93 premium friendly ? Looking for hyd and max rpm of 6000

350
10-1 CR
dart iron eagles 64cc -180 cc runner
weiand stealth dual plane
holley 750 vac secondary
700 r-4
2500 stall 3.07 gear.
GM hei

Mike,

Please find one of Pat Kelley's posts or threads with him in it and use the link in his sig. to get to his great "Dynamic Compression Ratio Calculator".

Read up on what Pat says about the program and have a blast playing around with it.

Use say .025" for the piston being down in the hole and say anywhere from a .015 shim to a .039" or so thick headgasket. (We like to shoot for about .040" quench dimension but it will vary per engine unless it has been created by building it that way)..

Then imput your motors spec's and start imputting cams into it until you come up with what you want.

CC's cams are made on 110/106 LCA/ICA dimensions so use this as a starting point for that info..

Good luck and come back and tell us what you come up with. I bet there will be several of the guy's here that can either approve or offer better cams then what you come up with b/c of real world experience.

Have fun and I will bet that you learn a thing or two...

pdq67

With 10.0:1 compression and iron heads, a cam with 280* advertised duration with a 110* LSA installed on a 106 ICL is about perfect for 93 octane. Any cam with an IVC angle of right about 66* should work nicely with 93 octane, the other cam timing events will effect the engine's power band etc.

This is basically how the DCR theory works.

If you remember the 4 cycles (Intake, compression, power, exhaust) you will notice that the intake stroke is right before compression; so the piston comes down during the intake stroke and goes back up during the compression stroke. The cool thing IMO is that in a high performance engine the intake valve remains open even after the piston passes through bottom dead center at the end of the intake stroke and stays open for several degrees while the pistons moves upward at the beginning of the compression stroke.

The point at which the intake valve closes is the point where compression actually starts to take place since you can't really compress anything in a cylinder with an opening in it (the intake valve). So the cam timing determines when compression starts to take place - the later the Intake Valve Close timing, the further up the piston is in the cylinder during the compression stroke and the lower the Dynamic Compression Ratio is.

Knowing the dynamic compression ratio is really useful to us hot rodders because we typically want the most bang for our $1.86 of premium pump gas. Trial and error has proven that a DCR of about 8.0:1 is max for an iron head engine and about 8.5:1 is about max for an aluminum head engine. 9.0:1 is the number 110 octane racers often shoot for. Of course these numbers are up for debate and depend on some other variables too, but generally speaking these numbers work.

Hope this helps.

thanks. i'll have to play with the calculator.

i was lookinh at the CC magnum 280...230-230 .480-.480 on a 110 LSA ICL 106. Only problem is i have a 700 r-4 with a 2500 stall and 3.07 gears with 26" tall tires.

i'm thinking it'll be very soft on the bottom ?

what do you think Eric ?

I think it would be fine with a 2500 stall on the low end. Might not like OD though at cruising speeds with that 3.07 gear. Too bad you couldn't swap in something between 3.42 and 3.73.

thanks Eric

those gears might come next year as the budget allows.

do you think this cam could be used or too short duration on the intake ?

Good idle, daily usage and off road, towing, performance and fuel efficiency, 2600-3000 cruise RPM, 8.75 to 10.75 compression ratio advised. (50 state legal, pre-computer, C.A.R.B. E.O. D-225-18) Basic RPM 2000-5000 PowerMax
H-272-2
replacing:
HMV-272-2

Cam Specifications


Degrees Duration @ .050 Int./Exh. Degrees Advertised Duration Int./Exh. Degree Lobe Separation Open/Close @.050" Cam Lift Int./Exh. Lash Hot Int./Exh. Gross Lift Int./Exh.
216 228 272 284 112 1 35 51 ( 3) .000
.000 .454
.480

the open and closing at .050 is throwing me off

Just imput the advertised duration values and LCA/ICA stuff into Pat's program and it will spit it right out.

pdq67

i acnnot download the program, must have a firewall here or something

Mike

I'm building a similar combo.

355
9.9 - 1 cr
Trick Flow 195 64cc heads with full rollers
Comp Magnum 280h
Perform RPM
Q-Jet
small tube headers with 2.5 flowmasters
2000 stall
700r4
3.55 posi

Pat Kelly's DCR calc says 7.89 DCR which I think is decent. I'll know how it runs next week. If you're not in a hurry on the cam decision I can post back or email you how the 280h works out.

that would be great.

i ordered some bare Dart iron eagles with 72 CC combustion chambers because i want to run a smaller cam than that

so the fully ported 64cc er's will go on ebay. cheap i might ad

let me know when you put them up for auction mike,
might be interested
Eric
bgn4chng@hotmail.com

I think that cam is too small. Your DCR would be 8.6:1, too much for pump gas and iron heads.

Something with 280* advertised on a 110* LSA with about 230* @ .050 would be fine. I've run an iron head engine with 10.3:1 compression and the Comp 280H (same specs as above). RPM band was 2500-6000 with Rhoads lifters.