Engine Assembly

Post date: May 10, 2012 3:01:17 AM

Finally getting the engine together!

Presently only the left head is attached, the right head and intake are just sitting on there, and the water pump is just there to get the gasket to seal.

How's it take over two months to get an engine assembled? Oh boy.

I got the el-cheapo Shars micrometers and bore gauge to do some close checks - so all my measurements may be off. I only needed them for clearance - not for absolute measurement - but it's still hard to know if my findings are within the precision of these things. The bores were pretty good, but generally 0.0005" variance. One was 0.001" wider in the middle. Nominal clearance was 2.5 thou, where I wanted it.

The rings were generally pretty good with 29 to 30 thou gap, but a couple of the second rings were like this: / | Thankfully they were tight, so some re-filing cleaned them up. The second rings could/should have been tighter around 20 thou, but they had all been taken out to ~29. So there will probably be a bit extra blow-by.

I caught three rods with the big ends 0.0008" too tight. The rest were perfect. Took 'em back, he said "Really? No way". I had the loosest one as a benchmark, and his gauge showed the same. So those got a quick hone.

The primary problem was thrust bearing clearance. Apparently some 403's have a problem where the #3 saddle doesn't have as much room on the outside edge as it should. Some bearings apparently were OK with this, but Clevite's most certainly are not. First I thought I messed up the thrust cap, so I bought another set of coated bearings. Wait two weeks. Check those, and same problem. The cap has a register that was actually forcing the cap to spread.

Sob story on ROP: Thrust Bearing Crush

Take it back to the shop, and they machine the register out. It actually looked really nice when he was done with it.

I also asked him to open up the main bearing oiling holes a little, and put in a new set of cam bearings. I got the fancy bearings with the back groove, but he installed them with the hole lined up with the oil galley. It should be at about 2 o'clock. Normal stuff - when Chevy's use that kind of bearing, there are three holes. Anyway.

Got it back home, and just couldn't get the thrust to look right. Clearances kept moving all over the place and checking with feelers showed lots of tight spots. Check the bearing with a mic, and its width varies by 4.5 thou!

So, I ordered bearing set #3 - this time uncoated because it's a heck of a lot cheaper.

Got those in late last week. Got 4 thousandths clearance right off, and it was nice and stable. A little bit of work and it got to 7 thou. The build has an uncoated thrust, with all the other bearings coated.

Finally everything was checking out on Saturday. Since I had to do this in the garage, we did the whole closed door and wet floor approach to control dust. It was wicked hot in there. Shaun stuck it out with me, though, and the short block went together in about 8 hours including all the cleaning and checking.

Crank went in nice and smooth. I forgot to lube up the cam, so did that with the crank already in. Ooops.

The short block went nice and easy. There was lots of trash in a couple of crank oil holes, and I had nicked one of the journals with a rod at some point. Some work with 800 grit and 2000 grit paper and it looked OK - this is on the #4 rod. So if that one spins, then I know I didn't do it right!

Pistons went in fine. Had to clearance the oil pump for the mains due to the halo girdle.

On Sunday I cleaned out the heads and tossed them on. Good thing I did that, too. Looks like the shop used a white grease which was showing some contamination. But one of the valves was hanging up - it got a burr on it and scratched up the guide a bit. Same thing - a bit of work and it looked OK. I'll find out of that one ends up sticking. I also forgot to chase the head bolt holes while cleaning the block, so had to do that with the shortblock assembled. Stupid. Lots of attempting to clean, but I'm sure there's going to be some crud in there.

Monday was measuring pushrods. Looks like 8.28" is about right, which is a standard length from Comp! Excellent!

Pushrods and engine paint should get in this week. I finally got on the phone with ARP to get a special length head stud for the A/C mount, so that'll show up next week. Can't strap down the right head or the intake until then, unfortunately.

There's a pretty good chance this thing will be running on the stand in a couple of weeks!