Small Port Small Valve Porting ??'s

[wyrmrider]

NICE

[Amilcar]

Amilcar, I have a set of the RHS LAX heads that I am working on also. The only issue is
that the ones I got only flowed 208 cfm out of the box. I had them around the 280 cfm mark and zigged when I should have zagged somewhere and they went into turbulence. I never wanted to get into porting, but those heads ended all of that. It has been a long downward spiral since then! I blame it all on the LAXitive heads. LOL's

It isn't about making power per se in circle track, at least not in the IMCA modified class. Even a smaller lower HP engine can spin the tires at will at any point on the track when it is dry. The key thing is to have the correct feel to the power. Until you have driven a car with the proper feel to the power it is hard to understand. It is even harder to get the driver to understand what they want. That is until you educate them. The 4 link rear suspension has created this mentality that every driver thinks they are hooked up hard, when all they are doing is spinning the tires. Very few drivers can feel when they are spinning the tires. I see it all the time.

Wyrmrider, we have played with the shaft adapters in the past (1999-2003) and they work really well. In fact we were looking for the drawings the other day. I don't think I have the photos on this computer, but I can ship them up from the work computer. The prototypes were made from H11 tool steel and were really nice. Aside from an issue of having too smooth of threads to hold the bolts in, they were flawless. So I agree that converting the newer style heads to shafts is an option, however, we don't know what IMCA might say about that. We tried it in Wissota and had an issue with amnesia when we got the engine working properly. Wissota forgot that they had agreed to let us do it. So after some costly R&D, they made it illegal. I don't want to repeat history with IMCA. I will have to send the photos to them to see if they will agree to allow it. I rather doubt they will, although they appear to be more receptive to things like that than Wissota.

Yes, now I remember of a post about that RHS.
I just can`t imagine what on these heads went so wrong, we know it`s about mass production and only yours were screw up.. Never heard of someone else complaining about that. Had a set of them with screwed VJ on ehxaust, contact point was on the outer wedge of the valve, had to sink them a bit to fix, could made better replacing the seat rings, but that´s all.
A bone stock magnum head flows around that much 205-210CFM, but it`s throat has only about 81% of the valve diam. the RHS went already around 88-89% of a 1.92 valve, that´s a huge difference.

Anyways, your mainly problem is not having an easily access to a flowbench to get on track of things.
That`s a tool that help us to investigate what´s going on, how good you will do with it, depends on how much time you spent trying to visualize what can`t be see. That´s not easy stuff and very time consuming.

I see you have the same problem with two completely different heads, that´s is telling , you`re paying much attention on CFM and that teach nothing to us. You keep on grinding, releasing more CFM and without knowing just making a critical spot of high speed worse yet.
Forget about CFM for while, i just mentioned they flow some # for exemple only, if they flowed 20CFM less, I wouldn`t care. It´s for small CID street performance, so making them bigger and bigger will just turn a engine peakey and a dog for it´s purpose. Once you go for that(trying the most cfm as you can), you have no choice other than give a lot of area to slow down the flow. It´s a usage especific and not always the best choice for everything.

Besides your bad experience with these RHS, trust me, they `re problably your best bet for you`re looking for.
There are no good head porter in this world that have not make mistakes, the good ones learn with the mistakes, that`s the nature of this job.

BTW. How was the oiling route for these shaft system

[340king]

The oiling went through the AMC solid lifters through the pushrods and into the rockers through T&D cup adjusters fitted into stock 273 type rocker arms. The T&D adjusters were a sweet deal as they had an annular groove that matched the oil ports on the rocker arms. No adjustment needed there. All we needed to do was plug the OEM oil feed to the pushrod tip since that was already being fed by the pushrod.

I have really tried not to go big on these 273 heads. I was following the work of the previous porter whose heads I totally loved. I would be perfectly happy with the 235 cfm that he had in those heads. I played with clay in several places to see if I could find something that the port wanted. I also played a lot with the various flow balls to see what the issue was. I am pretty sure the issue is a small difference along the hot wall. I think I can manipulate the wall with something like a .020" tapered blend to remove the little kink where I haven't removed as much material as he has in that area. I assume that is the issue as the smallest flow ball fixes the problem which I suspect is a detachment due to the kink bouncing the air away from the wall.

I never really wanted to touch the RHS heads. They were supposed to be good OOTB. I about had the owner send them back after the initial testing, but they were a Christmas present. I am totally comfortable with saying that I don't know what I am doing and therefore have gone very slowly and tried to remove the least amount of material possible to get a decent shape. If it were easy everybody would be doing it and doing it well!!

[zums]

if your going to be grinder limited with the port, with a high velocity cc restricted port i think the 3 areas that need the most attention are , make the pinch as large as the core will allow, 90% throat assuming 1.94 valve , and blend/ widen the ss as much as possible, forget what your calling a hot wall

[340king]

I finally got the time to cast up another mold to compare with the copy port. My port is on the left and the copy port is on the right. I think you can see the kink I am referring to on the left/hot wall (the common wall on Siamese ports) side of the molds. There are a couple of other very minor differences, Hopefully I can find that magic shape.

[340king]

Well I found the issue with the port that was making it go into turbulence at high lift. I was surprised by the finding also. It seems that this port really likes the sharp edge on the valve job where it intersects the short side radius. I had blended that area on the initial pre final seat cut. We left them a little shy of the final configuration to allow this rookie porter some insurance on not ruining the seat. Once we put the final cut back into the head, the flow stabilized up through maximum lift. So chalk that one up to learning. I was at 241.7 cfm on that port when all was said and done, 240 was the target.

I took one of the old heads I was copying to the shop and flow tested the comparison port that you see in the previous photo. That port flowed 262 cfm! But it went into turbulence at 0.530" lift also. I had copied the smooth SSR from this port into my work. Luckily we left enough room on the interim seat to catch the SSR and make the little ridge that apparently these heads really like.

Now all I have to do is figure a way to put the little ridge back on the SSR on the first port I worked on. I quit on it after trying several different shapes and moved on to a new port to see if I could crack the code. I hadn't cut the SSR on the second port nearly as much as the first.

I also had some time to mess with the LAX heads and found a sweet spot on those also that allowed flow all the way out the top without going into turbulence. I remembered that we had them flowing well and it all went south when I smoothed out that little ridge on the SSR on those heads also. Lesson learned. I will endeavor to check this out in the future prior to going to the final seat cut. That way I don't remove all the little ridges when they are needed. Luckily we have some room on the LAX heads to cut the final seat and put those ridges back in since we left them shy also for the same rookie reason.

[pdq67]

Don't know so thought I would ask sort a deal here.

I like the old 318" poli-head because of its valve arrangement.

Will a poli-head fit on your engine?

I don't know if the newer 273/318/340/360 engines will mount the older 318 engine's head is all.

pdq67