128 my take, anybody see it like this ?

[ClassAct]

307 601 10.5CR.png


I reduced CR to 10.5 and i did the calculus based on my new input Peak Power RPM which match the previous DCR. Now the program output 108 LCA, but its also 108hp down

I like all the parameters for 12CR. I dont know is it doable using 305 iron heads, flat top pistons and .43lift roller cam with 196int duration at 050 inch lift.

Do you see something why the engine above would not perform as the TM predicts?

TM is evidently predicting just peak values. I’d give up 20 at the peak to gain that much at and a bit lower than peak torque. Again, I’m talking about high compression (high compression relative to what everyone says can be done) pump gas street driven stuff.

[juuhanaa]

Do you see something why the engine above would not perform as the TM predicts?

TM is evidently predicting just peak values. I’d give up 20 at the peak to gain that much at and a bit lower than peak torque. Again, I’m talking about high compression (high compression relative to what everyone says can be done) pump gas street driven stuff.

I get that. You can’t do that with a V8 cam.

Smaller cid 2 valve engine can be less limited about valve size, so its not all about spreading the lobes to gain top end. Now just a side note, when its a pump gas street driven 4 valve stuff, i tend to retard the exhaust and run up to 19bar cranking press without any valve pockets ---> tighter LSA...

Was 158cc big enough to make torq under the curve with 220cfm, or is there some other problem?

[steve cowan]

If you are willing to learn to tune (we never stop learning do we??) you can easily get a “tight” LSA very driveable.

I think it's important to think in terms of overlap rather than LSA.
We know that the same LSA number could be very different in terms of EVC and IVO.
And I agree 100% with the carb tuning.
This is why I'm comfortable with 72 degrees of seat to seat overlap whereas I know of those that found it unfriendly on the street. That was 288/294 on a 110 (106 ICL).

Kevin,
Are you looking at degrees of overlap # because of the duration you want to use? I am trying to work out what the advantage is with more overlap/ low lift flow .

[steve cowan]

355" SBC
10:1 with ported 492 heads, Performer RPM, and Holley 600.

RPM---TQ--BHP
3200--436--266
3400--443--287
3600--445--305
3800--444--321
4000--443--337
4200--440--352
4400--440--368
4600--441--386
4800--441--403
5000--432--411
5200--422--418
5400--412--423
5600--400--426

The cam is 216/220, on a 112 LSA, and 108 ICL

Its almost like the right engine build, with a good induction package will dictate power curve characteristics more so than what lsa you have.

This !!!!!

[skinny z]

I think it's important to think in terms of overlap rather than LSA.
We know that the same LSA number could be very different in terms of EVC and IVO.
And I agree 100% with the carb tuning.
This is why I'm comfortable with 72 degrees of seat to seat overlap whereas I know of those that found it unfriendly on the street. That was 288/294 on a 110 (106 ICL).

Kevin,
Are you looking at degrees of overlap # because of the duration you want to use? I am trying to work out what the advantage is with more overlap/ low lift flow .

Hey Steve
I'm interested in a methodology for selecting a cam that was published several years ago. It falls inline with the 128 rule and TM. You can guess who may have published the article.
I'm going to assume it was presented so the average guy, without years of experience and experimentation (I'm certainly average but do have some experience and experimentation) can pick a cam to give the results the process is directed at. That would be maximum torque.
In it, it states that the order of importance in the selection process is (and I'll say upfront that the application is probably as finite as the 128 rule and TM):
Overlap,
LSA,
ICL,
Lift,
Duration.
Obviously items one and two determine item five. Symmetrical lobes too I would think.
I would venture a guess that this is done as the average guy doesn't have the means to determine the best IVO, IVC, EVO and EVC. I know this is how the pros might go about it.
So, having said that, I'm zeroed in on a overlap value that's worked well. 71°. And it worked well even though the engine wasn't optimized to utilize it to it's fullest. Namely the exhaust system.
How do I know? Testing and comparing. The last engine to use that cam was the strongest engine I'd ever assembled. it was also tame as a kitten on the street and knocked down some decent fuel economy. Win, win, win.
So, if I stick with an overlap of 71° (my choice) and use 128 to determine the LSA, which would be 108 in this case (and I'm right in the wheelhouse of the 128 rule spec wise) then I end up with something like 287/287/108/104. Lift would suit the heads in question which peak at about .550". (Decent valve job, 2.02"/1.6"). Lobe intensity is still very much a question mark. I could be anywhere between 287 with 242@.050" and 287 with 228@.050".
Projections are peak HP at 6300 and would require 250 CFM and a 179cc port (I've 255 without the intake and an as yet unmeasured port that started as 170cc before some basic porting). TM specs.
Right or wrong, it looks to fit perfectly into engine plan number 1. That being a strip specific car with open headers, the right converter (might have it already) and the right gears (might have that too).

So, to answer your question, I'm looking at those degrees of overlap because it suited what I was after before and should continue to do so.
As for low lift flow, if the exhaust is up to snuff, and I would think a tuned length open header would be, then that low lift flow should be enhanced. Using that exhaust induced induction has always been lacking in my builds and I'm really keen to see how that plays out. 71 degrees of overlap would work well. But that low lift flow I think is more the result of the port and valve job.
Thoughts?

[Geoff2]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

[skinny z]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

That's fair comment Geoff. And yeah, it's obvious I'm on board too.
That said though, we have a very knowledgeable individual as our resident cam grinder here at Speed-Talk. I wouldn't be one to argue with his advice either.
And you know, in all reality, at my power levels, and I'm just a guy that's going for another personal best (I've been quicker with each iteration of the old 350/352/355 and now 357) there may not be a lot to pick and choose between any cam spec that's designed for me.
But, even though my goals are modest, who's to say that I can't look for that extra little bit that comes from a slightly better spec? Or optimum quench? Or compression ratio?

