[DaleO]

I have just completed a compression test. It is interesting in that it involves the same short block but two different heads. There is nothing earth shattering or anything, we all know that when we put larger chamber heads on we'll see a lower compression ratio, but we like numbers so....

The short block is a 0.030 over 428 with an Engle cam p/n 2618H, 260/268 adv (yes two six zero/two six eight), 216/226 @ 0.050, .305 I lobe, .310 E lobe, .458 lift/1.5 and .468/1.5, 112 degree.

The first test had 62's pretty much stock and resulted in 212 psi, explaining the need for mixing race gas.

The second test with 6X-4 by Dave Bisschop resulted in 167 psi.

Some supportive info from the 1967 manual indicates 150-170 psi is around 8.6-9.2 cr and 185-210 psi is around 10.5-10.75 cr.
Some supportive info from the 1974 manual indicates 120-160 psi is around 8.0-8.4.

From other tables I've figured I'm at 9ish cr and this data seems to add up pretty well. So I'm calling it 9 to 1 cr and ask you help for a camshaft recommendation considering a couple significant upgrades since the 62 configuration. I believe there is probably a cam which better compliments ported 6X's and the TSP stall convertor which brake stalls at 2,500 rpm and flashes around 2,700/2,800.

The 6X-4 heads flow as follows:
intake
218 cfm at .400 lift
237 cfm at .500
245 at .550

exhaust
168 at .400
179 at .500
184 at .550

Maybe the cam I have with 9:1 is sufficient, but if not, I'm open to suggestions!

edit to add rear ratio. I have 3.23's right now but I am about to the pull the trigger on a new rear and am deciding between 3.50 or 3.60.

[steve25]

What intake is on the motor?

[DaleO]

Originally Posted by steve25

What intake is on the motor?

1967 iron, Dave filled the 6x crossovers with AL. Cliff built the 800 quadrajet.

[Jay S]

I could work backwards and get a close SCR ratio. Need a little more info though, first are those pumping numbers with the engine hot? 2nd what is your elevation.

Is it log exh manifolds and a stock tq converter? If those are stock yet I would not consider a cam swap. There would be some considerable gains if those two things aren’t stock with a cam swap though.

From what I recall Engle rates the seat timing for there cams differently. I am totally sure, but IRC, it is rated at .008” tappet. Engle grinds pretty nice cams, that cam is a pretty decent street cruiser. Bigger rocker ratios on the cam you have would work better with those head flows and that cam, has the intake pushrod tunnel been ground on for bigger rockers?

[DaleO]

Originally Posted by Jay S

I could work backwards and get a close SCR ratio. Need a little more info though, first are those pumping numbers with the engine hot? 2nd what is your elevation. Hot, (no choke flap to hold open), kept a battery charger on it to maintain the crank speed, 500 ft, basically sea level.

Is it log exh manifolds and a stock tq converter? If those are stock yet I would not consider a cam swap. There would be some considerable gains if those two things aren’t stock with a cam swap though. Hooker headers, 3" collector back to Dr. Gas crossover, 2 1/2 inch outlet through Dynomax mufflers and Torque Tech tailpipes. It is a TSP 9.5 inch which brake stalls at 2,500 and flashes at ~2,700/2,800.

From what I recall Engle rates the seat timing for there cams differently. I am totally sure, but IRC, it is rated at .008” tappet. Engle grinds pretty nice cams, that cam is a pretty decent street cruiser. Bigger rocker ratios on the cam you have would work better with those head flows and that cam, has the intake pushrod tunnel been ground on for bigger rockers?

It has Harland Sharp 1.5 but I wasn't smart enough at the time to have the pushrod tunnels opened. I can't comment on the seat timing, I'm looking at the catalog for it and it is not indicated. It actually is a pretty good setup for the way I drive it. I'm not interested in the jagged edge or even turning 5,500 let alone more, 5,200 would be good for me. I don't want to wreck the street manners but I think the TQ will buy me a little anyway. Rhoads are perfectly fine for me too.

[Jay S]

Wow. You have everything behind the engine sorted out nicely!

Probably could gain 50 HP with a bigger cam and not change how it drives or idles. Are you thinking flat tappet or a roller?

