I recently purchased a absolutely beautiful machined adapter plate to put a '28 Chevy head onto a Model T block. I wanted to show you all what I have, what I think, and what may be entailed in doing this swap.
This will be a long drawn out thread, similar to Donnie Browns speedster thread, so don't expect this done in a week. I also will be doing mock-up, not necessarily a running engine, at least at this point.
First off, the plate and water adapter are really TOO good for a Model T. Gene French started this project design and decided Scott Hansen needed something to do, so he handed the project to finish it and bring it to fruition. Scott has a very large machine shop. This is the kind of quality I would expect for a pure breed race engine part. Scott informed me it took 28 different tools in his machine shop to make the plate, these are all CNC'd.
Scott did supply me with hardware, and not cheap stuff either. These are high grade socket head bolts (allen head as some call them). Now the socket head hardware may not be for everyone, but except for the outer row of adapter to block bolts on the cam side, and the water outlet bolts, the rest are completely hidden. The ones in the adapter plate are all countersunk also. I suppose if you painted everything black, you could hide alot, essentially tricking the eye.
Setting the plate on the head, the first thing I noticed was how tight the chamber was around the valves. This may have to be opened up for a little more room in my opinion, which would also help to unshroud the valves a little--which is better for air flow. The fit otherwise to the bottom of the head is good, and the water outlet has a little play to fit a head if it is shaved slightly. The advantage of this water adapter over the Jern Thunderbolt kit is that the outlet does not need to be machined with the head, and it bolts to the plate offering a better sealing capability.
The first issue if you will (I don't personally believe you can do this without any issues--after all, think about what is taking place), is that the two end pushrod holes are partially covered by the head. This was unexpected, but but I can see why it is. Before I purchased the plate, I had asked Gene about pushrod alignment. When Gene had answered about this to me in a previous post about the issue, he said he had used the spindly 1/4" chevy pushrods shortened, and bent the rocker arm for better alignment. I don't know and will have to check about if he also experienced interference in the plate and head in this area. I'm thinking a little grinding here may be in order, but would like to find out what has been done first By Gene or someone else.
That is all for now, I have disassembled the head and sent it off to the machine shop for cleanup and deck milling.
Beautiful machine work !!
I spoke with Gene French, he said my head appears to have more casting material where the end pushrods go than his head that he used for mock up. He did however still clearance his head to clear the pushrods. That part of the head is purely superficial and can be cut off in reality. So I am unsure in the direction I want to go here.
On thing becomes quite apparent quickly though, there is pushrod / rocker alignment issues that need to be dealt with (I knew that going into this). This absolutely explains why the late Neal Jern (Jern Thunderbolt kit) used a 2 piece pushrod to deal with these issues. I may also go with two piece pushrods, Gene French said he was able to shorten stock Chevy pushrods and use as on piece.
We had to mill alot more off the heads deck surface than we intended to to make it flat. Somewhere around .030"-.035" was removed. This was because there was a crack in the center two water / steam holes and someone tried to weld it to seal it. When you do something like that, you create a low spot from the heat. Plus we are assuming by the look of the repair, that it was mig welded. That is not a stable repair in general to cast iron if especially if regular steel wire was used.
After machining, the weld still seems stable, albeit still ugly looking. All the pits you see can be filled with a little high temp silicone or if your particularly anal, JB Weld (best to do that before milling the deck surface though). Because we had to mill so much off to get a flat surface for the head gasket, we bolted the water outlet on for the final pass to make it all even. If your head is in good shape, as I mentioned before, you should not have to mill the water outlet with the head (such as the case was with the Jern Thunderbolt conversion.)
The other surprise bonus that turned up from milling the deck alot was I am now not stuck using a odd valve size. The excessive milling removed alot of the valve seat area. Normally you'd want to use a larger valve to increase air flow. The head gasket in this case is the limiting factor, and add to the fact the adapter plate shrouds the valve pretty good--not good for air flow. So in this case, I am going to downsize the valve size, use a smaller stem to also help save weight, Both which "should" help air flow in this case. The valve guides are completely worn out, so I will have guides pressed into the head to accommodate the valve stem size used. I should be able to have a bronze guide installed for better friction / wear properties. This particular head has been run hard and dry.
