This was in another post of mine, but I thought I'd bring it up again as I'm interested in feedback on it.

Been thinking about doing a quench build on a 225. Based on the factory numbers (and I have not yet specifically measured out this engine), the head chambers are recessed into the head about .200", while the piston usually sits about .140" in the hole. I'll use these numbers just for arguement.

If the 198 rods are used instead of the 225 rods, it will push the stock 225 piston roughly .147" OUT of the hole. This will give a quench (at the closest points between the head and piston) of about .073" with a .020" steel gasket. Mill the head .028" to clean it up and I'll have about .045" quench (considered good quench in most circles). But the compression will be way to high. So if I cut about a 18cc "D" type dish in the stock piston tops, I'll get roughly a 9.5:1 compression. I've seen this done to other types of stock pistons and assume it's possible here. All of this must be measured out on my specific engine (particularly negative piston deck, since as previously mentioned, it varies between engines, as well as the 198 rod to 225 piston skirt clearance).

I suspect this will work if I can dish the pistons. I'd love to find a piston already like this. The KB268 is close, but the CH is too low. I don't mind the idea of the stock 225 piston as I don't plan to rev beyond 5K anyway.

Any opinions on any of this?
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Vapir No2 Vaporizer

I don't think the combustion chamber in the head is machined (as cast?).

So there will be hills and valleys with regard to squish/quench and a flat piston top.


Not sure what effect that will have on combustion............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I think you would be better served going with the KB239 and the 198 style rod. I am not sure it would be worth all of the trouble if all you want to run is 9.5 to 1 compression. What purpose would building a quench engine serve then? Quench is used primarily to aid in turbulance and promote a more efficient burn allowing higher compression ratios to be run resulting in more power. If all you plan on running is 9.5, I don't see the point in all the trouble. Just my two cents.

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Rob

It is enough that Jesus died and that he died for me.

You sort of answered your own question. It is the turbulance, and 'cooling' effect of quench that makes it worth doing, and 9.5 compression is just a number for consideration. If I could use 10.5 to 1 with quench, I'd certainly go for it, and probably will. No, the KB239's don't have enough CH for quench, which after about .050"~.060" quickly looses it's effect.

Yes, I also realize that the combustion chamber might not match the piston top well, but that would be something to work on. I'll be researching this further.
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Ship sale

Cam would probably figure in to this also. Gotta figure where you are going to start pinging. 91 is all you can get in CA correct?

I would think properly jetted running the ethanol blend it would be somewhat detonation resistant.

Polish the chambers for less places to hold glowing deposits.

Or go hog wild and build a E85 motor with 14:1

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

By far the easiest way is the K1/Wiseco rod/piston deal. You will get just about a zero deck motor, and can adjust with small amt of block milling.

My new one on the stand has the pistons 0.005" out of the hole. I will have a 53 cc head and 0.045" gasket for 11:1 comp.

Lou

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Home of Slant6-powered fun machines since 1988

I like what your doing and you seem to be aware of all the in's and out's to watching out for. Your right the quench is going to help at any comp level if nothing else you want have to run as much timing to make the same power and gives less negetive resistance against the piston and this will result in more power.


WHen working out the dish, IMHO its worth trying to make it mirror the heads combustion chamber ( if possible). Plus you have ot remember the valves have to clear the pistons, and flow for the valves should be considered. Polishing combustion chamber is a no-no. Many may aurgue but thats the last thing you want in a cumbustion chamber. Sand paper roll finish is what your after and you want the marks from this sand paper to help you kinda guide your air/fuel flow as its going in and out of the chamber ( intake and exhaust flow). Think of the lines left by the sand paper roll like the lines in a dried out river bed where the water cuts its own path. Like as the fuel mix comes out of the intake valve, you want the mix to flow where, and how? Then directiing the exhaust flow, like helping to push the flow into the exhuast valve. PLus believe it or not but this type of finish will help hold a small, thin layer of carbon which will in effect insolate the chamber ( and you want the piston to have a slight rough finish like glass beaded) and piston which well help to keep heat in the chamber and promote flow and swirl ( think of a golf ball and a baundry layer of air for everything to glide across). Heat in the chamber makes for a more efficient burn which will be good for power and economy. And if the heat is not getting into the chamber walls, then you dont have hot spots to be causing det. Although sharp edges are still a bad thing, radius edges ( small but still rounded) is what you want on dish edges and such.

This is a subjject that all dont agree on, but the proof is there for what I am telling you. You want ot be real carefull with things like the head gasket hanging out into the cylinder, or being resessed and leving a gap between the head and block. Also you want the head chamber edges to match the cylinder wall ( mount the head on block with no pistons and veiw from bottom, you can even move the head around on the block to get better alignment, or even intake valve possition to help with unshrounding). This needs to be considered before trying to match a piston dish to chamber.


Needless to say there are many things that can get you into trouble when taking this aproach. And reshaping the heads chamber to achive the exact quench size,shape and angles along with the piston work is something that can be done also. And ofcourse you need to measure the piston deck thickness to see if you have the room to cut your dish ( and leave thick enough to hold up).


IMHO this is a advanced aproach to doin something like this and its not something that can be done without carefull planning and thinking completely through what your doing, before doing. I have seen 11.5 to 1 comp engines live on pump gas like this. Other things come into play when pushing limits like this ( camshaft design, engine temp, induction temp, car weight and gearing, fuel,power adders, ignition and timing needs). For example a engine like this with our bore size could need as little as 18* max timing at WOT and things like this is something you just have to test to find out its real needs. Nitrous or boosted engines have completely different needs when it comes to quench. Angle milling the head could be something to think about when doing this, the flattest/shortest chamber shape could be a good thing but valve angles,shrouding and CR have to be considered. Look at everything, think of the whole package and process all the way through before doing. Like they say one thing leads to another, and if you make one change midway through it could change everything else your trying to do. Start you a log paper and make notes of your plans as you make the plans on how to do it. This will help you spot problems and refine your process to get it all worked out. Start out by bolting the head to block with no pistons as I meantioned and look at the chamber as one pocked that has to flow fuel/air in and out, plus compress it. Use clay to make a model of the chamber with the piston in place to help decide your shape changes. And again smooth and polished has no place in a combustion chamber.


Good Luck - Jess

Great write-up Jess THANKS
Also along the same lines you can start a thread about YOUR build and ask for others input.
I will most likely do this with the Heart Shaped combustion chambers in my Argentine Head.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Thanks Jess, some good stuff there which I will be seriously considering. I'll have to read that over a few times!
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