[DaleO]

Originally Posted by Jay S

Wow. You have everything behind the engine sorted out nicely!

Probably could gain 50 HP with a bigger cam and not change how it drives or idles. Are you thinking flat tappet or a roller?

Flat. Hey thanks! I've been observing and things have been evolving for quite some time, career, I'm slow...$... you know. Thanks to the forums for learning and benefiting from what others have done.

I've been leaning towards a low 220's, I am very appreciative of any suggestions. I'd really like to be able to say I have 1 hp per cid (433) but I don't want to compromise a street package to say that.

[Jay S]

I am curious what pistons your engine has. I played with the numbers some and there was a little more difference in the pumping numbers than I would generally expect from the 62 to 6X-4 swap. Could be several things that influenced the pumping test though.

A cam that is little bigger than the low 220s would be better, it needs enough lift to get into an area that it uses the head flow better. A summit 2802 would run ok, but not my first pick. (224*/234*, .465”, .487”, 114* LSA, 109* ICL). I think 228* @.050” on the intake would run better so you can get the lift closer to .5” lift. You could go bigger yet if you were willing to run a Rhoads lifter or a HLJ R lifter. Something like a Crower 60243 would work with Rhoads. Without Rhoad's I think the Crower cams would run better in the low 220s, pretty much like your thinking.

There are better options than the Summit or the Crowers, a Bullet Racing cams H278/330C (228*@.050”, .495” lift) on the intake paired up with a Utradyne H32, 286*, 238*, .5” lift on a 112” LSA with the ICL on 108* would not need Rhoads, pump about 160 psi, idle pretty smooth, and run on a point or two lower octane than your Engle cam, it would make a lot more power. I would probably suggest the older Ultradyne 288/296 grind or something with a bit more seat timing from Bullet when using a variable duration lifter. Maybe even a couple degrees bigger, that could get it closer to 450HP, on 87 octane.

[DaleO]

Originally Posted by Jay S

I am curious what pistons your engine has. I played with the numbers some and there was a little more difference in the pumping numbers than I would generally expect from the 62 to 6X-4 swap. Could be several things that influenced the pumping test though. Can I say a bit embarrassed because along with not choosing the cam all I said was I wanted forged pistons. I didn't write the number down when I did the head swap but seem to remember the number started with an "L".

A cam that is little bigger than the low 220s would be better, it needs enough lift to get into an area that it uses the head flow better. A summit 2802 would run ok, but not my first pick. (224*/234*, .465”, .487”, 114* LSA, 109* ICL). I think 228* @.050” on the intake would run better so you can get the lift closer to .5” lift. You could go bigger yet if you were willing to run a Rhoads lifter or a HLJ R lifter. Something like a Crower 60243 would work with Rhoads. Without Rhoad's I think the Crower cams would run better in the low 220s, pretty much like your thinking.

There are better options than the Summit or the Crowers, a Bullet Racing cams H278/330C (228*@.050”, .495” lift) on the intake paired up with a Utradyne H32, 286*, 238*, .5” lift on a 112” LSA with the ICL on 108* would not need Rhoads, pump about 160 psi, idle pretty smooth, and run on a point or two lower octane than your Engle cam, it would make a lot more power. I would probably suggest the older Ultradyne 288/296 grind or something with a bit more seat timing from Bullet when using a variable duration lifter. Maybe even a couple degrees bigger, that could get it closer to 450HP, on 87 octane.

Wow, that potential is more power than I figured I would ever get, I think it would be cool to get a magical 1 hp/cid, I'll learn up on your cam suggestions, are they shelf parts?

[Jay S]

The Summit 2802 is in stock. The Crowers are not.

You can email Bullet or talk to them over the phone, give them that lobe info I provide or go off what they say.

https://www.bulletcams.com/

[DaleO]

Originally Posted by Jay S

The Summit 2802 is in stock. The Crowers are not.

You can email Bullet or talk to them over the phone, give them that lobe info I provide or go off what they say.

https://www.bulletcams.com/

Jay, first of all, thank you.

I will contact Bullet and will lean towards your suggested Ultradyne 288/296 grind as I was already thinking I would be using variable lifters. The TSP 9.5 inch converter I'm running also compliments it. This is my first step out of catalog cams so this is interesting for sure.