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Hello Brickboarders:
It has been several months since I first started up the B18B after it was rebuilt. Many of you guys were really helpful with guiding me on what should come with the rebuild.
The '67 122s with punched out .030 and K cam was an excellent combination! Before rebuild and after was like a night and day. Very zippy.
However...I am concerned about two things. There is almost 3,000 miles now on the engine, but still at idle (850 - 950 rpm) there is quite a bit of smoking which disappears at acceleration (when the engine is fully warmed up). I have already tested the compression. First cylinder is around 183 psi while the rest is around around 186.
I did wonder in the back of my mind if it is because of excessive clearance in the valve guides? I had all of the valves and springs replaced and the seats hardened, but opted to have the guides knurled instead of replacement with the new ones. Thoughts?
Second concern is that when I stop after about 20- 25 minutes of driving, the idle sticks on high ranging from 1100 to 1400 rpm. But if I give the gas pedal a quick tap, the idle drops down to normal (850 - 950). I don't think the SUs were the problem...they were also rebuilt and tuned. I've already tested everything for leaks but found none. I also checked the gas linkage but saw no problems. The vaccuum test showed a fast vibrating needle between 18 and 19 inches.
Any advice? I use 10w 30 oil by the way. The spark plugs looked very good..light brown with very slight light gray.
Any advice? Many thanks!
-DS
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Guys:
I really appreciate all of your input to my original question about the smoking...I am more assured that the cause is the oil coming through the guides of the intake valves.
Before I go for the expensive solution of having the head off to remove the old valve guides, replace them with new ones with machining to accept stem seal caps (any specific caps to fit 11/32 valve stems?), I will opt for a MUCH cheaper solution of trying heavier oil at the next change. 10w 30 may just be too thin to use in such hot weather in Florida. Maybe 10w40 would solve the problem!
Will update...thanks again.
-DS
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Changing oil viscosity won't help. Here's an idea that might. Domestic engines ran 11/32 valve stems in lots of versions. The Chrysler slant six comes to mind but you'd have to check. Their seals were umbrella type and sat on the stem above the guide. The problem is the Volvo spring inner diameter might be too small to accept them, but a bit of trimming might be possible. Then you merely have to remove the springs with compressed air in the cylinder through a fitting in the plug hole, and remove the retainer and spring and slide them on.
Otherwise pulling the head and having the top of the guides machined for a domestic engine 11/32 positive seal like the B20 one only bigger ID would be a solution.
That's assuming the guide to stem clearance isn't too large to begin with. Normally B18's hardly wear the guides.
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I encountered a throttle sticking problem recently, and although I doubt this is your problem as you say that your carbs were recently rebuilt, you might check it out.
On the rear carb, the screws locating the butterfly to the throttle shaft loosened enough that the butterfly could shift laterally enough to bind in the throat and not close entirely, causing a higher idle. (Blipping the throttle would sometimes, but not always jostle it back into temporary alignment and the correct, lower idle.) It required removing the carb in order to accurately locate and tighten the two screws securing the butterfly to the shaft. Problem solved.
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Thanks Danny! That is an interesting possibility. Will check on the screw tightness on the butterflies. Even professional rebuilders may have missed something.
-DS
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Re the smoking, assuming the valve cap seals were refitted, they aren't perfect but do work. Some of these caps are now very poor quality and split/break up, so a good idea to take the valve cover off and check them out. Change all if any are suspect. Compression numbers are very good.
Your carb problem often hard to pin down. Small misalignments will do it. needles might be rubbing a bit and there is a small amount of adjustment in the jet mounting. With the dampers out the pistons should drop instantly at the same speed for each. spindle clamps in the centre can push on the spindles a bit even though they are designed not to. Maybe loosen and tighten these being careful not to change the carb settings. Choke settings might not have any gap between the screw and the cam. Needs a little bit and the same on each carb.
Cleaning and oiling the mechanism always a good idea, including the ball joints and pedal.
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I'm not sure what theory those umbrella seals theoretically operate under, but I can't really see how they meaningfully keep oil out of the guides, on the other side of the spring retainer and 1/2 inch down the valve stem.
But smoking on idling is probably a little oil coming down past those guides. There's a lot of vacuum in the intake ports at idle, that really works hard at getting oil to suck down past the guides into the intake.
As for the idle sticking, it's very likely the carb hanging open slightly. There's really nothing else that's going to give you the same symptoms. One of the throttle valves is probably binding up on something (perhaps the carb throat) and failing to close completely. Could be a loose disc as mentioned, could also just be very slightly misaligned.
Might check for a little slack in the throttle shafts, not sure if the rebuild included rebushing those or not. With a little slack it gives the throttle plate ample opportunity to move around a little and bind up before closing.
