Cam recomendation?(Rough estimate)

[Illahe]

That is the bottom line hear. I want as stout a piece as i can build for my sons' Duster, but the off idle driving experience takes presence. Dwayne, I think you commented on the effects of total overlap, ( in another forum) is independent of engine size pretty much? So i am hoping to end up with a cam that can walk away from a stop sign with 3.73 gears and allow clutch engagement by about 1500 rpm without bad manners.

Interesting. "Dwayne, I think you commented on the effects of total overlap, ( in another forum) is independent of engine size pretty much?"

Isn't overlap having a proportional effect on cylinder fill? It would seem to me, that a larger cubic inch engine, or long stroke combination would need a proper "window" to fill the cylinder effectively, especially with a flat tappet's lobe limitation. Perhaps the roller profiles help get more efficiency out of a shorter duration due to their higher @.200" duration.

It would be interesting to get an education in the science behind the "short (or, reasonable) duration hypothesis." The information would make for a great thread!

 

[Illahe]

The 408 i built with the dyno numbers of 503 hp at 5700 and 518 tq at 4600 had flat tops, 10.5 compression, and iron 318b heads. I got away with that compression by using a slow ign curve , and a loose 4000 converter. The motor didn,t need more than 28 total lead, 16 initial and another 12 in by 4000 rpm. We started at 32 total on the dyno, but it just made more power at 28, running 93 bp gasoline. A part of the equation was the cam, 235/249/107 in at 105.

Did you install 2.02 or 2.05 valves in the 318B’s?

 

[Mean416]

Any of the larger cam recommendations here will need a matching converter. Proceed accordingly

 

[gregsdart]

Did you install 2.02 or 2.05 valves in the 318B’s?

2.02/1.60 valves, bowl ported only, flowed 270!

 

[gregsdart]

Interesting. "Dwayne, I think you commented on the effects of total overlap, ( in another forum) is independent of engine size pretty much?"

Isn't overlap having a proportional effect on cylinder fill? It would seem to me, that a larger cubic inch engine, or long stroke combination would need a proper "window" to fill the cylinder effectively, especially with a flat tappet's lobe limit

ation. Perhaps the roller profiles help get more efficiency out of a shorter duration due to their higher @.200" duration.

It would be interesting to get an education in the science behind the "short (or, reasonable) duration hypothesis." The information would make for a great thread!

I think the point was made that idle/ off idle quality was similar, but My guess is you are correct, window size of overlap may depend on engine size. However, look at the gen 3 hemis and LS cam overlap is much lower across the board because both have very superior head flow characteristics.

 

[PRH]

I don’t recall making the statement about cubes vs overlap, but I might have, depending on the context.

To “generalize”, I guess I’d look at that relationship of a cubes/rpm correlation that, the lower the rpm, the less the larger displacement helps.
This is in relation to low speed/part throttle operation.

However, All else being equal, the larger engine will get “up on the cam” at a lower rpm.

Greg’s scenario is one where after listening to the “tone” of the wants/desires of the build, I’d be focusing on the aspects of the cam that lean towards better “manners” as opposed to things the combo might respond to if seeking “more power”.

 

[Illahe]

I don’t recall making the statement about cubes vs overlap, but I might have, depending on the context.

To “generalize”, I guess I’d look at that relationship of a cubes/rpm correlation that, the lower the rpm, the less the larger displacement helps.
This is in relation to low speed/part throttle operation.

However, All else being equal, the larger engine will get “up on the cam” at a lower rpm.

Greg’s scenario is one where after listening to the “tone” of the wants/desires of the build, I’d be focusing on the aspects of the cam that lean towards better “manners” as opposed to things the combo might respond to if seeking “more power”.

Thanks,

There have been a lot of mid 230~ durations thrown around on the forum lately, and the 500/500 #'s gregsdart had put up prompted me to "re-think" engine combinations.

Also: I appreciated the information you posted about achieving 250 cfm from LA iron cylinder heads without extensive modifications.

 

[PRH]

Thanks, While the mods to the J heads were not “extensive”, they were done by someone familiar with what it takes to achieve those results.

I’m going to say a novice would be unlikely to be able to duplicate that work(especially w/o flow testing)…….Primarily the reworking of the SSR.

WRT the factory sb heads, my experience is that the X heads are easier to get past the 250 mark than any of the other OE castings.

 

[Illahe]

Thanks, While the mods to the J heads were not “extensive”, they were done by someone familiar with what it takes to achieve those results.

I’m going to say duplicating that work by a novice would be unlikely.
Primarily the reworking of the SSR.

I only worked one short turn on a set of iron heads and I hit water when I laid it back.

Never again…

 

[PRH]

Greg’s Thumpr cam had 87* overlap at the seat.
It’s kind of a lot if you’re concerned with driveability.

One of the old school “ruff idle” champs was the MP 292 cam……… 76* overlap.

 

[PRH]

I only worked one short turn on a set of iron heads and I hit water when I laid it back.

Never again…

Since we’re a bit off topic anyway……

I had a scrap 596 head here to use as an R&D piece for some FAST heads I was doing.
I put in a 2.05 or 2.08 valve(don’t remember which), filled a pushrod tunnel and started carving away.
After the bulk of reshaping had been done, I started in on the SSR.
I kept laying it back, the numbers kept going up.
I was at about 280, very little drop off at high lifts.
Success!! R&D over.
Shortly after that I get in a set of used, already ported 915’s with 2.02’s.
SSR are very inconsistent from port to port(typical), and they nose over pretty hard much past 245.
I compare by feel the R&D SSR to these and the R&D head is laid back waaaay more.
So, I start in on laying one back.
Barely even started in and a dimple appears.
I’m shocked, since it’s laid back way way less than the R&D head.
So I’m like, okay it’s core shift……. But on which head?

