SwedeSpeed - Volvo Performance Forum banner
1 - 15 of 15 Posts

·
Registered
Joined
·
55 Posts
Discussion Starter · #1 ·
My B18 sounds like a muscle car with a lumpy cam at idle and I can't figure out why. It idles rough and sounds like crap. It seems to run smoothly at speed but really chugs at idle.

Here are the details of the car:
- 67 122S with a B18 from a Canadian 123GT
- I bought the engine rebuilt, bored .40 over
- It's run lumpy like this since its first start up.
- Timing is set at 30 degrees and it will stall out if I take it lower than 25
- Just installed Pertronix ignition in a 009 distributor and it made no difference. Runs the same as when it had points
- New cap
- New rotor
- NGK plugs
- New Bosch coil
- Plug wires new from IPD but are some off brand I've never heard of
- Carb are rebuilt and I've had a couple guys tinker with them to get them right
-New fuel filter
- I've run everything from 87 octane to 91 octane, with no better results
- Brand new battery
- Valves just adjusted
- Compression test was good with nearly identical compression on each cylinder

Any potential culprits here that I am missing? Could it be a wiring issue? Or is it possible that it was just fitted with a hot cam?

I can post a video of it idling if that helps at all.

Thanks!
Dave
 

·
Registered
Joined
·
2,650 Posts
- Timing is set at 30 degrees and it will stall out if I take it lower than 25
Is that total advance? If so, it might tolerate a little more total advance to say 32-33 deg. If memory serves me right, if it is a B18B it does not have a vacuum servo on the distributor (centrifugal advance only). I am not really up on B18s; but, I am thinking the total centrifugal advance is about 25 deg. With 30 deg total advance your idle advance would be around 5 deg. A better number seems to be around 10 deg. A little more advance at idle can improve idle operation.

My experience is the B20E, so take this with a large grain of salt!
 

·
Registered
Joined
·
324 Posts
Timing at 30 degrees at idle?? Or total? If at idle, it is way, way too high. 10 degrees is about right.

As for the lumpy idle, have you checked for leaks around the carb throttle shafts? Assuming that you have SU's, you are displaying the classic symptoms of very leaky throttle shafts. You can check them with a 'wiggle test,' or more reliably by spraying something flammable (e.g., ether) around them, and listening for an increase in rpm.
 

·
Registered
Joined
·
55 Posts
Discussion Starter · #5 ·
Timing at 30 degrees at idle?? Or total? If at idle, it is way, way too high. 10 degrees is about right.

As for the lumpy idle, have you checked for leaks around the carb throttle shafts? Assuming that you have SU's, you are displaying the classic symptoms of very leaky throttle shafts. You can check them with a 'wiggle test,' or more reliably by spraying something flammable (e.g., ether) around them, and listening for an increase in rpm.
That's correct. 30 degree at idle, which I agree is way too high. The car will sputter out at 10 degrees at idle. I have read it should be 15-19 degrees at idle, and I just got it to idle at about 18. But at 18, in first gear, it is really hesitant when I start going from a stop. I let the clutch out and give it gas and it chugs and chugs and chugs then finally roars to life and accelerates like it should.

I also sprayed carb cleaner on the throttle shafts and intake where it could be leaking, which would have dropped the idle if it there was a leak. It didn't change at all. If ether would be better to test with I can give that a go tonight.

Also it is a centrifugal advance distributor and the previous owner tells me it is a C cam.
 

·
Registered
Joined
·
2,650 Posts
With 30 deg at idle, if you still have the mechanical advance in place, I would expect it to detonate like crazy under acceleration.

Are the carbs the original SUs? If they are, it might be useful to find out what jets and needles you are running. There are some experienced SU users on the forum who will be able to advise you whether the jets and needles are in the right ball park. The overbore will require some fuel tuning; however, I would not anticipate drastic changes. What do your sparkplugs look like? Do they look reasonable or like you have a grossly lean or rich mixture?

I know you said that your compression is good, so I would not expect the valve timing to be really out of whack; however, is it possible that the cam was installed 1-2 teeth out which would affect performance. There is a procedure in the service manual that will allow you to do a basic check on camshaft timing and it is not particularly difficult.

I am at a bit of a loss to come up with other causes for requiring such a huge amount of advance.
 

·
Registered
Joined
·
55 Posts
Discussion Starter · #7 ·
It detonates a little bit if I'm climbing up a massive hill and putting a lot of load on it, but otherwise it doesn't.

They aren't the original carbs - they were rebuilt by an SU specialist in the States. The plugs are a nice golden brown, so carbs seem to be set right.

I'll have to look up that procedure on cam timing. I didn't assemble to motor myself, so it's worth checking. I have checked the distributor drive gear and it is set correctly.

Thanks again for all the advice so far!
 

·
Registered
Joined
·
324 Posts
Something is very, very wrong for the car to require 30 degrees of advance to run--and then not detonate. I'm with 142 Guy. Go back to basics, and check everything related to cam and spark timing. Then move from there to carburetor basics. Do you have a friend with a known good set of SU's? After the timing (assuming that it is healthy, which I doubt that it is) it might be a reasonable next step.
 

·
Premium Member
Joined
·
9,303 Posts
Sounds to me like the cam gear is off by one or many teeth.
 

