Feel like 360 should have more power

-
You could trick the engine into thinking it has more compression by replacing even a similar duration cam with one having a narrower lobe separation angle.

As others have stated, high elevation coupled with low compression and big cam are not a marriage made in heaven.

Power can be made with lower compression, and challenging elevation but cam specs are even more critical in this instance.

Job #1, proper tune.

Job #2, find out exactly what cam you have now.
 
Are you sure that you have a 360 in that car and not a 318 with 360 heads on it? Since it seems that you just bought it anything is possible. I would expect a low compression 318 with 360 heads to have cranking compression like what you are seeing. Have you checked the block to make sure that it is a 360? 100-110 lbs seems really low to me. A stock 360 should have at least 140 lbs, unless that is a very big cam, something is not right. Could be as simple as you are loosing compression through the rings or valves, a lot of times an engine that is worn will have a substantial variation between cylinders, some will be quite higher than others. The variation on your engine is within 10% which is totally normal. The cam could have been installed retarded and that is what you are seeing. An engine with 100 lbs of compression will never make any power, it will be a dog.
 
standup303 said:
Good morning all, so I purchased a 69 Dart with 360 LA, 727, 8 3/4” with 4.10s. And I feel like the thing is a pig. When I first got the car I was strapped for time and I just wanted it running well so took it to a local “classic car”shop and they replaced a few plug wires that were burned, set timing, said they tuned the carb. I feel like it barely helped.

I did a compression check this weekend and checked plugs, below are those results and the only details I know of the motor mods. Also there is a pic of the plugs, all looked the same.

View attachment 1716166044

I found the #4 and #6 plug wires pulled right off the boot, so I’m getting a new set of plug wires and changing plugs while I’m at it. Also based on the plugs I’m going to richen up the fuel mixture a bit as well.

The car does emit a small amount of white smoke out of the exhaust, wondering if the rings are worn based on what I’ve read? If any of you have any tips to help me get this running a bit better I would greatly appreciate it, I’ve never tuned an engine up before.

360LA
Weiand intake
Edelbrock AVS2 650 cfm carb 1906
Long tube headers
2.5” exhaust
Stock distributor and ignition
MSD blaster coil

All taken with engine at 175 degrees, car had been sitting for 2 weeks

Cylinder #1 104
#3 108
#5 101
#7 106

#2 110
#4 110
#6 110
#8 106
Click to expand...
It's a pig because it's got the squeeze strength of a 90 yr old man with a bad heart and rheumatoid arthritis.
options....
Rebuild with better high comp pistons
Consider a smaller cam
Toss on some milled to 60 cc aluminum heads or iron.

Just ways to help. No matter what to do with the timing with only 100 lb of compression you're not going to gain much even with it locked at 36 *
 
Doh!
yeah so the cylinder pressure looks to be about the same as if you were blowing up balloons for your daughters 4th birthday party, lol.

Yes I read 6200 and that is your biggest enemy.
To get pressure that low the cam would have to have about the same Ica as the stock 2bbl cam and the Scr less than 8.4.
Same combo at sealevel should pump 140psi, still a slug...... IMO.
You need a supercharger up there.

eschewing that solution, will likely cost more, cuz it means a whole new engine, whereas at 8/1 or perhaps a tiny bit more, you are already in pretty good shape for a super.

At 6200ft your NA build would have to be specific to that elevation, and might not survive long at typical sub 1000ft elevations.
 
Last edited:
I checked the block when I bought the car and it is a 360. I’m finishing up some interior items and then going to start digging in the motor and get the cam specs, and see what’s going on in there. Thanks for all of the input
 
Not sure if anyone brought this up, but what's the chance your compression tester is faulty.
 
A few more pics

IMG_6179.jpeg


IMG_6175.jpeg


IMG_6178.jpeg
 
If you get 6 spark plug testers to 'look' at a plug to determine how the engine is running, you will get 7 different answers.......

Without knowing how long the engine was run, at what throttle opening, what load, how quickly the engine was cut....then it is nothing better than a good guess. And that is not factoring in the differences in today's fuels.

Those plugs look fine to me & not causing any problems. If they were black, sooty or wet......
But they are not.
 
cpearce said:
You could trick the engine into thinking it has more compression by replacing even a similar duration cam with one having a narrower lobe separation angle.

As others have stated, high elevation coupled with low compression and big cam are not a marriage made in heaven.

Power can be made with lower compression, and challenging elevation but cam specs are even more critical in this instance.

Job #1, proper tune.

Job #2, find out exactly what cam you have now.
Click to expand...
That actually wouldn't trick it. That would really give it more cylinder pressure, which is a good idea and endorsable.
 
RustyRatRod said:
That actually wouldn't trick it. That would really give it more cylinder pressure, which is a good idea and endorsable.
Click to expand...
I suppose you could say you trick the engine into thinking it has more static compression, by giving it more dynamic compression.
 
OP said white smoke and low compression on the left bank.
I would check for blown head gasket, cracked head...
 
Do you all think doing a refresh on this motor would benefit performance in any way? Thinking about honing the cylinders and installing fresh rings and obviously gasket kit. But with all the compression numbers close to each other it doesn’t seem like any one cylinder has any issues. I’m planning a 440 swap next winter so on the fence if I want to spend the time refreshing this thing.
 
Work on the basics
The compression numbers are fine for that elevation.

What was missed is a stretched timing chain which causes an engine to run "late" and contribute to the low power and probably the psi number. With the plugs out set the engine at tdc, distributor cap off, put a breaker bar/socket on the harmonic balancer bolt and rotate the engine backwards - see how far the damper moves before the distributor rotor moves....the chain will be stretched as they all stretch so ignore the blah blah blah that the timing chain tensioner does not work and install new chain and tensioner. 360's esp benefit very well when the timing is consistent. If the h20 pump is good reuse it. 195 degree thermostat as well!

The plugs need to be hotter, the timing should be at least 16 degrees btdc and a total of 36 or even more due to the elevation. Use the vacuum advance. Be sure the control box has it's own ground strap.

White smoke may be steam from combustion..are there bubbles in the coolant? Is the engine using coolant?
 
RustyRatRod said:
That would probably set it on fire compared to what it is now. That or maybe something like a 252-260 range. That's about as much as I would go.
Click to expand...
A comp 252 is basically a stone stock 360-2bbl cam
Duration and overlap are pretty much "dead nuts" identical. Comp has 15-thou more lift, that's it.
I've used them in 318s before with a noticeable improvement, stock idle but butt dyno sure feels improvement. AKA melling spd25
 
You must log in or register to reply here.
-

Back
Top