This calculator: http://www.hotroddersauctions.com/Dynam ... ulator.php

sez with my new cam(Erson 280) and 10.5 CR:


Your corrected Compression Ratio with boost and altitude is 10.20:1.

Your camshaft specifications call for an inlet valve closing of 46 degrees ABDC measured at .050.( same as cam card)

At 5000 RPM your intake valve is considered closed at 60.29 degrees ABDC.

Your chamber volume is 62.13 cc's. With this camshaft and RPM your dynamic, or effective stroke is 3.33 inches. Your dynamic compression ratio is 8.23 :1 corrected for cam timing, rpm, and rod length. Your dynamic cylinder pressure, corrected for cam timing, rpm and rod length is 190.21 PSI. Your dynamic volumetric compression ratio, reflecting static c.r., cam timing, rpm and 90 % VE is 7.41 :1. at 5000 RPM

Your minimum suggested octane is 91

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Sounds in the right ballpark. Personally, I think I would stick around 9.5:1 with that 280/270 cam (right?). You can run 10.5, but it is on the edge and does require premium gas and careful timing curve control.

I ran a similar cam (Crane 228 @ 0.050") with almost 11:1 for 1-2 yrs in my daily driver 68 Dart on 91-93 octane. No damage to engine, pinging evident at times, could see heat in the cyl head (baked off paint). I ran that same cam in Project V with only 8.8:1 comp and a better flowing head. Made about the same power.

Lou

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Home of Slant6-powered fun machines since 1988

Here is the specs with 9.5CR. The DCR seems low (7.43)

Your corrected Compression Ratio with boost and altitude is 9.20:1.

Your camshaft specifications call for an inlet valve closing of 46 degrees ABDC measured at .050.

At 5000 RPM your intake valve is considered closed at 60.29 degrees ABDC.

Your chamber volume is 69.32 cc's. With this camshaft and RPM your dynamic, or effective stroke is 3.33 inches. Your dynamic compression ratio is 7.43 :1 corrected for cam timing, rpm, and rod length. Your dynamic cylinder pressure, corrected for cam timing, rpm and rod length is 165.62 PSI. Your dynamic volumetric compression ratio, reflecting static c.r., cam timing, rpm and 90 % VE is 6.69 :1. at 5000 RPM

Your minimum suggested octane is 89........

This is the Comp 264s sheet for the setup in the car now

Your corrected Compression Ratio with boost and altitude is 8.95:1.

Your camshaft specifications call for an inlet valve closing of 36 degrees ABDC measured at .050.

At 5000 RPM your intake valve is considered closed at 48.57 degrees ABDC.

Your chamber volume is 71.26 cc's. With this camshaft and RPM your dynamic, or effective stroke is 3.61 inches. Your dynamic compression ratio is 7.83 :1 corrected for cam timing, rpm, and rod length. Your dynamic cylinder pressure, corrected for cam timing, rpm and rod length is 177.84 PSI. Your dynamic volumetric compression ratio, reflecting static c.r., cam timing, rpm and 90 % VE is 7.05 :1. at 5000 RPM

Your minimum suggested octane is 91 I run 87 no problem

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Yeah....Im the one who destroyed this rare, vintage automobile.....

There is definitely some slop here, as we all know. 10:1 is probably a good compromise, but 10.5 still sounds a touch high to me.

Will you mill head for comp, or??

Lou

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Home of Slant6-powered fun machines since 1988

I will deck the block..... the piston is still in the hole some. I hate to mill the head and get it wrong....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Sounds like they just recommend 91 for everything. I ran mine through and posted it in your other thread Sandy. It said the same thing.

My motor will run on 87, but will go quicker and faster on 91-93. It will slow down on 100-114.

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Official Cookie and Mater Tormentor.

I wasn t sure what you posted there Dennis......Ill have another look with that in mind.

Im not worried about running on regular with this build....think of it in terms of Lous 64 build.....but a tad milder.

The plan is for a fun Intercontinental Ballistc beater. Kinda thing a guy could run down to Redding with....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

The 10.5CR motor specs out pretty similar to yours Dennis.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

That is weird considering the cam is way milder and comp is almost the same. Cam is way milder than my 64 too.

Where are we setting our centerlines?? My guess is Dennis is around 102, mine is around 100, Sandy's? This should have a substantial effect if they are doing their math correctly.

Lou

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Home of Slant6-powered fun machines since 1988

http://www.slantsix.org/forum/viewtopic.php?t=24758

This seemed to be the best of the dynamic compression calculators that I found.

Sandy, can you try this one, vs the web compression calculator that you already tried, and see what the difference is in results?

Curiously yours,

Greg

Lou....109 2 advanced. 57 overlap

Im using 5000 rpm as my rpm and 90% VE

My rod length differs from Dennis' build.

Greg: I looked at that calculater but Im on dialup....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I would install that cam at 101-102 and not one degree more retarded. For a more radical cam, 100 would be better. I had my 228 Crane at 103 inst and would have advanced to 101 if I did it again, although only 8.8:1 comp there.

I have the 64 cam installed at 96 right now. Originally at 102 (not enough low end) on this motor build. 96 is too low end heavy with big sacrifice in top end, so I'll change it to 99 on my next delve into the engine to balance things out.

Lou

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Home of Slant6-powered fun machines since 1988

Sorry Sandy, I didn't realize your bandwidth limits.

If I get a minute, I will try to run it for you, and send you the results. PM me your email address, and I will send you screenshots as attachments.

I am curious to see if there are differences.

Thanks,

Greg

Aww, c'mon Lou. Just put it straight up and give it 100 shot of hose. You'll be glad you did.

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Official Cookie and Mater Tormentor.

Here are some guessitmates for you, Sandy. I tried to reconstruct your specs, based on what you posted.
If I made a mistake, let me know.

Here is your rod length calcs.


Here are your cam calcs


Here are your final calcs. I couldn't figure out what your actual combustion chamber volume was from your previous posts, so I tried two different ones that should be close





So, this comes out a bit different from what you were seeing from the other calculator. It might be that I had some of the input numbers different, but I tried to get you close.

Greg