Softening combustion chambers for boost or n2o

[sumfoo1]

Has anyone done it?

Basically just knocking down sharp corners in the combustion chamber to make sure they don't build too much heat and creat a pre ignition scourge right?

Is there anyone what's really good at it that would know their way around an fe head specifically a robert pond head?

[ScotiaFE]

The Pond heads have a fully machined chamber.
It is a large chamber at over 80 cc's.
How much compression do you have?
What does the piston look like? Flat or dome or dish.
How much quench do you have?
Piston at deck height?
Type of fuel?
Smoothing the chamber and piston top to stop hot spots will help, but it is even more important to get the machine work
as close to optimum numbers as possible. This will promote a much better flame front and thus lessen the chance for
detonation.

[sumfoo1]

Dish Pistons cr is in the mid 10s since its a 511cid  quench being dish Pistons and a 80cc head is probably lacking to the point it makes little difference. (It's going to be a turbo motor I think if I can talk myself out of just how cool a polished blower would look having out of the hood of a black galaxie.

But turbos will make more power and will be more efficient especially with an interview.

[RJP]

Dish Pistons cr is in the mid 10s since its a 511cid  quench being dish Pistons and a 80cc head is probably lacking to the point it makes little difference. (It's going to be a turbo motor I think if I can talk myself out of just how cool a polished blower would look having out of the hood of a black galaxie.

But turbos will make more power and will be more efficient especially with an interview.

Whats an interview?

[thatdarncat]

Whats an interview?

My guess is Autocorrect's version of an intercooler

[sumfoo1]

Yep

Damn you ios8!!!!

[Qikbbstang]

.....years since I played w/turbos but 10:1CR sounds high to add boost if using anything "pump" except E85

[My427stang]

Dish Pistons cr is in the mid 10s since its a 511cid  quench being dish Pistons and a 80cc head is probably lacking to the point it makes little difference. (It's going to be a turbo motor I think if I can talk myself out of just how cool a polished blower would look having out of the hood of a black galaxie.

But turbos will make more power and will be more efficient especially with an interview.

Quench has nothing do do with chamber size or dish size, other than they affect how large and how influential the quench pads are.  Its all about distance between the flat part of the piston and quench pad on the head.

As far as smoothing the chambers, I'd go at every sharp edge of the piston and the chamber.  Just knock it down and blend without going crazy.    Although there are stronger tools, a Dremel and some emory cloth will take things down without being overzealous.

Be sure to get a good measurement of everything after to see what your compression will be.  10:1 with boost will need something to to help it, meth injection, fat mixture, intercooler, you name it, PLUS a real good tune.  My hunch is it may be better to go with a little more dish

[sumfoo1]

Ok this is the whole story. Its about 10.4 with an .020 hg.  The plan was to try to chew up some aluminum and run an .060 ish MLS head gasket and try to get this thing down around 9:1 without changing pistons. It still has a pretty big cam in it so the DCR is pretty low even with the LSA widened.

Is this a dumb plan or should I just say screw it and change the pistons out?

Plan is 6-10 psi on waste gate pressure and then 20ish on race gas with a big air to water inter-cooler and ice or E85.

[My427stang]

Fuel injected or carbed?

I can't imagine a .060 head gasket will drop it that much though, did you do the math?  With only 6-8 psi, and a fat mixture/good timing control it may live, but I'd rather drop it down and let the boost build

[Qikbbstang]

Problem is "Dishing Pistons" increases surface area of the piston to the heat of the chamber and does exactly what you started this thread looking for answers on. Those dish edges are subject to getting extra hot around the tops of the ring lands and are less able to conduct it away then simple flat tops.   May not be end of world but dishing has got negatives just like the thick gaskets messing up quench.

[sumfoo1]

My understanding was on boosted motors to get "ideal" boost levels your quench is so jacked up it doesn't really play a factor.

I'm really just trying to make sure everything works out as intended.

Check this out and see what yall think. Problem is i don't think i can dish the pistons much more so i'd have to de stroke the engine to get everything where i want it which... i have a billet crower crank so that would make me sad.

It is fuel injected with Edelbrock's  pro flow  XT+ system... but i may change the harness and ECU to holly dominator  if it continues to annoy me.  Mostly because of the support and ease of use.

My other issue is i may have to look at longer push rods too if i lift the head up .06" won't I ?   should i worry about the intake too?

[Qikbbstang]

 I've built three turbo motors and did my best to try and understand them. JMHO repeat JMHO Nitrous and Blower Motors are best built specifically as Nitrous and Blower motors. There are specific traits from a NA motor that will compromise Nitrous and Blower motors and these have no place in them.  Compression as an example, if you have 10:1 in a NA motor and add 5psi boost (which is nothing today) on top of that when a piston starts its compression stroke instead of starting with a cylinder at 14. psi you have a cylinder starting out at 20 psi. (and that's only with 5psi boost) Simple math at 10:1 compression shows you a significant difference when starting the compression stroke at 14. psi then when you start with that same cylinder at 20psi.   Unless you want to deal with mega-high octane fuel you can't run much boost. I look at it as you want the "boosted" final compression ratio in the chamber to be about the equivalent of what you'd have with a NA at 10:1 for pump fuel.
   Now here's what I feel is the cool part of blowers & turbos, with a high boost and low static compression you end up with a large slug of fuel & air at X psi compared to high compression and low boost where you end up with a small slug of air & fuel at that same X psi.. I don't know about you but I think a gallon of A&F @ 160psi will pack a hell of a lot more wallop then a pint of A&F @ 160psi..
         Nitrous is pretty much the same deal since the nitrous is "rich" in Oxygen you are better off with a large chamber you can have more fuel& Air/nitrous in then in a small chamber of fuel& Air/nitrous at that same psi.
JMHO
 

[sumfoo1]

ultimately it's the temp not the compression that kills the motor that's why intercooled blowers and intercooled turbos survive better because you are heating the air up to 160 then bringing them back down to slightly above ambient before it enters the engine.  My primary concern is blowing head gaskets because they are too tall or something.  I'm actually good with turbos on a factory turboed engine  I had a 400 whp 2.5 liter subaru running 27 psi on 8.5/1 CR. Now i got ride of that car because i had 12k in parts on a car worth 7k that i could sell for maybe 8 or 10k  so i decided to build something decent.  Fell back in love with the FE (i have an original dual quad 427 low riser too) and now here i am trying to mesh the 2 together before the new engine is even in the car.  truth is it probably has plenty of power n/a but  i'm one of those too much hp is never enough kind of people  (used to be hennessey automotive's  motto).

The drag racer guys are telling me with a decent air to water intercooler and heat exchanger they wouldn't go lower than  10/1  run 4-6 psi on the street and when i can get good fuel (e85/c16) in it crank it to 15-20psi with ice in the water tank (which would drop intake air temp below ambient) I'm thinking 9/1 9.5/1 is really where i want to be for the blend of both worlds.