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B30 rod knock?

As far as I know the C and the K grind for the B30 are the same lobe dimensions as the C and K for the B18/20.

If that is true then definitely go for the K.

The B30 should have also gotten bigger valves in the fuel injected version. Much like the four cylinder motors.
 
- Pull all the plugs
- Hold the throttle open
- Crank and observe

It shouldn't be taking that many compressions to build up to a plateau. Maybe 3 or 4?
 
What PSI did it eventually puff its way to?

Might try a small squirt of oil into the spark plug hole and see what happens.
 
Most made it up to 155ish, and I had one lower at 135ish. My battery wasn't very good so it was kinda cranking slow. I'm going to do it again after work today with a freshly charged battery, and try it wet too. Then I'm going to pull the valve cover and measure how much the valves are getting depressed on each one. Then I think I'll be able to say for sure I have a worn cam. If the compression numbers go up on that low cyl with some oil I can say I need rings too, and at that point the whole thing can come out and get looked over.

I would much rather be able to throw a new cam on it and button it back up and ride, but if it has to get rebuilt...it has to get rebuilt.
 
Ok I got a different compression tester and did it again. I'm not sure if it matters too much, but since It was all apart I didn't warm up the engine first this time.

Cyl 1 dry-120 wet 120
Cyl 2 dry -130 wet -130
Cyl 3 dry - 125 wet -125
Cyl 4 dry - 135 wet -135
Cyl 5 dry - 127 wet -130
Cyl 6 dry - 115 wet - 115

Then I went through and measured the lift of each valve from it's fully depressed position. I could have stopped pretty early on, but I did them all for ****s and giggles.

Valve 1- 351
Valve 2 - 352
Valve 3 -357
Valve 4 - 360
Valve 5 - 236
Valve 6 - 234
Valve 7 - 168
Valve 8 - 355
Valve 9 - 358
Valve 10 - 355
Valve 11 - 273
Valve 12 - 362
 
Oops, missed that. That's actually pretty good news.

Could be that someone stuck a thick HG on it to handle low octane gas, or it's just got some leaky valves.

Yeah, time to pull the head.
 
Head is coming off, and I'll post up some pics of what I find. I appreciate you guys walking me through this, I truly need a mentor. This is my first time messing with any of the old pushrod carbed motors, so this is a learning experience for me.
 
I've about got the head off, and today I called around to see what it'll cost me to have the exhaust seats put in and a valve job done. I had one place quote me "$400-500" and another "about $200." Most places didn't want to fool with it, one said "I don't do any foreign stuff." lol I live in Kentucky, and the guy I found to work on it definitely sounds like a good ole boy. I asked him if he was scared of doing a volvo head, and he laughed. He said he's done stuff all the way back to 1942 so it shouldn't be a problem.
 
Last edited:
intothelabyrinth said:
Volvo B30 head off https://imgur.com/gallery/cMbNlkL

The cylinders don't even have a ridge at all. Everything looks pretty good to me. Coolant passages all clean, nothing gnarly that stands out anyway.
Click to expand...

If you pluck the lifters out and look at the cam lobes any flat ones will be pretty obvious. Cross hatching still in the bores? It looks like its in rather good shape.

I wouldn't buy any BS from a shop not wanting to do a basic valve job on a B30 head. They are pretty standard cast iron OHV setups. It isn't like its some exotic Alfa Romeo dual cam sort of thing.
 
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