big problem with shaved block

[mticar1]

I got my parts back from the machine shop Saturday. I just got the pistons back in the block. I asked the machinist to shave the block and to leave the pistons .005", he said he put the #1 piston and the #6 piston in and measured them and shaved the block. When I rotate the crank it looked like the pistons were coming out the block. I put a flat edge across the top of the block above #1 piston and it definitely moves up at TDC, I used a feeler gauge and got the gap on the edge of the piston to be .008", the #3, #4 and #5 piston come out of the block also. Before I start having a melt down am I missing something? Is the block completely trashed? Can I have him just shave the top of the pistons? Please help

[mticar1]

Could I have them resize the big end of the connecting rod and put bigger bearings in and recenter the hole?

[CandyCaneXj]

The head gasket added on would be like .04 compressed or thicker wouldn't it? Would that fix it then?

[mticar1]

I was going to use the Victor Reinz head gasket at .043", but I could just go with the stock at .051". I'm just concerned about the piston coming out the top off the hole. I'm doing a short rod stroker with SP 677ap pistons, block bored .030", and a comp cam 68-232-4, in a 97 TJ.

[SilverXJ]

Figuring in the head gasket compressed thinckess (.044") you will still have .036" clearance. Close, but it should be fine.

Using your checking method, what is the #1 and #6 piston deck measurement?

Since your pistons are already on the rods it could be risky to have them pushed off and the rods resized. Usually the cap is shaved then the cap bolted on and resized. That will shorten the rod a bit. No need for different bearings. I suppose they could shave a bit off the rod if a bit more shortening is needed.

[mticar1]

The numbers I get are
#1 +.008"
#2 +.002"
#3 +.002"
#4 +.004"
#5 +.004"
#6 .000"
Isn't the Felpro compressed head gasket .051"? If I use the compression calculator and use negative .004"(avg) and .051" for head gasket I get SCR 8.7 and a quench of .040", can I use still pump gas?

[mticar1]

Sorry DCR of 8.7, not SCR. SCR is 10.1

[Cheromaniac]

The numbers I get are
#1 +.008"
#2 +.002"
#3 +.002"
#4 +.004"
#5 +.004"
#6 .000"
Isn't the Felpro compressed head gasket .051"? If I use the compression calculator and use negative .004"(avg) and .051" for head gasket I get SCR 8.7 and a quench of .040", can I use still pump gas?

Even if you use the Victor Reinz 0.043" MLS head gasket the quench will come in between 0.036"-0.043" so it'll be absolutely fine.
My biggest concern is the 10.5:1 SCR (assuming 57cc chamber heads & 15cc piston dishes) that you're going to end up with now that you've shaved so much material (0.050"??) off the block. I suggest you have the combustion chambers and piston dishes smoothed over and polished. Hopefully that'll be enough to gain a few cc and lower the SCR so you can run pump gas without pinging.
The other issue you'll need to deal with is having to use shorter pushrods (possibly 9.575" length) to correct the lifter preload after the block shave.

[mticar1]

I thought the 677ap were dished 17.5cc? I think I'm going to go back to the machine shop and have them resize the rods so that the pistons are in the hole .005". That will make my dcr 8.4, which should be good enough for mid range gas?

[jeepxj3]

I got my parts back from the machine shop Saturday. I just got the pistons back in the block. I asked the machinist to shave the block and to leave the pistons .005", he said he put the #1 piston and the #6 piston in and measured them and shaved the block. When I rotate the crank it looked like the pistons were coming out the block.

Maybe the confusion of leave the pistons .005". Does that mean +0.005" out of the block or -0.005" down in the block?

[jsawduste]

Typical numbers for OEM rods that have not been machined for end to end length or checked for twist.

[mticar1]

"Maybe the confusion of leave the pistons .005". Does that mean +0.005" out of the block or -0.005" down in the block?"

When I originally talked to the machine shop about shaving the deck I said I wanted the deck to have 0 clearance. And then I started to get nervous so I asked the machine shop about 0 clearance, he said it would be safer to leave .005" and I agreed. So I don't think there was any confusion about what I wanted.

I just talked to the shop and he said I should be fine with 8.7 DCR running 91 or 93 octane, and that the pistons just being out the block +.008 should be ok. Is he bs-ing me?
Not sure how much of a deal I should make out of this? He said he used the same piston in all the holes to measure the clearance and that was the problem with using used rods.

[SheSaid]

Hello,

This is my first post here, but I am building a 4.6 with 10.25 SCR. I wanted my machinist to 0 deck the block and they are all .003-.0085 out of the hole the same as you. I could not be more excited. I am using a Mopar steel head gasket that compresses around .043. So my smallest quench will be .0345.

This is tight but the more I read I have NO concerns that this is TOO tight. Should work great, I hope. The quench allows for more SCR without pinging. I have always planned to run 93 anyways.

Good luck.

[Russ Pottenger]

Welcome aboard She Said,

Not much to add. SilverXJ and Cheromaniac both gave good information I'd agree with.
Your real safe at .008 out. The engines I build I'll shoot for .028 to .035 Piston to head.
I've seen it as tight as .020, but that is less than my comfort level would allow.
Rod stretch relating to intended rpm range, piston to cylinder wall clearance, cast pistons verses forged, engine warm up
procedures, is just some of the information needed to determine how tight we can get the quench.

I use a dial indicator indicating how much material I'm removing from both the cap and rod during
the connecting rod rebuilding process. That way I'm at least able to better control the center to center
variants.

[SheSaid]

Hello,

I am a little late to this dance but just an update that may help you.My quench on my motor was about .0345 and up. I got it started up this weekend and it ran fine. No problems. Have not spun it up to high RPM yet but it is not making any odd noises.

Just wanted to update in case you still had any concerns.