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Protecting valve seats when porting.

General engine tech -- Drag Racing to Circle Track

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hoodeng
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Re: Protecting valve seats when porting.

Post by hoodeng »

Port before.
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hoodeng
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Re: Protecting valve seats when porting.

Post by hoodeng »

One inlet and one exhaust port after 40 minutes, basic shapes and alignments done. There is a lot of metal to come out. Hour and three quarters/two hours will see a pair pretty much ready for finishing.

I can not imagine myself doing this balancing on one foot and one regulating on a pedal! I suppose it comes down to how many you have to do, a couple of sets some weeks speeds up the process. This was one reason i went to the larger hand pieces, set speed and go. Both would be run at about half speed.

I also use two hand pieces, one reduction box type for carbides and one direct drive for finishing.And as has been pointed out before, beware, these things bite if you are not 100% on the ball.

Cheers.
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mag2555
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Re: Protecting valve seats when porting.

Post by mag2555 »

Especially with Round shaped Exh ports like yours in conjunction with what your Exh port shows of not having even close to a ideal amount of short turn height to it , the work you did on the floor of the port and especially the gasket match was not the thing to do!

You just made the difference in pressure between the roof flow path and the floor even greater then stock , when the main goal along with increasing flow numbers is to even out this pressure/ velocity difference in this type of Exh port.

The only side of the valve guide as seen from looking down thru the bowl that should get Boat tailed / tapered is on the chamber side of the Exh bowl, not the Intake valve side.

This is a typical rework from not having a flow bench to guide your work, both in terms of Exh flow numbers in the normal direction of flow and in reverse flow .
hoodeng
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Re: Protecting valve seats when porting.

Post by hoodeng »

Hello Mag, i have included a couple of photos, one is of the flow bench i don't have and have not had for twenty five years,[had a 110 prior to that for a number of years] the head on it is the one i have no idea about [yes every head done here is tested] You have made a lot of presumptions from a couple of photos.

The exhaust port initial marker pen line is what a closed in small port gasket will cover, the finished port is what a thin section large port gasket will support, the port is 'D' shaped not round, changing the valve diameter lifts my short turn rise material by 2.5mm. There was no stock removal on the port floor, just a linish. The port in its unmodified standard configuration requires longer cam timing to overcome its flow restriction. But you could be right! i might just be doing it all wrong!

I have included a before and after graph of an engine with these heads, the lower lines on the graphs are the stock engine before. 96", good exhaust and air cleaner, the upper lines are the engine after modification, 106", Crane cams, 62mm throttle body, same exhaust as first test and professional dyno tune. For your assumption of ports that don't work, could i send a set to you and then test them on the dyno on the same bike that mine are on now, what sort of gain would you expect?

Sorry about the clarity of the dyno graph,but it went from 66.5hp to 130.4hp and 86ftlb to 116ftlb, and before these figures get jumped on, we realized at the time that .600" total lift for in and ex was way too short. It was a development cam given to me to try out, these heads were working fine at .700" you will see a plateau in the HP line before it noses over.

Cheers.
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mag2555
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Re: Protecting valve seats when porting.

Post by mag2555 »

My main concern really is the ports expansion rate, as I can tell by the photo even without you providing any size measurements that the flange exit area is darn close to to twice what the valve bowl minimum port area is, no?
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