low lift flow on all out drag engines

General engine tech -- Drag Racing to Circle Track

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Re: low lift flow on all out drag engines

Post by Carnut1 »

randy331 wrote: Fri Nov 16, 2018 9:42 pm
Carnut1 wrote: Fri Nov 16, 2018 2:56 am With more low lift flow the engine sees a larger overlap triangle so the Lca needs to be spread. The problem with that is if every other cam point is right for the combo you would change those points.
RIGHT !!
EXACTLY !!

That's why I'm so glad that's what you guys did in your cylinder head tests !!

I don't remember now, but how many different LSA/CAMS did you guys test with the BIG difference in flowZ ?

Randy
Due to issues we only got to test one tiny ft cam. Thanks, Charlie
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Re: low lift flow on all out drag engines

Post by Carnut1 »

MadBill wrote: Sat Nov 17, 2018 12:29 am
Carnut1 wrote: Fri Nov 16, 2018 2:56 am With more low lift flow the engine sees a larger overlap triangle so the Lca needs to be spread. The problem with that is if every other cam point is right for the combo you would change those points.
Since the increased LLF would likely also be a factor re optimum IVC timing, perhaps the intake lobe should be say 4-6°shorter but on the same CL. :-k
Bill, I would think that would work for getting the hp back to where it was but what should be done to make more? Thanks, Charlie
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Re: low lift flow on all out drag engines

Post by swampbuggy »

I have read all of this thread and the one remark that sticks in my mine is, (cylinder heads have changed as valve train parts have got better). I believe it is the other way around ??? Mark H.
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Re: low lift flow on all out drag engines

Post by groberts101 »

Carnut1 wrote: Sat Nov 17, 2018 6:30 am
MadBill wrote: Sat Nov 17, 2018 12:29 am
Carnut1 wrote: Fri Nov 16, 2018 2:56 am With more low lift flow the engine sees a larger overlap triangle so the Lca needs to be spread. The problem with that is if every other cam point is right for the combo you would change those points.
Since the increased LLF would likely also be a factor re optimum IVC timing, perhaps the intake lobe should be say 4-6°shorter but on the same CL. :-k
Bill, I would think that would work for getting the hp back to where it was but what should be done to make more? Thanks, Charlie
It still takes time for fuel mass to start flowing into the cylinder so wouldn't it make sense that improved low lift flow could allow shorter cam timing?

Look at the fuel flowing into this cylinder right off the seat. It is not insignificant and.. IF.. the induction pulse lengths are properly tuned for the peak powerband.. could it not become advantageous to a drag only motor?

https://www.youtube.com/watch?v=UvmBLqjaZxY
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Re: low lift flow on all out drag engines

Post by Carnut1 »

Finding the right balance if scavenging to start the intake phase, not drawing intake charge out the exhaust lowering ve and increasing fuel consumption will be a tough challenge. I actually think the steeper seats help this situation on high rpm engines. Thanks, Charlie
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Re: low lift flow on all out drag engines

Post by randy331 »

Carnut1 wrote: Sat Nov 17, 2018 6:26 am
randy331 wrote: Fri Nov 16, 2018 9:42 pm
Carnut1 wrote: Fri Nov 16, 2018 2:56 am With more low lift flow the engine sees a larger overlap triangle so the Lca needs to be spread. The problem with that is if every other cam point is right for the combo you would change those points.
RIGHT !!
EXACTLY !!

That's why I'm so glad that's what you guys did in your cylinder head tests !!

I don't remember now, but how many different LSA/CAMS did you guys test with the BIG difference in flowZ ?

Randy
Due to issues we only got to test one tiny ft cam. Thanks, Charlie
I guess your cylinder head tests are flawed then,... since you didn't change cams to match the flowZ ?

Randy
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Re: low lift flow on all out drag engines

Post by Carnut1 »

DV did change the valve job. I had a typical 45 degree seat. He changed the degrees and added radius. Which dropped high lift flow and gained llf. On the super short cam that may have helped. I developed those ports without llf consideration since they are so small. Thanks, Charlie
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Re: low lift flow on all out drag engines

Post by CGT »

Bla bla bla. I think Paul basically ended his own thread awhile back. We will all be curious to see how it plays out. Remember though, in a car that runs real good and ET's like his....it will take a decent power spike or loss to show up......hope it works out for him.

I would say start a new llf hlf thread but we all know how that will turn out.
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Re: low lift flow on all out drag engines

Post by randy331 »

Carnut1 wrote: Sat Nov 17, 2018 10:23 am DV did change the valve job. I had a typical 45 degree seat. He changed the degrees and added radius. Which dropped high lift flow and gained llf. On the super short cam that may have helped. I developed those ports without llf consideration since they are so small. Thanks, Charlie
The question was, is your testing flawed because no cam change was made for the different heads ?

You've stated before that if there is a flow change the ideal LSA - ICL etc will be different, and you have questioned the results of others who have changed heads without a cam change.....

So based on your own belief and previous statements about flow vs cams, is your tests flawed ?

Randy
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Re: low lift flow on all out drag engines

Post by Carnut1 »

Not my dyno test. I was just a helper. I would much rather have tested with a nasty hyd roller cam then change vj to radius and check results. Thanks, Charlie
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Re: low lift flow on all out drag engines

Post by Steve.k »

IMG_3161.PNG
IMG_3162.PNG
Here is two flow sheets on the same cleveland head. Note low lift increase in flow. The heads heavily massaged in 2nd test and bolted to car with no other modifications once so ever. Car picked up 1.5 tenths in 1/8. Although we needed to bump shift rpm 200 to get it there. Would nose over before.
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Re: low lift flow on all out drag engines

Post by David Vizard »

289nate wrote: Fri Nov 16, 2018 3:19 am Charlie, I would think the person designing the cam would want to be in control of the aspects of the engine regarding intake and exhaust sides for the specified displacement, budget, and rpm range in an all out effort. Otherwise, they are designing a cam around what you have and not based on what they can do.
289nate,

The big numbers I get for my street engines are because the cam is speced to suit the engine not the cam grinder!
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Re: low lift flow on all out drag engines

Post by randy331 »

Carnut1 wrote: Sat Nov 17, 2018 10:23 am DV did change the valve job. I had a typical 45 degree seat. He changed the degrees and added radius. Which dropped high lift flow and gained llf. On the super short cam that may have helped. I developed those ports without llf consideration since they are so small. Thanks, Charlie
Guess my question will remain un-answered ?

Randy
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Re: low lift flow on all out drag engines

Post by Carnut1 »

I am not 100% sure what you are getting at. Do you think the differences in flow between John's heads and DV/Charlie head warrant a different cam profile? Maybe DV can post a graph of both cfm and we can go from there. Just from the valve job I think John's needed a slightly smaller lc to have the same overlap as DV/ Charlie head.
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Re: low lift flow on all out drag engines

Post by David Vizard »

randy331 wrote: Sat Nov 17, 2018 11:03 pm
Carnut1 wrote: Sat Nov 17, 2018 10:23 am DV did change the valve job. I had a typical 45 degree seat. He changed the degrees and added radius. Which dropped high lift flow and gained llf. On the super short cam that may have helped. I developed those ports without llf consideration since they are so small. Thanks, Charlie
Guess my question will remain un-answered ?

Randy

Randy,
I can address this on the 2 heads are better than one thread.
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