Overlap Triangle

[TT5.9mag]

If you like math you’ll have fun. I have a love/hate relationship with math lol. When I get stuck I have my kid bail me out.

When he gets home for Christmas I’ll have him look over the math and see if he can adjust something to make it more accurate with exhaust numbers with manifolds.

Also if you have the book it gets into cylinder head math, induction math…pretty much all the math you need to build an engine.

I hated math in school/college but it’s because I was forced to do it. Now building engines I tend to like it. It’s definitely a love/hate though.

 

[74 Cuda]

You are correct about the engine builder, they should have the information to select the proper head for the intended application but the correctly designed cam will, for a lack of a better word, fine tune the velocity.

I have a love/hate relationship with math

Yes i'm the same, unfortunately my math skills only go so far.

 

[273]

There's probably no formula that's gonna give you the 100% ideal cam no matter how much specs are accounted for, there's probably always gonna be room for improvement. Questions is, is it gonna get you in the ballpark better/consistently than other methods.

 

[fishmens67]

Plus its damn hard to find one degree

and even if you did unless a gear drive is used that 1 degree will vary with a chain

 

[Danny Bellmore]

I also forgot to ask if you have cylinder heads have 5/16 or 3/8 rocker shaft bolts. If you only have 5/16 bolts I would chose less aggressive lobes that also had lift between .620-.640 just to help reduce stress on the bolts.

They are 5/16.

 

[74 Cuda]

Which heads are you using?

 

[Newbomb Turk]

They are 5/16.

Ok, let me find some lobes that aren’t so aggressive.

The valve train won’t take that with 5/16 bolts although I know someone will say they are running 280 on the seat and 650 over the nose with 5/16 bolts.

I don’t like that.

 

[Danny Bellmore]

Which heads are you using?

BPE by Rod Bloomer.

 

[Danny Bellmore]

Ok, let me find some lobes that aren’t so aggressive.

The valve train won’t take that with 5/16 bolts although I know someone will say they are running 280 on the seat and 650 over the nose with 5/16 bolts.

I don’t like that.

The last cam I ran was Comps 20-718-9

 

[PRH]

The last cam I ran was Comps 20-718-9

As a point of reference………That cam isn’t hard on parts.

 

[Danny Bellmore]

As a point of reference………That cam isn’t hard on parts.

I never said it was.
I lost a cam due to a bad pump gear contaminating my lifters.

 

[PRH]

Understood.
But there was a comment where someone was searching for lobes that weren’t aggressive.
I’m just pointing out the lobes on your current cam aren’t.

 

[Newbomb Turk]

Understood.
But there was a comment where someone was searching for lobes that weren’t aggressive.
I’m just pointing out the lobes on your current cam aren’t.

I’ll look up those lobes but I picked some lobes I would use but I wouldn’t use them with 5/16 bolts.

 

[Newbomb Turk]

The last cam I ran was Comps 20-718-9

Ok so it’s 269/276 .654/.655 on a 109. That’s a pretty nice grind.

I’ll look around and see what I can find but they have a 271 lobe that would be nice for the intake.

 

[PRH]

It’s a 106.
Grind # RX302S-R6

Comp Cams 20-718-9
Gross Valve lift (in 654) (ex 655) add 1.6 rocker arms.
Duration @50 (in 269) (ex 276)
Lobe Lift (in .436) (ex .437)
Valve Timing @50 (in open 45) (in close 77)
(ex open 81) (ex close 48)
Lobe seperation 106

I’d be curious to know what springs and installed height the heads were set up with to go along with the 1.6 rockers.

 

[Newbomb Turk]

It’s a 106.
Grind # RX302S-R6



I’d be curious to know what springs and installed height the heads were set up with to go along with the 1.6 rockers.

You are correct. I said 106 and typed 109.