Valve seat question
Turbo Mini Forums

Had new valve seats cut, and when i have started to lap the valves into the head, it appears the inlets seem to have a very thin seat in comparison to the exhaust.

(Click to enlarge)


Should/can I grind the exhaust out a bit more to leave a thinner valve seat? or leave as is?

Should i have thought about this before having the valve seats cut?

Also, its not got u/l inserts, so will a wider valve seat be beneficial wear wise, or make no difference?

I think viz mentioned somewhere that valve seats only needed to be about 60 thou wide...well my exhausts are nearly twice that...

Any advice or pointers would be appreciated.

Joe

Edited by joeybaby83 on 28th Jan, 2007.

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

If it's for Turbo use leave it well alone as the valve uses the seat to remove heat from the head of the valve.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

Ditto above. A wide valve seat esp on the exhaust wont do any harm.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Righto, thanks lads

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Just had a look at this. The guy who has ground your seat is obviously a wanker. Look at where the seat of the valve is. It's on the inner side of the existing seat. So where can you grind?

Here is a similar example from Minisport

Horrible 45degree seats cut with something like the thing on the right on this picture:


When grinding new seats on this head with proper equipment, we ended up with something like this:

The inlet valve is the same size, but the valve throat is 2mm bigger. That means that the head is effectively fitted with a 2mm bigger valve alathough the valve size stays the same.

Look at how much meat which is removed


I'd take the head to someone who knows their ass from their elbow.

go up a valve size on the inlets to 35.6mm and de shroude around the combustion chamber so the valve flows well
i dont hold much hope out for reliability with that seat
its too far down

If using a proper cutter, this will sort out the shrouding as well.

Is that a 33,3mm valve you've used for lapping?

Was`about to say that 3 angle seats would probably sort it out.
Regards
Dave

no, 30.93mm inlets, its a 295 head, not after mad power and concious of it cracking so sticking with smallish valves.

hmmm, it was doen by a local firm called Motivation, as far as i know theyre the only people on the island that cut seats.

Steve, if i whip this off and stick it in the post to you could you sort it for me?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

yes of course pm sent

Even so, fit bigger inlet valves. That is no good even if used with a 3 angle cutter. That will just ruin the next up size valve seat.

fishtits, just bought those inlets :(

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

veg, fitting larger inlet valves and then de shrouding around the valve to bring the flow Potential up

also opening the valve throat to suite the larger valve, these two mods togeather flashing the head will make a stormer of a head

also to flash the head to bring the cc in the CB back tho what is there now , what joey wants

Edited by BENROSS on 2nd Aug, 2007.

yes i agree V if the seat was cut like yours to start with but..... the valve seat has been taken too wide and the valve now sits on the btm of the seat

not good in my book

Exactly, so a bigger valve and a proper cut seat would make that head beatiful. There's sufficient meat there to do it. Buy 32mm inlets from Paul Ivey.

will keep you posted V

had a closer look today and i think you guys are right... :(

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

whack it in the post jo with all the bits for the head buddy

Only just got round to taking a few snaps of Steve's (aka Benross's) handywork rescuing my head:















It was a very quick turnaround, within a week iirc
I just cant wait to get the rally car done now, so I can get stuck into the turbo car

Thanks Steve, top work

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Now let's see those valve seats then! :) Don't like the look of that massive inlet. Too big a valve will be an obstruction there on a small bore as the inlet port and throat cannot flow sufficient air for that valve. How big is it?

33mm i believe, im sure it will do just as I want it too!

Vegards, I thought the 295 heads have comparable port sizes to 940s?

Ill pop one out to show the valve seat before and after

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

V thes valves are the correct ratio 18% differential and de shrouded around the valveto make them flow

in short its the SAME head and valve sizes as wil-h 998 road going head

I thought it looked like a AEG163 35,6mm inlet. That's too big for a 295head. If they are 33,3/29,4 valves they might work, although the valves are a bit bigger then necessary. They are however easy and cheap to get hold of.

Deshrouding is as you obviously know VERY inportant when fitting such big valves in those heads.

i had to strike a ballance with de shrouding the valves and getting the correct CR in there for joey

he will now have a head which will produce the goods for his blown 998 project