Engine rebuild

[gectek]

sorry, your link didnt work it just showed the link....yah well that is the only one. but people use the other LS pistons and make power too. in SBCs. anywho, that is prob forged into the design would be my guess. just get a nipple cut like a diesel piston.

and NO i have not seen an LS9 piston yet, because they are so hard to get. we have entire LS9s that are sold before we get them on hand to look at. they never reach us.

[project89]

thats milled flat with the fwd headgasket

thats streetable on pump gas
u could drop it slightly with just a .020 dish milled in liek a stock 3.1 piston

id do this if i could myself but if i build my spare motor im going to be hitting it with a minimum of 150 shot of nitrous i know they wont hold upto that

[geoffinbc]

Yea that might be OK on iron heads. With aluminum heads I would be all for it. On Iron I might have to run better than 87 octane though. Remember my cam choice is very conservative and I am after low RPM torque which will not lend itself well to higher compression.

[Ray Hamilton]

I figured it has 8.6 or so. How can you use the 2.8 pistons when the wrist pins in the 3.1 piston is in a different place?
What I did before was take an '87 S10 block bore it .040 over, put in a 3.1 crank and pistons and rebuilt 2.8 iron S10 heads with felpro gaskets. Changed from external to internal balance and that was it.
So now I have an '89 Firebird block that i'm going to do the same thing for my Fiero. With 3.06 final drive that extra little bit of torque should work OK. I'm also looking for suggestions on a cam grind.

[geoffinbc]

You can use the 2.8L pistons if you mill the tops down.

I figure I will use 3.1L pistons and mill the deck of the block and a little off the heads to give me about 9:1 compression.

I am stuck right now getting a couple broken exhaust bolts out of the heads. I have removed two successfully but have one remaining which I will take to my friends shop and throw on the milling machine. I broke my easy out in the bolt while trying to remove it. So if I can't machine it out I can use his EDM machine to get through it. The bolts were broke when I got the motor so I guess the previous owner was up to something. My Trooper also has broken bolts. Its weird because the bolts on my S-10 came out easily and same with the Camaro donor that went into the truck.

[gectek]

if the heads are cast iron....just use a blue wrench


by that i mean use a torch. thats the norm on cast iron heads with broken bolts.

[Ray Hamilton]

I just paid a shop $486 to remove 3 studs on the forward head in my Fiero.
The one that was the worse was the top stud on #2. Impossible almost to access. I would have done it differently but the weather here at that time was beyond horrible. 4 foot + snow, 20 F and I have no garage.

[gectek]

i had one taken out of my alum 3400 head, it only cost me $20. you got raped big time

[Ray Hamilton]

Was the head off? This car had to be on a rack, much stuff had to be removed. It was a bitch, I checked on it several times during the day.

[geoffinbc]

Yea I could see having to pay that much if they did the labor to get to the head. If the head is off of the engine it should not cost that much.

[Ray Hamilton]

If I would've pulled the head then I would've wanted to rebuild it, then you can't put one rebuilt head on, so then I should pull the engine and rebuild it and, and, and......................I don't know anything about Fiero's yet, just got it, and it looks like every repair will be far from easy. However, with so many of them getting chopped into kit cars, somebody has to keep them alive in stock condition, it might as well be me.

[geoffinbc]

Yea they are cool cars if you can find them in original condition.

Well I got the last stud out but I had to mill it out oversize and use a Heli-Coil to repair it. I have the intake sitting at my friends shop ready to go into his CNC mill to get bored out. I should have all that work done by tonight and then I will clean up some of the casting on the heads and block and then send it in for the machine work and maybe have a short block by the weeks end.

Does anyone have any experience with ceramic coatings on exhaust manifolds? My current plan is to wrap them since its cheap and effective. I am trying to keep the under hood heat down since my current engine runs a little hot when off roading in the summer time but cracking the hood lets it cool down quite nicely. But I guess I also need to consider how tired the current motor is and the fact I have no idea if some of the water passages are clogged.

[96ols60degree]

Just out of curiosity,how much of a overbore can you put on a 3100 block? All the shops tell me they cant overbore a 3100 because they are sleeved,is this true?

[geoffinbc]

Uhh no there are no sleeves they are cast in cylinder bores like most blocks. Perhaps they are confused with another 3.1L engine. I am boring mine .040 over which still leaves tons of meat on it. Some have even successfully bored their 3.1L to a 3.4L size but you have to be very careful about core shift and the cylinder wall thickness of the casting.

[geoffinbc]

Well today I took my stock 2.8L/3.1L intake manifold to my friends shop where we put it on his CNC mill to bore it out and accept a 4.3L throttle body.



The hard part about boring out the intake is the fact that the top is at a 4* angle versus the bottom. So you cannot just clamp it flat on the table and go to work. We used a piece of aluminum bar with a 4* angle block (not visible) and then used 2 blocks under the ends of the intake. Then we clamped the intake down and measured to ensure it was perfectly square to the head. Then we measured the stock bores to center the tool to begin the cutting (shown)



We cut the bores in 2 passes, just a little overkill. The first pass took out about 90% of the material and the second pass was done with a very high quality bit at a high RPM and a slow travel speed to give a mirror like finish. This shop produces molds for plastic injection so the tools and process we used were above and beyond the required precision to do this job. This image shows the size difference between the 2 bore sizes. No wonder there is such a noticeable difference.