S-L-O-W 1993 240 Classic wagon

[dmg4]

Originally Posted by tjanson

Just keep the poor thing out of the upstate salt

No worries. It's in my garage and off the road for Dec, Jan, and Feb every year. When it ventures out at all during those months, it's only when the roads are dry and only for test runs. The head will come out next week, so it won't be going anywhere until the new head is installed and tested.

[JE Jr]

Before you shave the head, make sure it has not been shaved before, I mean car is soon 30years...

If I recall correctly it is suppoaed to be 146.1mm between headgasket surface and valve cover gasket surface as stock.

[dmg4]

Originally Posted by JE Jr

Before you shave the head, make sure it has not been shaved before, I mean car is soon 30years...

If I recall correctly it is suppoaed to be 146.1mm between headgasket surface and valve cover gasket surface as stock.

Will do.

[dl242gt]

I would suggest you read up about tight squish if you are going to remove the head. It will help avoid the chance of detonation with the higher than stock compression from shaving the head.

[dmg4]

Originally Posted by dl242gt

I would suggest you read up about tight squish if you are going to remove the head. It will help avoid the chance of detonation with the higher than stock compression from shaving the head.

I read until I felt squishy. Planing the head .040" and using the OEM headgasket should raise static compression from about 9.8 to 10.2:1. I hope that's not something that should result in knock with the VX cam and reasonable timing. Unless I wanted to also resurface the block (more than I'd care to do right now), my options would seem to be reducing headgasket thickness, which would seem to be the same as shaving more off the head resulting in higher compression. Where does it end?

I'm probably missing something here. What is it? Perhaps I should just fuel it with 93 octane and declare victory.

[dmg4]

*BING* The lightbulb is lit!

OK, got it: aim to get the piston tops closer to the head for optimal cooling of the piston tops by either resurfacing the block or using a modestly thinner headgasket. I just found and read a wonderfully entertaining pissing match on this forum over the terms "squish" and "quench". Thank you, John V, outside agitator for enlightenment.

Sometimes dawn comes late in my part of the world.

[rb92673]

Turbo would be more fun. After all this is TURBObricks, not NormallyAspiratedBricks. =)

[dmg4]

Originally Posted by rb92673

Turbo would be more fun. After all this is TURBObricks, not NormallyAspiratedBricks. =)

Think of it as a Special Olympics for Volvos.

[dl242gt]

Glad you got the idea of the tight squish/quench. You won't need to deck the block. Just measure the piston height and calculate the head gasket thickness needed. The MLS head gaskets are available in several thicknesses. This helps a lot with detonation resistance and efficiency of combustion.

[shoestring]

They're nowhere near 9.8:1 as delivered. Mine measured out to 9.1:1. After a 0.040" mill and stock head gasket, it's 9.8:1. I use a V cam and feed it a steady diet of Shell 87 (R+M)/2 and have no detonation issues. Using 93 netted no measurable improvements of any kind.

[dmg4]

Originally Posted by shoestring

They're nowhere near 9.8:1 as delivered. Mine measured out to 9.1:1. After a 0.040" mill and stock head gasket, it's 9.8:1. I use a V cam and feed it a steady diet of Shell 87 (R+M)/2 and have no detonation issues. Using 93 netted no measurable improvements of any kind.

That seems quite a difference from an advertised spec. Was this taken on a new car following delivery and break-in, and are you confident that it's representative of the breed? And was this a turbo or NA car?

Anyone else lurking here have a similar or different experience???? I guess I could measure compression on my motor now for a reference point, but that would only indicate absolute compression on a motor and head with 150K miles, and before a valve job and shaving.

[esmth]

I've also measured two uncut late NA 530 heads (93 and 94 castings) at 54cc and change which math's out to the low 9's to 1 depending on the piston height.

[shoestring]

Originally Posted by dmg4

That seems quite a difference from an advertised spec. Was this taken on a new car following delivery and break-in, and are you confident that it's representative of the breed? And was this a turbo or NA car?

