Thread: 72elk

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Originally Posted by States

Didn't ask for lumpy idle, just asked for their recommendation, not even set on a comp Cam yet. I would prefer to stick around 9.5:1 compression. Any recommendations at what I should be looking at? Comp Cams did say that with the heads/springs/retainers I have that I am limited to a max lift of .525.

How would I do it ?
0.030" overbore to 4.030"
Stock stroke at 3.480"
Cubic inches 355
L31 heads with ~65 cc chambers (chambers generally pour a little larger than advertised)
Keith Black KB193-030 hypereutectic pistons w/ 5/64" rings (makes 9.5:1 SCR) This piston has a compression height of 1.561", so I would cut the block decks for a block deck height of 9.001". This will make a zero deck motor. (1.74" crank radius plus 5.7" rod length plus 1.561" piston compression height equals 9.001"). Using a Fel-Pro 1003 head gasket that compresses to 0.041" will give you a 0.041" squish/quench and will insure that the motor will run on pump gas without detonating.

Have your machinist insure that the angle between the heads and the intake manifold is zero so that there is no leak. If there is a bottom gap due to differing angles between the manifold and the heads, this will allow the motor to suck oily vapor from the crankcase every time an intake valve opens. Often, this is mistakenly blamed on valve seals or the piston rings not sealing up. So, make sure the intake manifold and the heads are dead nuts parallel top to bottom and end to end before final assembly. THIS CANNOT BE OVER-EMPHASIZED. if the gap is at the top of the ports, it can be found by spraying a combustible mixture onto the manifold while the engine is running, but if the gap is at the bottom, no such finding is possible, the motor will be an oiler and there is nothing you can do about it except disassemble and re-machine the surfaces or buy new parts and cut them to fit. Your machinist will know what to do it you show him this post.

Knowing what I know about motor oils, I will never recommend a flat tappet cam in today's world. Anyone doing so is just asking for trouble unless he takes various precautions and includes an oil supplement with every oil change. Extreme lubricants phosphorus and zinc have been eliminated from off-the-shelf motor oils, so you must add these chemicals to the oil in order to insure that the lifters will not frag the lobes of the cam. There are other precautions that can be taken if you just absolutely have to use flat tappet lifters......
http://www.crankshaftcoalition.com/w...ips_and_tricks

With 9.5:1 static compression ratio, my pick of cams would be a hydraulic retro-fit roller, Howards # CL110235-12.
https://www.summitracing.com/parts/hrs-cl110235-12
The lobe separation angle of 112 degrees will allow production of more intake manifold vacuum for power brakes. This is always a back and forth choice, with a smaller LSA favoring more low end power, less top end power and less intake manifold vacuum or a cam with a larger LSA favoring less low end power, more top end power and more intake manifold vacuum. Regardless, if you have power brakes, you need to address that need as well as the need for power. Most OEM cams are ground between 114 and 117. Most hot rod cams are ground between 112 and 106. You will have to figure this out for yourself. I made the choice of 112 for you because I think this will make enough intake manifold vacuum for power brakes and still make good power. Everything in a street motor is a compromise.
Intake duration at 213 is perfectly matched to your 9.5:1 static compression ratio. This cam will work with a 3-speed or 4-speed overdrive transmission. I would match it up with a 28" tire and a 3.50 to 3.73 rear ring and pinion with a non-slip unit of some kind.

I would use a minimum 2000 stall converter and a 2500 might work even better. Use a 10" unit that is build for the purpose rather than a 12" converter with the fins bent over.

Use 1 5/8" long-tube headers with an X or H tube installed immediately after the collectors. You may also want to install an air/fuel ratio device in the collectors that will tell you whether the mixture is rich or lean. 2 1/2" pipes from the collector to the rear of the vehicle with mufflers of your choice somewhere along the way will be fine. I like to run the pipes all the way to the back bumper to prevent my ride from sounding like an amateur build and reverberating the sound under the vehicle against the body or bed sheet metal.

Use a 14" diameter X 4" tall air filter assembly so the motor can breathe.
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