Hi, i am about to do the chevy head conversion on my -23 runabout and i have a complete set from Mr Neal Jern, who sadly passed away in the beginning of september.
Was Mr Jern the fabricator of the head gaskets or is it someone else? I could use a couple of extras, for the future, i believe.
Your car is still looking great
I think a generic ohv gasket from the vendors would fit the block side and a std Chevy 4 cyl gasket on the head side?
Here's Lang's OHV gasket: https://www.modeltford.com/item/3002OH8C.aspx
And here's a std chevy 4 cyl head gasket 1916-28 from the Filling Station: https://www.fillingstation.com/catalog/flippingbook/index.html#316
Did Mr Jern write anything about the cooling system in the installation instructions? The small holes for coolant in the adapter plate plus the small passages in the head may cause a need for a water pump?
Carefully check the sizes of the water passages and expect to need a water pump. A good friend had no end of grief with overheating and head gasket failures. He tried both the steel and aluminum adapter plates and everything (head, block, and both sides of the plates) checked and milled for flatness. Went through a bunch of gaskets, replaced radiator with a new one and still had issues. Using the same radiator and water pump he gave up on the Chevy head and installed a BB and all his problems went away. Others have had good luck with the Chevy heads, we still don't know why he had so much grief but he had "enjoyed" as much as he and his budget would allow. Plan ahead though for potential heating issues with a good radiator and open things up as much as the original castings in the head and block will allow. Oh, and get spares of the gaskets and hope you won't need them for a long time.
I HAVE 2/3 of a chev head replacement and wonder if an early block with heavy water jacket to T valve break through would be reserectable using the chev head. After all, the valves only need a longer sleeve insert to keep the water and oil separated.
just a thought.
Thanks Roger for Your kind words. The least thing i can do is to order these gaskets and look closer at them. Someone told me that the chevy head use a frontenac gasket. Wonder where to get one of these.
Thanks Walt and David for Your replies! I use a Berg's radiator and the engine runs too cold right now, can't get the thermometer to reach the proper degrees. The block/waterchannels are also very clean from rust. Walt, was the heat problem restricted water flow related or maybe broken head gasket related?
Heat issues were never completely identified. Some issues that we worked on that helped - replaced radiator with a new one and opened water passages as much as we felt safe doing. Both helped some but we continued to have both overheating problems and losing head gaskets. Some overheating occurred independently of head gasket failures. Of course a failed gasket usually caused overheating as well. We lost track of how many times things were resurfaced.
By the way, we tried installing the adapter plate, then fairly gently heating it with a torch and retorqued just the adapter plate before installing the head. Naturally we retorqued the head as well after a heat cycle.
Our issues were quite frustrating but I must give Neal Jern credit as he was willing to give advice and guidance as we encountered problems. He even provided the replacement steel adapter plate gratis. Others have had good luck with these conversion sets, we just gave up when hitting our heads against the wall quit being fun.
Oh, must say the car ran really strong when the head gaskets held and it wasn't overheating.
very nice looking car. i have some chevy heads i thought of using some day, has any one taken over mr jerns products, or is it the end of those kits?
Yeah i was wondering about reusing a block with valve chamber issues too by this method, Did he really die? Does someone still sell his adapters?
His passing was only recently announced. It's really too soon to bother his family about someone taking over the business.
I got to ask, How dose this improve performance? Looks to me that the added area of the plate will lower the compression to the point that nothing else will matter.
The Chevrolet head is flat as the Chevy pistons don't come all the way to the top like Model T's. The Thunderbolt site list several compression ratios. The kits are available in 6:1, 6.5:1 and 7:1 compression ratios. On the block side there is room for the T pistons to come up into. To raise or lower the compression depends on the configuration of the area the valves come down into. I think the plates are about 1 inch thick, at least the one I saw.
Compression ratio is determined by the thickness of the adapter plate. Anything from mild to fairly wild. There is no combustion chamber built into the Chevy head like is present in most heads. It is a flat surface with the valves at the surface level. That results in the combustion "chamber" being the hole in the adapter plate.
Jern's web site is still up with the instructions for installing the kit on a T engine:
There are some problems with using the generic gaskets - two extra 1/2" holes has to be drilled in the deck plane between cylinder #2 and #3 in the engine and one extra hole for coolant has to be drilled in the head, so corresponding holes has to be made in the gaskets - and there may be problems connected with modifying a head gaskets?
Anyone tried to make homemade extra holes in a copper head gasket? Maybe extra copper crush rings could be used to seal and secure around the new holes?
