• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

B18D Exhausted Piston

84B23F

84B23F

Well-known member
Joined
Feb 11, 2008
Location
Kansas, USA
Removed one oversized (0.020") piston today, and found what I thought was exhaust gases on both sides of pin, but apparently just oil stain via those two holes. Rings moved freely, not gunked up. I received this engine some years ago, but I thought he said this was rebuildable. After checking the bore in hole #1, it looks good, so I might re-ring it; rod bearing was excellent.

jvpUMgq.png
 
Last edited:
dl242gt said:
What car are you putting the pushrod power plant in?
Click to expand...

1975-244...project vehicle....either this 1960s B18D engine will be used, or 244's B20F. B18D was a freebie, and I discovered two compression rings were busted on the same piston (#2). Most likely, head/block got shaved and they used the same thickness head-gasket as OEM (which jacked up compression), or timing was advanced too much.

Question - Will B18D's intake/exhaust manifold for SU HS6 carbs bolt up to B20F head? I have not removed B20F's intake/exhaust manifold, etc., yet.
 
Yes, it bolts up. we have a B20 with a FI head on it in our 69 wagon stashed in the barn. Has HS6 on it with early aluminum manifold and later fuel injection exhaust manifold.
 
bobxyz said:
symmetrical
Click to expand...
All four pistons have the same design. in first post, I had not removed the other three pistons.

All 4 holes are in good shape, and except for #2 piston, the other three have good rings. #2's oil ring was sludged/stuck, and compression rings were busted.
 
Last edited:
Jack said:
show the car!
Click to expand...
.This 75-244 has a history of sitting, and mostly in the sun in earlier days. Rust free essentially, and with low mileage.
29iY2zs.png

.B18D engine was a freebie...still got fuel pump with glass dome. Bore holes are greased; unknown today about how it will be rebuilt. Green iron was for lifting engine off a pallot.
pGhbFPB.png
 
bobxyz said:
..piston...cylinder....
Click to expand...
0.20" oversized pistons and cylinder walls are all good, and within slight wear. Engine will either be re-ringed or rebuilt with 0.30" pistons.

Best I can deduce is either high compression or advanced timing busted two compression rings on piston #2.
 
Another suspect is low octane fuel. I don't know why but lots of folks like to run Volvos on regular gas which is not great fuel for a redblock. Unless of course it's gotten the tight squish treatment. Then it seems to be a happy engine with regular fuel.
 
dl242gt said:
Another suspect is low octane fuel.
Click to expand...
Good point...I'm not sure when states started checking octane specs, but I do know low priced fuel stations bought the cheapest gasoline available for many years until EPA mandated a detergent package be added in 1990s, or later.
 
FWIW. The oil expander rings should be offset to the wrist pin from each other. With the pin at 12/6 o'clock position the gaps should be @4&8.
Your picture shows it right above the wrist pin or at least past the oil holes.
 
dl242gt said:
Another suspect is low octane fuel.
Click to expand...
With the Clean Air Act of 1970, "GM reduced compression ratios on all of its 1971 engines to permit the use of low lead, regular leaded or unleaded gasolines and other automakers soon followed." And, "the higher-octane premium and super-premium leaded fuels gradually disappeared from most stations - leaving only lower-octane leaded regular and unleaded grades.... "

B18D came with 8.7:1 compression ratio, which is OK for regular, but if head/block was shaved, then "Can't You Hear Me Knocking?"
 
84B23F said:
With the Clean Air Act of 1970, "GM reduced compression ratios on all of its 1971 engines to permit the use of low lead, regular leaded or unleaded gasolines and other automakers soon followed." And, "the higher-octane premium and super-premium leaded fuels gradually disappeared from most stations - leaving only lower-octane leaded regular and unleaded grades.... "

B18D came with 8.7:1 compression ratio, which is OK for regular, but if head/block was shaved, then "Can't You Hear Me Knocking?"
Click to expand...
With my lower compression motors (the 8.7:1 specified by Volvo is optimistic based on measuring disassembled engines) I use 89 minimum. Once above 9:1 I like to give them 91 for peace of mind.
 
For Volvo it was 72 for the compression drop. They also added the hardened valve seats for unleaded then. I've seen valve recession on my friends 69 B20 and it was very interesting to see the valve seat surface be the cylinder head material. He had burnt an exhaust valve and it cracked the head of the valve.
 
dl242gt said:
For Volvo it was 72 for the compression drop. They also added the hardened valve seats for unleaded then. I've seen valve recession on my friends 69 B20 and it was very interesting to see the valve seat surface be the cylinder head material. He had burnt an exhaust valve and it cracked the head of the valve.
Click to expand...
So I keep hearing that earlier and earlier years had hardened seats. I don't quite buy it as I have had a bunch of '72-73 B20F heads pass through my hands and none have hardened seats. The one F head I have off a '74 or '75 K-jet motor doesn't have hardened seats either. The only head I've seen with hardened seats was one rather badly butchered example that I think came from a Penta engine.
 
You must log in or register to reply here.
Back
Top