4age bigport head: port & polish

[Os7213]

Ok sorry about calling it squish area just wanted to know if we can reshape the chamber and if that will act better then sqish area...

ive seen it like this: This in not a 4age head but just an exemple



and here a fast drawing from paint to simulate the air flowing with the new desing chamber:




If you remove material from the chamber to the cylinder bore you doing nice and open chamber area who can tranfer air more easily...i think!
Hope this is a good explanation...
Give me your idea about this

I know this is not a normal squish area but ive think about this and wanted to learn more
Btw i think a normal squish area is about 0.030in clearence or less right?


Thank
Ugo

[Os7213]

AH finally ive found a picture of what im talking about:



Look at the chamber reshape to the cylinder bore.

[jamiemirror]

Yes, open and close type combustion chambers.
http://www.billzilla.org/engcombust.htm

Read this. And take a look at Formula Atlantic prepared head.

Quote:Also important is the squish areas, for best power. A 'squish area' is a part of the combustion shamber that is made to very nearly come into contact with the piston when the piston is at top dead centre. There's usually less than 0.030" (0.75mm) clearance in these areas in such cases. What they do is cause the combusting gasses to rapidly travel towards the centre of the combustion chamber (or where ever intended) and increase turbulence, thus increasing the combustion rate.
It's increasingly important as the revs build up, so more attention is needed. Ford/Cosworth experimented extensively with so-called open and closed combustion chambers, and found that a well designed closed chamber always made more power. (In a naturally aspirated engine, at least)

I support Bill with suggestion that squish area will provide faster combustion rate (not too good English, sorry) - and this is important especialy in hi-rev engine.

PS: I modified your drawing a little by ADDING the squish areas and showing their role (see red arrows - this is faster gas/fuel mix flow due to squish areas presence).

[Os7213]

Yes okay finally with your drawing i agree...the air is suppose to exit faster...but in interrested in the force the piston need to waste to push the air on the squish areas VS the redesing one...But even there im not sure we can have something better with the redesing. I think the best thing is squish area!!!

And finally my last question! Do you khow how you determine the depht of the squish area...by the piston stroke or something? And does that help anything if we go with this kind of desing?(I know sometimes i ask weird question but if i dont ask i will never know!) Thank you for your answer!!

Ok here the way i see squish area praticly like your draw:



Cause ireally like the idea of pushing hard on air with piston to force it to exit.But the think i dont like its the 90˚ turn the air need to do for passing from the squish area to the chamber...think we can have a better result with a little angle instead of a 90˚??

Thank a lot in advance
Ugo[/img]

[NoHachi]

Run a google search on "squish vs swirl" and "tight squish engines". There is so much info out there, makes my brain hurt. I do realise now that its probably best that I don't come near a head with a grinder..don't know enough. Probably the first 10 heads you try will be ruined..also no good way of finding out if what you did helped without a flowbench and dyno.

[jamiemirror]

Maybe this modification will improve the chamber - unless you create too much piston-chamber clearance and lose the squish effect. I would recommend just rounding the edges of the area.
How to measure "depth" ? Why not just dry build + some modelling clay on the top of the pistons ? Sounds funny - I know

[Os7213]

lol nice idea! think this can work i will test for sure! btu i think a 0.005in-0.010in can do the job cause we only want more clerance between the top of the piston and the head where the cynlinder bore is.

And yes i have some few spares head so i can test anything i want
I will flowbench stock stock vs ported, ported vs modified ect till i found the best way to do it!And thank for the reshearch word i begin my reading!

I really want to have a nice hp output with my own porting
Ive also check for the desing of the port...but i will meusure it just to see if i have enought material to make it like i want! i will post it if me and friends think it can work!(The new port is a racing model...so the port holes need to be raised up a bit...)

Thank for the answer
see ya guys
Ugo

[jamiemirror]

Not my idea, I think I saw it first on Guy Croft's website. :wink:

I will leave at least 0.05-0.06 inch clearance over the top of the pistons.
You can find some N2 info on club4ag tech section. AFAIK N2 head have widened intake ports (67.5mm) - take a look at their dyno-sheet and decide wise ! Bigport head have 65mm wide ports stock ! FYI smallport one have just 50mm.

[Os7213]

Yes smaller ports that actually what i need so ill be able to reshape the ports with all the material i need the magic word is patience!
Umm just to be sure you think 0.050-0.060 clearance from top of the piston to the bottom of the squish area? Cause i dont know the height of the piston vs the block at the top dead center+gasket(I fugured to put a 0.6mm). Or you mean a squish area of 0.050in depth?!
Even if im on Club4age everyday i havent notice the N2 Specs until now thanks!
Ugo

[jamiemirror]

I mean that is best to ensure (via dry build + clay) that you will not interfere pistons and head. Leave at least 0.05 inch. About squish area depth (specific) the answer is "don't know" :wink: I read that more than 2mm (0.08 inch) is ineffective - so IMHO it's better to keep squish area "depth" as close to 0.05 (but not less! ) as you can, not crossing 0.08 (as general rule).