Valveseat comparison

General engine tech -- Drag Racing to Circle Track

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Newold1
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Re: Valveseat comparison

Post by Newold1 » Sat Feb 10, 2018 4:10 pm

Just goes to show you what I know about older BMW engines and how bad my reading can get sometimes ! Sorry for my unnecessary post.

MTENGINES
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Re: Valveseat comparison

Post by MTENGINES » Sat Feb 10, 2018 5:01 pm

turbo2256b wrote:
Sat Feb 10, 2018 3:01 pm
not realy crazy about the wide gaps between cnc cutter passes in pic
? What cnc cuts? Is there a diferent pic I'm not seeing?

Looks like shop B at least cares about a top and bottom cut.

Shop a looks like a 45 into the chamber then a 80 underneath.

I would favor B myself. But who knows until you test them.

MTENGINES
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Re: Valveseat comparison

Post by MTENGINES » Sat Feb 10, 2018 5:03 pm

bmwmaster wrote:
Sat Feb 10, 2018 5:52 am
Hi,

I gave two of my heads to different companies after manual porting and told them to cut performance valve seats and generate the best flow.

They have totaly different philiosopies as shown in the pics.

Company A Race seats look like this: (its somehow one big angle to make the seat wider and then a very tiny angle where the contact area is and very little gap to the chamber. Target seems to create as much as possible open area.)

https://picload.org/view/dagldaww/race.jpg.html


Company B optimized seats like this: (Its an 4 Angle Seat to create smooth transition to the chamber)

https://picload.org/view/dagldoow/4angle.jpg.html

Its an bmw m20 2.7l 2V engine. Will have about 11:1 CR 280° Cam and about 6800-7000 RPM sport street use. Both heads use 42/36mm valves which are modified to the seats

Would be nice when some experienced people could tell their opinion about the two types of seat cut. What should work better?

THX
Shop a probably used an exhaust cutter on both intake and exhaust. In return you got a big hole. Big holes flow more air. Lol

turbo2256b
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Re: Valveseat comparison

Post by turbo2256b » Sat Feb 10, 2018 9:54 pm

MTENGINES wrote:
Sat Feb 10, 2018 5:01 pm
turbo2256b wrote:
Sat Feb 10, 2018 3:01 pm
not realy crazy about the wide gaps between cnc cutter passes in pic
? What cnc cuts? Is there a diferent pic I'm not seeing?

Looks like shop B at least cares about a top and bottom cut.

Shop a looks like a 45 into the chamber then a 80 underneath.

I would favor B myself. But who knows until you test them.
nOT THE seats the port work finish and chamber

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