BBC Camshaft LSA question

[prairiehotrodder]

still learning about my new 540 engine. It has a custom ground cam by Chris Straub. Cam is cut on a 108 LSA. Just wondering how it would work if it was the same cam but cut on a 114? Like how would it run differently and what the difference in power would be. The engine is all new and i'm just in the tuning / learning process. The car went 10.65 at 127 at the track. It weighs around 3300 pounds and has 3.50 gears and it had a 4000 stall. I've bit the bullet and ordered some 4.11 gears but haven't installed them yet. I have a friend who has been racing BBC's for many years and he thinks i'm crazy to install a 108 LSA cam. I'd like to see this car running high 9's with the cam i have. I also got rid of the 4000 stall and went to a 3300 stall. Just trying to learn. thanks for any help.
Brian

[greywolf]

Provide us with as much info about the engine as you can, and speedtalk members can take it from there.

[RevTheory]

You can certainly widen it but it will come at the expense of reduced torque pretty-much everywhere. To be honest, I'm surprised it wasn't on a 105. Must have some pretty good heads.

[prairiehotrodder]

10.2 CR, AFR CNC 335 heads, edelbrock victor jr. , pro-systems 1000 carb, hooker 2" primary g-body swap headers, flowmaster 3" exhaust with super 44 mufflers and x-pipe. 28 x 9 ET drags. Turbo 350 transmission.

[BigBlocksOnTop2]

Do away with the Flowmasters. Pypes Race Pro or Magnaflow ''straight through'' are what you want. The Pypes are like Magnaflow.

[RevTheory]

If you absolutely can not get the car to hook up then widening the LSA would probably work. It's a bandaid though. Fix the car rather than hamstringing the engine, at least in my little world.

[Old School]

What is the duration and lift on the cam?
What is the primary use of the car? Street? Strip?
Where did you want power to peak?
How far past peak power do you want the power band to extend?

[GOSFAST]

still learning about my new 540 engine. It has a custom ground cam by Chris Straub. Cam is cut on a 108 LSA. Just wondering how it would work if it was the same cam but cut on a 114? Like how would it run differently and what the difference in power would be. The engine is all new and i'm just in the tuning / learning process. The car went 10.65 at 127 at the track. It weighs around 3300 pounds and has 3.50 gears and it had a 4000 stall. I've bit the bullet and ordered some 4.11 gears but haven't installed them yet. I have a friend who has been racing BBC's for many years and he thinks i'm crazy to install a 108 LSA cam. I'd like to see this car running high 9's with the cam i have. I also got rid of the 4000 stall and went to a 3300 stall. Just trying to learn. thanks for any help.
Brian

Hi Brian, we've done a bunch of those pump-gas 540's with cams ranging from the 108* L/S to 114*, depending on the components! All made between 725 and 800 HP.

Thanks, Gary in N.Y.

P.S. Just my opinion here, but your intake isn't helping, neither are the "small" headers! All ours used the "Super-Victor's" and a 2.125" minimum pipes! Some had 2.250" pipes.

[prairiehotrodder]

Cam is 263 / 265 at .050 .700 lift , 108 LSA. Peak power feels really near 7000 but that just a guess. Car is street driven lots. I've been told by lots of guys that i need to get rid of the 3.50 gears but i really like them. If i could run high 9's and keep the 3.50 gears i would be really happy.

[wyrmrider]

what did chris say

[Alan Roehrich]

what did chris say

Was going to ask exactly that.

[greywolf]

there comes a point when DECENT overall street manners and a DECENT time slip on the racetrack cannot be used in the same sentence.
From a 3.50 to a 4.10 gear ratio change could net you about a 3 tenths improvement, assuming traction is not an issue, but,
dropping down from a 4000 stall to a 3300 stall will give some ET back.
Your engine, and what gofast added, your 3300 pound car should be able to run 9's... the overall tune up needs to be correct as well (timing and carb.)
My 3100 pounds pump gas small block does, but without much street manners.

[prairiehotrodder]

Chris said it would make 800 hp at 6700 rpm. According to my math its making about 550 RWHP.

[Alan Roehrich]

Chris said it would make 800 hp at 6700 rpm. According to my math its making about 550 RWHP.

Any calculations that produce actual reliably accurate HP numbers assume a relatively efficient car, set up to make the best possible use of the engine, with the engine in the proper state of tune.

In other words, those calculations assume your car has the correct gearing in the transmission and the rear end to make the best use of the power created, in the RPM band it is created in. If it's an automatic, it assumes a near ideal converter (read $800+). They also assume that the car is able to put all of that to the ground without wasting it in tire spin and other wasted motion, meaning it has a properly set up front and rear suspension, and correctly sized wheels and tires.

Any less than ideal conditions in any of those areas quickly render the vast majority of calculations relatively inaccurate at best, and often wildly inaccurate.

So, if you have a converter that isn't at least 90% efficient, and properly built to suit your engine, anything less than ideal gearing, and less than optimum traction, I'd really question what math could accurately determine the actual power that engine is making.

Most cars with an average built automatic give away around 20% (or more) of the power available at the flywheel. So at best, 800HP at the flywheel times 80% gives you 640HP at the rear wheels. Leaving you 90HP behind. Less than ideal gearing combined with a less than ideal torque converter will account for that. Leaving out suspension, tuning, and traction issues.

Cases like this are why I have reached the point where any serious performance engine I build with any sort of power promise is tested before delivery on a known reliable and accurate dyno. It protects the customer as much as it protects me. The cost of the dyno session is part of the quote for the engine, the dyno is not mine, and the customer is strongly encouraged to attend the test. I normally have the guy who does my cylinder heads and carburetors present to help, as his name is on the line same as mine, especially since he and I always agree on what is necessary to meet the customer's goals and desires before a quote is given.

[GOSFAST]

Chris said it would make 800 hp at 6700 rpm. According to my math its making about 550 RWHP.

That cam in a 540" would most likely peak nearer 6100/6200 in my opinion??

I would add this, one specific test I recall with those "335" heads and a similar intake made about 680 with a 260 @ .050 and .750" lift, peaked at 6100. Customer supplied all parts! The intake definitely "killed" this one!

(Add) I had a Camaro a while back, 468"/11:1 (S/P 7053 pistons), C/C BB iron heads, solid-roller, around your weight (3250/3300) running 9.80's all day long! Never missed a beat! You should be in the 9.0's now. 660 @ 3300 should put you at or under 9.80? The ride must also be "efficient" however!

Thanks, Gary in N.Y.

P.S. If your "guesstimate" of "550 RWHP" is correct you are seeing 660 (nominal) HP at the flywheel.