Advantages of advancing the cam on a street engine?

[E.Roy]

It would have been interesting if they had followed up the first test with a higher ratio intake rocker, tested intake center-line for best position and then tried a small single plane.

Or adjusted the intake centerline to the 500ftlb level? Just messing with you E.roy!

LOL, zing! It's gotta be that easy right?

[F-BIRD'88]

Build a 383. You will make a ton of real torque using ported big valve vortec heads
on a 10.50:1 383 SBC. If it falls short of 500 ft lbs it will not be a lot short.

You are dreaming using a 350 cid sbc.

Get Mike Jones ( CamKing) to help you with the cam for the 383.

[GARY C]

It would have been interesting if they had followed up the first test with a higher ratio intake rocker, tested intake center-line for best position and then tried a small single plane.

Or adjusted the intake centerline to the 500ftlb level? Just messing with you E.roy!

I'm suppose to be the sarcastic one here... Your stealing my gig.

It would be interesting to see what could be gained through optimizing the one combo, I don't think it would be big power but a cool test none the less, plus it would show how it shifts the power band.

I think this is the same engine with a single plane but still a 1.5 rocker. https://www.youtube.com/watch?v=TvQHgt-tF7Y

It looks like they are with in a cpl of numbers of each other but the peaks are shifted up 250/300 rpm.

The 1.6 was worth 17 hp and no added tq.

[E.Roy]

It would have been interesting if they had followed up the first test with a higher ratio intake rocker, tested intake center-line for best position and then tried a small single plane.

Or adjusted the intake centerline to the 500ftlb level? Just messing with you E.roy!

I'm suppose to be the sarcastic one here... Your stealing my gig.

It would be interesting to see what could be gained through optimizing the one combo, I don't think it would be big power but a cool test none the less, plus it would show how it shifts the power band.

I think this is the same engine with a single plane but still a 1.5 rocker. https://www.youtube.com/watch?v=TvQHgt-tF7Y

It looks like they are with in a cpl of numbers of each other but the peaks are shifted up 250/300 rpm.

The 1.6 was worth 17 hp and no added tq.

Thanks for pointing out that episode was the same engine with the larger 242/250 cam they ended with in ep19.

[gottago]

In regard the original sledgehammer article, it says..

We had frequent PHR contributor David Vizard spec our cam, and he selected a custom COMP Cams hydraulic roller single-pattern grind, with 224 degrees duration (at .050) on the intake and exhaust lobes, and 0.352 inch lobe lift. David specified a relatively tight 108-degree lobe separation angle, which would serve to bring the torque on hard, and preserve cylinder pressure compared to a similar cam with a wider spread.

This is pretty well the cam that DV 's cam selection process picks if your compression and valve size is right for it. So I suspect the article is a bit misleading in that the compression was chosen beforehand in order to run a DV specked cam on that lsa. The intake centerline would be as good as you could do for tq and hp at the compression level and fuel chosen. Advance or retard would gain zip imo unless you were willing to alter compression. Not something you do as an after thought, it has to be part of the original plan when looking to max out a specific rpm band. I think DV's cam is optimized to the point where it gets close to holding too much pressure for pump gas if advanced especially if only to gain a 100 rpm or so drop where max torque occurs. . Hard to improve on that one the way it is.

The 400 sbc is easy to get big midrange with but the 383 can deliver pretty good too. Makes the difference where and how big the midrange torque can be on a steetable daily driver.

[GARY C]

In regard the original sledgehammer article, it says..

We had frequent PHR contributor David Vizard spec our cam, and he selected a custom COMP Cams hydraulic roller single-pattern grind, with 224 degrees duration (at .050) on the intake and exhaust lobes, and 0.352 inch lobe lift. David specified a relatively tight 108-degree lobe separation angle, which would serve to bring the torque on hard, and preserve cylinder pressure compared to a similar cam with a wider spread.

This is pretty well the cam that DV 's cam selection process picks if your compression and valve size is right for it. So I suspect the article is a bit misleading in that the compression was chosen beforehand in order to run a DV specked cam on that lsa. The intake centerline would be as good as you could do for tq and hp at the compression level and fuel chosen. Advance or retard would gain zip imo unless you were willing to alter compression. Not something you do as an after thought, it has to be part of the original plan when looking to max out a specific rpm band. I think DV's cam is optimized to the point where it gets close to holding too much pressure for pump gas if advanced especially if only to gain a 100 rpm or so drop where max torque occurs. . Hard to improve on that one the way it is.

The 400 sbc is easy to get big midrange with but the 383 can deliver pretty good too. Makes the difference where and how big the midrange torque can be on a steetable daily driver.

Knowing the compression ahead of time would be needed to make a good cam choice wouldn't it?

[gottago]

Yep, and knowing the cam you wanted to use for the desired power range would be good to know before setting the compression wouldn't it? Takes two to tango properly.

