Easy ways to increase compression ratio?

[mildphil]

I was thinking of buying a 72' Plymouth but the compression ratio is 8.7:1. I know you can increase the stroke but are there any other ways?

[TinCuda]

In a nut shell, you can replace the pistons with taller ones.  You can take your heads to a machine shop and have them shaved.  This will also require that you shave your intake manifold to match.  You can take metal from the top of your block.  All very simple concepts but nothing easy.

With an 8:1 ish compression, you might look into putting a supercharger on it.

Just spitballing here.

.,

[mildphil]

I will have to look into that, i think supercharging is out of the question considering the price.

[Chryco Psycho]

At 8.7 :1 there is not much you can do , smaller chamber heads are mostly alum needed one more point of compression to maintain the heat in the chamber You might gain you one point of compression up to 9.7 with closed chamber iron heads but you will not have quench as the piston will probably be too far down the hole anyway , but 9.7 is streetable .

[HP2]

head swap to later model, closed chamber magnum heads is possible. Of course, this also requires considerable amount of measurements to make sure things do not bonk into each other, plus new rocker gear and either new intake of intake modifications.

New pistons may be the most budget friendly, but require a considerable amount of work.

What cam do you have now? If the cam is too big for the compression, you may be able to gain some cylinder pressure with a cam change.

[mildphil]

Well I dont own the car, I was looking at a 72 plymouth with a 318 and wondering how I could pump out some extra power.so I dont know what cam it has.

[Changin Gears]

Changing compression to bump horsepower is pretty far down the list of things easy and/or cheap to do.

[Moparal]

You can over bore it and purchase pistons for like a 67/68. I believe the compression height was more, but you will still be limited with cam lift choices not having notched pistons.

[cudabob496]

have read that an older engine with normal carbon buildup will increase its compression ratio by .5.
Increasing CR is not a big power gain, and can create more problems.

8.7 is not bad. May be above 9.0 by now. There are other cheaper ways to increase power on that motor.
k&N filter
synthetic oil
free flowing exhaust
headers
good tuneup
new cam

Also, "Engine Restore" is a great product for increasing cylinder pressure in older engines.

[72cudamaan]

have read that an older engine with normal carbon buildup will increase its compression ratio by .5.
Increasing CR is not a big power gain, and can create more problems.

8.7 is not bad. May be above 9.0 by now. There are other cheaper ways to increase power on that motor.
k&N filter
synthetic oil
free flowing exhaust
headers
good tuneup
new cam

Also, "Engine Restore" is a great product for increasing CR in older engines.

I don't quite understand how using "engine restore" increases cr. The only thing it may do is free up the rings if they were sticky and
possibly restore the compression pressure that was lost. That usually doesn't work anyway. But how could it raise the compression ratio?

[72cudamaan]

Also, relying on carbon to raise the compression? It might do that, but what about the spark knock issues
that are created by carbon. I would want the carbon out of my engine asap. A good water injection would take
care of that. 

[cudabob496]

I don't quite understand how using "engine restore" increases cr. The only thing it may do is free up the rings if they were sticky and
possibly restore the compression pressure that was lost. That usually doesn't work anyway. But how could it raise the compression ratio?

You'e right, I meant to say cylinder pressure! Though, increasing cylinder pressure might have a similar effect on power, as would increasing
compression ratio.
Engine Restore seals scratches on cylinder walls, which allows the rings to seal better. My experience is it works great on older engines.
My Cuda engine is 10 years old, and uses thinner rings, so I've been using it lately. Also restored power in my older Hondas.

[cudabob496]

Also, relying on carbon to raise the compression? It might do that, but what about the spark knock issues
that are created by carbon. I would want the carbon out of my engine asap. A good water injection would take
care of that. 

I agree, but you can also increase gas octane, or back off timing a little. I think removing carbon in older engines will reduce cylinder pressure. But
each to his own.

[cudabob496]

I was thinking of buying a 72' Plymouth but the compression ratio is 8.7:1. I know you can increase the stroke but are there any other ways?

In old days, increasing CR made power, because cam choices were few. But now with modern cam and other technology, its not as big a factor on a street machine.

[mildphil]

all the ways you listed seem like much better ways, something I will do for sure when the time comes