Increasing compression?

[Coryduran]

I haven't actually checked my engines compression (friend of mine has the tools but eh.) but i know that in 67 273's came from the factory with 8.8. I want to get it up some, but I'm not sure what the first steps should be to try to get some more compression out of the engine (I'm looking for easiest/cheapest steps )

 

[1wild&crazyguy]

pull the heads and mill them, thats the cheapest.

 

[project360]

yup....

mill them down.. use a thin crush head gasket too.

 

[RustyRatRod]

Well, I agree...sorta. I think the first thing you should do is determine where you are NOW. since you're talking about yankin heads to mill and such, have them CC'd and also CC the area above the piston. That way, you'll have a baseline for modification.

 

[ab7fh]

If you mill your heads for compression, don't forget to mill the manifold surface for proper fit too. If you don't your ports will be misaligned. The lost flow may negate any gain in compression.

 

[project360]

do the push rods require shortening also ?? if you take .020 off the head, that increases the rocker stroke by .020.......right/wrong/bone head or N/A .....

 

[moper]

I wouldnt touch it...lol. You have the factory steel gaskets if it's original. You cant get anything that thin anymore. So you'd have to mill more, then mill for the intake to fit, etc etc. It's not worth it IMO.

 

[camd64]

I agree with moper, not worth it. The compression gained and power gained wouldn't be any big difference. A lot of work and time thats better suited to when you do a complete overhaul/upgrade. Stick with the bolt on stuff since you can easily reuse those parts on your future build.

 

[project360]

intake would be off anyways

 

[moper]

The problem is its a small chamber, small bore, small stroke. So you have to mill a bunch tog get much. Thnen you cant get a thin gasket (MP thin is twice as thick as the factory original steel)...

 

[Coryduran]

So should i just not worry about my compression then? Or is there bolt on stuff that'll help compression? I'm not all that familiar with compression so I'm not sure really how to go about it.

 

[moper]

I would say you will get more bang for you buck by adding a good flowing dual exhaust system, then the usual intake, small 4bbl carb, small cam, ignition, etc. A little at a time and you'll get good results.

 

[RustyRatRod]

These do require o-ringing the block or heads....but they ARE available and are .021" compressed thickness.

http://www.summitracing.com/parts/SCE-069152/

 

[caferacerx]

8.8 is plenty of compression for a mild street car, then do as moper suggested, that should result in a noticeable increase in horse power and torque

 

[jefflock]

There are thin gaskets available again. 0.025" thick

 

[Coryduran]

Yeah I was planning to put a new intake on it, get a dual exhaust system and a 600 cfm holley, but someone on these forums said that without higher compression the 600 cfm carb would be a step backwards, which didn't make much sense to me why but I figured I'd look into the whole compression thing anyway.

 

[Rockerdude]

I think 600 cfm would be fine on a nice mild cammed 273 with a good exaust system. 500 maybe better due to the small size of the motor though.

 

[Coryduran]

I'll look into some 500 cfm carbs then. Thanks a lot though guys. Anyone got a recommendation on brand of cams? Also what kinda cam do I need?

 

[Rockerdude]

Stock 273s have solid lifter cams, but from what Ive heard its easy to convert to hydraulic lifter cams.

Ive always liked the voodoo cams from lunati.

http://www.summitracing.com/parts/LUN-60401LK/

PS. This is my 273rd post!! YAY :cheers: 8)

 

[Coryduran]

How easy is easy? Ha ha, what's "easy" for some of the members on this board isn't "easy" to me at all lol, but I do have a well stocked garage to use, and friends and family much more knowledgeable than I am.

 

[Rockerdude]

Not a clue since my Darts a slant six.. But I think all you have to do is get the cam/lifter kit and use the rocker assembly off any later 318/360. Dont know for sure, tomorrow when the 'old more experianced members' are up, they'll help you out. Sorry I couldnt be of more help.

 

[Coryduran]

Don't worry you were plenty of help so far. You are officially cool in my book.

 

[Speedotann]

Thinner head gasket and/or mill your heads...... 1.6 rockers!

Or change pistons, But doing all of this or some of it will require other modifications....

I really do not know how accurate desktop dyno is, but I read in an article a while back that with just changing the compression of the engine from 9:1 to 10:1 without any other mods, they gained like 12hp and 8ftlbs.... Not worth the money IMO.... don't quote me on the #'s though! Good Luck

Brian