Chevy & GMC Vans

I don't know if your pistons have offset pins or not. The early smallblock Chevy had offset pins and Smoky Yunick used to switch them around on purpose because that "fooled" the engine into thinking the con rods were longer than they really are. Chev pistons used to have flycuts on both sides so that wasn't a problem. The offset pins are mostly for holding down piston slap noise at least in an OEM setup. If you don't tear this baby down, make sure that the hydraulic lifters aren't turned down any farther than need be to take the click out of them so they can't "pump up" at high rpm and know you can't change cams without dealing with it. Taking the whole mess back apart IS the thing to do and a lot easier to say if it isn't you having to do it but I don't think it's a total must do if the bore scope shows clearance.

Lots of good info here on engine building! The bottom line is that the valve reliefs are there for a reason. I see that you are running a GM performance cam...which would mean that you will probably have even less clearance than a stock cam. If it were my engine and I found out that the pistons were installed backwards there is NO WAY I would continue running that engine with out fixing the problem. I am amazed that it has not blown up already. You have a lot of time and money invested in this project so why would you not want to repair this issue? Good luck with your combination!

Rockwerx wrote:Lots of good info here on engine building! The bottom line is that the valve reliefs are there for a reason. I see that you are running a GM performance cam...which would mean that you will probably have even less clearance than a stock cam. If it were my engine and I found out that the pistons were installed backwards there is NO WAY I would continue running that engine with out fixing the problem. I am amazed that it has not blown up already. You have a lot of time and money invested in this project so why would you not want to repair this issue? Good luck with your combination!

I would defiantly put more weight on Rock's comments over mine because he has way more checks in the box then myself. He has been there, done that and I babble a lot (as it makes me feel better). Get you a few buckets and drain the coolant and pull the motor on the next long weekend. Heck, Where do you live? We all meet up and help you!

I really appriciate all the help everyone has given me. Now everyone realize that I have vortec heads. I dont know if that would make it differant. Anyways, my plan is to drop the pan, take one rod cap off at a time and slide the piston down to the bottom of the bore just befor the bottom ring pops out. Slide the "floating rod pin" out, turn the rod 180, install it and then turn the piston 180 and reinstall. Do I have a chance?

-Vance

I don't know if you can get the piston that far down. It's sure a different idea. Good luck.

I don't know for sure if that plan works either but it sounds worth a try to me. Do you, or any of your friends, have a short block setting around that you can practice on ? Heck, the concept may even be tryable on the V6 if it's still around.

ill just drop the pan and see. Worst case is i cant and I put it back on. I would be back were I started. If I pull this off, maybe I would look like less of an idiot.

-Vance

I wouldn't worry about looking like an idiot. They only people that haven't made a mistake are people too scared to try anything and that sounds like a mistake itself.

I think this is a very clever idea and I can't wait to see if it works. Also, while you're in there you may as well double check that the rods aren't backwards as well. Be sure that the chamfer on the big end of the rod is facing the radius on the crank journal.
Good luck!

Vance,
Just back in from work and read you are going to fix it and I think that is totally the right move.A in block piston fix would concern me for me to be sure I had 180 degree spacing of the ring gaps.With out taking it down and popping the pistons,I couldn't be sure that was the case.A ring "could" stick on the groove creating problems.

I too am not involved in taking it apart and therefore the advise is me not doing it,but I do think a teardown is in order to be sure it is done the right way.You do want to recheck the clearnaces on the rods the other way.Should be ok,but none the less you can't be too careful.

I don't think you should be too concerned about the mistake being on the forum.I mean hell that is what the forum is about in part,helping each other out.In years to come when someone else starts a thread about a 383 build,you can help them out.I think the new member who brought this to light should get a thumbs up.After all,he caught it.

Just keep posting and let us help you anyway we can.

6spd_monte wrote:I think this is a very clever idea and I can't wait to see if it works. Also, while you're in there you may as well double check that the rods aren't backwards as well. Be sure that the chamfer on the big end of the rod is facing the radius on the crank journal.
Good luck!

James-that is a good point,but I think it would have locked up right away.I was curious how the pistons where assigned to which rods for the balance??.And how the pistons where assigned to which bore given the final hone??.We have measured piston skirts and they do very quite abit.We finsh hone to each piston because of that.But on the other hand,cast pistons don't act like forged ones do where forged require more clearance.

the rods are installed correctly. They will not bolt up if they wernt. In fact, my first shot, I did have the rods in backwards and when i went to put the 5th rod in it wouldn't fit, so I corrected. I dont know exactly when I will tear into the bottom end of the 383, but you all will hear from me.

-Vance

GEJ wrote:Vance,
Just back in from work and read you are going to fix it and I think that is totally the right move.A in block piston fix would concern me for me to be sure I had 180 degree spacing of the ring gaps.With out taking it down and popping the pistons,I couldn't be sure that was the case.A ring "could" stick on the groove creating problems.

I too am not involved in taking it apart and therefore the advise is me not doing it,but I do think a teardown is in order to be sure it is done the right way.You do want to recheck the clearnaces on the rods the other way.Should be ok,but none the less you can't be too careful.

I don't think you should be too concerned about the mistake being on the forum.I mean hell that is what the forum is about in part,helping each other out.In years to come when someone else starts a thread about a 383 build,you can help them out.I think the new member who brought this to light should get a thumbs up.After all,he caught it.

Just keep posting and let us help you anyway we can.

in regards to this post.

I will disconnect the rod and first try to turn the piston by the rod. If I feel anything that feels like the rings turning with the piston, I will bail. The rings should stay in place due to the outward force they put on the cylinder wall. The piston just sits on the rings, so it should turn with minimal effort, or so I would think. We will have to see. thanks for all the help.

-Vance

okay vance been reading up on all this and even know it sucks i think it is right to tear it apart. let me know when you wanna do this i have my heater and we will go at it. at worst we pull the motor we are getting pretty good with pulling them it seems lol
Danny
ps. keep your chin high im gonna work your butt off this weekend lol

Here is a photo of mine (just out of the donor). You can see how much room there will be to turn the rod while keeping the other in place. Seems like a tight fit. Where you going to bore scope each cylinder first?

Good luck.