So basically, the ideal head might look like a bathtub head on one side and a modded swirl on the other?
Wayne H.
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or not that much more to itI'm glad someone else thought it looked like a bathtub style chamber! I was thinking the same thing.
I'm sure there is much more to it though!
Here is the FM head that is on my van.
Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]engine slowly evolving into weekend turbo beater.
Re-post the photo.....
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Actually now that I think about it more, it'd probably look more like an old wedge on the plug side, and the modded swirl on the other. Look at the FM head just posted and imagine the bevel on the exhaust side continued over to the intake side. I'd probably fill in the top of that side to where it would be flush with the head deck surface for quench purposes. Or maybe with a slight angle towards the center.
It is much like starting with a 'G' or bathtub chamber but one item that is beneficial on the FB is the shallower chamber.
This provides an improvement on the short side turn due to the seat rings being further into the chamber and the gain on the port radius.
It's minimal but every little bit counts.
I will have to agree with everything you have posted in this thread. The best 8V head for performance would have had attributes from both castings.
I have found the G head to be easier to make close to right. The next head I do will be a Swirl, but not for me, for a friend.
The best performing chamber I have done ended up like this.............
best 1/8 ET-6.16 sec. best 1/8 speed-119.70 Best 1/4 MPH 145.5, Best 1/4 ET 9.65 sec. 8 valve NO NITROUS!!
Warren,
Everything you do is pure art. I wish I had the skills and talent to do what you do.
I am soaking up everything in this thread. The timing couldn't be more perfect, as I'm preparing to get started on my latest motor build. This information is priceless.
I do have a question for all you guru's though. I know we are talking about theoretical best chambers, but if you guys are suggesting filling in the chambers for better quench, what do you do about compression ratio? Doing that is going to raise it tremendously correct? And if so, how do you compensate? Larger dish in the piston? If so, doesn't that negate the squish you are trying to create by modifying the chamber?
Sorry for the newby type questions, just hoping to expand my knowledge of combustion chambers...
^^^^^^ good question!!!
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Shape the dish in the piston to mirror the chamber, set the pin height to achieve proper quench with the gasket you'll be using while setting the depth of the dish to achieve the desired compression ratio.
Yep, custom pistons are a must if we hope to get real benefits.
Mike
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if there is also material taken out to deshroud the valves I think its kind of a wash. Plus, with better tuning abilities now and "other" fuels, I don't think compression is that big of a deal? especially when changing the camber design, that is what is trying to be accomplished, a chamber that is less detonation prone and better flowing, win win! ive also ran g-head pistons with a swirl head up to 18 psi, I'm sure I could have taken it farther but wanted to be "safe" on lw rods.I do have a question for all you guru's though. I know we are talking about theoretical best chambers, but if you guys are suggesting filling in the chambers for better quench, what do you do about compression ratio? Doing that is going to raise it tremendously correct? And if so, how do you compensate? Larger dish in the piston? If so, doesn't that negate the squish you are trying to create by modifying the chamber?
I think with a tighter squish and larger quench area, this would also negate the "extra" compression if there ended up being any after the rest of chamber work was done. I still think a better piston design would help much more, but that equals way more $ for custom pistons than most would want to spend... maybe one day...
I would say that if you're willing to use custom pistons and chamber modifications then you're probably also willing to tune for the new ignition requirements/knock characteristics and probably willing to tune for a higher octane fuel like e85. But yes it seems like by the time you bring the piston anywhere close to the 'squish pads' you'd need a pretty big hole in the middle to keep similar compression ratio.
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I'm of the opinion that chamber and piston design is totally dependent on intended application.
If we are talking about a moderately boosted street engine, on pump gas, then squish becomes a desirable design
consideration.
On the other hand, an all out turbo race engine, on good race gasoline or Meth, squish and quench can be unnecessary or even counter productive, especially with a small bore engine like our 2.2L. The pressure differential between the intake port, and chamber is so high at the moment of valve opening, that mixture motion and charge homogenization are pretty much guaranteed.
I have essentially no squish in my race engine and it has a wide and forgiving tuning window. I don't know, maybe I got it all wrong, but it works for me.
best 1/8 ET-6.16 sec. best 1/8 speed-119.70 Best 1/4 MPH 145.5, Best 1/4 ET 9.65 sec. 8 valve NO NITROUS!!
It's one of those things where you either build for it, or stay way away from it. Flattop pistons and compression benefit from quench more than a low compression engine w/ dished pistons would. I have heard the theory that for high boost, lower compression and .060" or more clearance to the head works good because of the increased volume of air/fuel mixture.
I have a set of Venolia flat tops that I've been hanging onto for a high compression turbo street engine build. Planned on milling block until piston deck height is set to have .035 or .030" quench w/ a standard FelPro gasket. Not sure which head yet.
Last edited by Force Fed Mopar; 12-07-2016 at 10:06 PM.
Now, who has access to a CNC machine and can make copies of all these heads easily and reliably?