·
Registered
Joined
·
2,650 Posts
I have checked the distributor drive gear and it is set correctly.
I am guessing you mean the orientation of the distributor drive gear with respect to the camshaft drive gear? If so, that establishes the correct orientation of the distributor to the camshaft. The camshaft can still be screwy relative to the crankshaft causing the valve timing problem. If the camshaft gear is out by a tooth, it may be difficult to adjust the distributor to get the ignition timing in the proper range relative to the crankshaft pulley marks. If the cam gear is out by two teeth, I suspect it may be impossible to adjust the distributor to get the ignition timing in range because the distributor will be bumping into the end of its adjustment slot - may give you some clue as to what is going on.

If the color of the plugs looks reasonable, the carbs are probably not the primary source of your problem.

I wait future developments with baited breath as I think you have established a new limit for base ignition timing on a Volvo red block without having it detonate a hole in a piston :).
 

·
Registered
Joined
·
55 Posts
Discussion Starter · #11 ·
I wait future developments with baited breath as I think you have established a new limit for base ignition timing on a Volvo red block without having it detonate a hole in a piston :).
Well at least I've accomplished something!

And yeah, what I meant was I set the distributor drive gear correctly in relation to the cam, based on this article:
http://www.sw-em.com/Volvo Ignition from Scratch.htm

How can I check the cam timing in relation to the crank?
 

·
Premium Member
Joined
·
9,303 Posts
How can I check the cam timing in relation to the crank?
It's a pain. You have to pull the front cover and see if the two little marks meet. There's a pockmark on the crank gear and cam gear. Some people get it wrong because the gear is helical-cut and it twists as it goes on, if you engage the wrong tooth it lands in the wrong spot and people don't always check.

If you pull the cover, you need a new paper gasket and it's kind of hard to center the front seal with the oil pan tight to the block. You need to tighten the bolts around the front case evenly, from top to bottom going down both sides. Then use a feeler gauge between the flange and the crank journal to e sure it landed on center, before tightening the bottom bolts to the oil pan and installing the felt seal. You can use a plastic hammer to tunk it into a better spot, if you're careful. It sounds hard, but it's not too difficult once you get the hang of it.

You could do a quick check by setting the timing mark to TDC and seeing if the valve rockers are all in sensible positions. The #1 or #4 cylinder should be fully disengaged (depending on which piston is up), but since someone has adjusted the valves since then, it's going to be hard to determine. You might have to roll the crank and see when the lifters start to move, and guess a little.

The angle of the distributor drive gear really doesn't matter a lot. When timed, the distributor will be rotated into the appropriate angle, and if the gear is off, it just needs to rotate more. Getting it at the right angle just means the wires and vacuum hose (if present) aren't stretched or anything. So, that's not it.
 

·
Registered
Joined
·
2,650 Posts
There is a separate procedure in the Volvo service manual (green book) which does not require the removal of the front cover. It required the use of a dial gauge and a holder for the dial gauge. Its been about 4 years since I did it so I am a little hazy. As I recall, you had to open up the clearance on one of the valves to a specified amount for the test and then check the lift on a specific valve when one of the timing marks lined up (as noted, I am a little fuzzy on all the specifics).

It does require that you have or scrounge a dial gauge. Other wise you will have to do as tmtalpey suggests. The advantage of the process is that it will show problems with either an incorrectly timed camshaft or an incorrectly fabricated camshaft. I am sure that there are scanned copies of the green book for the Amazon if you don't have a paper copy. If you can't find a copy, I can scan the section out of my green book. The test procedure specifications are specific to the camshaft. I don't know whether the book has the specs for the C grind cam since I was focused on the procedure for my D grind cam.

Edit - if you look at the photos in post #14 in the following thread you can see the type of dial gauge / holder arrangement I used. In this case I was confirming lift; but, it was the same arrangement for confirming the valve timing.
http://forums.swedespeed.com/showthread.php?201780-What!-Another-142-Project-Car
 

·
Registered
Joined
·
2,650 Posts
The angle of the distributor drive gear really doesn't matter a lot. When timed, the distributor will be rotated into the appropriate angle, and if the gear is off, it just needs to rotate more. Getting it at the right angle just means the wires and vacuum hose (if present) aren't stretched or anything. So, that's not it.
tmtalpey is of course correct. Save for twisted wires, there is no limit on how far you can adjust the rotation of the distributor to set the timing relative to the crankshaft. I was thinking of a different engine where the base of the distributor was rotated by slackening off the retaining bolt in the block.
 

·
Registered
Joined
·
2,650 Posts
I checked my service manual and you should be able to do the camshaft timing check procedure without the use of a dial gauge; however, the dial gauge makes it easier.

The procedure is as follows for the B20B engine which has the C camshaft.

Cold engine.
Set the valve clearance on the #1 intake valve to 0.057"
Rotate crankshaft and the #1 intake valve should start to open at 0 deg (TDC)

By setting the dial gauge actuator on the valve spring retainer, it is really easy to get an accurate indication of when the valve is just starting to move open. However, by eyeballing it you may be able to get a 'good enough' indication for doing a rough check on the timing (at least good enough to determine whether you are out by a tooth or more).

Remember to reset the clearance on the intake valve after doing the test.
 
1 - 15 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top