I hoped it was a more scientific test, because was only about "seat of the pans" dyno.
On a good stock running ford 302, that had heads removed for gasket check. I notice a massive edge on the intake valve. Flowed the head in stock form, them with the back cut on the intake. I have the notes somewhere, but remmember the improove was HUGE.
Valve job was very good, nothing more was changed and I could not feel any difference.
With the smallish stock cams, I don`t know if it was caused by;
- Reversion (I doubt)
- Flow demand was already there ( With maybe .300/400" lift and 175/180@.050" cam???)
- Degradation on the fuel atomization ( appears that edge was there on purpose to help on this)
- The improove is so small ,it barely can be noticed? ( flow improove was more than evident till around .300" lift)
- All of the above together???
back cutting valves
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Re: back cutting valves
For a bone-stock engine I probably wouldn't mess with it. There are too many other things that would give much better results.bigblockmopar wrote: ↑Wed Jan 03, 2018 4:48 pmCan imagine this on a cammed engine. But wouldn't that mean a backcut on the exhaust valve in a bone stock engine wouldn't hurt in this case?
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Re: back cutting valves
Maybe I'm repeating myself, but isn't this a two part question. First, does the particular back cut in the particular head achieve "better" low lift flow? Second, does the engine benefit from that better low lift flow?
For example, if it's a four-cam engine without any easy and cheap aftermarket cam options, it seems to me that efficient low-lift flow could be just the right ticket to move the rpm range higher in a cost effective way.
For example, if it's a four-cam engine without any easy and cheap aftermarket cam options, it seems to me that efficient low-lift flow could be just the right ticket to move the rpm range higher in a cost effective way.
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Re: back cutting valves
Why ?randy331 wrote: ↑Wed Jan 03, 2018 10:08 pmThat would be good argument for NOT back cutting valves.ProPower engines wrote: ↑Wed Jan 03, 2018 1:32 pm YES
Back cutting both int. and exhaust helps low lift flow.
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Re: back cutting valves
its a diesel so the head is flat int.valves 1.41 ex valves 1.23 only a 2 valve head.not much lift or duration.
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Re: back cutting valves
I'll answer this because it is so evident.Belgian1979 wrote: ↑Thu Jan 04, 2018 10:03 amWhy ?randy331 wrote: ↑Wed Jan 03, 2018 10:08 pmThat would be good argument for NOT back cutting valves.ProPower engines wrote: ↑Wed Jan 03, 2018 1:32 pm YES
Back cutting both int. and exhaust helps low lift flow.
Randy
With less low lift flow near the seat yet not decreasing any higher lift flow, a larger duration camshaft can be used successfully to make more ultimate power.
Adding low lift flow is like adding low lift camshaft duration ... that is why it works so well with stock type engines having very small camshafts.
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Re: back cutting valves
If this diesel already has the head apart for valve and seat work then I think you could radius the exhaust valve margin and do a small 30 degree back cut on the intake valve to try and improve some of the low lift flow but my thought is it probably won't make a "Rats Ass" difference on that diesel engine!
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Re: back cutting valves
I'm not a diesel guy, but don't you have to re-calibrate the injection before you can make any more power with a ported head? (And if you're messing with that anyway, chances are you can crank the fueling/power up quite a lot on the stock engine before it gets too smokey...)
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