Chad When you do your valve guides, that small pocket/recess at the top is an oil gallery, it holds oil to lube the valve stem. It is part of the valve/rocker arm lubing system. As is the area around the base of towers, it's should be kept about half full, along with the felt pad that would lay on the rocker arms.
The hole for the push rods is going to be around 1/2" in the plate, the push rod are smaller. It's not a guide just a pass thru.
Mark, I did see the recess on the guide and assumed that is what it was for (oiling the valve stem). Thank You for confirming that.
I wanted to add oil drain back lines to the bigger reservoirs, but apparently there is coolant there in that small wall between the reservoir and the intake side of the head. I figured that way it would never get too full and start spilling over. But I don't see a good way at this point to do that.
Chad: thanks for the notes on your conversion. I also purchased one of the adapter units from Scott, but have two other projects going, so won't get at my engine build till after the first of the year, So your info is much appreciated.
not The Thunderbolt setup I worked on; came with a side plate that covered the area around the exhaust ports and sealed down to the adapter plate. The top of the head was milled to seal the Thunderbolt valve cover to the head and side plate to allow the excess oil to drain back down thru the push rod holes in to the valve chamber below. This one was on a Model A and made use of the oil pump to lube the rocker arms. I wish I had taken photos of the setup at the time.
Depending on what valves you use, you may need to reduce the height of the valve guides so the spring retainer does not bottom out on them.
I am just going to consider this a loss oil system and keep the moving parts lubed and not worry about pumping oil to the rocker arms when I get that far in my project.
Thanks Chad very much for the great photos and comments, this is certainly a racing adventure, Gene French is a great source of information Let us know how the project goes I will put in the classifieds more on current prices etc. I have ten more adaptor for sale,
Again thanks Chad for the great photos. I assembled the plate to the model T all the pushrod holes are a model T pattern, 7 of the pushrods were easily done i had to grind a small relief on the chevy head to get number 8 in. please try to make it work,single pushrods is the best, on our head no rocker mods. are needed. I should be done machining 10 more adaptor plates soon 5 this week. Iam going to offer two bolt kits, one is for the adaptor plate and water adaptor which needs to be shcs / allen screws, the other is 8 bolts for the chevy head, this way if you want to have to use period fasteners you can Thanks Scott.
The first word in my above posting should not have been "not" it is THE". My curser sometimes jumps and I don't see all the mistakes all the time.
I ordered up some valves, not sure if what I ordered will work as they are a little special. It will be an experiment. If it all works out, I will have a super light valvetrain set up. I will warn, this will not be a "period looking" build for me, but all the concepts will transfer to those looking to make it that way.
Scott, When I talked to Gene, he said that he did have to bend the rockers to meet up with the end pushrods. You have to either do that (bend the pushrod side of the rocker), run a two piece push rod, or have custom offset rockers made (something I will look into). The spacing is just to far off between the two brands.
You don't have to modify the rocker arm if you just bore out the valve guide in the block to 1/2". I punch the valve guides and the lifter guides so I can use ford Y block lifters.
Jeff, that is an interesting idea for sure. Do you know what the diameter of the head on the tappet is compared to the T tappet? Basically I am wondering if there are any clearance issues.
The only downfall to doing that mod however is you obviously can not return the block to standard service.... well easily. You'd have to rebush the guides and tappet bores back to standard. Of course if you have a block that is damaged for whatever reason, it might not be a bad way to go.
I was trying to keep a stock block, so this could be bolted to any block, with the only major mod being two holes drilled between cyl 2 and 3 on the blocks deck for cooling purposes. Something that would not effect putting a regular head back on.
being able to go back to STANDARD is important ...that is why I used the 1 piece pushrods on my test engine 15 yrs. ago ...I did have to bend the rocker arms on the chev. head ...BUT , I was able to remove the overhead unit and put .015 oversize valves into the reamed original valve guides and re-ground valve seats and re-sell the short block in a standard configuration ...no harm done to either the T block or the chev. head ...I still have the chev. head and modified 216" chev. pushrods and will probably install this adapter set on my 1921 speedster ...am building my retirement home now and weather will turn bad soon ...a good springtime project ...always an optimist ...gene french
Nice project thanks for the info While you were at the mill, you should have shaved off the bow ties.
