Think I blew my 3400

[IsaacHayes]

Yeah IExploiter isn't on this machine, and never will be. This thing has not caught any virus or spyware or trojan/etc at all. A friends new machine loaded with IE7 I had to battle some nasty trojans.... IE still sucks!

So is the quench really that bad? Is the quench ok with just 3400 bottom and 3500 heads or is that screwed up too?

[torq455]

well....8.65 cr 3400 with 3500 heads. now if you enter iirc the deck clearance of the 3400 (-.020) with Ben's figures, then you get 9.6. soooo if that's right, then cr of 3400/3500 is 9.15.

[IsaacHayes]

What about the quench though? Does that stay the same I'm guessing with 3400 pistons and 3500 heads... It's just the chamber thats larger right, and the quench is the area that isn't the combustion chamber correct?

EDIT
What about 3.4camaro pistons, 3500 heads? Compression is?

Wasn't there a 3400 running 3400 heads and a cam and camaro pistons Ben helped setup?

[geldartb]

Wasnt there just a big discussion on using the camaro or DOHC pistons? Either compression is too high for pump gas, or the quench isnt ideal with all of the combinations of head gaskets, heads, and pistons.

yeah it was something about the quench not being right. i was gonna build up a cammed 3400 with the camaro pistons but never got an awnser to suit my liking.
i already have the camaro pistons but never found which gasket to use to keep it happy

[IsaacHayes]

Hmm. Are the domed? I couldn't tell from pics on google if they were domed or what? Possible to machine them down some maybe flat or would that kill the compression way too much? I used another PC with IE and came up with like 12.66 compression with 3500 heads and maro pistons.

[torq455]

no they have something like a 8cc dish. iirc our quench goal is .030".

Quench, or squish area is typically the flat area on the top of the piston that's almost level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench.
If you look at a combustion chamber, you will usually see these flat areas, and they will have the volume of the actual combustion chamber between them. When the piston is compressing the mixture, as the piston nears the head, the flat areas on the head and piston come together and force the mixture from those areas to "squish" into the chamber, where the spark plug and burning mixture reside, so you achieve a more complete burn.
The quench area also runs cooler than the rest of the chamber / piston. These lower temperatures are where the "quench" comes from.
When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios, and due to this they are considered "artificial octane" by scientific types.
Bottom line is "properly designed, quench is good".
--theoldone.com

[geldartb]

stock 3400 head gaskets and camaro pistons and 3500 heads will net 11.56.1 using the .0095 piston deck clearance for the camaro pistons

now with using the camaro head gaskets its like 12.33.1

with a .050 thick head gasket it would be 11.93.1 which is still up there but alot better than 12.33.1.

i remember someone mentioning something about a head gasket with a compressed thickness of .050 but dont remember who or what brand or where to get them also what would the quench be with the .050 gaskets.

[IsaacHayes]

Hmm. So how do you compute quench? 11.56:1 is good should be able to run that on pump gas with a good tune.

[geldartb]

yeah but i think the whole thing was with that combo and the stock head gaskets was too much quench and creating KR

the 11.5.1 was the CR i was aiming for which is why i was gonna go the ironhead 3.4 piston route but i never got anything definate so.

