does porting change compression?


anytime you raise the exh port you lose compression, so you have to redo the heads to get back what you lose with the porting
 
you will not lose hp SS, redsnake, yes, like Mr.Viper said, anytime you raise exhaust port it will cost you compression, but not as much as you're missing. not for the porting that you did anyways.
 
exactly, to put those two points together: You can port an engine (raise the exhaust ports as well as expanding) without shaving the heads to get the compression back to stock or better, but you're power is not maximized as well as it can be while still being safe. Basically, you're plenty safe, so bump the compression at least up to where it was to go with the porting.
 
so let me get this straight. i already have my heads cut from cpr for the triple pipes but your sayin i could safely cut them a little more? about how much more?
Thanks
 
depends on how aggressive the porting is ;)! And the cutting your heads that you have done for the pipes was probably just to even the compression out on all cylinders for the pipes, not actually bumping the compression to increase performance. With the porting you can cut the heads a little more to bump the compression back up to where it was or a little better.
 
Alright i got a question..... I got my engine ported Aggressively.. and Yes i have Race Heads, But i also Have a Stock viper head aswell.. i kinda want to use the stock viper head when im not Racing To save on gas.. so when i put them on its costing me some hp??!?!? i still want the same hp with the race heads as i do Stock viper head, so will i have to get them manchined, i still want to use Pump gas unlike race gas.. this is why i want to keep them
 
you're race heads are a lot more compression than the stock head, which is why you have to run such high octance high quality fuel, and you make more power as a result of the increased compression. If you put the stock head on to save on gas, it is a lower compression head which is WHY you can run the cheaper gas, but it won't make quite as much power as with the race heads. Too much compression on lower quality fuel results in detonation and a trip to the dealer for pistons. The stock head will allow you to run regular unleaded no problem instead of race gas. More clear?
 
if you raise the ports (as they do), some compression will be lost regardless of whose port job it is. Some may lose more or less than others, but they all lose some if the ports are raised. In most cases the increased power from the porting will mask the slight loss from the decreased compression, but if you are really worried about it (as i would be), get the heads machined too in order to get the compression back.
 
Raising the compression can also help restore some of the lost bottom end horse power. That can accure with raised exhaust ports. Bumping the compression back up after porting, is commonly done to mountian sled's. Because of the thinner air at altitude, the cylinder pressures are reduced, (compared to sea level).
 
would removing one layer of the head gasket be sufficient to restore compression, again based on race logic porting. basically wondering how much to take of the head?

what about when using aftermarket heads such as megapower or peak, still require machining or can you just change dome insert?

thanks
 
if you went with aftermarket heads, you can just change the domes to get your desired compression without maching anything.
 
i already have a head that is machined so should i just shave some of the cylinders? i dont really want to mess with the heads since they're already pretty low.
 
You must log in or register to reply here.


Back
Top