'88 GT Convertible - Croatia, Europe

Long time no write

Okay...wooohooo...
a) Block is home from machinist. Went to +0.020" bores. Need to verify, I trust only to my eyes...
b) Crank grinded down to -0.010", just to be sure.
c) Heads milled straight (head and block side), new valve seals installed.

I allready have some parts delivered:
-Melling SYB51 camshaft, racing camshaft bearings,
-CB634HN -0.010" rod bearings
-MS590H -0.010" main bearings

Waiting for:
-H273CP 0.020 pistons
-E251K 0.020 rings

I done what I could... soon it will be time (I hope) for this 302 to start burning rubber, tranny and diff for next couple of decades

Ohh...I am pulling old pistons from rods. Checking each and there is nothing wrong with rods/wrist pin on #5 which was knocking...

But see this picture and notice wear on top...this #5 piston may have knocked due to a "simple" piston wear in first place????

7991LXnSHO said:

That looks like 60 grit sandpaper was used on it. (60 big grains of rough grit per square inch. How do they measure it in metric?) I do not know how much that would knock, but it had to pass oil and combustion gas. Do you have a way to measure it to see how much is worn away?

Click to expand...

Hi!
Yes, looks like it was pulled thru gravel
We also have grits 60,120,240...to superfine 2000,3000.

This #5 piston was the reason I teared engine (knock at oil filter). When I removed heads and pressed piston on it's way down it made distinctive knock. I found it was rocking in cylinder and made a nice hole below and hill in upper part.
It went out with .020 boring.

Unclear thing is... was it wrist pin? Rod small end? Or only a cylinder wear.
Unfortunately I pushed pins out with threaded rod before measuring them, so I don't belive piston skirt measure will be correct...

This is like hitting a wall... Guys I need help again - cant find con rod specification or tolerances for small end.

This is what I roughly measured with 3-point micrometer:

1 0,9101574803 *smallest*
2 0,9104330709
3 0,9104330709
4 0,9101181102
5 0,9107480315 *largest*
6 0,9103149606
7 0,9102362205
8 0,9103149606

Click to expand...

Note #5 which was knocking, and it is 0.0003 more than largest bores (#2,3)....
I still need to inspect roundness with 2-point instrument.

Wrist pin is 0,912 by specification I found.
I don't know if this is safe to assemble.... anyone?
Do I also need new rods?

+.020 nice shiny 273CP pistons and rings arrived.
Still need to verify bores and verify what actually machinist did.

Soooo then I bite the bullet again, and....well as I went so far with block I just want to make sure I won't be tearing down bottom engine due to my ass reusing suspicious connecting rods.
I have ordered SCAT bushed rods and will go with floating pins.
If all of the machining was done as it should and assemble goes fine, theoretically I should have a brand new short block.

Furthermore, I have a trouble taking out two coolant NPTF plugs on sides of the block.
Currently I am at the point to drill MF's out... OR NOT TO TOUCH THEM anymore and leave them as they are?
How importaint they are when draining in real life?
I drained coolant once (when I bought the car) and it was pretty clear...

Thnx!

Howdy!

Thnx for the help up to now guys!!!
Well, I washed the block for the last time (after machining), aaand oiled my pants and shoes more than block afterward.

I made measuring mistakes due to bad equipment before washing, so I rely more-less on feelers from now on. Good or not, we will see.

1) New H273CP pistons went in bores with 0.05mm feeler strip at the side of skirt which is ~0.00196 inch. I count on piston to wall clearance. Piston box say minimum is .0015" so I would say I'm good to go. Pistons are measured and are in tolerance as the box states. I plan to put "bigger" ones to outside bores, and "smaller" ones to middle bores due to heat accumulation and thermal expansion. Am I thinking right?
And thoose pistons are tight as a ..., You look them wrong and they will be stuck in bore...

2) New high performance cam beraings went in with home made tool perfectly. Cam went in as butter. Turning easily with one figer. A back cast plug I punched in with thin coat of black RTV. So, new Melling cam is inside.

3) Plasigage, that great invention. I put in new performance bearings and crank. All main bearing show between 0,0015 and 0,002 oil clearance. I would say exactly 0,00175 . I think we are good to go.
3a) First rod bearing checked with brand new SCAT con-rods also measure exactly the same. I did not check rest due to dangerous con-rod manipulation without piston in bore. I think crank was machined okay.

4) Next I pushed 1st rings about 1" down the bore. All 8 of them can accept feeler from min 0,45 to max 0,55mm so from 0,0177 to 0,0217 inch out of the box.
4a) 2nd rings also 1" down the bore can accept feeler from 0,6 to 0,7mm so from 0,0236 to 0,0276 inch out of the box.
For 1st rings therefore I have 0,004-0,0054 per inch bore, and for second 0,006-0,007 per inch bore. According to what I read and specification we should be good to go without any file job...

5) New piston with rings and pins weight from 773 to 765 grams (old ~805), new rods 561 to 564 grams (old ~555). Total weight of piston+pin+rod differs only 6 grams from 1329 to 1335 grams.
Unfortunately I don't have a balancing service here neither I don't know where to get it here... I can just hope for the best. Should I fine tune them to inside 1 gramm??

To be continued.... wish me a good luck with build!
I will upload some pictures later from mobile phone and edit post

Okay, guys all the pistons with rods are +/-1 gramm, I mixed them for a whole day until I got it

Ohh boy are thoose pistons tight... cam is inside, all eight pistons and cam with crank turning nice.
All crank and rods tolerances as per specification.

Piston to head is 0,15-0,2mm (0,006 -0,008 in) in the hole, measured as on second picture.

I got few scratches (see last two pics) and I hope they will be leveled with piston rings seating and won't cause smoke.
Also, when turning to check I saw a lot of dirty oil in bores, allthru I clinically cleaned pistons and bores before installing. I used a bit of assembly lube on skirts also when I saw this...fingers crossed on this one... :-/

Timing cover, water pump, heads...here we come...

Noobz347 said:

You can still see crosshatch in that so it just knocked off the top but I might oil it a bit more before turning on it.

That also brings to mind: First Start Fuel... Consider a gas/oil premix for the first start to keep from washing the rings down with gas.

Click to expand...

Thnx. I oil bores all the time (above and below). And yes, crosshatch is still there in that scratch line...

Thnx for the gas/oil premix idea, might be a pretty smart thing to do, only not so cozy for looks (exhaust smoke) ha ha ha