Don Terrill’s Speed-Talk

Should I drop this cam in at 108, or advance timing gear to 104?

Mexican 062 vortec heads with mild bowl clean up but runners are untouched, 1.94/1.50 valves 5 angle job.
runners are at most 170cc max(unaware the 062 vortec mexican head was the worst until after work had already been done.
COMP Camshaft is 248/252 .050 duration, .510 lift 108*



750 Holley with 850 base, 1" spacer allowed.....I have an open one and 4 hole one to use if needed
2716 Edelbrock intake,
.040 2256L forged sealed power piston 5/64. 5/64. 3/16 rings
5.7 stock rod, arp bolts. 10/10 cast crank 3.480 stroke
dirt oval, 1/4-3/8 , on american racer kk704 tires.
.025 below the deck, likely running .039 stock head gasket with a roughly 67-68cc head chamber. 9.3-9.4 comp,
3000-6800 range, with a 7000 limiter

I'd probably put it in on 105ICL.

I would put it in at 103, especially considering your compression is so low for the cam selected.

Is there a compression rule? Zero deck it if possible and 104 icl... that cam is big for those cubes and that comp ratio.. that’s a lot of rpm for that intake, but it’s doable..

What kinda car, what’s it weigh?

3000 lbs, 1/4 dirt track

102 to 103 ish of you want to come off the corners hard.
you can play with the lash too.
Use a felpro .015" steel shim headgasket.
Why are the mex 062's checking at 67 68cc if so mill to 64
Compression is your friend. (torque)

I've raced in similar classes,Install the cam at 104 ,.015 head gasket,1.60 exhaust valve open the throat to 88% ,angle mill the heads .120, an open spacer and a quick fuel 650 made best power

Another vote for a skinny head gasket... Compression is your friend.

If you don't already have the cam get Mike Jones to grind one for you... Then get ready to pass the competition.

Why so much deck? At .064, (.025 + .039) you're almost double what's needed.

Kind of a tight budget. Rule has to be under 10.0:1
Pistons have very small valve reliefs, and I would love to run what Mike had recommended to me on a similar build, but I'm dealing with piston to valve issues so I'm trying to keep the lift down.
Head builder had to sink valves a bit to get the proper spring height etc. Chambers untouched. When i cc'ed the chamber it was around 66 on most.

If you want to be competitive in whatever type of racing these rules apply to, you need to change your perspective a bit: 1. Pick the cam that best suits the application . 2. Estimate how much thinner the head gasket can be to closely approach 10:1 CR.* 3. Cut the valve reliefs to suit the lift and piston/head clearance. *Allowing for the larger valve reliefs.

It's illogical to shackle yourself to a sub-optimal cam just to save a little machining of the valve pockets. Ditto using a head gasket that gives excessive squish clearance and significantly lower CR.

88bluestar wrote: ↑Sat Feb 10, 2018 4:37 pmdealing with piston to valve issues so I'm trying to keep the lift down.

How much valve-to-piston do you have? Duration plays an important role in this, as well.

First, is the car hooked off the turn, if it is install at 104. If it aint dont waste the power down low, degree cam up until you get the car hooked. On wet track sticky you can run at 104, maybe even lower but as summer comes on and track dry slick redegree cam up. . Lock the timing, probably 36/38. Man get compression as high as u can get it. Headers or manifolds?
reed

MadBill wrote: ↑Sat Feb 10, 2018 5:19 pm If you want to be competitive in whatever type of racing these rules apply to, you need to change your perspective a bit: 1. Pick the cam that best suits the application . 2. Estimate how much thinner the head gasket can be to closely approach 10:1 CR.* 3. Cut the valve reliefs to suit the lift and piston/head clearance. *Allowing for the larger valve reliefs.

It's illogical to shackle yourself to a sub-optimal cam just to save a little machining of the valve pockets. Ditto using a head gasket that gives excessive squish clearance and significantly lower CR.

Read this one twice.

Erik at reboco can rework your valve pockets, maybe cut you a mirror dish so you can tighten your quench up,
He is reasonable $$ wise,
He will tell you a number and you will say "each?"
Nope that's for all of them