First engine rebuild

[proshadetree]

Re: First engine rebuild

Pistons must be feeler gauged at minimum. I used a inside mic 1 inch down bore and an outside mic at the top middle and bottom of piston to determine. Piston placed in bore 1 inch down and a thin gauge used is about the minimum way to do. If you are referring to rod bearing clearance, anywhere comfortable in the revolution should read the same.

 

[LAC_STS]

Re: First engine rebuild

Do I need to know where to measure the piston to wall clearance? All I know about these from the model # is that they are :

For 71-80 L82. Piston OD 3.998 to 3.999". This 350 standard, pressed pin, high performance piston has a 9:1 compression ratio with 76cc head chamber volume (ID# 336747, 464664 or 464692).

I think that means it was an OEM or GMPP part. Right or no?

Can I measure anywhere?

In my manual it says that the Piston clearance should be .0007 - .0017 Then under that it says service limit .0027 Max

The feeler set I have only has .0015, and .002. So I need to get another feeler gage with more in that size.?. The .0015 one feels really close. It drags just a hair on the pin side of the piston but drags a little more at the skirt side. Ill get more feelers or maybe Ill look for some mic's. I dunno.

Anyone know what the piston to wall clearance should be on this engine with the pistons listed above? (350 2 pc seal 2 bolt main)?



Thanks again everyone.

I cleaned off/out the block really good and installed one piston (and rings, the #1 one) just to get a feel for it and check the Plastigage on that journal. It came out .002 which is good according to my manual (.0013 - .0035).

 

[LAC_STS]

Re: First engine rebuild

Ok I have a problem.


The #1 Piston went in pretty easy. Just a couple light taps with the rubber handle of a little hammer.

When I went to put the #2 piston in it wouldn't go in. So not wanting to force it I took it off and out of the ring compressor and checked it out. If I try to put it in without the ring compressor the way you would install it into the block it wont fit.

It wont fit any of the bores like the #1 did. The skirt (?) or bottom of the piston wont go into the bores. I put the ring compressor on the whole piston including the bottom where the skirt is, and tighten it really tight I managed to tap it into the bore but it took more force than then #1 piston. I never beat or slammed it hard to get it in but I def had to use alot more force.

I plastigage'd both # 1 and 2 connecting rods on the crank and both came out fine. I lubed up the bearings and saw if I could turn the crank and I cant its really hard. That piston it too tight. I already took it back out. No damage done to the bore.

With the #2 piston out the crank turns freely. Best I can tell is the #2 piston has 0 clearance. I didn't put the #2 in every bore obviously but I carefully put the rod in the bore like I was going to put it in but on every cyl it didn't fit.


I also just went and checked all of the other pistons besides #1 because #1 is installed already and went in fine.

All of the other pistons fit fine where the skirt is. Except for # 2 and 8. I tried swapping them and it didn't work. They're too big.


Whats up with this?

 

[dockwrecker]

Re: First engine rebuild

"Finish disassembling the block
Checked block for cracks
Honed block
Cleaned/boiled block
Checked main alignment
Checked all rods and pistons.
Reconditioned 3 pistons
Installed freeze plugs (parts included)
Installed cam bearings (parts included)
removed timing gear from crank

Are these the ones that don't fit? Usually when reconditioning, the skirt gets hatched to expand it's dia. Are these the ones?

 

[proshadetree]

Re: First engine rebuild

I am wondering this too. No reason an old piston will not fit in a block it came out of. Is it on one of the 3 they reconditioned?

 

[Fishermark]

Re: First engine rebuild

When I went to put the #2 piston in it wouldn't go in. So not wanting to force it I took it off and out of the ring compressor and checked it out. If I try to put it in without the ring compressor the way you would install it into the block it wont fit.

That's not good. It should fit into the bores without any issues. Time to get the skirt measured.

I put the ring compressor on the whole piston including the bottom where the skirt is, and tighten it really tight I managed to tap it into the bore but it took more force than then #1 piston.

Never a good idea to try and force a part to fit. If the piston doesn't fit without the ring compressor, then you definately do not want to squeeze it to fit into the cylinder.

This is getting to be a long post, and I have forgotten some of the details, but if you had the pistons reconditioned, I would suggest taking them back to the shop that reconditioned them and asking them about it. But to be honest, I cannot see reconditioning pistons anyway. If they are worn, it is time to buy new ones. They are not terribly expensive.

 

[LAC_STS]

Re: First engine rebuild

I thought the shop reconditioned 3 of the rods. Maybe it was pistons though since thats what I put.

Im gonna have to go down there and see whats going on. Sucks

 

[LAC_STS]

Re: First engine rebuild

Heres what Im talking about.

Im gonna ride by the machine shop in a little bit and see what they say.

 

[proshadetree]

Re: First engine rebuild

Something is whacked thats an old piston. Try in all bores. I had an AZ engine with 2 diffrent bore sizes. I would hope your shop checked that

 

[LAC_STS]

Re: First engine rebuild

"

Are these the ones that don't fit? Usually when reconditioning, the skirt gets hatched to expand it's dia. Are these the ones?

What does it mean to get "hatched"?


I didnt make it to the shop today so I will go for sure tom.


Im gonna ask again but I'm pretty sure it was 3 rods that were refurb'd. I dont think it was the pistons. The shop was still supposed to check the pistons. When I piscked the stuff up from the shop the guy said he chekced everything out and numbered the pistons and caps (with a punch). He told me all of the pistons were fine and that only 3 of the rods had to be recon'd.


