MTFCA Forum

It has been a few years since I was on the forum, a move to Alaska and having a son at the age of 5o kind of put me on the side track. Nice to be back working on my 1926 skiff speedster.

I have a chance to but a Rajo model B head (figure 2). My brother found it laying in someone's yard of all things and the guy (who hates Fords) gave it to him. My brother has offered it to me at a good price. It has the valve train, the valve cover, all but one of the push rods, and the machine shop just told us that it has no cracks anywhere. It is missing the intake and exhaust manifolds. The only other significant issue is some corrosion around one of the valve seats (figure 1). My question is how to deal with it. The shop who did the magnaflux says that it might be possible to re-cut the seat and run it, but they though putting in a new valve seat would be better. I also have a shop in Santa Rosa that says they can rebuild the seat by welding it up. I know that the web between the intake and exhaust is very thin so I wonder about putting in a removable seat. I think it will probably take a new valve guide.

Has anyone here rebuilt the valves on a Rajo and what worked for you? Also, is there anyone in the Sacramento area that people have used for old car work or who they can recommend for the job? I used to use a shop in Sparks when I lived in Reno, Nevada, who used to do a lot of work for Bill Harrah in the old days but getting it there is a bit of an issue with me being in Alaska now.

Thanks in advance for any advice.

1st off, there is no one in Santa Rosa that I would let weld on that head, nuf said on that. My opinion only. Seats are bad mojo in those heads due to the thin area between the valves as you noted I think I would 1st try just grinding the seat and see where you end up- not ideal and the seat will be sunk but . . . . . The seat does not need to be 100% perfect for you to get some good miles out of it.

Dan McEachern wrote: ↑

Tue May 26, 2020 7:14 pm

1st off, there is no one in Santa Rosa that I would let weld on that head, nuf said on that. My opinion only. Seats are bad mojo in those heads due to the thin area between the valves as you noted I think I would 1st try just grinding the seat and see where you end up- not ideal and the seat will be sunk but . . . . . The seat does not need to be 100% perfect for you to get some good miles out of it.

If that were mine, I would go very VERY light on hand (not machine)-grinding those seats, the absolute least you can get away with. Go easy, go slow, and check often. And all it has to do is seal... not be *perfect*. Take no more than what is necessary...

As an aside - LISTEN TO DAN. DO NOT let ANYONE weld on that head first. I also know of no one in Sana Rosa I would trust to do this, no way, no how, no no. There ARE people that I *might* trust, but they'd have to show me a whole passel of success stories doing this, with pictures and documentation. And that's only if it's cracked. No cracks? No way, Jose! I don't like even RESEATING valves that close, the few I've done were always nail biters - on fairly modern iron.

My 2¢...

I agree with Dan,

If you go lightly you can probably clean that seat enough to use it for a while. I didn't realize it was that thin between the valves, then again my budget at the moment doesn't allow for overhead toys.

Tim

All the advice you've received so far is spot on, but FYI, around 14 years ago when the Rajo B head was off old #4 for a little overdue maintenance the shop that does my work called me and said we can't do anything with your valve seats, they're to worn, to many valve jobs, we need to put new seats in. I said "no way I don't want "removable seats". Anyway I finally agreed and let them do it. Knock on wood, I haven't had any issues since, in a lot of somewhat hard miles. So as much as I didn't want them......it worked for me.

Ed aka #4

If the only other option was using it for a door stop, one could always install the smallest diameter seat available to clean up the damaged material, and reduce the valve size to match. The valves and ports are dramatically oversized for the performance expected my most owners anyway. Who knows... running smaller valves may even improve the flow characteristics...?

I have a similar problem with my Akron-Hed project, and have reduced the valve size to 1.710” to allow a smaller seat and buy some “insurance”

A quick look at what a really bad valve seat looks like... . With a .250” lift cam, the exhaust valve face would have just barely raised above the combustion chamber floor

YellowTRacer wrote: ↑

Thu May 28, 2020 6:00 pm

All the advice you've received so far is spot on, but FYI, around 14 years ago when the Rajo B head was off old #4 for a little overdue maintenance the shop that does my work called me and said we can't do anything with your valve seats, they're to worn, to many valve jobs, we need to put new seats in. I said "no way I don't want "removable seats". Anyway I finally agreed and let them do it. Knock on wood, I haven't had any issues since, in a lot of somewhat hard miles. So as much as I didn't want them......it worked for me.

Ed aka #4

Ed, if I can ask, who redid your seats? I have a fronty SR head that needs to have magic done to it (tho not as bad as that B head that started the thread) and I'd love to find out the yeas and nays they had with yours... Would you trust them again?

And "hard miles"? No, NOT you... I can't imagine #4 being pushed to the edge... Somehow I keep thinking "Only to Church on Sundays" but if Church would be the San Jose Speedway... or maybe Calistoga... Indy? Daytona? Or South Bay Commute traffic? --ha ha ha ha--

Be well, you and yours!

