Two... questions

[67Dart34dr0]

Would a '79 Diplomat's A/C setup be able to replace the factory A/C on my '67 Dart (only the underhood components) and what would it take to run an 11:1 compression small block on pump gas? (something around there, 340 w/ 9.5 pistons and 318 heads)

[moparteacher]

The AC should bolt up, but I would look at Bouchellon for new brackets and compressor.

As for 11 to 1....E85 or racing fuel. Supreme gas may work if, and that's a big IF, you run a long duration cam (think high rpm), a cool engine (under 160 degrees), fresh air intake, maybe even water injection.

E-85 is your best bet.

[67Dart34dr0]

So would bringing the CR with gaskets be a better idea, and would a 10.5 work okay?

[75Dart440]

I'm running a 10.5:1 compression 440 on the street with 160 thermostat and fresh air off the hood, on 93 pump gas.  It'll run on 89 if I don't put so much timing into it.

[67Dart34dr0]

Well, it is the Dart your grandmother used to drive. (factory manual steer, /6, A/C, vinyl int., two tone, manual 9in. drum car) Stock-ish cam in the 340 and the 318 heads would just be an easy way to get hardened valve seats (could get them off the same engine as the A/C stuff). Only a street car, so it really should run on the street, thanks for the tips 75Dart440.

She's got a '71 big block Fury radiator and A/C fan.

As for the A/C, I got a box of most of the miscellaneous stuff to get it setup, just not everything necessary.

[fourspeed]

As a rule of thumb, you can run a maximum of 9.5:1 with stock heads, and a stock cam. My 340 with 10.5:1 and stock cam was NOT happy with unleaded premium. Do your 318 heads have those heart-shaped chambers? Those heads DO raise compression.

Be aware that 318 heads have smaller ports and don't flow as well as a 340 or 360 head. If you could find a 360 in the junkyard with the heart-shaped chambers, that would be the way to go. They're hard to come by, though. Next best would be a pair of 360 heads with hardened exhaust seats put in. I know, machine work is costly, but fresh heads make the engine run nice. 

Somewhere around 1980, I think they started using Sanden compressors for air conditioning. They're round vs. the old V-twin compressors. The intake manifold bosses are all different, some hoses come out in different places... It doesn't work out well, UNLESS you go with some aftermarket brackets and pulleys... but that's expensive. You can try going this route, but beware. If it's a V-twin compressor, you should be fine. The drier, condensor, etc should all be ok if they'll physically fit. Don't leave the system open or discharged longer than necessary.

[75Dart440]

My car is a factory air car as well.  I have a Sanden AC compressor from a 90 Caravan that I am going to use.  I've already got the compressor, new drier/receiver and expansion valve, just need the hoses, pressure switches and AC condenser and should be good to go.  Hoses will have to be custom made though....which could get expensive.

[67Dart34dr0]

It's got a V-twin compressor as you called it, fourspeed.

Are the heart shaped chambers the hardened valve seats?

I'm aware I might well be giving up HP, but having gone up one path and not having much luck, cost is an issue.

I hate to admit that I don't know the cam specs, but do know it was changed, by the guys who built the motor for the owner two owners ago.

I think the parts in the car (almost all but compressor) have been unhooked for around 6 years or so and the wires being cut to ease engine installation shorted out the wires leading to the temp sensor, which then shorted out up to the guage and this is looking like a good candidate for the big cause of this car's dash area electrical problems, including gas, temp, oil, and possibly park brake.

Did you do anything with the 340 to get it to run on pump gas?

[fourspeed]

It was the late 80's. I tried Edelbrock water injection. No good. Octane booster probably would have helped, but I had no money at the time. A longer duration cam would have lowered cylinder pressure, and that would have helped. I quit driving it because it was running like crap. I took the heads off and ALL the exhaust seats were recessed. It MIGHT have had factory hardened seats. After a valve job, who knows?

There were special castings made that had the heart-shaped chambers I mentioned. The 318 used them from '85 until '91. The casting number ends in 302. The 360 had similar heads with a 308 casting number. If you don't have these heads, then you have a regular wedge-shaped chamber, which is ok.

318 heads will fit, they have considerably smaller ports. If it were me doing that, I would think about using an intake with 318 ports too, so there's not a "shelf" where it goes from a large port in the intake manifold, to a small port in the head.

Are you sure the 318 chambers are smaller than the 360 chambers? I am not aware of a significant difference.

[67Dart34dr0]

I think they're like 62cc chambers. The car is mostly original and if switching to the 318 heads, would also switch to a 273 4 barrel intake.