How to get .040" quench w/ open chambers?

For small blocks. How is this achieved? Without going with closed chamber. This is for 10.5:1 91oct E10. Thanks.

Quench pad pistons and lots of GOOD machining and measuring. You'd have to equalize all the "open" area of the chamber (probably have to machine them) and then cut the quench pads of the Pistons to give you your .040".

Have a piston recommendation (stock stroke 360)? Who does your machining? Kens? Comp?

No I don't have a piston for you to use but I'm sure some of the SB guru's will have some recommendations. I used Millar Racing Engines in Winkler for a 440 I had rebuilt as a teen and it was a good engine. He has a pretty good rep to this day, maybe give him a call. Are you in Manitoba?

Yeah, peg. Winkler's a bit of a drive.

There's a local BB guru (Mike Arsenault) who uses Competion Engine for his machine work. Mike builds some pretty stout BB's. He's got a 70 Satellite with a 588 B1MC that runs high 9's

Yahhhhh I know MIke. I'll go see the boys at Comp 2morrow. Thanks a bunch.

When I did it, I hand ground all of the chambers to the same depth, then cut the deck a TON to get the pistons .070 out of the hole. It is a long time consuming project to hand grind each piston to clear the edge of the chamber from there!

Yeah KB has the rough cut pistons. Toooo much work for this cat.
I think a cam in the 108ish LS & 236ish @ .050 should be enough
to get by on 91 on the street. Thanks guys.

get some KB 372 pistons in the OS your block requires. narrow the rods to 1" for them (it says required with them). machine open chambered head recesses just enough to get em equal/level. As said carefull measureing/machining of piston plateau keeping in mind gasket choice to get the SCR range you are after for .035-.040 quench. You'd need to bore to size then mockup the 4 corners & rock the pistons & check heights plus square decking the block. Need a good machine shop that will work with you. with 91 you will need quench & 040 is the very max.

It Takes some work but like said it can be done a few different ways. One I remember doing had the block decked enough to have a KB107 come out of the hole, then clearanced for the head. I did the same on my old 340 with the KB243. It required some more work for clearance because it was a 4.100 bore.

I took the easier way on this 360, KB107, Zero Deck, Edelbrock RPM heads milled a little, and a Fel Pro 1008. 11:1 91 Octane 500HP(11.16@119.5@3525lbs)

Yeah I was thinking about it. The KB373 pistons @ .005 below deck, with a .040" compressed gasket should give me .040" quench. Correct?

the quench plateau is .085" above the piston perimeter. you'd want .035-.040" between that flat and the head flat

Then get a set of closed chamber heads if you aren't interested in doing the job right.

Getting .040 quench is not a throw it together task with as cast iron heads .

read post #2087607 Johnny-be-bad But as per usual your right.. I'll do the quench pistons the right way.

you mean this ??



It makes no sense if you have an OPEN chamber head ????

was talking about the .085" quench pad on top of the piston.

.005 below deck + .085 quench pad - .040 gasket should be .040 quench.. no?

Mr. Bush would say.....Fuzzy Math.

It depends on how recessed the open area of your chamber is. Say it's .100", you have a .040" head gasket and the pistons are at zero deck, You'd need your quench pad to be .100" to get a .040" quench.

You are wasting your time trying to fight for quench.

Leave the combustion chambers big. Stick the piston out of the hole as far as you need to. I'd have to look to be sure, but I ended up at .050-.060 out of the hole.

How do the stock eliminator guys get quench with 8.5:1 and open chamber heads? Even the 10.5:1 guys don't get the kind of quench you want.

Get the chamber correct, with the right valve job and a good top cut, get the compression where you want it and let it go.

It's a pepper and fly poop deal.

iirc the recesses were ~.120" deep as is on my SB 308's. I did not go for quench on that build but wanted to get a rough baseline on how deep they were (& as you know it'd be more after machining to level/smooth/equalize em).

Has anyone ever gotten the open part plasma sprayed to fill them in and then deck them? I know it's probably not cost effective but could be if someone already had the heads (I think the OP is using W2's?). Cadorath Aerospace in Winnipeg does plasma spraying and they're known for doing it well in the aerospace business (they were when I worked there 15 yrs ago)

Unless you are racing in a class requiring stock heads, it is really easier to just get closed chamber heads and run flat top pistons, plus the new heads will flow better too.

I did this many years ago with the KB-232 pistons. I think these were really designed for a Magnum engine with the narrower rod ends?
As mentioned, rod ends need to be narrowed to 1", the heads and block milled to get the correct quench clearance, cylinder head chambers normalized to the same cc's and the "eyebrow" between the valve and quench area needs to be reduced, or the pistons clearanced for it.

I must have missed the .085 quench pad ??? I know nothing about that KB piston .

One other thing I don't see mentioned is how deep is the open part of the chamber in the heads ... at least I didn't see it ??? .... were they machined to be all the same? If you think they are all the same ... chamber to chamber ... AS CAST you couldn't be more incorrect. doing that is the biggest, and most important part, of the whole job.