Mark & Walt, thanks. Sounds like with a high alloy plate, cut for just valve clearance, this could add a lot of bump. Thanks again for the insight.
At the risk of a little thread wander, Ford in the late '50's (actually I think it was 430 and 472 cu in only offered in Lincolns and Mercurys) built some V8s that had a similar head/combustion chamber. The head was flat and the deck of the block was machined on a angle to create a wedge shaped combustion chamber. It made it awkward to bore the block and I believe that a special adapter plate was offered to mount cylinder boring bars. It was a idea that did not catch on. I recall seeing one in a wreckers with the heads off. The slope was to the outsides of the block.
The "problem" (and maybe that is not the right word) with the T overhead conversions and the Chevy's is the not really great combustion chamber shape. They were able to ultimately get lots of compression and good big valve areas and ports. BUT they rapidly became VERY sensitive to spark knock/timing variations.
A "wedge" combustion chamber greatly reduced this sensitivity by creating a "quench" and thus slowing very slightly the speed of flame propagation in a high compression motor.
By 1933/34 the industry had become widely aware of the problems and potential solutions. Partly this was driven by the advent of "tetra-ethyl" lead gasoline which allowed consistent high octane gasoline to be made cheaply. And so the HP race was on!!
The model B ('32) Ford still had a "primitive" combustion chamber (better than a A), which the Z is a copy of.
The model C ('33-34 4 cylinder) Ford had a greatly improved shape, which the Sherman is a copy of.
Anyway I apologize for the thread wander, but I thought some might find it a bit interesting.
I have thought about making a OHV head for the T with a wedge chamber. Then I come to my senses!!!
OT - The Chevy 348s and 409s also had an angled deck and flat head surface:
Walt, do You remember which plate Your friend used? 6-6,5 or 7.
Did the gasket always break at the same point? Did You use Mr Jerns gaskets from the kit or some others? Where they copper, steel or composite?
Has anyone heard if the model A kit also have this "problem" or is it just the T kit?
Les, all input are educating, let it come.
I will take some pics of the different parts tomorrow.
Hey thanks for the education
Kevin Pharis makes copper shim head gaskets for the T (with a few "tweaks" around the valves). If you strike out he might be able to help you.
My dad did this conversion using a '28 Chevy head on a T block about 30 years ago. He used a machined adapter plate with bore sized holes. I don't think it came from Jern.
It didn't add any performance but looked neat. A T engine with one of Ralph Zaichek's heads is a much better performer.
A guy in Hood River, Oregon use to make them, 30 years ago would be the right time frame. His were steel plate.
I was wondering if the original Chevrolet outlet was used and if a water pump was added. The original outlet is fairly small and the Chevrolet engine was designed to use a water pump to push the water through the block.
Gaskets - The first set at least came from Neal with the kit. Others later came from a variety of sources, some copper, some steel.
I think the adapter plates were the 6.5 version but were milled (just to verify flatness, not to raise compression) a couple of times.
A water pump was added, electric type rather than early style belt driven. The same pump has been in use with the current BB head with no heating problems. The overheating and head gasket issues went away when the head was swapped. The kit from Neal included a water outlet rather than the smaller Chevy version.
Performance was great with the Chevy head, equal or better than the BB when using similar carburetion.
Thanks for Your input. I will not use this set up for performance, just the 20's look and because it's cheaper then a rajo kit, in the short term... I have a Z-head right now and a Tillotson X carb and i'm very satisfied with it, but i like the look of visible rocker arms a lot.
The deck, plate and head are plane and i can even think of enlarging the compression chambers to lower the ratio for keeping the heat/stress down. I also use standard diamension after market valves, so it will not be an saturn rocket.
How about using Purple Ice or similar for extra cooling?
Was it the upper or lower gasket that failured?
Here are the pictures i promised. Open up the four small holes can't be to difficult in the composite gasket. Studs for Chevy head instead of bolts. Heat and retorque the adapter plate several times before assembly. Adding a waterpump. Well, i will give it a try but i could sure need some extra upper and lower head gaskets.
I hope it all works well for you. Let us know how it works out.
i wonder if Royce father used a water pump for that conversion 30 years ago?
Kep, You shouldn't have. Tee Hee.
But i really am wondering if a water pump is needed.
You can buy small copper rings that could be swedged into place like an eyelet for just this kind of use, so I was told by someone that has been dealing with this kind of stuff for a long time.
I would think it really should have a water pump. Remember that the water is pushed in the Chev engine. The water jacket does go somewhat around the exhaust ports. If the water was not pushed it might want to form steam pockets in those areas. But I guess if you use the larger outlet from a Model T and put all the passages between the block an head, I don't know and can't wait to find out!
