Rat Rod

How would i increase the compression ration in my 1990 accord besides with the use of flat top pistions, and high spark producing plugs? Will porting my heads increase the compression ration?

GhostAccord

It's known as a ratio..
High spark producing plugs will not increase the cylinders compression ratio nor will porting your head.

Pistons are the most reliable way to increase compression ratio.
While milling the head or decking the block works. It also reduces the piston to head and piston to valve clearances. Using a thinner head gasket is also another way, but it will also alter the factory clearances.

Whether or not milling, decking or running a thin HG will constitute a valve hitting a piston face or the piston crashing into the head. Depends on how much material is removed from each of the components. 0.08" intake and 0.1" exhaust or 0.040" all around is what I read that most builders consider to be the minimum Piston-2-Valve & Piston-2-Head clearance.

How much compression are you looking to gain?

Rat Rod

Yes ratio was mispelled. Since my engine comes stock with an 8.8:1 compression ratio. I would like to have a compression ratio any where between 9:1 - 10:1 not to exceed 10.5:1 if possible since im not goin to turbo charge it.

chikin pickle

You're better off ordering custom pistons. Spec'd out the way you want them, and if you are going to bump the compression, you might as well just go all out and run 11.5-12.0:1 and at least make decent power.

Spark plugs will not alter the compression ratio. Only changing the size of the combustion chamber will. Either by making the chamber in the heads larger/smaller, increasing/decreasing piston dome volume, or increasing/decreasing the bore diameter.

Bwill9886

I'm confused about your statement with your desired compression. You wouldn't want to turbo it with around 10:1 anyway (you can it just gets tricky).

Regardless, you should keep in mind that raising the compression ratio to your desired limit is possible and will result in an alright bump in power (though honestly not that much). However, if you really want to get the most power, reliability, and best power potential out of it you will probably want to get it tuned.

If you already knew that, disregard the last part haha.

Good luck with your project.

nus_dogg

Well, the OP meant he's not going boost; therefore, he wants to go 10.0:1 CR. You can do 12:1 CR pistons by having a company make you a set of custom pistons for a reasonable price. And OP, flat face pistons lowers the compression. You'd want dome top pistons cause it sqeeze the combustion tighter as the combustion chamber gets smaller.

Pistons would be an easy way to up your Compression Ratio besides milling the head, thinner headgaskets, and flat face valve.

GhostAccord

Actually a set of flat tops would raise the compression. Considering our stock pistons have a dish that is approx. 15-16cc. A flat top piston with a set of 3 to 4cc valve releifs will actually raise your compression to approx. 10-11:1 CR.

Bwill9886

I realize that. But to get real results with N/A power, the OP should go higher on the compression right? So that was just a bit odd.

Also the OP, saying he just wanted around 10:1 compression, sounded like he thought he should have MORE compression if he were to turbocharge it.

I doubt he/she meant that, it just looked confusing was all I was saying.

Truth

Rat Rod

Im not confussed at all. I said around the 10:1 area because a 12:1 ratio may put a bit of a strain on my motor and i do want it to last a few years at the minimum. 11:1 seems a little high for an engine that comes with an 8.8:1 compression ratio but while getting the head hot tank, ported and polished, the valves reseated, i will also get the head milled a few thousanths in order to give me a slite increase in compression. This should raise my compression level to at least bettween 9.5:1-10:1.

Bwill9886

No one said you were confused. I said the way you worded things was confusing.

Honestly you'd be surprised how long a high compression engine can last. It's all in maintenance and how you are planning to use it.

Alright so you are going for 10:1. What are your power goals and what else is being done?

GhostAccord

In order to reach a 10:1 with stock pistons you will have to remove approx. 0.07". You may want to re-think removing all of the material from the head alone. Maybe remove some from the head, block and use a thinner head gasket if you are so against buying a set of pistons.

Note: 10:1 CR with -15cc dished pistons may not have the results you are looking for. Yes your static compression ratio will be what it is. But the design of the dished piston may not be ideal for a reliable build???? Never tried it myself so I'm just saying!

Rat Rod

My power goals are to just gain as much as i can with minimal mods. the only thing that has been done so fair is a short ram air intake, iridium plugs, ngk wires, new distributor, boared out throttle body, full exhaust with high flow cat. Very soon I will have the street and strip clutch kit installed which consist of presure plate, clutch and heavy duty through out bearing, ported polished and milled heads, performace head gasket, reseated valves, proted intake manifold and upper plenum. Then if possible ill try and find a cheap performance tuned ecu. I will occationally race it on the track but it will be a daily driver.

Rat Rod

I think ill just be on the safe side and remove 0.03 from the head because im not for a thin head gasket nor do i want to mill down the block. So ill just get the head milled down to a safe amount. I may not get 10:1 compression but it should be some where near even if its only 9.3:1 as long as its more than the stock 8.8:1 ill be a little satisfied. Thanks what u posted was very informative.

dragon_lowrider

Ok I have a question, what is the power gains from stock 8.8 to 9.0-12.0 jus wondering cuz my brother in law is looking to do an n/a build but still be daily

nus_dogg

Yeah, I got flat top confused with dish pistons. Lol.

nus_dogg

I learn in engine overhaul class that you gain 5-6% in horspower for every one point in compression increase.

Rat Rod

cool thats good to know