Research other brand pistons CP Height and stick them above deck, you can also put chevy rods in the mix if you cut the crank down.

You can also hunt for older,but heavy domes pistons.

I'll measure them today and report back.

Alright so I measured all the chambers quench pad, they were all in the
.078x" range.

.078 + .039 gasket = .118" quench

.118 - pistons @ zero deck + .080 piston quench pad height = 0.038"

Is that good? I know its a roughed in & final machining will make it more
accurate.

You would need to mill the OC recesses smooth/equal then mockup a piston/rod in each corner then measure to see how much needs to be milled off of the piston plateaus or the block decks to get that .035-.040 clearance EDIT & keep in mind the thickneses of available gaskets. plug it in to an online calculator to get the SCR as close as you can to where you want it & still maintain quench

Thanks

What is the RANGE??? Did you measure front to back and inside to outside?

It needs to be the same across the chamber and the same chamber to chamber.

When I did it I set the heads up in a Bridgeport and machined each chamber flat. I had an NOS 452 BB head that was .110 out at the ends and the center of the head was .125. The first 2 times I did heads I freehand cut them, what a pain cutting that arc in 2 axis . The last set I did we had installed a Prototrack(CNC) on one of the Bridgeports and that made my life easier.

The heads should be surfaced first so you know it's flat if you chose to machine the chambers inside of attempting it by hand. You also should use a radiused cutter, you don't want the edge of the chamber cut square.

You'll probably have to have the heads surfaced again if it takes a fair amount to get everything flat because it will make the chamber CC larger.

You'd have to really want to use open chamber heads to go through all that, being that the OP is building a small block and the Enginequest heads are so affordable it would be a natural choice for me, zero deck it, .040 head gasket and be done! Being able to use SBC roller rockers is another great benefit

As I posted earlier, the OP is practicing mental masturbation with the quench deal.

There is ZERO benefit to running a SBC rocker arm. Most Chevy guys don't use them.

The correct way to do what you want is outlined above. If you tested the two combos side by side, with compression equal, the tight quench engine might be, maybe 4-5 HP more, but I highly doubt that.

@ madscienctist; not looking for horsepower, just no knocking w/ iron heads & 10.5:1 cr running on 91 E10 swill.

@ JohnRR measured the quench pad in the chamber across 3 points.

@ GTS340.. yeah no way I'm using a Magnum head.. let alone POS SBC rockers.

Don't need quench to run a 10.5:1 360 on pump gas. Been doing it for years.

Correct, they sell race gas at the pump ...

10.5 with iron heads and no quench on 91 octane .... Ok ...

No, not really , using what I had because I already had too much money tied up in them to just toss them in the scrap heap ...

Dang.. learn something new everyday.

Thanks gents!

Just asking, is there enough quench area in the head to justify using, looks kinda small to be effective.? Is there a formula for bore size to quench size?

Here's a video. Motor has gone a best of 11.49@116 in the car in my sig.

https://www.youtube.com/watch?v=iyjFpyQ1ASI

We did it with KB's. Touched the chambers up with a 3M green disk until they were all pretty much the same depth. Then decked the block and milled the heads until we were .030"-035" quench. Worked very well. Car with a decent 260@.050 cam and 12.5-1 ran on 93 octane with no issues. It was way better than the 250@.050" cam at 10.5-1.
Doug

I was planning 230ish @ .050, 108ish LSA cam w/ open chambers.

Our motor is a .508/292 purple shaft. I think it's around 230 @.050. KB107's w/minimal deck.

That cam is more like 250@.050. The mopar cams have real long lazy ramps. They bleed a lot of cylinder pressure, that is the only way to get a no-quench open chamber head to live on 91 octane.

Yeah.. forgot about that tried and true cam.. 248 @ .050" is just the ticket I need too.

I run 11.08:1 MEASURED on 91 octane pump, and I'm not using s slow ramp cam.

Where were you guys in the 1980's? I was using 10.5:1 on iron heads all through them on pump gas, all the while the Chevy guys were calling me a liar.

It's not a speed secret.

Guess I was late to the party. Just tell the chevy guys you run 7:1.. typical MoPar engine.

Cough up your cam specs then.

Jesus, do you doubt everything non magnum?

283/283
255/255 at .050
.620/.620
105 LSA installed at 105


Edit: the advertised numbers are at .020 lift. If you use the lash numbers it is actually .280/281 advertised.

First of all I am not Jesus.

Second as I suspected that cam is huge in my opinion, just letting people who are considering doing what you are doing know they need a huge (again in my book) duration cam to make it work. You made it sound as if you were running short duration cams with high compression.

