|12-15-2010 05:33 PM|
Well to let you know your not alone. I built a brand new everything 350 sbc roller motor last year and I used world product sportsman 2's and from day one the problems would just get worse over time. I kept getting oil on my plug threads and after about two months between carb issues and the stupid heads I would have to change plugs.
I kept having miss fire problems with engine and kept checking everything and just could not find out what would cause it. Eventually it got so bad my engine would not idle very well anymore.
Anyways long story short world products uses umbrella seals on there dual spring setup heads and that is a no no with dual springs. I took the heads off and had them checked by the machine shop and I only had less then 3000 miles on my heads and the clearances was horrible on the guides and all my intake valves was just full of oil and carbon deposits.
I had all new bronze liners put in to get everything in spec and I also had the heads done up with a port job and valve job and I had them machined for viton positive stop seals. 600 bucks later they are way better then when I got them new. I will never buy a brand new set of world heads again. They are nice in themselves if everything is up to spec and better valve seals. Umbrella are about worthless to me in my opinion.
There tolerances are horrible and they don't put care into there heads like some others do. A lesson I learned when getting new heads take apart if fully assembled and check everything.
I almost lost my engine cause of carbon getting into the piston rings and I have a few scars in my cylinder walls because of it and am having to rebuild whole engine again just so its all clean. All of this cause of world being cheap on the valve seals and too much guide clearance.
|12-15-2010 02:33 PM|
The answer about pressure vs vacuum is the deal with using umbrella seals.
Usually, iron heads do better with iron guides, aluminum do better with bronze because of their different expansion rates...
|12-15-2010 06:33 AM|
|cobalt327||Regarding bronze liners, I've found that setting the geometry up spot-on to be essential for good durability from them. This should be done anyway, but seems to be especially critical when using liners.|
|12-14-2010 07:56 PM|
Teflon "white" seals are often the cause of excessive oil use in SBC. Usually the installer trys to install them cold and damages the sealing surfaces..
If you use the "Blue" Fel-Pro type positive intake seal. You will get better oil controll.
I tend to use a good "umbrella" seal on the exhaust side. Remember there is negative pressure on intake and positive pressure on exhaust. The exhaust can use a little more oil flow and won't run down stems/guide while running.
As for bronze liners. PROPERLY INSTALLED they are the best economical repair. Will last three times as long as iron and can be run tighter clearances.
|12-14-2010 06:18 PM|
|DoubleVision||In the past, I had bronze guides installed. This was way back in 1996. Anyways, I didn`t get 20,000 miles out of them and they were shot which really ticked me off. Instead of having them reinstalled I used cast iron guides this go round. I put many a mile on those heads, likely over 50,000 and when I sold them the guides were still in good shape. I`ve had others tell me they`ve had good luck and long use out of bronze guides, I never did so I`ve stayed away from them. When the bronze guides were removed, we noticed the ones with the most wear were worn crooked. They were fine at the top but worn to one side on the bottom which made me think it likely had some valve train geometry issues or the guides weren`t installed straight by the first machinist.|
|12-14-2010 01:46 PM|
I am pretty confident that the intake manifold is sealed up but it is definitely worth checking before I start messing with the valves. I used some Edelbrock intake gaskets with high temp black RTV on the ends. The block was milled slightly to zero deck the flat top pistons but the clearances seemed to be very consistent when I set the intake in place prior to final installation. Thanks for all of the input.
Any pros and cons to having bronze valve guide sleeves installed if excessive guide clearances are indeed the problem?
|12-14-2010 01:18 PM|
|dromero5||Double Vision is right on the money if you can feel play and the clearance on the guides is really more than .004 it is going to suck oil in regardless of the seal you use which is what happened to my heads. I was not aware that you should always have new heads gone through by a machine shop because they all say the quality control is not that good and naturally they would error on the side of using/burning more oil than a tight set up where something is going to seize up. Also if the block has been milled/decked the heads are likely to not seal up if they haven't been machined as well.|
|12-14-2010 12:47 PM|
|DoubleVision||If you use the rope trick in the cylinders when you do this you can pop the spring and let the valve fall slightly down and shake it, if you feel excessive play no seal is going to stop the smoking. However, another thing that`s worth mentioning here is are you positive the intake sealed? If you can pull the carb and see oil in the plenum the intake didn`t seal. What intake gaskets did you use?|
|12-14-2010 12:17 PM|
Thanks for the reply.
What is interesting is those are the same heads that I am using. I picked them up used and they had just had a 3 angle valve completed on them. Hopefully new seals take care of my problem as I and my wallet would hate to have to replace the heads.
|12-14-2010 11:17 AM|
|dromero5||I use that type of spring compressor and it works better than those ones that try and clamp the spring itself to compress. I had horrible luck with a "Blueprint TBI" 383 engine i purchased with the same smoking issues. They used World Product Sportsman II heads and from the factory the valve guides were way loose and it used about a quart of oil every 400 miles and was fouling plugs. They wouldn't warranty it saying that there were no defective parts. Anyways I purchased Trick Flow heads and had no further problems and i think you are fine running Vitons on both intake and exhaust, I did and never regretted it.|
|12-14-2010 08:58 AM|
SBC valve stem seals and spring compressor
I have put about 75 miles on the SBC 350 that I rebuilt. I have noticed a bit of blue smoke on startup and suspect that it is the teflon comp cams positive stop valve seals that I installed. I am planning on removing these and replacing them with the viton positive stop seals instead. I have also read quite a few threads that have mentioned using the positive stop seals on the intake valves and umbrella seals on the exhaust valves. Is there any particular reason why you shouldn't run the viton positive stop seals on all valves?
When I originally installed the valve springs I used a rented compressor from Autozone which was a piece of junk and very frustrating. I have been looking at this type of compressor manley spring compressor and am wondering if it will work for occasional use. Does this tool provide enough leverage to easily compress the spring?