Heads!?!?!?!?

[Bradley Palmer]

Has anyone tried to cc there chambers, mill the heads, and get bigger valves??? Im getting them ported and polished and a custom cam but any help is needed. Thanks

[CheapGuy]

:cool: Sure thing, BP. One condition though . . . You teach us all the fine art of the neutral drop.
:D

[Bradley Palmer]

Any help from somebody that knows???? Thanks

[AMinor65]

Bradley, how's all this new compression gonna work with your supercharger/nitrous setup or whatever? Stick with the port and polish, and maybe a 3-angle valve job. Well, that's the extent of my heads/compression knowledge.

[ April 24, 2002: Message edited by: AMinor65 ]</p>

[MustangEater8251]

If I am not mistaken Nitrous works just the same on low or high compression motors. BUt Super/turbo, work better on low compression motors. Milling the heads, you have to be careful that everything still lines up with the intake manifold, and you will be boosting the compression. SO basically there is a good chance you will have to mill the Intake manifold, and change the angle on the intake manifold to match the heads. Does not sound cheap, but I am not an expert in pricing custom machine work.

As for bigger valves I was wondering the same thing, but I been looking very slightly into 3.4L, haven't even touched the 3.8L, might be able to use some Intake/exhaust valves off soemthing else, but not sure on the exact thickness, height and what not of the stock valves.

remeber with doing modifying the valves and milling the heads you may run inot clearance issues and pretty mcuh getting your nice new valves banging your pistons.

*Side Note* is it called piston slap if the piston is hitting valves? or is it piston slap when the piston hits the head? Just curious.

[pvtschultz]

I would say that piston slap is whenever the piston hits anything. Either way, it isn't going to be good. If you are going to run any power adder, you are always safer with the lower compression. When using a super charger or turbo-charger, the lower your static (non-boost) compression, the more air and thus more fuel you can force into the cylinder. This is demonstrated by tractor pullers with their large diesel engines. They lower the compression ratio from about 20:1 to around 9:1 and use a sh*t load of ether to start it. But I got off subject.

Small milling of the heads will make up for the compression lost in working the combustion chambers. Too much and you might have problems with piston clearance and intake line-up. Just take enough off to true the surface. The V6 already has high compression at around 10.5:1 to be using pump gas. Thank God for computers. I have to use 92 octane with my Impala at 10:1 to get away from knocking.

[pgriffith]

Supersixmotorsports is milling my heads 20 thousands. He said that will be safe and will require no other work because the mill is so small. But it will raise my compression from stock 9.4 to a little over 9.8.

Stock v6 has 10.5 compression? What are you talking about?

[pvtschultz]

OOoops!!!!!!!!My bad. For some reason I was thinking of 10.5, but I think I was remembering that from some special thing GM did with the Monte. Sorry about that. 9.4:1 is the correct CR

[Shadly]

Piston slap? Those two words together give me the heebie-jeebies. I've heard of valve slap. That's when the valves aren't adjusted tight enough. I'd imagine you wouldn't have piston slap for long enough to even name a condition after it.

[WickEdSix9838]

the reason supers/turbos have to have low compression is they make boost, creating more compression and if you get too much, you start blowing head gaskets, or getting too much compression from boost causing it to detonate..

[DominusEtDeusNatus]

<blockquote>quote:</font><hr>Originally posted by WickEdSix9838:
the reason supers/turbos have to have low compression is they make boost, creating more compression and if you get too much, you start blowing head gaskets, or getting too much compression from boost causing it to detonate..<hr></blockquote>

So why lower the compression and add more boost? Wouldn't it be the same to up the compression and lower boost? You'd get the same cylinder pressure. Why is one way better then the other?

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Dom:
So why lower the compression and add more boost? Wouldn't it be the same to up the compression and lower boost? You'd get the same cylinder pressure. Why is one way better then the other?<hr></blockquote>

Boost is on demand. It allows lower compression (less wear and tear) most of the time, and the benefits of higher compression when needed.

Another advantage of boost, is better filling of the cylinder when the intake valve opens. Instead of the cylinder having to draw in air, it's there waiting to push itself in...

[WickEdSix9838]

my guess to why you would want more boost is because, the combustion will be stronger if you have lower compression with more boost because you will have more air adn fuel in the chamber than a small chamber that holds less air/fuel...

[pvtschultz]

The lower the compression ratio the more boost you can afford to have. The more boost you have, the more air/fuel you can stuff into the cylinders to create power. More fuel=more power. Kinda simple. But on our street cars, there is a limit to what the moving parts can handle over long periods, that is why turbos are great. The higher the net compression ratio, the more efficient the combustion. That is one reason why the diesel cycle is more efficient than the gas cycle. So low static compression + high amounts of boost + high net compression = POWER. Ain't that word great?!?!?!?

[jjd98]

<blockquote>quote:</font><hr>Originally posted by Shadly:
Piston slap? Those two words together give me the heebie-jeebies. I've heard of valve slap. That's when the valves aren't adjusted tight enough. I'd imagine you wouldn't have piston slap for long enough to even name a condition after it.<hr></blockquote>

piston slap is when there's too much piston skirt to bore clearance. what happens is when the piston goes up the bore, the angle of the connecting rod pushing up causes the bottom of the skirt to knock against the cylinder wall. when the piston reaches TDC and goes over, excessive clearance lets the piston 'rock' a bit, causing the other skirt to bang against the other side of the bore. when it goes past BDC, the cycle starts over again. piston slap. the solution is to bore out the cylinders and get bigger pistons.

'valve slap' as you call it is when the valves come down and contact the top of the piston. this is much worse, because it starts a whole bad sequence of events: if it hits hard enough, the valve will get bent. then it doesn't go back up in the valve guide and just hangs there. the next time around it'll punch a hole in the top of the piston, possibly busting the piston pin boss or snapping the connecting rod. either way, the piston is now floating around the cylinder without a connecting rod. the connecting rod will start to smash the piston around, causing the piston to make a quick exit through the path of least resistance, usually the side of your block. sometimes the piston doesn't exit and gets wedged, this may cause the crankshaft to break when the connecting rod tries to go up and it can't. bad news all around