turbo 350 to 235 six
 

Will a turbo 350 mate up to a 235 six or does one need an adapter plate?

Re: turbo 350 to 235 six
 

Here, the search took about 30 seconds.

The site says they DON’T recommend the TH350 for the 235; don’t know why. Didn’t follow up. I’ll leave that to you.

http://www.langdonsstovebolt.com/sto...egory=18665953

Re: turbo 350 to 235 six
 

Thanks for the link. I'll procede with caution

Re: turbo 350 to 235 six
 

That is odd can't image it takes anymore power to run than a Hydro. Probably need to use a later model 235 bellhousing adaptor for a powerglide and add a new trans mount. PG and TH350 have the same bellhousing bolt pattern.

Re: turbo 350 to 235 six
 

200r4 700r4 have a better first gear for low power engines

Re: turbo 350 to 235 six
 

Yup, like he said. Depending on what rear your running, a TH350 will be revving high with a 235 at highway speeds. You are better with some type of overdrive ratio like the 700R4. I went with a T5 5-speed, kept original pedals.
Highway all day at 65MPH...

Re: turbo 350 to 235 six
 

I read about a guy who has or was doing that. Had to find an adapter I think. I'll see if I can find the website. Not sure if he ever finished it though...

Re: turbo 350 to 235 six
 

One line of thought is that the 350 takes more power to operate than say an aluminum powerglide.

Thing is that you look around and GM put some pretty small engines in front of a Turbo 350 in the 70's . As far as top speed you can run a 3.0 gear and buzz down the highway at a good clip with one if you want to. It might not pull stumps out of the ground or win stoplight drag races or pull a trailer very well but we all have different ideas of what we want as far as performance goes.

Big rub with a 235 and turbo 350 or aluminum glide is that you have nearly 400 bucks tied up in the adapter before you get to the trans.

Re: turbo 350 to 235 six
 

i'm with mr48. lots of money tied up in adapters etc. why not use the overdrive unit if you're gonna spend the bucks. then you get better low end and can still go highway speeds without overclocking the old 6.
would you use a new trans cross member and mount along with the existing front engine mounts and rear engine mounts? if so there would be a good reason to replace the old mounts so all are fresh and flex about the same amount, hopefully. otherwise there are 3 mounts in a row and that can cause some issues with stress if they have different ratios of compression. like a kids see saw effect, if one end gets loaded up it can pivot on the middle and cause the other end to unload or whatever. just something to think about.

what about a complete new drive train. if you want to stay with a 6 how about, say, a 4.2l inline 6 from an envoy/trailblazer with an overdrive trans already connected or a 4.8-5.3 from a pick up. they would have fuel injection and an overdrive trans. always start easy, give great mileage and drivability, no foul odors from the exhaust etc etc. it would be some work but if the truck is in good shape it would make it a lot more fun to drive. buy a write off donor vehicle and you should have all the stuff you need.

your truck and your pocket book. do what you want and have cash for to get the job done in a timely manner. otherwise it may be on the back burner longer than you think. thats how projects end up on the for sale list.
do a feasibility study first so you know the totals before you start. for the auto swap this is at least a partial list, maybe not complete.

-adapter plate and flex plate kit
-transmission and torque converter
-trans filter and pan gasket kit
-trans torque converter seal
-trans output seal
-fasteners to mount flex plate to engine, trans to engine, cross member to frame, trans mount to trans, etc
-rear trans cross member
-rear trans mount
-trans cooler lines, fittings and retaining clamps
-trans cooler hoses (to allow for flex near cooler connection)
-hose clamps etc
-trans cooler and mounting hardware
-trans fluid
-custom fit drive shaft for length and to fit rear axle yoke. include the yoke to fit trans
-automatic floor shifter to match trans, floor boot and linkage or steering column swap for one with auto shifter to match trans, with shift linkage and related wiring
-wiring, fuse and switches etc for park interlock (to allow starter to only work in park/neutral) and back up lights
-remove old clutch pedal assy and linkages
-plug for hole in floor where clutch pedal used to be

Re: turbo 350 to 235 six
 

I'd have to believe that is the primary reason. Low gear on a turbo 350 isn't that low and the low numerical gears you need for highway speed being 3.0 or maybe 2. something with the 350 trans are a hard pull for a low powered engine.