I dive into attacking the SSR on the neighboring port on the R&D head.
I don’t get it anywhere near the one that went 280, and blow right thru the floor.
The one that went 280 just happened to have a bunch of extra meat on the SSR of the R&D port.

Ever since then, I tread a lot lighter on the ssr’s of the factory sbm castings.

 

[TXOval]

My 416 has a Comp Hyd Roller, 280/288 duration, 224/230 at .050.

110LC, .537 lift with 1.5 rockers

Comp does not make this cam anymore but it performs like you are looking for.

I originally ran it with 3.73 rear gears but switched to 3.23 and I like it better

 

[SixPaksRule]

Many - no make that most - a street driven stoker engine is overcammed...

 

[Newbomb Turk]

Many - no make that most - a street driven stoker engine is overcammed...

Thats not what my testing shows.

 

[PRH]

My experience is that often times what the customer wants for power, and how the car will be used…….. can pose a contradiction in cam selection direction.
Where the desired HP would require a bigger cam than what the usage criteria would dictate.

 

[gregsdart]

My experience is that often times what the customer wants for power, and how the car will be used…….. can pose a contradiction in cam selection direction.
Where the desired HP would require a bigger cam than what the usage criteria would dictate.

Bingo! That is the exact issue I want to avoid hear. There is no loose converter to coverup for too much cam. Case in point. 1970, i get my first decent v8 car, a stock 1968 coronet with a 383, fourspeed, and 3.23 gears. I stopped at a stopsign, let the clutch out, and it was sluggish but walked away from the corner cleanly. Then i realized i WAS IN THIRD GEAR! My first thought was, damn, i love this car!
So that may explain why i want a docile cam, not a max hp type street cam. The performance goal may end up in the mid to high twelves, since we will optimize exhaust and have 3.73 gears behind a 408. But that is ok.

 

[PRH]

For cars that will rarely(if ever) see the track, I try and focus on finding a decent balance of street performance and driveability, and not pay much attention to what the HP will be.

On the flip side, if the customer thinks they want 500hp, and the combo sounds like something that would be better with a 400hp cam…….. then there needs to be a meeting of the minds, so everyone is on the same page.

“Usually”, making the power isn’t that hard.
Making the power, and have the engine combo be something the customer can live with is often the challenge.

It’s easier when the car will see regular track use, and there’s an et target.
Then you build for the target, and if that’s not very street friendly, then….. oh well.

 

[TXOval]

In my case I bought the cam for my original plan, which was a cam, head, intake swap on my supposedly recently rebuilt 340.

Once the existing cam was pulled and the bearings were crap…this led to further investigation, which led to rebuilding the engine and going with a forged 4” kit. I stuck with the 280/288 cam which is fairly mild for a 416. Car is very driver friendly and can still blow the tires off at will…I just reach max hp at 5200 rpms

 

[Demonx2]

Bingo! That is the exact issue I want to avoid hear. There is no loose converter to coverup for too much cam. Case in point. 1970, i get my first decent v8 car, a stock 1968 coronet with a 383, fourspeed, and 3.23 gears. I stopped at a stopsign, let the clutch out, and it was sluggish but walked away from the corner cleanly. Then i realized i WAS IN THIRD GEAR! My first thought was, damn, i love this car!
So that may explain why i want a docile cam, not a max hp type street cam. The performance goal may end up in the mid to high twelves, since we will optimize exhaust and have 3.73 gears behind a 408. But that is ok.

"...mid to high 12's"? You'll have a hard time keeping a 408 that slow. These things make big-boy torque down low - and you can decide whichever cam you want. They'll still do it.

But I will say that my 408 with a 251/255@.050 SFT is pretty rowdy if I never wanted to take it to the track. I'd still love it but it may be a bit much for some that don't want a really "rambunctious" engine. With the torque it makes, camming it down would only increase an already stout-feeling package.

 

[gregsdart]

In my case I bought the cam for my original plan, which was a cam, head, intake swap on my supposedly recently rebuilt 340.

Once the existing cam was pulled and the bearing were crap…this led to further investigation, which led to rebuilding the engine and going with a forged 4” kit. I stuck with the 280/288 cam which is fairly mild for a 416. Car is very driver friendly and can still blow the tires off at will…I just reach max hp at 5200 rpms

That cam sounds pretty close to the characteristics we want, balls out torque from 1500 on, and coming up with heads, intake , carb, etc that will stretch the hp curve as well as possible. Maybe ending with a package that wants a shift point of 5800? TX, what was the LSA of that cam?

 

[TXOval]

That cam sounds pretty close to the characteristics we want, balls out torque from 1500 on, and coming up with heads, intake , carb, etc that will stretch the hp curve as well as possible. Maybe ending with a package that wants a shift point of 5800? TX, what was the LSA of that cam?

110LSA

I have the 190 CNC ported Speedmaster heads (2.02 and 1.8)

Dual plane air gap intake, Holley super sniper. I originally used TTI headers but switched to Sanderson DD9’s for more room in my early A-body.

Chassis dyno, 400hp at wheels, but at 5200-5400rpm. I imagine the header change hurt me up top.