Quench Question

[leahymtsps]

14.30 using Renegade 112 or Late Model Plus

It won't stay together with 112 but should be fine with LM+

Tom

[leahymtsps]

You don't run any dirt engine at 9000rpm.

Well, that's not exactly true.

Tom

[houser45]

Set it at .045-.050 squish. Pop the pistons out and machine a dish to get compression at. 15.5-16 to 1

[Bigchief632]

Pretty sure, the engine the OP has for sale in the for sale section, that this thread was started about, is done and dynoed. It made good power, and interestingly, made the power at 29 degrees total, pretty common on an sb2 deal, so, it appears, the big gap on piston to head clearance made no difference. I wonder if it ran on the 112 fuel? Thought I'd bump this. Remember, it had .094 piston to head, it should have been a no power detonating mess!!, what's going on here?

[perfconn]

Made 2 pulls with 28*,2 pulls with 26*(lost power - rich) & 2 pulls with 28.5*.Last 2 pulls were with 1000cfm carb(lean) first 4 were with 950cfm carb.All were on Renegade 112 gas.Dyno sheet looked spastic but it was before we discovered dump valve on brake needed opening up a little more.We don't use jets in it just a barrel valve.

[Bigchief632]

Made 2 pulls with 28*,2 pulls with 26*(lost power - rich) & 2 pulls with 28.5*.Last 2 pulls were with 1000cfm carb(lean) first 4 were with 950cfm carb.All were on Renegade 112 gas.Dyno sheet looked spastic but it was before we discovered dump valve on brake needed opening up a little more.We don't use jets in it just a barrel valve.

So, essentially, it made best power at the "typical" total timing they usually do, and it did not detonate on 112. Thank you for the update. Good luck with the sale. I wonder if this will even "click". lol.

[perfconn]

Yep,best pull out of 6 we made was the 1st one,actually the 2nd. We never record the 1st because the rings need to seat.Anyway best pull was with 950 Stealth dyno carb with 28* timing.I think it would do more with my Divinci 1050cfm & I would make a couple of pulls with 30* just to see if it helped.The dyno sheet is posted in the for sale section for anyone interested.
Chief,some things just never seem to click to some people.

[Bigchief632]

Anyone? Care to elaborate why this engine worked so well with such a big piston to head clearance? Is it possible it's just not that important? If anything would be sensitive to this, it would be a 444 inch sb2.2 deal. It wanted a little more timing, as predicted, and made so much TQ they were having a problem holding it back with the break and it didn't detonate on the 112. I'd bet it won't be so critical to have the timing dead on either, it will be more forgiving, reducing detonation potential. Which basically is the opposite of what most believe would happen.

[Warp Speed]

High squish velocity typically increases burn rate. You see many nitrous guys run up to .090 piston to deck height for that very reason.
That being said, typically NA engines prefer a high squish velocity/tight deck height, but that can also be rpm/chamber dependant.

[perfconn]

Warp,
These were new 8C Hendricks heads with 33.4cc chambers.Actually that was what caused the build to progress in the manner it did.Normally every SB2.2 head I have dealt with were in the 44 - 45cc range.

[Warp Speed]

Warp,
These were new 8C Hendricks heads with 33.4cc chambers.Actually that was what caused the build to progress in the manner it did.Normally every SB2.2 head I have dealt with were in the 44 - 45cc range.

The 8C heads were designed for a 37cc finished chamber. I can see how with a large ci deal it is hard to get compression down.
With our 4.180 bore 3.250 stroke and the chambers finished (soft blending) they ran best at 34-36*.

[perfconn]

Warp,
Are the 10C a better head ? We had some of them & the chambers were radiused to the quench side.These 8C heads were brand new,never ran was the reason I used them.

[Warp Speed]

Yes, the 10C was a better head.

[PackardV8]

. . . . one way is not right & the other way wrong,just different.

Attributed to several sages over the centuries:

"It is not enough that I succeed. For me to be truly happy, my best friend must have failed."

[Bigchief632]

High squish velocity typically increases burn rate. You see many nitrous guys run up to .090 piston to deck height for that very reason.
That being said, typically NA engines prefer a high squish velocity/tight deck height, but that can also be rpm/chamber dependant.

That's not the question here. I think? most guys understand that, my point, and the reason I brought this up again, is that guys think they won't even run, they'll detonate, they won't make power, et etc if the quench isn't ideal, in this case, .094. Go look through the thread, the OP should have gotten new pistons, longer rods, decked the block, etc etc, needed C25 or some other expensive fuel, or it was going to be a detonating, no power mess. As seen in this application, it wanted a little bit more total timing than his typical combo, and wanted a little more jet, for the very reason you said, had less squish velocity and slower burn rate. I've mentioned the NOS example many times in these "quench" discussions/debates. You run a big piston to head, and a soft chamber, to slow all that down, to reduce detonation, and make the engine less sensitive to timing giving it a wider tuning window before it melts down. The exact same thing happens NA, just not to the extreme, but the example like this thread is about, it is LESS likely to detonate, similar to a noS combo, because it is a more extreme example with the tiny chamber and big swept volume, but most guys think running .027 piston to head will reduce the potential for detonation, and will want less total timing. It wants less total timing because of the increased squish velocity and burn rate, and has the potential to detonate easier, that's why it wants less timing, and is more sensitive to it, on a given fuel. The only reason it might gain power, is it has more compression, and reduced negative TQ, which is minimal. As you know, just saying, for the guys who thought the opposite would happen here.

Obviously in your world, fuel consumption and efficiency is important because of pit stop strategy, refueling etc. For the average guy, if it gets a half a mile per gallon less, it's not a big deal. In most cases like the guys on here, trying to reinvent the wheel to optimize this is usually not worth the expense for a small gain, that actually works the opposite of most think. It's interesting to see you run softned chambers and 34-36 total.