In regard the thread tittle, desired usage changes everything; would someone just looking for big midrange power #1 priority choose to start with the same compression and end up on the same lsa as DV cam in the article? Not likely.. imo If you start with the wrong cam for your particular combo and power requirements to begin with, advancing can help but only so much.

Better off back to the drawing board.

[GARY C]

Yep, and knowing the cam you wanted to use for the desired power range would be good to know before setting the compression wouldn't it? Takes two to tango properly.

In regard the thread tittle, desired usage changes everything; would someone just looking for big midrange power #1 priority choose to start with the same compression and end up on the same lsa as DV cam in the article? Not likely.. imo If you start with the wrong cam for your particular combo and power requirements to begin with, advancing can help but only so much.

Better off back to the drawing board.

Normally you would start with a parts list needed for the goal your trying to achieve, part of making that list would be to know what compression is needed. From there you could pick the cam.

I can tell you fisrt hand that the engine was not built around the cam specs and when they contacted DV with the project engine info and he specd the cam the conversation went as the article says.

[gottago]

OK if you say so. That cam was optimal for that combos desired use and at that compression. Just seems there was more coordination in the choices than the wording would lead to believe. Even shaved the heads a bit to tailor the compression. All coincidental, no prior exploratory phone calls ? But I guess am a little jaded on anything I read now a days..

[GARY C]

OK if you say so. That cam was optimal for that combos desired use and at that compression. Just seems there was more coordination in the choices than the wording would lead to believe. Even shaved the heads a bit to tailor the compression. All coincidental, no prior exploratory phone calls ? But I guess am a little jaded on anything I read now a days..

The tech writes are not given enough budget to do a custom engine but there are plenty of SBC part out there that building a 10.1 to 10.5 compression is not difficult and it is the compression that most shoot for on this type of build.

Base on the amount of info for this build, it has been done many times, by many people, most believe that Speed O Motives dyno was reading about 20 horse higher than what this build should produce.

[randy331]

That cam was optimal for that combos desired use and at that compression.

Who says, and how would you know if you didn't try a different one ?

Without trying anything else you wouldn't.

Randy

[GARY C]

That cam was optimal for that combos desired use and at that compression.

Who says, and how would you know if you didn't try a different one ?

Without trying anything else you wouldn't.

Randy

It was apparently optimal enough for their goal that the other 2 guys that brought cams left without trying them.

[gottago]

That cam was optimal for that combos desired use and at that compression.
Who says, and how would you know if you didn't try a different one ?

Without trying anything else you wouldn't.

Randy

That's true, but read through hundreds of similar combos with their dyno results. This was as good as most any 350 street combo with a real midrange on almost any dyno sheet. (no exotic parts) Perhaps that dyno was reading off then this gets a bit more mundane and could possibly be improved on. As said, don't hold too much faith in magazine articles, just questioning the big numbers and how they got there. Doesn't usually happen without a plan and build sheet from beginning to end. Everything has to work together perfectly to get these sort of results.

[GARY C]

That cam was optimal for that combos desired use and at that compression.
Who says, and how would you know if you didn't try a different one ?

Without trying anything else you wouldn't.

Randy

That's true, but read through hundreds of similar combos with their dyno results. This was as good as most any 350 street combo with a real midrange on almost any dyno sheet. (no exotic parts) Perhaps that dyno was reading off then this gets a bit more mundane and could possibly be improved on. As said, don't hold too much faith in magazine articles, just questioning the big numbers and how they got there. Doesn't usually happen without a plan and build sheet from beginning to end.

Yes, 420/430 tq and 420 horse is probably more common and about where DV thought it would fall based on the parts, it was meant to be a budget build not a big dollar championship engine. If I recall without rereading it, it was suppose to exceed 400 horse on the cheep!

[E.Roy]

That cam was optimal for that combos desired use and at that compression.
Who says, and how would you know if you didn't try a different one ?

Without trying anything else you wouldn't.

Randy

That's true, but read through hundreds of similar combos with their dyno results. This was as good as most any 350 street combo with a real midrange on almost any dyno sheet. (no exotic parts) Perhaps that dyno was reading off then this gets a bit more mundane and could possibly be improved on. As said, don't hold too much faith in magazine articles, just questioning the big numbers and how they got there. Doesn't usually happen without a plan and build sheet from beginning to end.

Yes, 420/430 tq and 420 horse is probably more common and about where DV thought it would fall based on the parts, it was meant to be a budget build not a big dollar championship engine. If I recall without rereading it, it was suppose to exceed 400 horse on the cheep!

You're correct, they were shooting for over 400hp (dont think they were concerned about torque).
Vizard spec'd the cam to accomplish 400hp on the motor spec, and they even adjusted the engine after by jumping from 1.5 to 1.6 rockers, because they worried it wouldn't top 400hp with Vizard's spec. Talk about crushing your goal with 10% more hp, if the dyno wasn't optimistic.