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[edberry78]

I read here that in 1985 the compression ratio was increased to 9:1 under specs on the police cars. Did they do the same on regular cars? Just trying to figure out the compression ratio on my 1986 model (318).

[Dippy.org]

[lsm360]

Yes, an '86 318 was 9:1

[DobaMark]

I read here that in 1985 the compression ratio was increased to 9:1 under specs on the police cars. Did they do the same on regular cars? Just trying to figure out the compression ratio on my 1986 model (318).

Only the 2bbl engines had the increased compression. 4bbl police car engines did not see the increase in compression.
The increase in compression came with the high-swirl heads and a switch to the Holley 2bbl, as well as a recommendation for premium gas. The changes were likely driven to meet increasing emissions and gas mileage requirements. The police cars were not subject to gas guzzler laws. The civilian cars were.

[Derekb]

under the valve cover would have casting 302 for the high compression heads

[edberry78]

Thanks, fellas!

[lsm360]

Yes I should have been more clear. The 2 barrel cars went from 8:7 to 9:0. Thanks Mark.

[80 Lebaron Coupe]

4bbl police car engines did not see the increase in compression.

What was the CR for these 4BBL engines to handle the 360 heads?

[lsm360]

What was the CR for these 4BBL engines to handle the 360 heads?

I think it was 8:5 but need to look in my Chrysler Police Encyclopedia to be sure and I'm goofing off at work right now.

[DobaMark]

I think it's even lower, like 8.2 on the 318-4 engine.
The earlier 318-2 was 8.5.

[lsm360]

Encyclopedia says 2 barrels got 9:0 and 4 barrel cars 8:4 with the 360 hp heads.

[80 Lebaron Coupe]

Encyclopedia says 2 barrels got 9:0 and 4 barrel cars 8:4 with the 360 hp heads.

One would think it should be the other way around considering the 360 heads drop the CR 1 point.
IE: 9:0 would be 8:0 with the 360 heads. and 8:4 would be 7:4.
7:4 doesn't seem like enough to get out of its own way.

Maybe I got the info wrong from here, and the point is from the bottom end, like 8:4 would be 8:3 with the 360 heads.

[lsm360]

It explains it in the Encyclopedia, sort of anyway. Can't say I know enough about heads, the burn, etc., to understand completely. Wish I could scan and post.