2,200 miles on rebuild, decel smoke

[TobyB]

Yeah, I'm with Andy- just the shot of the end gap was wrong...

 

...and I don't buy that the ring 'forms' to the bore.  It should match the arc of the bore closely enough

that light won't shine thru for an internet pic.  Maybe just a glimmer when you look closely, is all.

 

That shadow is a watermark.  It got wet, and etched the bore a little.  I wouldn't sweat it if yiu

can't feel it catch a fingernail.

 

So you measure the piston 90 degrees off- axis to the pin, 1/2" below the oil ring.

Then the bore.  The difference should be 0.0018, +- a few tenths.

 

And lean that poor thing out! There's a lot of buildup for 2500 miles...

(I belong to the holy rolling church of the wideband, but there are lots of tuning religions)

 

This is good- new rings and a hone (assuming the bore is in range) and a few jets,

and off you go!

 

t

[jimk]

23 minutes ago, TobyB said:

So you measure the piston 90 degrees off- axis to the pin, 1/2" below the oil ring.

Then the bore.  The difference should be 0.0018, +- a few tenths.

I like to use long feeler gauge method slid in with the piston.  That eliminates my poor measuring technique.

[TobyB]

My feelers are just too short for that sort of thing, Jim.

 

 

But on a 'fresh' engine, that works, too.

The 0.0015 should fit,

the 0.0020 should not.

 

t

[RD02]

Well, Thursday, with my low budget mic and bore gauge (Fowler) I measured pistons and cylinders. Pistons ranged from 3.5418” to 3.5427”. Three cylinders were 3.5466” and one was 3.5460”. That gave clearances of #1= .0048”  

#2= .0040”  #3= .0046”   #4= .0039”. 

I doubled checked everything a couple of times and got repeatable measurements.  I’m not a pro by far, but even if I’m off a thou or so, they’re still excessive.

 

And JimK, I tried your method too, to verify what I got. I held the rod, slid the piston in upside down from the top then tried to slip in a feeler gauge. With the feelers I have, .003 was biggest I got in.

 

 

Yesterday I pulled the block out and stripped it apart. I really want to save this block, mainly because this car is so original and I’ve tried to keep it so. 

What are my options guys? 

 

I need a pro to look at it, and I wouldn’t be comfortable going back to the machinist I used. I live in the SF east bay. Anybody have a good machine shop you’ve used you could refer me to?

 

Thanks everybody, couldn’t do this without ya.

Robert

Edited April 16, 2018 by RD02

[Dudeland]

You are living my nightmare.  It is all about trust... and you just don't know until it is too late.  I would have my engine out in a minute if I thought that I had a good honest builder that wouldn't take 6 months to build my motor. 

 

 

 

 

[andyleonard]

What a drag! You've done everything right and spent the money and you missed by a thou or 2. Not your fault. So sorry.

 

Without knowing how invested in the block you are - was it align bored, specially decked, sonic checked, etc, - or is it just a block and you are fond of the stamped number?...you now either have the wrong pistons for your block or the wrong block for your pistons. In the old days we'd knurl the pistons a little, hand fit them to the holes, buy new rings and go racing... but folks don't do that anymore.

 

Simple thing to do is throw money at it, bolt it back up, and forget it ever happened. You can buy new bigger pistons, sell the new/old ones in there now to offset the price, and rebore. You can buy a used block for $100 and recheck and rebore and reuse the pistons (and keep the original block with the car for next time.) You could resleeve and rebore the block and reuse the existing pistons ... or even return to the original size bore and get standard pistons if you're one of those guys. Maybe even ask someone that's smart about a coating for the pistons that might add up to your clearance shortfall.

 

In any case, you need a real machine shop.

 

Go for it and get back on the road. It'll make a good story when it's over.

 

 

[Einspritz]

You might give Tim Morgan a call at Morgan's machine in Walnut Creek. He does mainly Hot Rod 'Merican stuff, but also does the sleeving for the Ferarri restorer on 10th street in Berkeley.

 

I have only had him do minor machine work machining out corroded studs.

 

Also, Norman Racing in Berkeley off of Gilman; mostly Alfa stuff.

 

Call Bavarian Professionals off of Gilman too, and ask Nat for their recommendation.

 

That's all I got for now.

[mac]

Remember the piston manufacturer?  Source?

 

Mac