133.5 Cam # & Edelbrock’s Supposedly Lame BBC ‘E’ Heads

[andyf]

Mike,

I'm doing a series of magazine articles on a Mopar 470 inch big block with the new Trick Flow heads. It currently has a Comp HXL/HXX solid roller in it. If you have a cam that will move the torque curve up across the board then I'll do a dyno shoot out and write the article.

[CamKing]

Mike,

I'm doing a series of magazine articles on a Mopar 470 inch big block with the new Trick Flow heads. It currently has a Comp HXL/HXX solid roller in it. If you have a cam that will move the torque curve up across the board then I'll do a dyno shoot out and write the article.

Send me the specs.

[GARY C]

The LSA (or LCA as is used by DV) and generalized rules or formulas to make a camshaft pic may work for low rpm type engines.

A LSA that comes out of the DV calculator certainly does seem "tight" by many. A narrow LSA opens(and closes) the intake valve early and opens the exhaust valve late (relatively speaking).
The effect of an earlier intake valve closing is higher cranking pressure - and the later exhaust valve opening uses more of the exhaust energy and makes more torque (in some applications).
However (a big however), depending on engine displacement, cylinder head port size/flow, full exhaust, rpm range etc.. the early intake valve timing and the late exhaust opening is all wrong.
For low rpm streeter type BBC builds the 133.5 number may work out.
As displacement increases and rpm goes up the exhaust valve needs to open earlier to avoid pumping losses.
As cylinder heads get better (which they are from 40 tears ago) we do not require the very early intake valve opening.
Higher rpm operating range also dictates later intake valve events and earlier exhaust valve events.
What is the result? larger LSA's.
The intake valve events and required exhaust valve events are chosen for the application (rpm, induction, head csa/size/flow, compression ratio, exhaust system, etc..)
The resulting LSA is just that - a result of correct intake valve events and exhaust valve events.
LSA is certainly not the first design calculation for a camshaft - it is a result.

JMO of course.

All of this is addressed in the equation and was partially covered in the OP.

[Wolfplace]

Ok, I am not sure if I am doing something wrong but if I were to use this number/formula I am coming up with 102.35 LSA for a 582" 11.0 compression BBC with a 2.300 intake valve?
I don't think I am real comfortable with that but,,,, I have been wrong a time or two before,,,,

[F-BIRD'88]

Ok, I am not sure if I am doing something wrong but if I were to use this number/formula I am coming up with 102.35 LSA for a 582" 11.0 compression BBC with a 2.300 intake valve?
I don't think I am real comfortable with that but,,,, I have been wrong a time or two before,,,,

I get 105.16 to 105.6 LSA 133.5- (582/8 /2.3 x.91) corrected for compression ratio above 10.5 add (.45 to .9 ratio) correction factored for 1/2 to 1 compression ratio increase over 10.50:1cr


I'm always wondering if I'm doing something wrong HA ha

[Wolfplace]

Ok, I am not sure if I am doing something wrong but if I were to use this number/formula I am coming up with 102.35 LSA for a 582" 11.0 compression BBC with a 2.300 intake valve?
I don't think I am real comfortable with that but,,,, I have been wrong a time or two before,,,,

I get 105.16 to 105.6 LSA 133.5- (582/8 /2.3 x.91) corrected for compression ratio above 10.5 add (.45 to .9 ratio) correction factored for 1/2 to 1 compression ratio increase over 10.50:1cr


I'm always wondering if I'm doing something wrong HA ha

That's not what I am reading?
I read it as the adding .45 (half of .9) not multiplying
Even the ProStock example posted adds
Stated as .9*6=5.4

[CamKing]

Ok, I am not sure if I am doing something wrong but if I were to use this number/formula I am coming up with 102.35 LSA for a 582" 11.0 compression BBC with a 2.300 intake valve?
I don't think I am real comfortable with that but,,,, I have been wrong a time or two before,,,,

Don't feel bad, I just did the calculation for a 665ci BBC with 9.5:1 and a 2.35" intake valve. If I did David's math right, I come up with a 97 LSA.

I'm sure I did something wrong

[1989TransAm]

"The writers all love the idea, but as soon as they float it to their editor, it gets shot down. There's no way they would allow their biggest advertisers to get shown up like that."

And that is exactly why you will not see any contest in the magazines. The advertisers.

[andyf]

Ok, I am not sure if I am doing something wrong but if I were to use this number/formula I am coming up with 102.35 LSA for a 582" 11.0 compression BBC with a 2.300 intake valve?
I don't think I am real comfortable with that but,,,, I have been wrong a time or two before,,,,

Don't feel bad, I just did the calculation for a 665ci BBC with 9.5:1 and a 2.35" intake valve. If I did David's math right, I come up with a 97 LSA.

I'm sure I did something wrong

And where would you install that cam if you did have it ground to those specs? 4 degrees advanced?

[canada1]

All of this is addressed in the equation and was partially covered in the OP.

All of this is certainly not covered in the OP - it is somewhat glossed over - yes there is a factor to spread LSA .9 for every point more than 10.5:1 CR.
I did not see anything about rpm range, cylinder head size/flow, exhaust parameters etc... Each of these would require another
"bandaid" fix to the "formula". All increasing the LSA from the original number 133.5.

The facts are this "formula" may work for very mild, very low rpm engines in some instances.
The OP should mention that this formula may work for some low rpm, smaller cam timing applications.

Cheers

[MadBill]

The formula doesn't cover RPM range; that's addressed by DV's overlap chart, which together with the LCA calculation gives duration.

[David Vizard]

All of this is addressed in the equation and was partially covered in the OP.

All of this is certainly not covered in the OP - it is somewhat glossed over - yes there is a factor to spread LSA .9 for every point more than 10.5:1 CR.
I did not see anything about rpm range, cylinder head size/flow, exhaust parameters etc... Each of these would require another
"bandaid" fix to the "formula". All increasing the LSA from the original number 133.5.

The facts are this "formula" may work for very mild, very low rpm engines in some instances.
The OP should mention that this formula may work for some low rpm, smaller cam timing applications.

Cheers

Question - just needs a yes or no answer.
Does a 511 inch 717 lbs-ft 809 hp BBC running 87 octane fuel with a cam to the 133.5 rule sound 'Mild'? (or for that matter the 1340 HP BBC Terry Jack and I did at Waltersengines.com)

DV

[David Vizard]

And I forgot to add to the last post a significant piece of info from my original post so here it is again.

Remember – in case of disputes I don’t have an opinion - I have a dyno!

[prairiehotrodder]

This is the same formula thats illustrated by the graph in your BBC book? I have one tiny question that threw me for a loop when you commented on my post yesterday. Are LCA and LSA the same thing?

[David Vizard]

This is the same formula thats illustrated by the graph in your BBC book? I have one tiny question that threw me for a loop when you commented on my post yesterday. Are LCA and LSA the same thing?

Yes - LCA is a result of my English upbringing!
DV