So I guess well see tom.


I knew this was all seeming too easy.



Thanks everyone. Its SOO great to have a community of help and instrest with this project.

 

[LAC_STS]

Re: First engine rebuild

Something is whacked thats an old piston. Try in all bores. I had an AZ engine with 2 diffrent bore sizes. I would hope your shop checked that

I did. I checked both the # 2 and # 8 pistons and they will not fit into any of the bores.

 

[1kwik72]

Re: First engine rebuild

So, did you or the machine shop number the rods/pistons to keep them in order? They should go back in the same bores they came out of...even if you turned the crank. Are you checking the clearance between the pistons and the cylinder walls and checking ring end gap? You also want to check the clearance between the rods that are on the same crank journal.

Are you planning to re-use the valve train components as well? If so, did you keep those in order? (i.e. #1intake/#1exhaust, #2...etc) If not, I would go with a new cam, lifters etc.

I admire your willingness to tackle this rebuild, the first 3 I did I had someone with lots of experience helping with EVERY step...

 

[pnwboat]

Re: First engine rebuild

I assume the machine shop was the one that removed and re-installed the rods on the pistons. Looks like you have "pressed" in wrist pins. It requires a lot of pressure to push the wrist pins out and to re-install them. It's usually done by heating up the connecting rod around the wrist pin hole and using a large hydraulic press. I suspect that the machine shop has inadvertently deformed #2 and #8 piston slightly during this process. They're probably a little oval shaped rather than round which is causing the problem. Just a few thousands of an inch is all it takes to prevent them from going into the cylinder bores. I would take them back to the machine shop to see what they can do to fix the problem.

 

[LAC_STS]

Re: First engine rebuild

Im thinking it has to be something done to the pistons. Those pistons came out of those bores and the #2 and 8 wont fit into any of the bores. So something is wrong with those pistons.

Im going to the machine shop in a little bit.

 

[LAC_STS]

Re: First engine rebuild

I'll post more when I get home but the machine shop said that they checked all of the rods before and didn't check the pistons. They said I didn't tell them to. Which is kinda bs cause I did ask them to check everything.

But anyways they measured the piston right below where the oil ring goes and then measured it at the bottom of the skirt.

The pistons were normal right below the oil ring but where the skirt is #2 and #8 were almost 6 thousandths bigger than 4". The guy said he don't know how it coulda got like that unless I was beating on the piston skirt, which I didn't.

So I have to bring all of the pistons back there tom and have them check them. I'm gonna end up needing all new ones I'm guessing.

I'll post kore when I get home.

 

[GLENN M]

Re: First engine rebuild

i worked in a machine shop for six years,i dont know how beating on piston would make it grow.unless you put it in a vice and squeezed it till it deformed,and if you did i would say stop now and cut your losses,if you didnt take everything back and do it right,all pistons are garbage,resize all rods resize crank,all new bearings [main,rod,cam] new timing chain,oilpump,have them bore and install pistons,better yet get them to assemble bottom end.you install oilpump,new cam, chain,pan,lifters,heads,intake,and all the rest.they are responsible with doing the most important part and doing it right and this way is only right way.reusing old parts is mickey mouse and i no i wouldnt want to be stuck with a half as ed piece of j k

 

[LAC_STS]

Re: First engine rebuild

i worked in a machine shop for six years,i dont know how beating on piston would make it grow.unless you put it in a vice and squeezed it till it deformed,and if you did i would say stop now and cut your losses,if you didnt take everything back and do it right,all pistons are garbage,resize all rods resize crank,all new bearings [main,rod,cam] new timing chain,oilpump,have them bore and install pistons,better yet get them to assemble bottom end.you install oilpump,new cam, chain,pan,lifters,heads,intake,and all the rest.they are responsible with doing the most important part and doing it right and this way is only right way.reusing old parts is mickey mouse and i no i wouldnt want to be stuck with a half as ed piece of j k

I dunno that's what the guy said. All I did with the pistons was remove them and put them in a cardboard box. Then I took them with the block and crank to the machine shop.

So I'm gonna bring the parts back down there to them tom. If I get a new set of pistons I need new rods???

I know it would be alot easier on me to just have the machine shop do the bottom end but I wanna learn.

 

[dockwrecker]

Re: First engine rebuild

If the rods were ALL resized they'll be OK. The new pistons should come with wrist pins. Don't skimp on piston quality! Poor pistons can vary several grams in weight causing balance problems.

 

[proshadetree]

Re: First engine rebuild

Post a pic of the skirt side of the pistons in question. Something had to change this. If the shop screwed them up they should be responsible. Take those pistons to a different shop to have them checked. I would spend a few bucks for a digital caliper and check all myself.

 

[LAC_STS]

Re: First engine rebuild

Ok heres pics of each side of the 2 pistons in question right now.

These are the #2 and #8 pistons.

The guy at the shop showed me where you can see the piston was rubbing. I think he means rubbing on the piston wall from before.

There are tiny grooves or marks that go horizontally around most of the piston. You can see the lines rubbed off at the bottom of the skirt.

But on both pistons the lines are rubbed off on one side alot more than the other side. Maybe this indicates damage to one side only or one side more.

I dunno heres the pics.