Interested in seeing fellas personal experiences with the Rajo 4 Valve cylinder head, including recommended carb, cam, compression etc for a fast road spec job.
In addition comments on the Australian made version are of interest.
I ran a 4 valve on my speedster for several years. It was an OK but not super performer but I would like to qualify that a bit. Mine came to me with an incorrect rocker setup - it worked but was a basic 1 to 1 ratio rather then the typical 1 to 1.5. A proper rocker ratio would have helped significantly. I was using a tame regrind and stock advance on the timing gears. Again, a more aggressive cam would have helped. I used stock T pistons and would not recommend that again with these as the domed pistons would probably really wake the motor up with this head. I used a Model A intake and exhaust manifolds with a Tillotson carb. The car ran pretty well but could have been much stronger. If I were to do it again, I'd get a good cam grind, proper ratio rockers, high compression pistons and a better carb. I think these can be a real good medium performance head. Not real wild and crazy but a major boost over a stock flathead.
BTW, a good cam, carb and opened up exhaust runs mighty darn well in a T with a Prus or Sherman head. My friends have been running these with Model A or Scat cranks and are very happy. You don't really need an overhead to pump out the ponies.
John. I have one of the Australian made cast iron heads. I have not ran it yet, but I can find absolutely nothing wrong with it. I hope to have it going by spring. I believe that most of the problems encountered with the Rajo 4 valve repro heads has been with the aluminum version. There have been several different owners of the patterns, and I believe the quality of work was not always as good as the original cast iron repro heads. I have found no record of any of the first issue cast iron heads having problems, It seems the Australian maker did good work but had a delivery problem (sometimes you got what you bought and sometimes you did not get anything). I have heard horror stories about some of the aluminum heads. Things like head bolt holes drilled in wrong places, the rockers just barely catching the valve stems, rocker tower bases not machined square, ect. I believe those problems were from poor machining by the later aluminum head makers. It is also possible that some heads that were meant to be thrown in the scrap dumpsters, may have made it home with someone and then later made their way back into the market thru estate sales, swap meets, ect. I am no expert on these heads, but I did a lot of research, and talked to a lot of folks about them, before I bought my cast iron 4-valve. Seth (from Alabama) is running a cast iron 4 valve on his speedster. He bought his about the same time I bought mine. He may chime in with his thoughts. Other than a blown head gasket and needing to block off the intake seat area in the block to add more gasket sealing surface area, he seems to be pleased with the 4 valve head. But his blown head gasket could just have been a defective gasket, as it had no complete fire rings on the gasket in the cylinder area. One other thing of note is that the 4 valve Rajo is the only aftermarket overhead that fits on a stock Model T with no modifications to the firewall and can still run the original coils in their stock location. I have also found out that a stock original 4 valve Rajo rocker cover will not fit on a repro head. It seems the rocker towers are taller on the repros. More than likely the rockers were some stock (off the shelf) more modern item that was used in the design of the rocker assembly (I have heard that they are possibly Dodge rockers .????) But with an original vintage rocker cover sitting on top of the rockers there is about a 3/4 inch gap all the way around the bottom of the rocker cover and the head. I think that is why the repro heads came with the two separate rocker covers. The two separate rocker covers is not a copy of anything from back in the day. It is an item made for the repro heads, but will also work on an original vintage head if a person wanted to use them on an original head.
Here are couple pics of my setup during mock up time. I will need to make two 2 inch spacers for the intake because Im running the cast iron dual exhaust manifold. The "S-adapter is to move the carb back inside the frame rail to the stock carb location.
John I have an Australian made aluminum 4V Rajo.
Of note - if you are swapping to this I highly recommend getting in touch with Olsen's gaskets and have them make you a gasket with a full copper fire ring around the combustion chamber. The current ones from Langs do not have a full fire ring and are useless.
Also, you need to fill in the intake valve port. Either with lead, or I used old valve heads and made them level with the deck. That way your head has plenty of surface to squish against.
Highly recommend that you get a single stainless steel rod to act as your rocker arm. The rocker towers are not very sturdy on their own and several folks have had the towers move so much it damages the head. You can eliminate this problem by just running one shaft from the front to the back.
Having gotten the negatives out of the way, THIS HEAD GOES LIKE STINK. I have a Stipe .280 cam, dual exhaust manifold, and dual Zenith S4BF carburetors running into a dual intake manifold I made. With a stock rear end and aluminum Warford in overdrive she will run 65 mph with gobs of throttle left.
Here are some pics
In regards to head gaskets for these we are having some made from solid copper in the next couple of weeks. $60.00 plus postage
Head gaskets are prone to trouble on these heads. I sure wish I had a solid gasket when I ran one. If you have a four valve Rajo, don't miss the opportunity Les is offering. Also make a one piece rocker shaft and use high compression pistons.
Erik - are you able to confirm the 1 PC rocker shaft material and surface hardening? What other mods are required to fit the 1 PC rocker shaft / besides the rocker cover
Thxs guys for all the details so far !
I used 5/8" stainless shaft. No modification other than the covers.
Thank you to all who have ordered/inquired the head gaskets. I believe I have responded to all.
Does anyone find best performance on a particular induction system - intake and carb.
My plan is dual Winfield 5V carbs on individual intake pipes - perhaps a balance tube is advantageous ?
John my input is to mimic the intake I have. I started with individual tubes for the carbs and never could get the car to start very well or run right. Definitely a balance tube the same size as the intake runners, and then as short and close to the engine as possible.
Good tips Seth, your intake reminds me of a unit I used on a British race special - though the balance tube was of smaller diameter then the primary runners.
The Rajo ( Winfield ) type intake looks sharp though it may be too trick in that it projects very high to point of needing bodywork mods for clearance. Still very sharp looking.