Just throwing this out there into the realm of ideas. 2-cyl Autocar engines used an offset lifter. However, those lifters are keyed to keep them from rotating. A custom lifter could be slotted and a small pin (or two would probably be better) inserted in the lifter boss to keep everything square.
Walter, keyed lifters are widely used in the performance industry. I work for Cummins and we have a couple engines with slotted lifters with screw retaining pins also.
However, the issue isn't at the lifter. The lifter and pushrod stay in line, it's when you get up to the rocker that the mismatch occurs. Many ways to overcome as spoken here.
Thank you all for sharing, it is great to see the out of the box thinking that goes on.
hope the pictures go through this is my Chevy Conversion setup as I explained in my last post everything is Chevy and T parts Slide the Rockers back and forth to align with the pushrods bend the tips to align with the valves the guides are 5/16 T the pushrods a 5/16 Chevy drove it a lot of cruises over the summer and no major issues if anyone wants to get in touch I can go over a lot of the details
pictures of over the 250 someday I'll figure out how to shrink them
Karl, you can email them to me at crazydart400 AT yahoo DOT com.I will post them up.
Whoops, sorry about that. I misunderstood which end was being discussed with the earlier talk about oversizing lifters and valve guides.
I'm not trying to be smart about this and I understand why people do it today, but it's hard for me to digest the "poorman" angle on this project from an economics standpoint. Way back when people were doing this, did they have some more economical way to fit the head like a cheap adapter ordered out of a catalog?
the term " Poormans Rajo" seems to have originated during the heyday of small time county fair racing ...a person with a small budget could have an adapter machined in a local machine shop and go much faster with only a small investment ...as always speed cost ...how fast do you want to go ?
this was a way to compete with the bigger buck cars/drivers and during the 1930's thru 1950's the model T and Chev. parts were cheap , junk yard items ...today these parts are still reasonably cheap compared to an original overhead valve head or the new reproductions ...and there is the added bonus of doing it yourself ...always an optimist...gene french
It would be interesting to find out the back history of who and when the idea came from. I would imagine that most of that info is lost to time and the passing of folks that first came up with the idea. Me I would have called it something else with Frontenac in the title but RAJO is more marketable.
That's very true Mark, Poormans Fronty would be far more accurate.
And as far as who did it first, probably like most things in the performance world, some did it, someone saw it, someone borrowed the idea, repeat, repeat, and on and on it went. Kind of like an old folklore story.
Walter, The poorman aspect is still a valid term in my opinion nowadays. It is really all relative in relation to dollars, but you can do this setup for half or less of an original (or Reproduction) Fronty or Rajo setup.
However, if your the guy that scours the barns and finds an original setup, you may come out to roughly the same cost. I am never that lucky.
I am not going to say any particular head is better or worse, there is plenty of info out there on that topic already. I know where I will stand with this head and setup, and to me it's a perfect fit. If I did come up with an original direct fit performance head, for a reasonable amount of money, I would jump on it. One was on here recently, unfortunately through my best efforts, I was a few dollars short. But even that one, I was calculating what it would take to put it on and getting running, I will still be cheaper with the Chevy conversion.
I believe you can do this Chevy head conversion using alot of what I have shown for under $1500. If your real lucky, you might be able to do it for under $1000, but you better luck into parts dirt cheap. I personally am already at the $1000 mark.
Thanks for the feedback. I was either grossly overestimating the cost of the adapter plate or underestimating the price of Rajo / Frontenac parts. I'm not terribly knowledgeable about either one and I find your project interesting.
No matter which head you use, just looking at the buy cost is in my OP were the big savings is using the plate. Between Frontenac, RAJO and Chevrolet head you still are going to encounter the same cost when it comes to things like valves, rocker arms and push rods. Although the Chevrolet parts might be easier to source then the other two.
