No more high compression street builds for me

[Thunderdan]

Perhaps I missed something in this thread, however how was the quench with the Icon pistons?

Much of my reading (no personal experience so far) was that the relatively large bore and head design was that TOO LITTLE quench can cause detonation, while the tighter the quench, the more resistant the combustion is to preignition.

 

[lewtot184]

Perhaps I missed something in this thread, however how was the quench with the Icon pistons?

Much of my reading (no personal experience so far) was that the relatively large bore and head design was that TOO LITTLE quench can cause detonation, while the tighter the quench, the more resistant the combustion is to preignition.

Preignition and detonation are two diferent things. Preignition can be instant death for the engine. Detonation takes a little longer to kill things. I use quench distance for detonation resistance. Some folks get quench distance a little distorted. .040" is the minimum, not the target. .060" is condidered maximum for building good detonation resistance. Quench distance by itself is only one piece of the puzzle.

 

[autoxcuda]

Yes. 12.80s - 12.90s. 108 - 109 mph.

3.23s
Factory 12” converter
BFG - P235 70s (2.05-2.10 sec. sixty ft times)
MP 0.455” cam
Exhaust manifolds and 2 1/4” exhaust.
Locally ported 915 heads. (245 cfm)
Six Pack
10.3:1 CR
4200 lbs

Considering part of the discussion is the value, or no value in compression, l’m not sure mine is a great example.

But conversely, put that drive train in a 3,800 lb car, sticky street tires and a 9.5:1 CR, it would be well into the mid 12s.

I’ve thought about re-doing this. With what I’ve learned since then, I think I could get to 12.50s at 112 mph with a better cam, 2 1/2” exhaust, better ported factory head, and 9.5:1 CR. I’ve actually assembled most of the parts.

Impressive! All on a 440 stock stroke, right? You run stock rockers?

Where do you think most the HP gains came from? What helped you the most to get those ET's and MPH?

 

[weedburner]

I've spent quite a bit of time flogging really low compression 87octane builds, I have found the results can surprise you.

It all started back in the late 90's, an engine built using left over dirt track parts. Super low compression with a cheap "claimer" piston short block paired with a dirt latemodel solid roller with tight LSA and ported -10 Brodix heads. Only cranked about 90psi on the starter, but nitrous really woke it up. Made about 700hp on 87 octane gas, more octane just made the headers glow. Not much to write home about NA.

The next build was the result of a new obsession with making power using cheap pistons. I had turned to ebay hyper "rebuilder" pistons, they had reduced compression height and were about $90/set at the time. On those cheap $90/set pistons I was putting a $800/set Total Seal Advantage rings, basically a stock eliminator ring package with ported groove spacers to fit thin low drag rings into stock width ring lands. Quench was about .097". The rest of the build was basically the same as the first, except this time I put a proper nitrous cam in it with 114LSA. This is the engine that really surprised me, as it got 20+mpg drive to/from the track and ran 5.73 in the 1/8th.

Eventually my obsession evolved into having my cake and eating it too... a high rpm 87 octane nitrous engine with street manners. The current version is a flat top 4.030" bore 355sbc with .084" quench. 251/261 114LCA solid roller, about 7.1:1 dynamic depending on what numbers you use. Lightweight crank, aluminum rods, forged pistons. 342cfm -11RI Brodix raised runners with titanium valves and shaft rockers. It spins past 8500, can idle below 400 if I set it that low, still gets 20mpg on long drives.

I just recently started experimenting with pushing the envelope in the mpg direction, might add a vacuum advance distributor as a switchable alternative to my current crank trigger. Last weekend I reset the base timing to 49* and put a 15* pill in the retard box, which allowed me to switch back and forth between 49* and 34* timing by flipping a switch. Basically 34* representing my current timing with the crank trigger, 49* representing 15* more during light loads if I added a vacuum advance distributor to the mix. With that I took a 40mi drive in mid 90's weather, kept rpm mostly between 2100 and 2500. I found that the 49* timing resulted in 5* lower engine temp, also 2"Hg more crankcase vacuum drawn by the pcv valve. I would imagine that would translate to even better fuel economy than the current 20mpg.

Grant