Third as for my "magnum obsesion" I just have a hard time understanding why people don't embrace newer, usefull tech that don't cost a fortune to use, I mean I can buy a core 5.9 all day for $150 with all the better sealing, better flowing, roller cam useing, modern combustion chamber technology that they have over the old 360. When I started messing around with them more seriously around 10 years ago I was very supprised how much better they do all that stuff. The only thing I don't like is the AMC rockers but it seems to be of no consequence till waaay over 6000 RPM (with quality stuff at least 7000RPM) where most people operate their engine so I just quit losing sleep over it and now me and my customers are all happier for it.

I'm not going to hash out th magnum deal with you, but if YOU have ring seal issues with an LA engine that's on you.


If I was running 408 inches would the cam be HUGE? Nope. Size is like opinions and fart holes and I'll leave that be. Your definition of HUGE is different than mine. In fact, I spent a CONSIDERABLE amount of time on the phone before I ended up with this cam. It could have been way bigger if I was going to wind it up or use more displacement. If an 1100 RPM idle bothers you, unplug the tach.

As for roller cams...that is 100 % horse dung. The issue is with HYDRAULIC roller cams and LA based engines. I'd bet I was building HRT LA based engines before you tried it. Then, I realized that a hydraulic lifter is a hydraulic lifter. They are pretty much junk for any real performance engine. So I now do hydraulic roller cams with solid roller lifters. I wasn't the first but it is a hundred times better than a HRT.

Strike TWO.

As for rocker arms, junk is junk at any price and ANY stud mounted rocker system is JUNK. I spent YEARS telling Chevy guys how stupid they were for not using shaft rockers when they were as cheap and available as they were for the GM guys. Most I know have not used a stud mounted rocker for years. Then th backwards magnum guys want to tell me that junk is cool, where its at?? You are RETARDING MoPar racers back DECADES.

Strike three.


There is no such thing as too big a cam. Too small an engine, maybe.

No ring seal issues here, never said that.

Just the 10 bolt valve covers and machined valve cover rails seal way better for longer than the cork 5 bolt rough cast LA heads. Dry exhaust bolts instead of coolant in the threads, one piece oil pan gaskets... stuff like that is what I mean about sealing. I build my engines with the intention of lasting many many years with lots of miles not so much just drag engines that never see rough weather and only get freshened up every couple years so that stuff matters to me.

I agree about cam size being subjective, but I do know my customers when they put the pedal to the metal are happiest with shorter duration and big lift, if you can not get a HRT to do that then that is on you. Every one of my customers has tried to talk me into bigger cams then I recomended but in the end they rant and rave about how hard the engine runs and I usually get a couple more builds from his word of mouth advertising.

I also agree the shaft rocker is way better... in very high RPM and lift aplications, but I just don't see it making any difference in most engines. Besides check these out

http://www.hughesengines.com/Index/produ...mp;partid=25628

What were we talking about ?

Apparently how Magnum engines will rock your world

Those are pretty!

madscientist, seems you've got it figured out for running highish compression without quench (although you posted earlier your Pistons are .060" out of the hole, with a head surface and thin gaskets you might actually have some) but your doing it with a big cam. Yes we can discuss the finer points about how a 250+ @.050 isn't that big on a 408 but it's a big cam for most street builds (even on a 496 that would still be a burly cam!)

I was thinking of going zero deck, .060" cut on the head, .020 gasket, and end up in the neighborhood of .038" quench w/ a 248 @ .050" cam.

What would the static compression be with these #'s?

Static COmpression ratio w/ 71cc head 10.319. Dynamic would be 7.714:1 with that cam.

Is the head 71cc w/.060 cut?

haha whoops

10.8 static/ 7.93 dynamic with 67cc heads.

I do NOT like cutting the hell out of a head to gain compression. I have seen and junked many heads because some hero took .060-080 off the head and now the surface is right down on the top cut of the intake valve job. I'd rather stick the piston out of the hole because the block can take a .100 cut and not even blink.

On my set up, I'm running .059 gaskets and I'm 11.08:1 and I have some .039 gaskets I can use that will put me at 11.25:1 if it rattles with the quench a bit further away than I wanted.

As far as cams go, my cam will idle at below 1000 RPM. I won't let it, but it can. Decades of brainwashing by comic books, trackside tuners and whiz bangs in gym shorts has retarted the hobby. We are now on out third generation of people who think of a car as an evil rather than a good thing. A computer and phone is more important to status than what you drive. You can have a cool phone, the coolest phone, and drive a Honda and I will think you a goofball. So for people to say a cam is too big, when the engine builder (ME) and the cam grinder (Jim Dowell of Racer Brown cams) spent hours going over flow numbers, valve job angles, port areas and many other things and JIM came up with this grind (which are very new lobes) and the gurus on here think it's too big! It is the correct grind for the application. Could I have used LESS cam and still keep the CR where it is? Hell yes. We had many options. I wasn't set on CR when I first called Jim.


So to say my cam is BIG is stupid. It is the correct cam for MY application. If my engine was 400 CID I would need another 15-20 degrees of timing. Would that be considered WAY too big.