Another "How much will it make?" Project "Special Needs"

[randy331]

So now you have the exact pattern that needs machined on the pistons. Just take .010" off in the "scribed area" only and you can keep comp close to where it is now.

Randy

[zums]

looks like its cast in solid granite
Tom

[zums]

Hard to tell from the pic since the head looks textured, only witness i see looks like the chamber edge above #7 plug
Tom

[CGT]

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Sad times for SN. No piston to head contact. Bore scope lied to me. Cant really see alot wrong so far. But...she was definitely oiling!

[zums]

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Sad times for SN. No piston to head contact. Bore scope lied to me. Cant really see alot wrong so far. But...she was definitely oiling!

Put a profilometer on the bores and some eye loupes on the rings for starters
Tom

[CGT]

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Sad times for SN. No piston to head contact. Bore scope lied to me. Cant really see alot wrong so far. But...she was definitely oiling!

Put a profilometer on the bores and some eye loupes on the rings for starters
Tom

Yeah, that's part of the plan. Put some torque plates back on it, freshen the bores up, fit some new rings, bearings and try it again. At this point, I can't explain it, but I think there is some kind of weird deal going on with my oil rings. It's something I really pushed the limit of, using a low tension 4.00 expander in the 4.040 bore.

They have definitely backed off even more on tension from when I assembled it. The oil rings will go in the bore with no compressor at all now, and are flush with the piston. They surely weren't doing much towards the end I'm sure. Just not sure if that could somehow disturb the seal of the other two rings and cause it to not pull much vacuum from the vacuum pump.

The rings look good to me, I see some scratches in the cylinder that had valve to piston contact in Randy's car, but otherwise good. The second ring(Napier) picked up a few thou of end gap from when it was assembled, top rings did not(Steel Conventional) but I'm not sure how normal that is. I haven't had one back apart with this little run time and measured that in the past.

I will go much safer on the oil rings this time around for sure. Maybe it just took some run time for the problem to surface. I'm just not sure. But looking forward to ring seal .., along with my Grumpy 10hp re-hone. This engine had less than 7lbs of rotational torque to turn the short block over, so pretty damn loose. Thanks Tom.

[rustbucket79]

The engine in my thread, SBC dyno results, where do I go from here, had a couple of seasons on it than sat in my basement for 3 years. I pulled it down, cut the seats and valves, and plate honed the block. Rings/bearings/head gaskets/etc all reused. Rings were a custom set by Keith Jones with a Napier second and 8 pound oil assembly, moly standard top ring. I was sceptical but it all sealed up quite nicely.

[CGT]

The engine in my thread, SBC dyno results, where do I go from here, had a couple of seasons on it than sat in my basement for 3 years. I pulled it down, cut the seats and valves, and plate honed the block. Rings/bearings/head gaskets/etc all reused. Rings were a custom set by Keith Jones with a Napier second and 8 pound oil assembly, moly standard top ring. I was sceptical but it all sealed up quite nicely.

Good job, I have been following your thread. I've been around several engines, very similar to yours on the dyno. Yours is right in line with what I've seen. My motor had some time sitting as well, not 3yrs but regardless. I believe the expander I'm using 3mm...is rated at 11-13lbs in the recommended bore size not .040 under. So.....I may have gotten greedy. But I don't mind the experimenting.

[RevTheory]

The engine this thread is about has 2.08 intake valves, but 50* seats. So I figured up the actual window area this set up has vs a common 45* seat at the low lifts. ( .050" - .200" ). If one were to spec LSA with 128 for this engine, would it be fair to use the valve size that, with a 45* seat, gives equivalent window area at these lifts?

Below is the valve size that gives the equivalent window area with a 45* seat as the 2.08" valve has with a 50* seat.

Lift----valve diameter
.050"----1.890"
.100"----1.875"
.150"----1.921"
.200"----1.928"

So, about equal to a 1.90" valve on average at those lifts.

359 / 8 = 44.875
44.875 / 1.90 = 23.69
23.69 x .91 = 21.49
128 - 21.49 = 106.51

Is my math right?
Should special needs have a 106.5 LSA ?
And rounding down is better so 106 ?
Or would 105 be even better cause it's still short on flowZ at .250 lift vs a conventional 45* 2.08" valve?

Randy

Now what LSA did the winning EMC end up at again?

I'm just flippin' you shit. I'm running back through this thread as I'm planning something along these lines but nearly 1,000 rpm lower peak and I saw this.

I wasn't able to find it so I'll have to ask; what was the mcsa on those heads?

[randy331]

Now what LSA did the winning EMC end up at again?

You would need to ask the winning team that question.
Everyone knows any heads I've done don't have anywhere near enough low lift flow to win the Engine Masters !!

I'm just flippin' you shit. I'm running back through this thread as I'm planning something along these lines but nearly 1,000 rpm lower peak and I saw this.

I wasn't able to find it so I'll have to ask; what was the mcsa on those heads?

Average csa would be 2.25" ish and mcsa would be about 2".

1000 rpm less would get by smaller.

Randy

[RevTheory]

Thanks, Randy. The heads I'm eyeballing are supposedly at 1.92 mcsa. I just wanted some sort of frame of reference.

[RevTheory]

Does that seem in the ballpark for a 357 ci that I'd like to peak just shy of 6,500 rpm, preferably at 6,000 and carry over? Pipemax says it may be on the small side.

[CGT]

Any guesses on what much better ring seal on special needs will be worth power wise?

[n2xlr8n]

Any guesses on what much better ring seal on special needs will be worth power wise?

26.313 HP.

You're going to have more friction loss.

[CGT]

Any guesses on what much better ring seal on special needs will be worth power wise?

26.313 HP.

You're going to have more friction loss.

Negative 26.3 or positive 26.3?