In the end it comes down to two things. will the engine trans, rear axle combo let you accelerate at a reasonable rate without having your foot on the floor.

On the other end of the spectrum you need to have an rpm at highway speed that the 235 is comfortable with. With the 1 to 1 final ratio that means around 3.0 while and over drive trans should be able to run with 3.5 or 3.7 gears at the same rpm.

If you are driving the truck now you can stick a tach on it and see what rpm it likes to cruise at and then use one of the tire/gear/rpm speed calculators on the net and you can figure out what the desired final ratio needs to be.

I'm not going to argue the stick VS automatic as we all have our reasons for wanting one or the other be it that we think old trucks have to have three pedals or we can't drive a stick and have no idea how to push a clutch and move a shift lever at the same time. My 71 year old left knee keeps lobbying for an automatic behind the 292 and it just might get one if the knee doesn't feel better. I've got the 350 that I had in my 71 before I put the
Cad 500 in it and I have a couple of 400s that could be rebuilt. I've also got a nine inch with real nice 3.0 gears I want a 5 speed but my knee may win out.

This is an electrical vehicle chart but it is rather nifty because you can plug in variables and it will give an answer for the one you don't plug in. http://www.advanced-ev.com/Calculators/TireSize/ It doesn't give a trans ratio outside of 1 to 1 though.

This one shows rpm for auto, AOD manual and 5 speed OD that are somewhat accurate. https://www.ringpinion.com/calculators/Calc_RPM.aspx

Re: turbo 350 to 235 six
 

Lets go over the numbers and it will become apparent why 200r or 700r vs th350.
I am only talking about 1st and 2nd not direct or overdrive and does not take into consideration the rear ratio

Trans ratios

Powerglide 1st - 1.76 2nd - 1.52 (Direct)
TH350 1st - 2.52 2nd - 1.52
th400 1st - 2.48 2nd - 1.48
200R 1st - 2.74 2nd - 1.57
700r 1st - 3.06 2nd - 1.62

Stock 3 speed standard truck SM318
1st - 2.94 2nd - 1.68

As you can see the 200 and 700 more closely replicates the stock low gear second gear ratios. If you change the rear gears this changes your choices for transmission
200 and 700 of course have an overdrive and all transmissions had 3rd as direct 1:1, PG is the exception

Trying to pull out in traffic with a 90HP engine and a tall 1st like 2.52:1 could be a problem so some.

Re: turbo 350 to 235 six
 

Actually 2nd on a glide is 1 to 1 as there are only two gears.


Transmission/Gear 1st 2nd 3rd 4th 5th 6th Reverse
Powerglide 1.76 1.00 - - - - 1.76
Powerglide 1.82 1.00 - - - -
TH200-4R 2.74 1.57 1.00 0.67 - - 2.07
TH350 2.52 1.52 1.00 - - - 1.93
TH400 2.48 1.48 1.00 - - - 2.00
TH700-R4 3.06 1.62 1.00 0.70 - - 2.29
4L60 / 4L60-E 3.06 1.62 1.00 0.70 - -
4L80E / 4L80-E

According to the above chart a powerglide would be a lousy choice for a small engine with either the 1.76 or 1.82 gear reduction in low gear.

Re: turbo 350 to 235 six
 

Tom Langdon is a wealth of knowledge and is glad to share it. Call him up and ask him

Re: turbo 350 to 235 six
 

You need an adapter to bolt the 235 to a 350 , 400 , 200 or 700 r transmisions. If you have 230 , 250 or 292 they will bolt right up .

Re: turbo 350 to 235 six
 

I just pulled my 261 out of my 54’ 3100. It had a TH350 with the Langdon adapter plate. It is for sale for $300 too. It ran fine but I bought it from my neighbor like that. It had an Isky cam, Fenton header, Clifford intake manifold, K&N filter, Federal Mogul pistons, Holley 4 barrel, HEI ignition. It was great but am in a LS swap frame off conversion now. Landon’s Stovebolt is a wealth of knowledge.