--
'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)
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Thanks JohnMc. I used some quick start spray all around the SUs, and as far as I could tell, there were no vaccuum leaks around the throttle shafts. Will have to check further for any possible binding or loosening.
-DS
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I think the "theory" is that the umbrella seals stop oil pooling in the recess in the retainer and around the collets. Mostly that oil would drain down when the engine is stopped and cause a bit of smoke on start up. The build up of oily carbon on the backs of valve heads is sometimes very bad.
Might also mute the tappet noise by a fraction of a db but I doubt if you'd ever notice it.
Would be interesting to know if they could be used to compliment the guide seals on a B20. B20 guides much shorter than B18 so support the valves less well.
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Derek, I did explore into the possibility of B20 guides being machined into the B18 block, but other than the guides being short, the inside circumference of the guides are 5/16. The B18 valve stem size is 11/32, so that would mean the B20 guides would have to be bored.
I would think it better to use new B18 guides and just machine them so that the B20 caps can fit on them...just the intake ones.
-DS
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All of that is true re the sizing. It could well be that the knurling process wasn't effective. Although it's reckoned to hang onto the oil that does get down the guides it's usually done to tighten up the clearance and to save you from having new guides fitted. Better when bronze guides are used. If your valves are new and still have unworn stems I think that a new set of standard guides should cure the smoking. There has to be a small amount of oil going down the guides and the clearance is set to allow this along with the small changes due to heat. New guides means that the valves and seats will have to be recut, to line everything up again. If the valve seals have survived that long, after say 100k miles, they might help stop a bit of smoking but by then it'll be caused by some wear in the guides. B18 seals can be replaced easily at any time. B20 ones not so easy but you can hold the valves up with a length of nylon cord down the bore while you change them. The shorter B20 valve guide will allow more valve rock as it wears and benefits from a better seal. I believe there is a modern Ford seal that can be used there, better material. Someone here will know which it is.
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Thanks, Derek for sharing great information. I see quite a lot of 11/32 seal caps up for sale on eBay- What are the outer diameter of the B18 valve guides? Can the guide tips be machined down to .530" or .500" for certain size caps to slip on?
-DS
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Yes, but make sure they are small enough to fit inside the springs.
Our machinist screwed up on our last B18 head and installed a different style than he usually does and the springs chewed up the new valve seals.
IMHO, you should only use one style or the other, but not both styles of valve seals at the same time on any valve.
FYI, if you have good valves and guides, the umbrella valve seals work just fine. But I will say that when we have the opportunity, we suggest to our customers to update the valve guides to accept a new style valve seal "that fits under the spring". And when we rebuild an engine, we always update the valve guides and seals.
--
Eric Hi Performance Automotive Service (formerly OVO or Old Volvos Only) Torrance, CA 90502
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Thanks, Eric! That would mean I will need to know the outer diameter of the guides and then see if I can find the right valve seal caps with the same outer measurements. That way, the caps would be flush with the modified guides.
-DS
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I am not quite sure what you mean.
But what I know is there are several different valve seals that are designed for 11/32" valve stems, the odd size of the B18 valves, to fit various non-Volvo engines that will fit inside a stock Volvo valve spring.
Our machinist does not always use the same valve seal, a problem I will now correct, and he would custom machine the stock B18 valve guides to fit whatever 11/32" valve seals he had laying around. And until recently, that has not been a problem, but on the last B18 head, he used valve seals that were just a little too large on the outer diameter and the valve springs chewed them up.
So I will get together with him and come up with a specific valve seal that we will always use in the future. This will also allow us to have the valve guides custom made by his supplier with the end correctly machined to accept our selected valve seal.
So if your valve guides have not been already custom machined to fit a valve seal, I should be able to recommend a valve seal in the next day or so.
--
Eric Hi Performance Automotive Service (formerly OVO or Old Volvos Only) Torrance, CA 90502
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Sounds good about finding out the best valve seat to recommend, Eric. Thanks.
-DS
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When I was researching about updating the valve guides on the B18B head, it occurred to me that rather than getting new guides, just insert the sleeves (lining). But I would like to know the pros and cons of doing that other than price.
Thanks!
-DS
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Conversely, I have seen where folks have machined the top of B18 valve guides to accept the better B20 valve stem seals.
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Danny: That was other possibility I thought of...get new B18 valve guides and have the tops be machined to accept B20 stem seals. BUT...the B18 valve stems are 11/32 in diameter...would B20 valve stem (size 5/16 I believe) still offer good seals?
Thanks,
-DS
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Thanks Derek. The valve caps -rubber umbrellas- were new when installed. But I will check to make sure. is there any other way to pinpoint the cause for smoking whether the valve guides are to blame or not?
Thanks also for the tip on what may be the problem with the SUs. Will check about the pistons dropping down evenly.
-DS
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