I have been following your car for a long time and have always been impressed.....now, it just got better
You and I have the same tastes....
I also have a '28 Chevy head and have been contemplating doing the same conversion....so I will be watching this one closely.
What about a Solid copper gasket custom cut out of .070" - .090" solid copper shim stock?
Thanks a lot Clayton! We both love the little T's but i must say You are living the dream. The TROG must have been a adventure.
I feel that someone must know where to buy the chevy head/frontenac gasket. People are using the frontenac head today and someone must manifacture the gasket.
How about water flow efficiency? I will put a pump on the engine, but pushing or drawing? A Texas T part one for pushing into the engine or a modified bracket and a -36 one for sucking?
Upper water pumps suck.
If you spin it faster than the water can flow, it will cavitate and not pump anything. I believe that has always been a problem in the early V8. Moderns always mount the pump down low.
OHV gaskets for T blocks should all be the same.
Another real problem with upper placed pumps is that they are operating in heated water from the engine rather than cooled water from the radiator. Makes a difference with shaft gaskets of modern construction, they may not last.
Some overhead gaskets for 16 valve Roof heads had crescent cutouts for the valves as the combustion chamber was larger than the engine bore.
Chaffins mentioned in an old thread that they had them in steel and copper.
Or try http://www.headgasket.com who might have something ready-made, or be able to fab some to your specs.
I bought a Fronty gasket from Lang's recently.
Thanks guys for Your replies. A Texas T parts pump then.
The chevy head has just 8 bolts/studs and i wonder if not the water outlet will be the weak spot with a bad sealing against the adaptor plate, What do You think?
The one I worked on was on a Model A speedster. I don't remember right now if it used a Model A or B water pump but I don't recall it being an issue. I think the instructions call for the casting to be installed and surfaced to the same level as the head. We may have ran an extra bead of sealer around the openings between the gasket and casting at the passages. We did not pull the plate off the engine, only the head off the plate. The gaskets were newer and the engine had only been run briefly so they were reused. The engine was in to do some work on the oiling system that had been installed for the rockers so the head had to come off to machine a spot for the rocker cover to sit on. We also installed new rockers and shafts at the same time.
There was a small issue of one of the center bolts for the plate to block on the drivers side being very close to a water passage. There was a small amount of weeping there but some Black RTV in the hole for the bolt took care of that. Remember this is a Model A setup so passage ways and stud holes in the block will be a little different then Model T.
I remember even for a more or less stock Model A engine it did have a different sound, I liked it!
Thomas, nice ride. To highjack your thread, do you have photos of your pitman set up, and anything to add about the parts used?
Jon, it's a -30 steering column with box. I cut the flange and fabricated the bracket. It consists of three parts or actually of five parts. You need a piece of steel inside the frame for supporting, when you thighten the u-bolts. Take out the bearing before you cut the flange or you have to buy a new bearing.
Drill a hole in the lower plate through the frame and into the chunk of metal. Thread it with a 3/8"
UNF. Just to keep everything fixed.
Roger, you could perhaps use a water cutting machine for the water channels, it will not harm the composite between the two copper layers. So.. an original T-gasket with the extra holes cut and a original Chevy gasket. Now we just have to seal the water outlet.. Hmm..
Maybe Marks idea with copper rings into milled grooves.
The original -28 chevy head gasket.
Jon, the idea is from Mr Ford himself. Front engine mount.
Photo courtesy Chris Olsen.
This is with a standard -28 engine.
model T chart for comparison;
Very slick. Thanks
Here is my dyno chart with a chevy head and model A crank
Jeff, was that rear wheel hp? Were any std model A tested with the same equipment? (considering the model A was rated at 40hp at the engine, likely without fan, generator, muffler etc, but anyway
Thomas, Yes, I think head gaskets can be modified, though I hope you're lucky and can use the ones supplied with the kit for a long time
Since there is a market for this kit and for supplied for the running cars already built, it's likely the production will be restarted some day?
That was rear wheel HP in a TT truck with high speed gears in overdrive so there were some loses due to friction. The dyno couldn't drag the truck down in direct drive so we had to test in overdrive. The reason the graph drops off suddenly is I didn't want to rev my engine any higher so I backed out of the throttle.
I misread and thought it was a Model A engine that got a lower hp rating with a Chevy head than original.. Ok, 4000 rpm is quite high for a T bottom end, guess you have pressure oil too?
4000 rpm with high speed 5.17:1 TT gears would give 74 mph - that'll deliver the goods fast enough