So true Mark. If you found an original Fronty / Rajo head, It would probably be foolish to use the 80 year old springs for a performance application. You can pretty much guarantee it's going to need valves and a valve job, and more than likely valve guides or guide liners. If you can do all that yourself, great. If you have to pay someone it's going to cost.
I can grind seats and valves, but I will have my machinist do it because he can make everyone exactly the same and all the valves will be at the same heights. With his hi-tech machine and cutters, it is super easy. If I had to do it with my tools (which are perfectly adequate for the job, just a slower process) I would have way more time into than I really have to spend. Pay me now or pay me later.....What's your time worth?
Anyhow, minor update. These are the valves I am hoping to use. These are 7mm stem, 1.630", coated heads, titanium valves and titanium spring retainers. Super light weight, and way overboard for this application. Courtesy of an Ex Chevy Nascar engine. The valves need to be shortened and have the lock groove recut for these to work. Neither one of those mods should be a big deal. The bigger deal (not really though) is I have to shorten the guides in the bowl of the port, to accommodate these, but that will also promote airflow.
Titanium valves? That's just plain cool. You have good/lucky connections... :-)
I was gonna ask about the rockers: Can they simply be bent/adjusted more into T alignment? Heated or cold? That stumps me.
The notion of a Poorman's Overhead has intrigued me since I first heard of it and the last I studied the subject, it suggested; increased compression?
Perhaps not but good flow! :-) I sure could be way off base.
I have three of those bent crank little buggers here (28 Chevrolet's) and since two of them are destined for another singular project, I have a spare head! :-)
And also, I'm "color" blind in that respect, I myself would highlight the bowtie and the casting numbers on that head. ;-) But that's just me. :-)
Shoot, I've had John Deere, Farmall and Minneapolis-Moline/Twin City tractors (Vive la Minnesota!) here; all at the same time. :-) Even worked on those little Ford N type tractors. Built a wiring harness for one of those little things. Hah! The 45 Ford dump truck here was filled many times by one of those little N things.
Now to pry my clutch open and entertain a new conversion adapter. Sorry for my babble Chad.
Thanks for doing this thread, no matter how long it takes and thank you to the Hansen-French Connection! Pun not intended. :-)
Here are Karl's pics he was trying to upload. Alot of interesting stuff to see here. And I REALLY am digging the fact he is using the original coils, like I want to do also.
Karl, does it run good with no water pump? Any head gasket issues?
I really like the survivor look! I plan on using coils also but need to do some dry fitting to see if there will be room where they come out the firewall with the head in place. If not done so, the only thing I would add is freeze plugs in the ports to seal them off.
A plate like the lifter covers would look nice to cover your holes.
No issues with temperature even in the summer heat I also own a 25 Chevrolet and had quite a few extra head gaskets I used the steel head gasket from my Spares and couldn't stop it from weeping as soon as I changed it out and install a copper head gasket that has seemed to take care of it as far as the intake exhaust ports I do have the freeze plugs I thought about a side plate haven't quite decided
Karl; What plugs are you running?
I have Champion W 89 d my 25 Chevrolet with the 28th head on it is running Autolite 3076 even though they don't reach into the combustion chamber I've had no issues with them put the 3076 in the conversion happened to find the Long Reach Champions so I put those in
Karl was gracious enough to let me stop by his place yesterday. Very cool shop, very cool individual. Thank You for your time and the tour.
His conversion was done with a old cast iron adapter plate. Let me tell, it runs good (even on a worn out engine) with a bunch of torque....which is needed for the hills around his area.
This better explains how he fixed the geometry issues between the pushrods, rockers and valves. Do a little grinding on the sides of the rockers, shove the end two over until the pushrods line up, and bend the valve side to meet the tip. So simple a cave man can do it. Of course I'll probably take a harder route. This needs to be done to number 1 and 4 cylinders.
Hey Chd, Matt from the Schoharie area here. There's a guy on the MTFCA Facebook page named Philip Reinhardt Who's just finished a poor man's Rajo. I'm sure if you have any questions he'd also be happy to give you some input. I like it!