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B20F Head porting valve guides

Isn't it a good idea to raise the floor a bit as well? I believe I recall seeing that somewhere over the years of reading forums and such.

The wizards agree with you; but, raising the floor is a lot more work as it involves filling the port floor with weld and then reshaping. I have seen photos where people have had steel tongues fabricated, welded to the exhaust flange and then inserted into the port to try and accomplish the same thing. I think member Canuck has posted pictures of ports where he has filled the floor for flow testing purposes. Phil Singher had also posted photos of B18 / B20s with filled ports (years ago and that may have been on the Sweedespeed forum).

Of course there was an over the top Swede who completely filled in the ports with weld and then machined in new ports where the central axis came in closer to a 45 deg angle relative to the valve stem. Obviously would have required custom manifolds; but, they didn't have photos of a completed engine, just the head with modified ports. I often wondered what they did with the water jackets and whether the head actually worked, or was just somebodies mantel piece.
 
Ah, good to know. Im hoping to run water-meth injection at high boost, as well as sequential spark through the use of MegaSquirt and a CAS in place of the dizzy, so that'll hopefully keep exhaust valve temps low enough. I may try to polish the portion of exhaust valve that isn't in contact with the guide to hopefully help it reflect some heat.

Modest spraying of water / meth will cool the intake charge which can be effective in preventing detonation. That may have little effect on the actual temperature of the combustion gasses. As an observation, if the engine capacity is fixed increased horsepower generally comes from three things
- increasing the compression ratio
- increasing the RPM as long as the volumetric efficiency does not go in the toilet
- jamming more fuel and air into the cylinder (forced induction)

Since you appear to be planning on the FI approach, jamming more fuel and air into the cylinder must increase the amount of heat released on combustion to result in a power increase. Ergo your exhaust temperatures must go up. You need to figure out whether that is going to be a problem for you. If you spray enough water to drop the combustion temperature you are going to lose horsepower.
 
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The wizards agree with you; but, raising the floor is a lot more work as it involves filling the port floor with weld and then reshaping. I have seen photos where people have had steel tongues fabricated, welded to the exhaust flange and then inserted into the port to try and accomplish the same thing. I think member Canuck has posted pictures of ports where he has filled the floor for flow testing purposes. Phil Singher had also posted photos of B18 / B20s with filled ports (years ago and that may have been on the Sweedespeed forum).

Of course there was an over the top Swede who completely filled in the ports with weld and then machined in new ports where the central axis came in closer to a 45 deg angle relative to the valve stem. Obviously would have required custom manifolds; but, they didn't have photos of a completed engine, just the head with modified ports. I often wondered what they did with the water jackets and whether the head actually worked, or was just somebodies mantel piece.

I was thinking about the welding "tongues" into the exhaust in order to simulate the floor of the port being welded, although Im not sure how you could keep gasses from getting shoved underneath the tongue. Also, from what Ive read, just welding the floor helps, but while you're at it you might as well widen the ports in the horizontal. Basically taking the normal "vertical rectangle" port shape and turning it sideways. Not really something I want to try since Ive got some really nice headers, and don't want to warp my head.
 
Hey, is this Cameron from Swedish Relics? You rebuilt my M41 a couple years back. Cheap as in around $60 - $100, wouldn't need to have valves, guides, springs or rockers, and could be a real junk head as far as I care.

Yep. No longer at the same location (so don't swing by!), but I've got lots of heads you can choose from. Give a call and we can set a time.

Thanks,

Cam
 
I had a talk with one of the leading Volvo B18/20 race engine builders in the US about removing the guide hump. He advised me to remove all of it for racing, and shorten the guide so it is flush with the new contour of the port. Culberro mentioned the same thing earlier.

A look at the guide length to be removed in the cutaway photo shows that at the most only about 10% or less will be trimmed off. Because of the the extra long length of the guide that Volvo engineers choose to use for long term durability a shortened one doesn't cause any problems in actual use.
 
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If you dont use seals on valve stems for exhaust valves you can put the valve guides slightly higher and let the guide length be approx same as stock.
 
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