0.020
- bottom comp. 0.010-0.025
- oil 0.015-0.0055

I ran across this...http://www.strokerkits.com/new_page_77.htm

Hope it helps. I'll be building a 383 Stroker pretty soon myself, so I'll be monitoring this thread for a while. Keep us updated.