Topic: Valve Train Swap

[Blitzburgh207]

I was advised by Ken at CycleX, when inquiring about top end parts compatibility, that I should swap an earlier valve train (pre K6) to my K8 head.  He said "we always do this for hot rod situations". 
Well, I have a K4 parts motor, so I proceeded to buy springs and guides rom what I think is the K0-K6 section.

So, from what I understand, I will swap everything but the cam towers and cam from the K4 motor, and install it in the K8 head.  This includes pressing out the K8 guides and pressing in my new ones from CycleX because I will need to use the K4 valves and retainers with the new springs from CycleX.  My question is: Will the K4 valves seat properly in the K8 head, or will I need to have them ground?

Any other problems you guys see me running into? ...I'm going to start a build thread soon, I've just been too lazy to upload pictures!

Thanks!

[Bankerdanny]

I'm sure someone here will have the info, but you might also follow up with Cycle X about this. Since he advised you to make the switch and you are using his parts he should have no problem providing the guidance you are looking for.

[lone*X]

Valves are lapped to their specific seat.  The only way to ensure a proper seal when installing new valves or moving valves to a different seat or head is to have them properly ground and lapped. 

Added note:  If you know the valve angle and seat angle are the same you might get by with a good lapping, paying particular attention to the contact area which needs to be sufficiently wide to ensure a complete seal.

[Blitzburgh207]

I've talked with Ken further a little bit but I thought I would get more feedback on here (and faster response times). 
Thats what I figured.. I'm not sure what It will cost me to have them ground, but I'm really going for reliable here so I shouldn't cheap out on having valves sealing properly.  ...I guess I'm more worried about taking it to a machinist and having them eff up my head  than I am about the cost...

[MCRider]

Valves are lapped to their specific seat.  The only way to ensure a proper seal when installing new valves or moving valves to a different seat or head is to have them properly ground and lapped. 

Added note:  If you know the valve angle and seat angle are the same you might get by with a good lapping, paying particular attention to the contact area which needs to be sufficiently wide to ensure a complete seal.

Yeah, its not so much an issue of which K they came from (though that question should be confirmed by crossing part numbers or the like), just the fact that they are different. An aggressive lapping at least, and maybe a valve seat cutting is in order.

[754]

If you change guides you must grind the seats..
 get a good multi-angle grind while you are at it..

[MCRider]

I've talked with Ken further a little bit but I thought I would get more feedback on here (and faster response times). 
Thats what I figured.. I'm not sure what It will cost me to have them ground, but I'm really going for reliable here so I shouldn't cheap out on having valves sealing properly.  ...I guess I'm more worried about taking it to a machinist and having them eff up my head  than I am about the cost...

After confirming the K4 to K8 swap is OK, any machine shop that does small engine heads should be able to do it no prob. They have sets of cutters, or machines, of all sizes and angles.

[MCRider]

If you change guides you must grind the seats..
 get a good multi-angle grind while you are at it..

Oops I missed that, 754 is right. Replacing the guides makes a full valve job necessary.

[Blitzburgh207]

Ok will do!  What is a multi-angle grind?
...bear with me I'm new to this! 

[Bankerdanny]

I think they are generally referred to as a 3 angle valve job.

As I recall (and I could be recalling wrong) its the way the valve seat is cut, rather than one single taper it is three different, increasing angles (from the inside of the seat to the outside, 30-45-60). It's supposed to improve airflow. I think it is also the default style of valve job for most shops these days.

[Gonzowerke]

Ok will do!  What is a multi-angle grind?
...bear with me I'm new to this! 

Imagine you have a head cut in two across a valve seat. Looking at the seat from the side, instead of a smooth arc or curve, you have a series of straight flats making up the curve, like an early video game that rendered curves with straight lines. Or, put another way, imagine countersinking a screw hole, but instead of using one bit at 45 degrees, you use 5 at 30,35,40,45,50 degrees, leaving a series of flats on the seat. The car guys swear by a 5 angle job, but I don't know what the 750's like. I don't think a 5 angle job would be bad. Oh, also the valve head is ground with the same angle flats, so that when it seats, it seats perfectly in those flats, sealing better than a radius job would.

[Blitzburgh207]

Ok, I think I remember seeing that in the shop manual now.  Does that make it so the valve contacts a smaller area for a tighter seal?

[Bankerdanny]

No, the contact area on the valve would be about the same as a single angle. I think the steeper angle on the inner part of the seat improves air flow.

[Blitzburgh207]

Ohhh gotcha.  I'm headed over to the shop now on lunch to see what they can do for me.

[Blitzburgh207]

I was quoted $10/valve so $80.  Does that seem fair?

[MCRider]

I was quoted $10/valve so $80.  Does that seem fair?

They are doing the seat in the head, then the valve, for that? Pretty good i think. Be sure of what you're getting.

[Blitzburgh207]

I was quoted $10/valve so $80.  Does that seem fair?

They are doing the seat in the head, then the valve, for that? Pretty good i think. Be sure of what you're getting.

...now I'm confused 

[MCRider]

Sorry. just seems a little inexpensive, maybe not. I would simply ask what he's going to do in 15 words or less.