heres a little novel

What is the most, exact precisely defined occurrence in all piston engines? It isn’t ignition timing, combustion, crank indexing, or valve events. It is Top Dead Center. You can’t build an engine with an error at Top Dead Center because TDC is what everything else is measured from. Spark scatter, crank flex and cam timing can move, but TDC is when the piston is closest to the cylinder head in any one cylinder. The combustion process gets serious at Top Dead Center and about 12 degrees after TDC, most engines want to have maximum cylinder pressure. If maximum cylinder pressure occurs 10 degrees earlier or later, power goes away. Normal ignition timing is adjusted to achieve max cylinder pressure at 12 degrees after TDC. If your timing was set at 36 degrees before TDC that is a 48 degree head start on our 12 degree ATDC target. A lot of things can happen in 48 degrees and since different cylinders burn at different rates and don’t even burn at the same rate cycle to cycle, each cylinder would likely benefit from custom timing for each cylinder and each cycle. Special tailored timing is possible but there is an easier way—“Magnificent Quench”. Take a coffee can ½ full of gasoline burning with slow flicking flame. Strike the can with a baseball bat and you have what I would call a “fast burn”, much like what we want in the combustion chamber. The fast burn idea helps our performance engine by shortening the overall burn time and the amount of spark lead (negative torque) dialed in with the distributor. If you go from 36 degrees total to 32 degrees total and power increases, you either shortened the burn time or just had too much timing dialed-in in the first place. If you have really shortened the burn time, you won’t need so much burning going on before Top Dead Center. Now you can retard timing and increase HP. Did you ever have an engine that didn’t seem to care what timing it had? This is not the usual case with a fast burn combustion but an old style engine with big differences in optimum timing cylinder to cylinder will need 40 degrees of timing on some and others only need 26 degrees. If you set the distributor at 34 degrees, it is likely that 4 cylinders will want more timing and 4 cylinders will want less ( V-. Moving the timing just changes, which cylinders are doing most of the work. Go too far and some cylinders may take a vacation. Now what does quench really do? First, it kicks the burning flame front across and around the cylinder at exactly TDC in all cylinders. Even with spark scatter, the big fire happens as the tight quench blasts the 32 degree old flame around the chamber. Just as with the coffee can, big flame or small flame, hit it with a baseball bat and they are all big instantly. The need for custom cylinder-to-cylinder timing gets minimized with a good quench. The more air activity in a cylinder you have the less ignition timing you are likely to need. When you add extra head gaskets to lower compression you usually lose enough quench that it is like striking the burning coffee can with a pencil. No fire ball here and that .070-.090 quench distance acts like a shock absorber for flame travel by slowing down any naturally occurring chamber activity. A slow burn means you need more timing and you will have more burn variation cycle-to-cycle and cylinder-to-cylinder, result more ping. Our step and step dish pistons are designed not only to maximize quench but to allow the flame to travel to the opposite side of the cylinder at TDC. The further the flame is driven, the faster the burn rate and the less timing is required. The step design also reduces the piston surface area and helps the piston top stay below 600 degree f (necessary to keep out of detonation). All of our forged pistons that are lower compression than a flat-top are step or step dish design. A nice thing about the step design is that it allows us to make a lighter piston. Our hypereutectic AMC, Buick, Chrysler, Ford, Oldsmobile and Pontiac all offer step designs. We cannot design a 302 Chevy step dish piston at 12:1 compression ratio but a lot of engines can use it to generate good pump gas compression ratio. Supercharging with a quench has always been difficult. A step dish is generally friendly to supercharging because you can have increased dish volume while maintaining a quench and cool top land temperatures. You may want to read our new design article for more information. ".

By John Erb
Chief Engineer
KB Performance Pistons

http://kb-silvolite.com/article.php?action=read&A_id=39

[torq455]

frickin NICE!!!!!

[IsaacHayes]

Cool, I understand that. I found a few compression calcs that had info for what we need, and came at about 11.6:1 so that sounds right. But could not find a quench calculator.

EDIT, head gasket thickness - piston deck clearance = .05 something. So yeah no good. (if thats how you figure it)

[geldartb]

i figured one of them with the camaro piston deck clearance seen as how thats what was going to be used.

even that number doesnt change it that much maybe like 2 tenths.

that was the first and only artcile i found on quench, i was actually looking for a calculation on how to calculate it.

[IsaacHayes]

Where does the -.020 number fit in the calculator? I know the 3400 pistons sticks out of the block .02 but the stock specs in the CR calc don't show that anywhere....

[bszopi]

The -0.020 is the "Piston Deck Clearance". Since the piston protrudes out of the block, the deck clearance is actually negative.

[tejohnson]

The -0.020 is the "Piston Deck Clearance". Since the piston protrudes out of the block, the deck clearance is actually negative.

Head gaskets also add to the equation. Stock is something like .060 crushed if I remember right. If you need more clearance/volume I have some copper gaskets on eBay that are .070"x3.750". Adds clearance, but slightly lowers compression.