MTFCA Forum

I was talking to a neighbor about his T.
He would like to go a Z head, because the RAJO is way to many horses and has to keep the top oiled.
He is saying that he would need a to replace the block as well.
I was thinking that he should be able to pull the head put valves back in and should be pretty much good to go.

The only way to determine who is right is to pull the head and that is slated for this winter.

I have not seen a RAJO head off the block, but is only makes sense that it is a bolt on option.
Or is there some machines work that has to be done to the block?

That's pretty much it in a nut shell.., bolt on performance, But.., some bored out the valve guides or did no repairs to valve seats during a rebuild then installed the over head valve option. Pandora's Box!

Hank

The valve guides may have been drilled out to accept the pushrods. When installing our head, we recommend they be drilled out to 7/16 to allow the use of our 5/16 pushrods. The 7/16 clearance is necessary as the pushrod moves from side to side during operation. The block can be changed back to the use of stock valves if 7/16 OD sleeves are installed with an ID of 11/32. Hope the helps answer you question.

That's why stock Rajo pushrods are 1/4" diameter. Same with stock Frontenac. Your friend will just need to pull the head and see what condition the block is in and then make a decision. Trashed valve seats or enlarged guide bores would require the block to be removed from the car, unless you have the ability to do any repair work with the block in place. It could be done by the right person but would most likely be beyond the average model T owner.

Smith Brothers makes 1/4 " pushrods to your length specifications. They run $12-$15 a piece. I'm sure there are others that make them.
If your building a hot rod you may want to put some thought into an engine. If your looking for more power going up hills and to help with general driving I would think 1/4 fine. I have a set in a RAJO set up and there hasn't been any problems. Yes you have keep your top end oiled, but I haven't found that to be the end of the world. If it's a Model 30 or 35 and you have an original manifold it should all be pretty simple. Get an OHV head gasket. If you have one of the B's you will have to move your exhaust system. I think in the day this was considered pretty much a bolt on deal unless you were building a race car.

Also remember as you're building your "fast" motor, the top end is only the beginning. Once you're developing more compression via breathing and flow, you're getting more dynamic force onto the lower end... Of course, the first thought is usually the bearings, but it actually goes deeper than that, and the deeper down the rabbit hole you go the more you're dug in... Some of the things to think about are oil (specifically pressure oil), Cranks better than the "bent paper clip" Ford gave you, Journal size, Rods, more bearings, cooling, pistons... Then there's carburetion, brakes, gearing...

It's a rabbit hole. You can do amazing things to a T engine, but you need the base to build it on. WIthout that you'll have a very fast motor that will shuck it's mortal coil similarly fast, in a rather sad and depressing manner. And the way these heads (Rajo BB, Fronty SR, et al) breathe you have the potential of overrunning your motor unless you give consideration to the motor as an entire system. Add a large Stromberg or Winfield carb to the mix, and whoo doggie yee haw!!!

BTW - measured all my pushrods, and the ones on both the BB and the SR are 0.249-0.250 and change... (I have them separated out by diameters...)

I have a question, however... what are people's practical thoughts on studs, washers, and nuts for either of the aforementioned heads? Figure studs would be a more stout and secure way to adhere the parts together than bolts, but up in the air about what others are running...

Studs are always a step up from bolts, but depending on the firewall situation on a particular body/ firewall, and the need for the extra height to pull a head with studs in the block, it can be an issue. Removing the firewall/body in order to remove the head can be a major PITA.

Downgrading from a Rajo to a z head is going to be disappointing. Like to see as much speed equipment as possible being used. Who wants to have the fastest shelf.

Andy