35fountain

Hi everyone..Last winter I had 2 sets of 781 GM heads done for my big blocks. For some reason my shop did not machine the valve guides on the exhaust ports and left them with no seals..The engines run great except each time I start them up after sitting for awhile they start to smoke blue for 1- 2 minutes or so..I know the oil when hot is seeping down the guide into the cylinder. My maching shop said that having a bit of oil in the cylinder helps lubricate on start up. On the other hand, I really don't like seeing the smoke so here's my idea.
Since I don't feel like removing both sets of heads again I was going to look for a single valve spring with damper to replace my dual springs with dampers on the exhaust ports only, and use a unbrella seal which should cut down the oil seepage .I have the Compcams 924-16 DP on the engines now and I was looking to replace them with the Compcams 911-16 single spring with dampers. The specs are very close.
I was wondering if anyone could help me on this..

BillK

35,
If they did not machine the guides down, I dont think there is an umbrella seal that will work without hitting the valve guide even if you do go to a different spring. Personally I would say you really do not want to go to a single spring in this type of application especially if it is a hydraulic roller.

I prefer to put positive seals on both intake and exhaust and that is how most new engines are set up but there are a gazzillion old Big Blocks with either no seals at all or just seals on the intake and it really does not hurt anything. The oil that runs down the stem is such a small quantity that other than the puff of smoke at startup, you probably will never notice it.

Personally, I would put up with the smoke rather than compromise the valve train performance.

Bill Koustenis
Advanced Automotive Machine
'Waldorf Md

35fountain

BillK, Thanks for your response. No Roller cam.. I have a Flat Tappet Hydraulic. I called compcams and they said the double spring outer (#924-16) is almost equal to the single spring outer (#911-16). Spring height set @1.90 #112 seat pressure. cam lift on exhaust is .531. that leaves opening@ .369 open load 320# coil bind @ 1.200 The stock unbrella seals will fit the single spring setup with damper. I also prefer the positive seals on both valves but for some weird reason they forgot to machine the exhaust guides...The liitle bit of blue smoke i do notice but it goes away with 15 seconds. I pulled all the plugs to make sure and none of the plugs had any kind of ash build up or oil deposits on them. I do agree with you about the little bit of smoke rather than compromising the valve train performance by having 2 different set of springs. MAYBE I WON"T MESS WITH IT

BillK

The little bit of oil is not getting into the cylinder, it is just getting ont he back of the exhaust valve when you shut the engine off. Thats why I would not mess with it at this time.

gsxr1216

When i rebuilt my motor the shop that rebuilt the heads did them with no exhaust valve seals at all. i asked them about that and they said they do tons of them like that, and worse case i get a puff of smoke at start up. occasionally i do get a puff at start up, not all the time though, and its really just a puff when it first fires up, 1-2 seconds tops.

35fountain

gsxr1216, No valve seals on the intakes? I heard that could cause a problem with detonation. Today I noticed less puff's of smoke..It seems when the engine is hot and I shut it off and the start it a few minutes later it smokes..but if i let it sit a few hours, no smoke..

gsxr1216

it has intake seals, no exhaust seals.

35fountain

Oh sorry misread.. I went from Amsoil Z-rod 20- 50 oil back to Amsoil regular 20-50 oil and it seemed to be less puff's of smoke

http://s1071.photobucket.com/albums/...5897563644.mp4

dereknkathy

do you have the steel umbrellas on the outside of the valve springs? probably not. they are mainly a stock spring thing. but if you put them on and the o-ring under the valve spring keeper, it should keep the oil out without changing spring geometry.

cubicinches

That's all small block stuff... No spring shields or O-ring seals on a big block.