Thread: Freshly Built 383, Oil question

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Yeh I live i perth, which is about 2500kms away from where I bought the block from, these guys had a good rep which is why I bought from them and not local. The 4 bolt block prepped with scat crank rods and mogul hypers rings and bearings and cam bearings cost me 3000 aust, the rest cost me close to another 7000 so it hasnt been a cheap exercise. Really not happy if yours is simply standard and within 1" tolerance, it actually pisses me off. Ive been told the reason the block was decked so much is because high comp pistons dont have a good flame front, so what they do is put dished pistons in and deck the block to bring up the compression, that way you get your high comp but you also get a good flame front. The local engine shop wasnt that surprised about the differences but he was surprised that they didnt machine the tops of the pistons to even it all out. And was even more surprised when I said they commented standard quality gaskets would be fine, as this gave me as little as 12" clearance. I went through some old mechanics books I have and the bare minimum they recommend for piston to head clearance was .035". Goddamn not happy
Steve

It's amazing how these so called 'performance' shops can be such hacks sometimes. I would take that block back to where you got it done, and tell him to get busy. Why should you be throwing your good money away? Im not a fan of ever having the pistons above the deck, for any reason. Thats just asking for trouble. (As you see!) Man, Im sorry to hear of this problem. Nothing much short of a re-do will fix this one. I personally wouldnt worry about the oil seeping out of the pushrods, as long as you're getting oil up there, you dont need it to be spraying out. Im also not a fan of oil restrictors, I think they cause more problems that they help. But that's just my opinion. John

Yeh your roight for experts they really make you wonder, Im not to sure which way to go, firstly Im not going to riip it apart and then ship it back 2500kms just for them to stuff with it again. I dont know whether to use a decompression gasket to accomodate for the piston pop, or whether to remove every piston and machine them to zero deck height, on the worst piston this means removing 27" from its head, then its all gonna have to be rebalanced ect. From what I can work out these pistons are meant to have 25" deck clearance so god only knows how much has been decked, If I go with a decompression gasket it will still keep my compression around 10:1 if I machine the pistons and go back to zero deck height I get about the same. I have my own lathe and mill so if I was to go down the machining path Ill do it myself. Is there any downside that anyone knows about using a decompression shim and standard head gasket. How can I work out how much decking has been done so far
Any info is really appreciated
Thanks Steve

I don't see any reason to mill the pistons and rebalance everything when a change of head gasket could solve the problem. Give it a try and then go from there.

Centerline of the crank to the deck is the deck height. Scat is decent stuff. You should not have that much tolerance stacking. It's up to you what to do, but I would find the problem.

yeh gonna redo everyting measurement wise. One of the guys at work pointed out because there short skirt pistons you get a lot of rock, he asked when I measured the items did I measure them on edges or centres I said edges, so he reckons rock the piston full aft measure rock the psiton full forward and meausre, he believes I may have measured pistons at different rock angles. He can see differences of maybe 5 thou but not 21". Remeasure and go from there
Steve

A new engine should not have that much rocking going on. But still, when measuring you have to measure from the centerline of the pistons long ways with the block. Can you push the pistons around in the bore. Just asking because that much rocking would indicate a sloppy fit

I just went and checked it then the block is still in the car but heads are of, theres no movement that I can tell from pushing around on the pistons, it looks solid, and this is with the psitons at the top of there travel. I mag particle inspceted the heads and there not cracked, theres light marks on the one piston where Id say it made light contact. It does however have on a couple of the top of a couple of the pistons a gunge like a filthy grease that you get under your car. It comes of but its really really sticky, certainly wasn there when I assembled it, im assuming this is carbon build up whilst still wet and fresh. Anyone got a good way of measuring piston height without dial indicator is there a better way, I may be getting some movement when turning the arm on the magnetic base, dont really think so but maybe
Steve

The only other way I can think of would be with a slide ruler(I think that's what it's called) beings they are out the hole.

It's a height and depth gauge.

dphtgage.jpg

Actually you just made me think, thanks for that I actually have a vernier depth gauge made by starret with a wide foot tucked away forgot all about it. I can place the foot on the piston and mic down to the block. Excellent. Any ideas on the gunge, would this be simply wet carbon, if it was bad oil ring staggering what would I get.
Steve

Sounds like the engine needs to "break in" and seat the rings. I wouldn't worry about that too much. It will cleanup with some driving most likely.

Thanks for the fast reply mate, youve been a saver this time around with plenty of good advice. Didnt even think about the fact that the rings have to bed in. never stripped an engine before after running it for only 10 minutes. Well thanks and Im going to go out and remeasure using the depth gauge I have and start again. The heads wernt cracked and the pistons still appear to be pretty good.
Appreciated
Steve

Thanks for the help guys, its all back together and running sweet, machined down the pistons and even installed decompression shims to bring compression back to 9.6:1. No knocking gee what a surprise, one last question if anyone can help out Im running 10 degrees initial timing and I just drove the car and turned it off came back about 6 minutes later tried to start her and ended up cooking the starter motor, and melted the battery terminals. Is it reluctant to start hot because of the amount of initial timing, it cant be vapour lock because I dont run pump petrol just lpg which works only by a vacuum draw. Rummm youve got the same camsaft as ive got whats your vac readings at idle or a specific rpm. If i bring initial timing back up to say 2 degrees wont I loose performance, went through the camaro manuals and they run between tdc and 10 deg advance. Recommendations
Oil problem was engine honey from assembly took a bloody long time to come through, now got plenty of oil everywhere
Thanks guys