Increasing Compression

[FSJfan]

My engine is soon to have some valve work done. It has a mild cam and everything else is basically stock. What have all of you done to increase compression in your 360s? It’s quite gutless at the moment. I’m thinking getting a new 4bbl, intake, exhaust manifolds vs headers is tba, and distributor MSD or HEI.

[REDONE]

Well, nothing on your list effects static compression, so I don't know that we're all on the same page.

With 3rd Gen AMC V-8s, your basic options are to mill the heads (lots of math) or taller pistons (full rebuild). Nothing else has any effect on compression.

If you poke this bear on the internet, you're going to get a whole lotta bullsh*t thown your way and you'll walk away either confused or discouraged. There's a lot of passion in engine building, and more than half comes from people who've never built an engine. Another 1/4 is people who build engines for very specific purposes that aren't the one you're after.

This is one of those times where the answers you seek out yourself are going to be far more valuable than the answers thrown at you.

[For the trolls, there's no point talking about dynamic compression until static compression is established.]

[rocklaurence]

Redone, your so right. I know that I have considered the same and I'd like to increase compression but dont want to run 91 octane, So, is 1-1.5 points worth the expense on a daily driver? IDK

[FSJfan]

If that’s the case then what’s a rough estimate of milling the heads? It’s gonna come off anyways to get valvework done. And I’ve heard mixed opinions about putting a new cam in so the rod sets with the cam properly any reason to have to put a new cam in? As far as the other mods such as distributor, intake, and 4bbl would that be enough to make my 360 have some ponies? If it gets milled would I need more tolerance and would I need to run a higher octane?

[Stuka]

The problem with milking the heads is then you also need to do the math for push rod lengths and such too. Not the end of the world, just something to be aware of. As well as piston and valve clearances.

[letank]

gutless.... set the timing at 15 add 1 degree for every thousand feet above sea level

How many miles on that 77, wide ratio??? what gearing with the 33's probably 3.54 on a truck

[FSJfan]

I’m in the Midwest so it’s not even a 1000ft above sea level. It’s got 3.54s. It’s already been rebuilt with sub 10k miles on it. I’m not expecting to have an animal but something that isn’t anemic would be nice. I’m not sure if most people have done any head work or just done the typical bolt ons ex: 4bbl, intake, distributor, etc. it’s basically a stock engine with a mild cam. Any rocker arm ratio change?

[Cheapthrills]

Im no engine gurue but, My mechanic friend suggested for me to have the heads shaved no more than. .010 and do a 6 angle valve grind.... but told me not to port and polish them because it would take away low end torque. Maybe ask a machine shop what they think. An rv cam doesn't require any special valvetrain mods.

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[Cheap Hobby]

How many miles on your exhaust system? Is it plugged?
If you do mill the heads take to your machinest about matching the intake to the heads for proper flow. If a lot is cut off the heads you will change the angle the intake sits at.

[FSJfan]

I’m not sure on miles. It’s pretty cruddy.

[rocklaurence]

If it were me and I had the motor torn-down, Id put in a set of 343 piston but I'd take a little material of arounf the valve relief and polish the chambers. This setup is close to 10:1 witht the late model heads. But now your in the area of needed to run 91 octane.

[letank]

so back to gutless, which ignition do you have at the moment?

77 could still be the ill famed dual advance vacuum of the prestolite distributor known for its no-lite standards

better go with duraspark distributor, brain from the later models, and add the TFI coil from the ford

bypass the ammeter if still present and redo all your grounds

and back to basic, compression, burning oil??? dragging brakes...

[FSJfan]

It does burn oil about a quart every 1000 miles or so. It’s looks to be whatever stock was It was a Jan build I’m not sure if that helps at all. I will be upgrading to an Hei or Msd when the time comes. The burning oil is the reason head work is to be done.

[Stuka]

Have you ever done a compression check on this engine? If its burning that much oil, you need to check this. Could explain a lot.

The only way head work will fix oil consumption is if you have bad valve stem seals. And even then it will only really burn oil at startup.

[FSJfan]

Well on start up is when I really notice it.

[440sixpack]

You could shave the heads and gain a little. pistons are the best solution.

You could also get some smaller chamber heads. but by the time you bought asset and had them rebuilt with hard seats pistons would still be the better option.

[letank]

It does burn oil about a quart every 1000 miles or so. It’s looks to be whatever stock was It was a Jan build I’m not sure if that helps at all. I will be upgrading to an Hei or Msd when the time comes. The burning oil is the reason head work is to be done.

a quart every 1000 miles is withing specs...

Worn out valve seals gets you a quart every 250miles, yes it is most noticeable on warm start up, been there done it... fixed the valve seals and consumption dropped to a quart every 2000 miles, depending on driving conditions.

[FSJfan]

I’m trying not to have to pull the engine if I don’t have to. I’m on a high schoolers budget. It’s been burning oil noticeably since last summer and has been getting progressively worse. It is worse in cold conditions. When ever I first turn it on I have to give it some gas to what seems like burning out the oil in the cylinders. It is a relatively new(low mileage) rebuilt motor which I would think wouldn’t be burning a quart every thousand miles or so.

[440sixpack]

That's a lot of oil.

Rebuilt means lots of things so don't put much faith in anything you don't know what was done and who did it.

If it's mainly on start up it could just be the seals . if they put the POS white Teflon seals on it you will burn oil and they need to be changed, they're crap . I fought this for a year on a fresh 383 Mopar before I figured it out . the blue green viton umbrellas are a good replacement.


you can change stem seals with the heads on the engine with a few simple tools.

[REDONE]

Redone, your so right. I know that I have considered the same and I'd like to increase compression but dont want to run 91 octane, So, is 1-1.5 points worth the expense on a daily driver? IDK

Well, if you ever move out of the swamp up to the top of Mt. Everest, you can run 12:1 on 87. Provided it's not -50*C.

THX BTW, I toned down my first post about ten times trying not to be a negative nancy, but I couldn't stop premonitioning the cacophony of "get-this-use-that" that was about to be thrown this poor unwitting souls way!