[Tom68]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

Advice comes with natural bias (one man's thumper idle is another's nightmare) do your own research including David's tests and make a choice based on your needs, budget and bias restraints.

[skinny z]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

Advice comes with natural bias (one man's thumper idle is another's nightmare) do your own research including David's tests and make a choice based on your needs, budget and bias restraints.

Well said Tom.

[bob460]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

Tested 19,200 cams.............i call BS!!

Testing 1 cam a day, 7 days a week, 365 days a year, for "50 YEARS" still dosn't get to 19,200 cams. ........

[Tom68]

Testing 1 cam a day, 7 days a week, 365 days a year, for "50 YEARS" still dosn't get to 19,200 cams. ........

Several change a day on a Quad cam.

[steve cowan]

I think it's important to think in terms of overlap rather than LSA.
We know that the same LSA number could be very different in terms of EVC and IVO.
And I agree 100% with the carb tuning.
This is why I'm comfortable with 72 degrees of seat to seat overlap whereas I know of those that found it unfriendly on the street. That was 288/294 on a 110 (106 ICL).

Kevin,
Are you looking at degrees of overlap # because of the duration you want to use? I am trying to work out what the advantage is with more overlap/ low lift flow .

Hey Steve
I'm interested in a methodology for selecting a cam that was published several years ago. It falls inline with the 128 rule and TM. You can guess who may have published the article.
I'm going to assume it was presented so the average guy, without years of experience and experimentation (I'm certainly average but do have some experience and experimentation) can pick a cam to give the results the process is directed at. That would be maximum torque.
In it, it states that the order of importance in the selection process is (and I'll say upfront that the application is probably as finite as the 128 rule and TM):
Overlap,
LSA,
ICL,
Lift,
Duration.
Obviously items one and two determine item five. Symmetrical lobes too I would think.
I would venture a guess that this is done as the average guy doesn't have the means to determine the best IVO, IVC, EVO and EVC. I know this is how the pros might go about it.
So, having said that, I'm zeroed in on a overlap value that's worked well. 71°. And it worked well even though the engine wasn't optimized to utilize it to it's fullest. Namely the exhaust system.
How do I know? Testing and comparing. The last engine to use that cam was the strongest engine I'd ever assembled. it was also tame as a kitten on the street and knocked down some decent fuel economy. Win, win, win.
So, if I stick with an overlap of 71° (my choice) and use 128 to determine the LSA, which would be 108 in this case (and I'm right in the wheelhouse of the 128 rule spec wise) then I end up with something like 287/287/108/104. Lift would suit the heads in question which peak at about .550". (Decent valve job, 2.02"/1.6"). Lobe intensity is still very much a question mark. I could be anywhere between 287 with 242@.050" and 287 with 228@.050".
Projections are peak HP at 6300 and would require 250 CFM and a 179cc port (I've 255 without the intake and an as yet unmeasured port that started as 170cc before some basic porting). TM specs.
Right or wrong, it looks to fit perfectly into engine plan number 1. That being a strip specific car with open headers, the right converter (might have it already) and the right gears (might have that too).

So, to answer your question, I'm looking at those degrees of overlap because it suited what I was after before and should continue to do so.
As for low lift flow, if the exhaust is up to snuff, and I would think a tuned length open header would be, then that low lift flow should be enhanced. Using that exhaust induced induction has always been lacking in my builds and I'm really keen to see how that plays out. 71 degrees of overlap would work well. But that low lift flow I think is more the result of the port and valve job.
Thoughts?

Seems overlap/ LLF seem to go hand in hand so to speak,I am not here to be critical of anyone or what they do.
Larry meaux has done plenty of dyno testing showing high low lift flow reduces torque to peak but shows an increase in peak hp,i find that interesting.
When you are looking at overlap that you want to run for your application do you look at IVC,EVO events for your engine size,valve size, rpm ,etc.
I know a guy ready to dyno a 355 sbc who is testing 2 x different hydraulic rollers with a big change in duration, I am looking forward to his results and see if cams show a huge tq/ hp change over the curve.
Me personally doubt there will be 10-15 hp between the two.

[Super_Stock]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

Tested 19,200 cams.............i call BS!!

Testing 1 cam a day, 7 days a week, 365 days a year, for "50 YEARS" still dosn't get to 19,200 cams. ........

Well the guy does post here, he has his own sub section, so maybe someone could ask him how many cams and how that maths works out?

[hoffman900]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

Tested 19,200 cams.............i call BS!!

Testing 1 cam a day, 7 days a week, 365 days a year, for "50 YEARS" still dosn't get to 19,200 cams. ........

Be careful, he might make a Youtube video about you and all his fan club in the comments will eat you alive.

[Stan Weiss]

D. Vizard claims in his SBC book that he has tested well over 10,000 cam combinations in 40 yrs of cam testing. In another publication, he says the number 19,200 cams.
I have no reason to doubt either claim. Has anybody tested more?
I know this much: I will take his advice until I find someone who has tested more...

I would be interested in the source of that information.

I have talked with David about this and what I was told was, over 10,000 dyno pulls testing cams. Each cam was tested with different phasing and other changes in each test engine. There were 3 test engines, each was different from each other. It has been a while seen we talked about this but I seem to remember they did a good number of tests per day.

Stan