The combustion chamber has to be closed. Yeah, it may bump up the CR.

Downside -

• CR will be higher, and some people ( all people? Not sure.) will need to put in new pistons.

Upside -

• Less detonation prone ( if designed correctly)
  Less ignition advance needed (again, if designed correctly)
  lower emissions (again, if designed correctly)
  Better valve placement, resulting in unshrouding ( possibly? I am thinking of some of the twisted wedge heads that sell for the Ford 5.0)
  Better spark plug placement (Goofs up older spark plug tube heads, but still good)

I think that it may be possible to keep a similar head volume, and have it be a closed, quench sort of design. It may require shorter valve stems, due to the bias of volume closer to the valves and spark plugs.

Another thing to keep in mind is that Aluminum heads generally can go with a higher CR, due to the better head transfer. Some people point at this, and suggest that Iron heads are more thermally efficient, wasting less of the heat energy into transfer.

My $0.02.

Greg

That there is a very, very big "if". Combustion chamber configuration has an enormous impact on detonation resistance, driveability, emissions, power and fuel economy...in other words, every possible reason someone might use a non-stock head! Guessing at combustion chamber shape would be a waste. If there is no money for direct development of a combustion chamber (and, let's face it, unless one of us wins the lottery...there isn't!), then our best bet is to find an existing good combustion chamber of the correct size and valve placement and copy it exactly. Downsizing or upsizing something else (e.g. the Jeep chamber) would be tricky to get right, and very much unguaranteed, since combustion refuses to behave the same in a smaller version of a given chamber as it does in a bigger version and vice versa.

Maybe the "fast burn" chamber, already worked out by Chrysler for the slant-6 (just never put into series production, though we know from the '85-'89 318 heads that the concept works well) and known to exist in a couple of slant-6 heads that are floating around in the real world, would be the one to go for. Sure, it's only late-'70s technology, but that's a whole lot better than the late-'50s combustion chamber technology we're running now!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agee! Obviously the person or persons who take on this task will have to make the decision on what chamber to replicate. The guys and gals who will want an aluminum head are probably more of the performance breed than the economy breed. Trying to please both will probably satisfy neither. I would be interested in seeing what engines made today that are similar to a slant 6 specs ( bore, pushrods, cast iron blockw/ alum head,etc. ?) have in their head design that makes them unique. The ability to shave it would be good

My experience (and I believe many others too) is that head flow on a Slant is a much bigger deal than chamber design. People have made as much as 350 crank HP with the stock chamber design. Optimal ignition timing advance (28-30 deg total) is already way lower than that needed for big bore motors (V8s, etc, are 32-38 total).

Detonation seems to be less of a problem than with V8s too. I've run 11:1+ on 92 octane with no destructive effects for many 10ks of miles. That's with the earliest head chamber (67-down), too.

I'm not advocating forgetting about chamber design, but holding up the process to design the "ultimate" chamber may not be necessary. Compared to most V8s, the Slant already has a very small combustion chamber.

Someone who has welded and reworked the combustion chamber design is Mark Goodman (Team Green Lancer and Valiant). Seymour Pederson has pictures of his work, I believe. Seymour can only be reached over the phone (see "racing" page on ss.org homepage for his number/address).

Lou

_________________
Home of Slant6-powered fun machines since 1988

i agree that the chamber basically needs to be designed from scratch to work properly. the closed chamber is something that will probably happen. using this head would probably require custom pistons to cope with the added compression and power that results. i know the program my friend has does stress testing but i don't know about checking chamber design testing. again more research is needed here. i am open to all suggestions anyone may have.

zedpapa

_________________
1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

Could the head be made open chamber with a deck thick enough to mill down to make it closed chamber? Taking all stock bolt on stuff sounds good. The raised ports sound great. Let me know when they ready to ship.

that is possible and probably a good idea. it might make the head applicable to more people(turbo, NA). it would also help with keeping compression under control. it would still allow bringing compression up if wanted.

that will be something that will be taken into consideration.

keep the ideas coming and input coming. we have yet to put a design on paper. we are still trying to get the details worked out.

zedpapa

_________________
1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

I had a visit today from "gearhead" (Karl) who has been living in Charlotte and is moving back to Porland, OR next week.

One of his ideas is to move the intake valve over about 0.040 toward the exh valve (valve guide replacement). This would allow a bigger int valve with less shrouding, since the int side could use more flow help than the exh side. You would run something like 1.80-1.88 int and 1.40-1.46 exh. This would take mimimal adjustment to the rocker arm placement - just a different set of shims along rocker shaft.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Interesting. 2 valve engines have, little by little, been moving toward smaller exhaust and larger intake valves for years.

Any thoughts on reconfiguring the combustion chamber at the same time? I have some ideas, but I need an engine with zero deck pistons. The problem with going zero deck on a 225 is the compression ends up over 10:1 with a .040" thick gasket and 60cc chamber. If the chamber is done right 10:1 shouldn't be a problem. I know it sounds radical, but there are cars running with aluminum 4 valve heads and special pistons running over 13:1 on pump premium. Heck, new Toyotas and Hondas are running 10.5:1 (advertised) on regular. Actually, if I had it my way, the slant 6 chamber would end up smaller and the piston would have a dish. Coming up with the time and money for the experiments are something else all together.

P.S. I wouldn't mind meeting Karl. Pass on my e-mail if you don't mind and we can get together once he's local again.

_________________
Joshua

Mine now is at 11-1. I raced it on 89 octane opening day.

_________________
Official Cookie and Mater Tormentor.

Cool! Got any pictures of the combustion chamber?

It is a stock '76 chamber.

_________________
Official Cookie and Mater Tormentor.

right now, I am running 1.88 intake and a 1.5 exhaust with a 75 head.



and here are my flow numbers:



this cost me $800 about six years ago. new valves (duh), guides, full port and polish, 3 angle valve job and milled .090. engine was bored .060 over and milled .065 which gives me 10.4 to 1 comp.

my point is to make a cost to gain comparison, not to start any arguments, just for feasibility, to give an example to show folks to compare ideas.

I will leave you fine folks to decide if you feel it was worth it or not, but I have to go back to strangling my realtor. I just came on here for a much needed break.

Exactly what do open chamber and closed chamber mean?

Sick6,

Just so you know, you got a SCREAMING deal on that head. If you walked into a speed/machine shop today, they would charge you at least $1500 for those flow numbers and headwork, more like $2000.

Lou

_________________
Home of Slant6-powered fun machines since 1988