WD45 Head rebuild?

I am considering having a WD45 Head Ported and rebuilt with larger valves. Any suggestion on what valves will work?
Also I noticed that some WD45 head have longer reach spark plugs then others. Any comments?
Thanks, Lunker

What are you running for an engine?

I use a few different valve setups, but it depends on how large of an engine and what you are doing for a carb and manifold. It's not going to do you any good to shoehorn a 2.02" intake valve in an engine that is getting fed through a near stock carbuerator and a bone stock manifold. You'll have such low velocity past the valve that the engine will make less torque than one with a perfected 1.72" valve.

As far as long reach vs short reach, I suppose in theory the long reach is better as it gets closer to the center of the cylinder, but I bet no one can prove it, or cares. I've used both and never had any reason to think that one is better than the other. You're dealing with a combustion chamber with to many other shortcomeings than the spark plug.

Sometimes I use a John Deere valve from the 202-219 diesel engines, or the 6 cyl versions, 359 etc, all the same valve. I use these in the smaller engines. They are just large enough to clean things up and get the bowls and seats shaped right over a stock valve. It's an easy swap as the exhaust seats just need a trimming, the stem size is the same and your keepers, retainers and springs swap over.

Other times I'll use a +.200 long Chevy small block valve and cut it down to desired size. A lot of the heads I do for the mid sized engines I use a 1.85" head diameter. At times I'll use a Ford valve from a 351, but I prefer to cut down the Chevy valve. Ford uses a longer tip length and it just causes more spring pressure.

Most of the times I use a spring from Howards or SBI, they have a common spring that is cheap and works well with any of the JD, AC or automotive valves. I use a Howards 98111 spring most of the time and I pull the inner damper out. It's a 1.24" diameter spring, enough more spring pressure that valves won't float at any normal RPM, but not enough pressure to be hard on parts and the spring won't get close to coil bind with any cam and rocker arm combo on these engines. The spring fits in place of your stock springs and retainers, or fits with the Ford or Chevy valves with their 1.25" retainers. Very simple and the springs are cheap at $30 for enough for 2 engines.

I do quite a few of these heads and have sets of parts on hand if you want a set of something without having to buy duplicate parts.

So you have a 325 cid engine running at 2060 RPM, you want to make peak torque at say 1600 RPM, this gives you the best range to "size" your parts to. 

Now someone's going to come on here and say with a 4.5" bore you should have a valve sized XX% of the bore....they read it in a hot rod magazine but have no practical experience with these parts and a flowbench at hand or experience at the track.  The truth is that you have a carb that will only flow a little bit of air.  If you put in the theoretical valve size, your carb and manifold is going to restrict the airflow from the atmosphere to the cylinder in such a manner that the speed or velocity past the valve is going to be so slow that the calculated valve size is just to large.

One more thing, you bored the neck of your manifold out, but did you fill the corner where the neck and manifold meet?  Cut the largest radius you can where that air needs to turn 90*.  The larger the radius, the more air that manifold will move and the easier it will move a set amount of air.  If I take a manifold and hook it to the flowbench and pull a set amount of vacuum on it it will flow XXX CFM of air.  The larger the radius I cut on the throat the more air it will flow at that set vacuum, until I find the next shortcomeing, which will be the other corner where the manifold turns to meet the head.

Lets just say I pull 28" of water vacuum on a stock manifold port, it flows say 115 CFM of air.  I cut the largest radius I can on that carb neck and maybe that manifold will get to 140 CFM.  I weld the corners and fill them, cut larger radiuses and then find 175 CFM of air at the same vacumme. 

Now I take that TSX 464 carb and pull a set vacuum on it, say 40.8" of water which is about equill to 3" hg or mercury.  Lets just say that the carb moves 125 CFM of air.  The vacuum that I am pulling on the carb is standard rateing for single and double barrel carbs, so lets apply that to the manifold.  At that testing depression the manifold flows more air than it did at 28", so I should test my manifold at the same pressure (or depression) as the carbuerator is tested at.....I'd have to do a little quick math or check my notes to tell you a number but my point is that the manifold with a little work will far outflow the carb.

Your 325 CID engine at 2060 RPM needs about 160 CFM of air available through it's carb for peak torque, or even less if we figure a lesser RPM, less yet if I figure a lesser volumetric efficiency, and these engines are not very efficient.  In this case the engine will make good torque at say 1200-1400 RPM.

So now we need to size a valve to the engine to keep good air speed past the valve. We've already established that your carb is the shortcomeing.  We can figure a theoretical flow past a valve for a given lift.  You have a head with 2 nasty 90* corners in it for the air to bend around before it finds the valve seat.  Each time the air needs to change direction, lose speed, gain it back again.  It's a mess in the head and you just can't get that much air around the corners of the head, so much for that theoretical flow past the valve....it'll be much less in the real world than it is on paper.

Do everything you can to eliminate those corners and make the transition as gradual as you can.  But a 1.85" diameter intake valve with proper seat angles and bowl shape will far outflow the capacity of the rest of your system.... in fact a 1.75 may just be optimum.  The only thing is that the larger valve will help max your carb out sooner in the intake cycle, though kill the velocity later in the cycle.  That incoming air charge has a lot of speed and mass to it, keeping the speed up when the piston slows down around BDC will help it ram-charge the cylinder.

I'm not going to say what size valve to put in, I don't know, no one does.  But if I were working on it I'd go for something around a 1.75"-1.85" range.  I feel any larger will hurt more than help and much smaller will hold the engine back.  I'd use a 1.85" if I had more carb hanging on it than a TSX464, but I'd use a 1.75"-1.8" in this case.


Edited by wi50 - 12 Dec 2013 at 5:33pm

wi50! Thanks for all the info, I rounded the shoulders (curves) in the top off the throat like you say until I dulled all my cutting bits. I will pick up some more cutters and go at it some more. I do have a bigger carb, but would have to make an adapter for the bolt pattern. What larger carb will bolt up to a stock manifold? What about the Vinson manifolds? I think the standard intake valves are 1.687" which sounds pretty close to what you recommend. I do plan on trying to do some porting in the head. What about the size and porting of the exhaust valves?
Thanks again, Lunker

Thanks wi50, time for me to go to work!!!