Kevin thanks for posting that. I was going to post a question if that could be done, seats with smaller valves, then use a higher/longer duration cam to replace lost air flow.

Mark Gregush wrote: ↑

Fri May 29, 2020 9:22 am

then use a higher/longer duration cam to replace lost air flow.

Believe it or not... the 1.710” diameter SB chebby valves are produced as intake valves for restrictor plate racing applications. As I understand it, a bit of port work along with these noticeably smaller intake valves can outperform the larger valve equipped competition.

Every intake runner/port/valve system flows at a unique rate dependent upon a seemingly unlimited number of factors, and an engines output is arguably directly related to the capacity and efficiency of this airflow. A camshaft with too much lift/duration can be just as detrimental as not enough.

It would be interesting to flow the head with both size valves to understand the loss, or even gain in airflow at the same valve lift height. Didn’t Mark Chaffin reduce the port (and valve?) diameter in his new RAJO...? I pretty sure this is the case with the new Miller heads for the Model A’s.

I have flow data on a B/BB Rajo and the intake port flow curve continues to rise even after about .500 lift. Those heads will flow an insane amount. If you compare B/BB Rajo flow data to just about any other era head, most intake port flow curves flatten out at higher lifts as would be expected. I'm not sure what effect a smaller intake valve would have, but I suspect the result would not be an increase in flow in this instance.
With regard to the new Miller heads, Steve did a considerable amount of flow bench testing with different port configurations to arrive at his current design. I'm not sure if any flow testing was done by Mark. Perhaps he will jump in here.

Dan McEachern wrote: ↑

Fri May 29, 2020 7:28 pm

I have flow data on a B/BB Rajo and the intake port flow curve continues to rise even after about .500 lift. Those heads will flow an insane amount

And all this airflow is great... if only one could use it all! How much volume is really necessary to fuel a “hot” T? Excessive port volume and flow capacity is proven to be a bottom end efficiency killer... which is where our T’s live

Ha! when did we start being concerned about "low end efficiency" with any of this?
My comments regarding port flow were directed at your earlier statement, not anything to do with resulting performance. You can't change the fact that more air = more fuel = more power.

You said:

Where is the freaking like button! So much good info in this post if your an engine junkie!

And Dan, Yes, More Air, More Fuel does equal more power----but only if you can use it all....even on the top end of the RPMs.

There is always a saturation point of diminishing returns. If the head flows such a great amount on the top end of the lift that the low lift air flow #'s aren't that good---and more importantly the low lift Port Velocity suffers, it definitely has an effect on drive-ability. The end question is what is the intended application. Cam, Compression, and Head flow all work hand in hand.

But all this is getting away from the OP question in fixing the seat. I personally try to run a slightly bigger valve to see if I can grind out the seat to make it usable. I have no issues with installing valve seat inserts, it's just these old T engines and alot of the overheads don't leave alot of material to do so. Anything can be done, including installing a seat and reducing the valve size....although I'd want to carefully blend the step of the seat into the port. If its just the one seat and port, maybe it can be spray welded.

As far as the guide, I know alot of the bigger valves ran bigger valve stems. With today's tech, reducing valve-train weights can help to make more power, , but more importantly, help the valve-train survival rate. So think about having an insert installed with a reduced diameter valve stem, vs. having a whole valve guide replaced. It'll save the original guide. You can move pretty easily to a 11/32 valve stem and there are tons of valves in various head diameters and lengths that you should be able to find one. I'm using 11/32" stem, 1.88" diameter head, +.100 length in my Fronty T head. This particular valve is used as a big block Chevy exhaust valve.

Dan McEachern wrote: ↑

Sat May 30, 2020 12:07 am

Ha! when did we start being concerned about "low end efficiency" with any of this?
My comments regarding port flow were directed at your earlier statement, not anything to do with resulting performance. You can't change the fact that more air = more fuel = more power.

Your formula is undeniably correct, and a smaller valve diameter is without a doubt a smaller orifice. I would never argue against this logic. My later comment was simply trying to make a point that an oversize port for an application could have an adverse effect on “drivability”

I would be interested to hear some of your port flowrate numbers for the various types of heads tho... I’m sure some heads are like breathing thru a straw, while others you could darn near pass a tennis ball thru. Also, if anyone has ever considered an ideal flowrate for a full bodied, speedster, or hill climber engine. I know there are several simple airflow calculators online to help predict the CFM required to produce an estimated HP... but given the reduced efficiency of the T/A engine designs... would these estimates still apply...?

You guys have a place called valley head service on the west coast. Is that an option to go with depending on what you choose to try?

I for one would love to see flow data on any of these heads. I am trying to find a flow bench locally that would flow my Fronty T head.