low lift flow on all out drag engines

General engine tech -- Drag Racing to Circle Track

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joespanova
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low lift flow on all out drag engines

Post by joespanova »

I just sent my heads out to a "reputable" shop. The task was , titanium intakes and copper alloy seats , latest and greatest "state of the art" valve job.
By THAT , it means 55 degree seats on intakes. Flow heads BEFORE and AFTER , on one pair of ports , just to indictate whatever the change is.
Surprisingly , the change or , AFTER , shows a loss of about 20 CFM from .100 up to .400 , (EX. 218@ .300 before and 194@ .300 after ) AND then from .500 up they start to out perform the BEFORE numbers by about 10 cfm. Ex. 318 @ .750 BEFORE and 327 @ .750 AFTER.
So ,what does this mean to the engines performance?
Cams are generally around .760 /.720 and used in a stick car that sees close to or at 9000.
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Re: low lift flow on all out drag engines

Post by Old School »

It means you will go faster. When you got folks that have won the engine masters contest trading low lift flow to better flow at higher lifts that should cause some serious thought processes.

Will everything be the same on your car except for the valves and valve job? Should be a very good way to compare different valve jobs.

Best of luck, hope you pick up some et and mph.
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Re: low lift flow on all out drag engines

Post by CGT »

BES did the heads if I remember correctly. Your likely gonna go faster. I wouldnt worry at all about the low lift flowz.....not one bit.
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Re: low lift flow on all out drag engines

Post by joespanova »

Old School wrote: Wed Nov 07, 2018 10:01 pm It means you will go faster. When you got folks that have won the engine masters contest trading low lift flow to better flow at higher lifts that should cause some serious thought processes.

Will everything be the same on your car except for the valves and valve job? Should be a very good way to compare different valve jobs.

Best of luck, hope you pick up some et and mph.
Yes , everything will be the same. I can't speak from experience , obviously , at least from the standpoint of what happens from the "trade off" but since low lift is part of the overall "curtain" I would imagine it has to have some bearing..........and besides , everything is supposed to be "state of the art". Which begs the question........what could they have done to diminish flow at ANY lift? In other words , is it not realistic to expect more flow at every point from a good valve job and greater seat angles? One of those seat angles has to bearing on low lift .......so , I'll call and ask.
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Re: low lift flow on all out drag engines

Post by zums »

In a very basic explanation, it restricts in/ex communication at overlap and increases the^p in the runner when the piston is headed in the right direction, that should equal more window dc and ve if your cam timing is right, my question is why did you change anything if you were so happy with your old combo, if it is just to do an acid test,{everything the same except seat angles} then thats good because that will teach you alot about how an engine breathes , but if you increased valve size, rocker ratio or duration,without doing the math, you might be back to the same valve window curve vs piston position as you were with the previous seat angle. Watch you jets, bleeds timing and plugs, they will point you,. It will be interesting either way for you
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Re: low lift flow on all out drag engines

Post by mag2555 »

If you motor was hitting / making its peak hp level due to the whole Intake tracts minimum amount of port area , that will not change !
If the head is now going to flow more air due to the valve job then you WILL be seing your peak torque and hp numbers come in at a lower rpm , that's it!!!!

Conversely if you where not reaching the air flow rate to tap out the Intake tracts minimum port area then you will see a higher level of torque and hp being made at a higher rpm.
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Re: low lift flow on all out drag engines

Post by blykins »

That's a pretty common result with a steeper seat angle.
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Re: low lift flow on all out drag engines

Post by Ron E »

Its better.
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Re: low lift flow on all out drag engines

Post by joespanova »

zums wrote: Thu Nov 08, 2018 6:40 am In a very basic explanation, it restricts in/ex communication at overlap and increases the^p in the runner when the piston is headed in the right direction, that should equal more window dc and ve if your cam timing is right, my question is why did you change anything if you were so happy with your old combo, if it is just to do an acid test,{everything the same except seat angles} then thats good because that will teach you alot about how an engine breathes , but if you increased valve size, rocker ratio or duration,without doing the math, you might be back to the same valve window curve vs piston position as you were with the previous seat angle. Watch you jets, bleeds timing and plugs, they will point you,. It will be interesting either way for you
Tom
To your question , I 've had problems with intake seats moving around ( concentricity ). Had steel valves , valve control etc etc heavy and springs not able to control , beating the seat/seats around.
So I switched to titanium for the obvious reasons , then you have the new seats they require and while we're in here lets do the "latest and greatest" valve job....AND , give me the before and after results.
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Re: low lift flow on all out drag engines

Post by CGT »

Joe. What camshaft are you running?
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Re: low lift flow on all out drag engines

Post by joespanova »

CGT wrote: Thu Nov 08, 2018 9:07 am Joe. What camshaft are you running?
This one is a Bullet grind..........I've several in my "arsenal". Its like .278/ .288 or .280/ .290 ish or something like that. I have to look. It is on a 109 though.
Everything you guys brought up was confirmed about 15 min. ago.......LOL
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Re: low lift flow on all out drag engines

Post by CGT »

joespanova wrote: Thu Nov 08, 2018 9:15 am
CGT wrote: Thu Nov 08, 2018 9:07 am Joe. What camshaft are you running?
This one is a Bullet grind..........I've several in my "arsenal". Its like .278/ .288 or .280/ .290 ish or something like that. I have to look. It is on a 109 though.
Everything you guys brought up was confirmed about 15 min. ago.......LOL
I would be very surprised if the car didn't pick up....and your fast already.
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Re: low lift flow on all out drag engines

Post by WeingartnerRacing »

Low lift means nothing except lift rules in the .480 range.
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Re: low lift flow on all out drag engines

Post by joespanova »

ok , THANKS TO ALL . I know at least a couple of you are porters.
This thread is complete..... 8)
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Re: low lift flow on all out drag engines

Post by gruntguru »

Another way to look at this.

Increasing high-lift flow at the detriment of low-lift flow means you need a cam that spends more time at high lifts. This is OK for two reasons:
1. Its an all-out race engine so idle quality, vacuum and low rpm performance are less important.
2. Reduced low-lift flow probably also means less flow in the reverse direction (which only happens at the "ends" of the duration ie low-lift and unfavourable revs)
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