Cam combo

You're getting a lot of pretty good but confusing information here. I've built a bunch of motors and consider mystelf to be a bit of a cam expert (self titled)

First- the sound you want isn't "loop" it "lope" (just don't want you to do too much talking about "loop" Lope is the sound the engine makes as it begins to stall due to poor signal at the carb (usually caused by overlap and/or very tall valve lift while at low RPM)

Second- Your cam is 218 intake and 218 exhaust @.050. This is a mild cam. Not an RV cam, but mild and builds hp to 4500 rpm. YOu want one that builds to 5500-6000.

Third- with a stock converter, I think the Comp XE274 may be a little too lumpy for a stock converter. That cam (even with the fast intake ramps) has just a little too much duration. You could do it, and it would sound nice, but you'll sacrifice some down low. It's up to you. It would sound really nice. The XE268 is 226/230 @.050. This cam won't lope too much unless you idle at 600 rpm due to the ramp rates. This cam is really nice in terms of some lope, good low-end torque, nice cylinder pressure and vacuum. I have this cam in my very built 327 corvette and it pulls to 6000 rpm. I'll attach a sound / video file so you can decide if this is a good sound for you.

65 Stingray w/ EX268 and hp manifolds:
http://www.corvetteforum.net/classics/maximillian/corvette_web.wmv

Also, just keep in mind that you don't want to go further than 230 degrees MAX duration on the intake @.050. with your compression ratio and stall converter. As for "ping" it's not an issue unless you are 10.5:1 or higher with iron heads. As for lift, keep it under .5" and you'll be fine.

Blown4.6 said:

You're getting a lot of pretty good but confusing information here. I've built a bunch of motors and consider mystelf to be a bit of a cam expert (self titled)

First- the sound you want isn't "loop" it "lope" (just don't want you to do too much talking about "loop" Lope is the sound the engine makes as it begins to stall due to poor signal at the carb (usually caused by overlap and/or very tall valve lift while at low RPM)

Second- Your cam is 218 intake and 218 exhaust @.050. This is a mild cam. Not an RV cam, but mild and builds hp to 4500 rpm. YOu want one that builds to 5500-6000.

Third- with a stock converter, I think the Comp XE274 may be a little too lumpy for a stock converter. That cam (even with the fast intake ramps) has just a little too much duration. You could do it, and it would sound nice, but you'll sacrifice some down low. It's up to you. It would sound really nice. The XE268 is 226/230 @.050. This cam won't lope too much unless you idle at 600 rpm due to the ramp rates. This cam is really nice in terms of some lope, good low-end torque, nice cylinder pressure and vacuum. I have this cam in my very built 327 corvette and it pulls to 6000 rpm. I'll attach a sound / video file so you can decide if this is a good sound for you..

Click to expand...

He said his car is a manual. So, since it doesn't have a converter, he doesn't have to worry about it.

Blown4.6 said:

65 Stingray w/ EX268 and hp manifolds:
http://www.corvetteforum.net/classics/maximillian/corvette_web.wmv

Click to expand...

2 things:

Without doing all the math, a .30 327 is about 40-50 cubic inches bigger than a 289 so the 289 may idle slightly worse.

Those off brand motors have a much higher exhaust flow to intake ratio. What works in a 327 won't neccecarily work that well in a SBF.

Blown4.6 said:

Also, just keep in mind that you don't want to go further than 230 degrees MAX duration on the intake @.050. with your compression ratio and stall converter. As for "ping" it's not an issue unless you are 10.5:1 or higher with iron heads. As for lift, keep it under .5" and you'll be fine.

Click to expand...

Comp will tell you not to run the XE at much over 9.5:1 in an iron head motor.

I still think the Crane is a better choice, but thats me.

The valve sizes make me more concerned about the P/Valve clearance. Other than that I'm still on the Crane side of the fence.

Keep digging, the more you can find out the better quality of reccomendation we (and the cam companies) can give you.

There's not been enough talk of heads/ports/valves. Each of these being stock or being changed will DRASTICALLY affect what would otherwise be the "right" cam for the job. If the heads and valvetrain is completely stock then I think the cam he has is not that bad, on the smallish size yes, but not "too small". Put some AFR205s on there and he's WAY undercammed.

BULLETSTANGV8...what kind of heads and valvetrain do you have now and what are you prepared to do or intending to use long term?

D.Hearne said:

Mine pulled all the way to 7500 and would have gone further, but the lifters wouldn't stay with the cam. Mine had Canfield heads and a B303 roller. Good thing the lifters started jumping, any more than 7500, and it probably would have shed a few rods.

