The Stovebolt Site Forums The Shop Area Engine Shop Stock 51 temp probe in a 55 235

Changed my 216 for a 55 235. I want to use my stock gauge but the 235 has a huge hole for the temp gauge compared to the original temp probe on my 51 half ton. Can I use a bushing to go from the course thread to the standard thread on the temp probe?

you need to keep the adapter that matches the sending unit probe, the probe has a taper that seals against the adapter and the nut hold it against the seat.

I think my issue is that I don't have an adapter but I might have found one at NAPA...part number 7011798. It will be in tomorrow and we'll see if it fits both the head port and the probe stud. Got my fingers crossed.

This might be the NAPA part number: BK 7011542 (their photo of the part does not look right)

Weatherhead (Eaton?): 202X5X4

Classic Parts

ADspudnut, please let us know if your part NAPA number works. The NAPA picture for your number looks better than the picture for my number.

What's the casting number on your head? The '55 should still have the smaller temp sensor hole, as they still used the mechanical temp gauge. It sounds like your engine may have a later head on it. That's not a bad thing, as the 848 head is superior to the earlier one.

> Hey Longbox -
In what way is the 848 head superior? I have a '59 3836848 head on my '54 235 block. Always wondered if there is any difference vs the original '54 head. I believe that the rocker oiler may be different than the '54 head.

> ADspudnut -
I have a reproduction mechanical temp gauge on my '54 with '59 head (see above). It requires a reducer like Tim showed. I bought it from NAPA, but I don't think that it is the NAPA reducer that Tim showed. I had to file the center opening in the reducer to enlarge it a little to accept the bulb. Perhaps the bulb on the Chinese Commie reproduction is a little larger diam than the original (?)

The 848 head is a higher compression head. I think it may also use larger valves, but I may be confused with hot-rodders using the 848 head on a 261 and being able to install larger valves.

Kurt

I believe that steam holes need to be drilled in the 848 head to put it on a 261.

Kurt has hit right on it, higher compression. I'm not 100% sure if the valves are any larger, they might be. Using it on a 261 nets even a bit more compression, due to the larger cylinder displacement. Don is also correct about the steam holes when using it on a 261.

The head on my 235 is the 848 even though the block casting shows its the early 235 built in 54 and installed in the 55 trucks (55X toward the back of the distributor). I also had to drill out the NAPA adapter...part number 7011798....so the stock probe would fit.

All full pressure 235s and 261s use the same size valves. It works to install the larger 1950-52 splash 235 intake valves.

ADspudnut -

Glad you got your temp probe to fit your 848 head. The '29-'57 MPC notes that the 848 head came with a reducing bushing to accept the temp probe. And thanks for confirming that the reducer needs to be reamed out to allow the probe to fit.

Sorry I hijacked your thread with my question about the 848 head. But since I already hijacked it, here is some more engine trivia ...

According to GM specs, the valve openings are the same on both heads.

Here is HP and Torque specs for 235.5 cu in truck engines from the GM Heritage Center:

> 1954:
7.5:1 Comp ratio
112 GHP / 105 NHP @ 3700/3600 RPM
200 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM

> 1955 1st & 2nd:
7.5:1 Comp ratio
112 GHP / 105 NHP @ 3700/3600 RPM
200 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM

> 1956:
8.0:1 Comp ratio
140 GHP / 123 NHP @ 4200/4000 RPM
210 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM
(Musta fed those horses more oats to get that HP gain)

> 1957:
8.0:1 Comp ratio
140 GHP / 123 NHP @ 4200/4000 RPM
210 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM

> 1958:
8.25:1 Comp ratio
145 GHP / 125 NHP @ 4200/4000 RPM
215 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM

> 1959:
8.25:1 Comp ratio
136 GHP / 115 NHP @ 4000/3500 RPM
217 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM

> 1960:
8.25:1 Comp ratio
135 GHP / 115 NHP @ 4000/3600 RPM
217 G Ft-Lb / 195 N Ft-Lb @ 2000/2000 RPM

Not sure of the first date that the 838 head was used on production vehicles. It is listed for '53-'57 235's in the 1929-1957 MPC. Casting #3836848, part #3730415. It is not listed in the 1929-1954 MPC.

The "848" head was first used in 1956. It was the replacement head for 53-63 235 engines in the 1957 and later MPBs.

The NAPA reducer had to be reamed but I do not think that the Classic parts one has to be reamed. I'll try to remember to check the other NAPA part and the Eaton/Weatherhead part (next time I am at the main NAPA warehouse).

I think that Pre '68 Dave once explained why/how the compression changed on later 235s (all with the 848 head)? Carburetor might have been the reason?

Here is a good engine-specs website.

This is the one I used on my 1956 head,fit perfect and no reaming. Temperature Sender Reducer Bushing


Tim

That's one of the parts in my earlier post, Tim.

I bought it several years ago from Chevy Duty (now Classic Parts). It did not have to be reamed.

Go figure....I buy most of my parts from Classicparts..just not this time for the reducer. Hope the NAPA part doesnt leak when I fire the engine up.