Anyone else lurking here have a similar or different experience???? I guess I could measure compression on my motor now for a reference point, but that would only indicate absolute compression on a motor and head with 150K miles, and before a valve job and shaving.

I've measured enough piston dishes and combustion chambers to know this is absolutely representative. NA car. I concur that a 530 year is about 54cc. Normally a hair more. NA piston dish is 8cc, turbo is 16.

[culberro]

Originally Posted by shoestring

They're nowhere near 9.8:1 as delivered. Mine measured out to 9.1:1. After a 0.040" mill and stock head gasket, it's 9.8:1. I use a V cam and feed it a steady diet of Shell 87 (R+M)/2 and have no detonation issues. Using 93 netted no measurable improvements of any kind.

Yup
I’m pretty sure Volvo left out the HG volume when they did the calculation for publication.

My experience with 87 vs 91 may be different (it overall doesn’t really matter), but the CR thing is real 100%

[OldCarNewTricks]

Originally Posted by culberro

Yup
I’m pretty sure Volvo left out the HG volume when they did the calculation for publication.

My experience with 87 vs 91 may be different (it overall doesn’t really matter), but the CR thing is real 100%

Anyone know about the higher comp B23F engines? I have one in my 83, it's apparently 10.3:1, but maybe they also left out the HG?

[2manyturbos]

Originally Posted by OldCarNewTricks

Anyone know about the higher comp B23F engines? I have one in my 83, it's apparently 10.3:1, but maybe they also left out the HG?

Those run a flat top piston. That is what increases the compression ratio.

[HiSPL]

Originally Posted by dmg4

*BING* The lightbulb is lit!

OK, got it: aim to get the piston tops closer to the head for optimal cooling of the piston tops by either resurfacing the block or using a modestly thinner headgasket. I just found and read a wonderfully entertaining pissing match on this forum over the terms "squish" and "quench". Thank you, John V, outside agitator for enlightenment.

Sometimes dawn comes late in my part of the world.

How I miss John V.

He's a weird one, but that particular Mr Grinch certainly knew his sh1t.

[shoestring]

Originally Posted by culberro

Yup
I’m pretty sure Volvo left out the HG volume when they did the calculation for publication.

My experience with 87 vs 91 may be different (it overall doesn’t really matter), but the CR thing is real 100%

Interesting. I always wondered if it was a "highest possible result" given maximum allowable tolerances like deck height and the 0.5mm cleanup they allow on the head. Like you said though, it doesn't really matter.

The truth is out there. Just like on X-Files.

[OldCarNewTricks]

Originally Posted by 2manyturbos

Those run a flat top piston. That is what increases the compression ratio.

I remembered that, I'm just curious if somone has done a CC fluid test on the B23F heads to check for spot on accuracy. I do recall my compression readings being pretty high when I did a comp test.

[dmg4]

Just for fun, I warmed up the engine and ran a compression test.

1= 132 psi
2= 138 psi
3= 138 psi
4= 140 psi

Assuming an atmospheric pressure of 14.696 psi, a 9.1:1 compression ratio works out to 133.7 psi

It fits.

Not bad for an engine with 145,000 miles. I'll post the new numbers after the head is shaved.

[culberro]

Those are really low numbers for cranking pressure on a warm NA motor.

[dmg4]

Originally Posted by culberro

Those are really low numbers for cranking pressure on a warm NA motor.

What am I missing in my assumptions? A temperature effect of compression in PV=nRT? It was a "dry" test (no oil added to cylinders).

[Cwazywazy]

Originally Posted by culberro

Those are really low numbers for cranking pressure on a warm NA motor.

Even with a VX cam?

[dmg4]

Originally Posted by Cwazywazy

Even with a VX cam?

Why would that matter? Aren't both valves closed the time that the maximum pressure is reached, or is there overlap that results in one being open on the compression stroke?

[Cwazywazy]

Originally Posted by dmg4

Why would that matter? Aren't both valves closed the time that the maximum pressure is reached, or is there overlap that results in one being open on the compression stroke?

It matters. My engine makes like 120psi cranking compression with the IPD turbo cam. A stock stock one would make 160+