piston to head clearence

[wed3k]

yea i learned that today, cams are very important. the less overlap the better

you want overlap for high revving engines because the suction from the exhaust pulls on the intake side,thus creating a ram air effect. but for low rpm's it may be more detrimental so you just want the right amount.

camshafts are a whole other ballpark, i barely know anything on it, lol.

also...if you are going to be putting the trick valvetrain shit, a fucking mill only costs 50 bucks. im sure you can afford another bare head if you can get all the trick shit.

[KeeleDesign]

If you spend the money to build a head, I would suggest upgrading the bottom end as well... nothing is worse than dropping $1000+ into a head just to put a piston into it! The h22 stock bottom end is very strong, but these motors are old. Plus, headwork and an improved valvetrain would benefit from a higher redline, and revving beyond the stock redline with old stock parts holding the bottom end together could end up disastrous. It may not... but is it really a risk worth taking?

Pistons can be changed with the block still in the car, but you have to hone the cylinders. You CAN do it yourself, but most people I know would prefer a machine shop to do it. It's not too hard to remove the internals with the engine still in there, I don't think... as long as you don't mind working under the car.

Once you pull the internals out, the bare H22 block is EXTREMELY light. I have one in my shed that I got from bruno. I was amazed at the weight! I can lift the sucker with one hand! Get the guts out, and you don't need a hoist to remove the block. You and a friend would have no trouble doing it by hand (and a friend is only needed due to the awkward angle you'd be working with alone).

he is verry right...

perhaps the most important part of an engine is the connecting rods.
the connecting rods have to be strong, because their stress load goes up exponentially with rpm.

Because of their largely dynamically impossed loading, rods must be light as well as strong.

Rods also must be bulletproof because their failure will claim the entire engine.

stock import rods are usually verry strong compared with their domestic brothers. Import rods are almost always forged or sinter forged with PIM technology.

Imports have beefy rod bolts and spot facced shoulders.
although most import rods are strong the stress level above 7500 rpm's and the power of 200 hp, in most cases are pushing the limit.

a good way to strengthen a rod is to have it shottpeened, although you may need to make sure this does not distort the rod. What this does is remove any casting lines that underpreaser would possibly create failure...

[deevergote]

you want overlap for high revving engines because the suction from the exhaust pulls on the intake side,thus creating a ram air effect. but for low rpm's it may be more detrimental so you just want the right amount.

camshafts are a whole other ballpark, i barely know anything on it, lol.

also...if you are going to be putting the trick valvetrain shit, a fucking mill only costs 50 bucks. im sure you can afford another bare head if you can get all the trick shit.

Bare heads don't cost too much. Even H22 heads, if you're patient and look in the right places (and know the right people... I do, it seems!)

Camshafts have a lot of factors involved. Lift, duration, and ramp speed/angle are the three main ones. Slight changes in these things can make a huge difference. When dealing with VTEC cams, it's doubled.

Overlap is necessary for NA (and often causes the lopey idle) At low RPMs, considerable overlap can make an engine soggy. Up high, it helps things breathe. Adjustable cam gears are the way to tune the overlap for the most gains in the widest range. Turbo cams should have little to no overlap. quickangel, that's probably what you've been reading, since you're going turbo (this is one reason why wild NA cams are not a good idea for turbo... and while the stock cam is just fine for most turbo setups)


As for revving high to make power... that IS usually the case with small displacement OHC engines. It depends on the application, honestly. You can have a sky-high rev limit of 12,000, and your powerband could be between 7,500 and 11,500. That would work for a drag motor. For a street motor, that would be idiotic. Hell, I'd buy some spike strips and put them down in the street if you drove by my house on a regular basis at 10,000 RPM!

For a street motor, you want the majority of the powerband to be in a range that you'll use. You don't need to make power from 2500 up... but you don't want that to be soggy, either. You want decent power from 2500 to about 4000-4500. Then it's good to have the majority of the power from there to redline, if possible. IMO, that's the ideal NA street powerband. (VTEC keeps the low end acceptable in this case)

For autocross or road racing, you want to make the powerband as broad as possible, as you'll be using a very wide RPM range. A 700hp drag car (like the description above) running against a 400hp road race car with a wide powerband on a road course would probably lose. The 400hp car may have nearly half the power, but it can use it when it needs it.

[wed3k]

also a drag car, will make its power for 12 seconds and be shut off at the end of the strip.

a roadracing vehicle will need to have the power and be able to be subjected to the abuse.

[deevergote]

Precisely.



Chris, if you're going to take your engine to 8500, I'd still upgrade the bottom end. It might last, it might not... but if it doesn't, you're risking the head you're putting all that money into. If the rod bolts fail, the piston isn't going to push through the crank... it's most lilkely going to let go when it's going up...

It may last, it may not. It's a risk. Understand that, and at least you made an educated decision, even if it turns out to be a poor one.

[Chrisisiced]

Precisely.



Chris, if you're going to take your engine to 8500, I'd still upgrade the bottom end. It might last, it might not... but if it doesn't, you're risking the head you're putting all that money into. If the rod bolts fail, the piston isn't going to push through the crank... it's most lilkely going to let go when it's going up...

It may last, it may not. It's a risk. Understand that, and at least you made an educated decision, even if it turns out to be a poor one.

You'd better be at the meet next weekend cause i want to hear more info and input from you, cpmike, and larry cause i was talking with cpmike last night and he thought it wasnt a bad idea.... make sure you're there!