Click to expand...

a B303 roller cam has a lift of .480"/.480" and good for low end torqe and horsepower above 4000rpms. never seen a b cam rev that high but maybe you should get your tach checked out.

Nothing wrong with my tach. The lift on this B303 is now .510, with 1.7 roller rockers. And with the breathing capabilities of the Canfield Heads and the Vic Jr. intake, it's not a problem to pull to 7500. You don't need a huge cam to rev that high, just a good set of heads.

PoliceInterceptor said:

He said his car is a manual. So, since it doesn't have a converter, he doesn't have to worry about it.

I somehow missed that. My bad. In that case, I'd go XE274 all the way. You don't really need much vac. (you don't have power accessories or A/C do you?) so, what the hell.

2 things:

Without doing all the math, a .30 327 is about 40-50 cubic inches bigger than a 289 so the 289 may idle slightly worse.

Those off brand motors have a much higher exhaust flow to intake ratio. What works in a 327 won't neccecarily work that well in a SBF.



Comp will tell you not to run the XE at much over 9.5:1 in an iron head motor.

I still think the Crane is a better choice, but thats me.

Click to expand...

True, but they are going to sit on the side of caution. They don't need the aggrevation. I'm running 10.5:1 exactly in the 327 Stingray. The heads are ported and polished cast iron. On crappy 91 octane fuel in California (where I live now) it doesn't make a sound.

Bottom line is that cam selection is an art for sure. Also, many things come into play. I just try to keep it simple. You could go into modified heads, single plane intake, lobe separation angle depending on the carb size......all these things will make the "perfect" choice a little different. A roller cam is always going to be better (and WAY more expensive and complicated to install). I just think you can't go wrong with the XE274 or XE268 kit from summit based on his objectives. Done and done.

What's difficult about installing a roller cam? It sticks in the same as a flat-tappet and the lifters drop into their holes the same. Only difference is the all face the same direction and have either link bars between them or are held in place by a "spider" that's held down by two bolts. Actually a roller is in many ways easier than a flat-tappet to deal with for first timers. You don't have to worry about mixing the lifters up if you reuse them and there's no "break-in" for the cam, just fire it up and go.

Hr = $$$$

Not if you start with a roller block. This evens out the playing field on cost.

Back on subject.....

Well,

Bullit, to answer your question. If there were piston to valve interference, you would have to either go to a smaller cam, of cut valve relief in the pistons. There are cutters that replace the valve and allow you to do this. Obviously, you have to pull the heads.

Since you do not know exactly what was done to the motor it makes this a lot harder. One would assume that a person who would have the heads cut for larger valves (2.02 intakes are much larger than stock) would also have ported them or had them ported. One would also think they would have used quality pistons and so forth. You may very well end up having to tear into the engine to figure it out. You might find that it is not even a 289…

One other thing that I would like to know is, what do you want the engine to do (or do better) that it does not do (or do well) now?

There are several things that you could do without changing the cam to help, such as replace the exhaust rockers with 1.7:1 ratio ones. On the other hand, you could change them all to 1.7:1 too. Replacing only the exhaust ones would give a very slight increase in exhaust duration (about 2 degrees) and a good bit more lift.

I think that we may have given you the idea that the High Energy 268 (what you have) is an awful cam. It is not. It certainly is not the best choice, and it is an old grind but it is good at doing what it was intended for which is to give improved performance, good sound, and every day drivability.

That said, it escapes me why anyone would put a single pattern cam (same intake and exhaust specs) in a Small Block Ford. With a few note able exceptions, every head out there can use more exhaust duration and lift than intake.

Keep trying to get more information about the motor. If you can see the front of the heads at the deck surface post a picture or describe lines cast into them at a right angle to the deck. Also look and see if there is a “GT” or any other identifying mark cast in near the head bolts on one end. See: http://www.stangpro.com/html/articles/gt40p_files/gt40p1.htm

You never know……………

D.Hearne said:

What's difficult about installing a roller cam? It sticks in the same as a flat-tappet and the lifters drop into their holes the same. Only difference is the all face the same direction and have either link bars between them or are held in place by a "spider" that's held down by two bolts. Actually a roller is in many ways easier than a flat-tappet to deal with for first timers. You don't have to worry about mixing the lifters up if you reuse them and there's no "break-in" for the cam, just fire it up and go.

Click to expand...

It doesn't just "go in" You need to modify a block built for a flat tap cam to accept a roller. Been there, done that. It's not that bad, but definately more work on top of the much more expensive kit.