340-6 Tuning?s Autolite 66 + 195 T-Stat too much?

Wanting to install a 195 Stewart Components Thermostat in a 1970 340-6 Pack but can't seem to figure out which part # I need to buy. Anyone know or is there a better option? Thanks

Why a 195? Might consider a lower temp especially with a 6 pack.

be quiet and pay attention #2 poster

COOLING system:
The engine must have a 195 degree thermostat
195 degree high flow thermostat- Stewart Components has the best quality thermostats part # 306
These are manufactured by Robert Shaw and modified by Stewart. They feature a balanced sleeve design and are designed for high flow, high RPM applications. They work! Road course tested.
A very normal operating temp is 195-215.
220 is warm
230 is HOT
240 is very hot

Use a mixture of 40% coolant/60%distilled water and a bottle of coolant conditioner

Beware of high under-hood temperatures. Measure it! Lowering the minimum operating temperature of the coolant to 180 or 160 degrees does not correct this problem. Measure the temp at the base of the carb on intake manifold. It should be the very close to the water temperature. Lean engines and or improperly timed engines create lots of under the hood heat. Power steering pumps create heat so a cooler should be installed.

Part #??

Wow another temp freak on this site I thought I was the only one Are you using thermocouples ?

Part # I believe is 306 for Stewart Thermostat. Not readily available.

I cannot seem to get the six pack to run any other way but rich. Currently has a Murray 180 stat and plugs were Autolite 65s

Got the center carb mixture screws 2 turns out. 6 pack guide says 1/8 to 1/4 out on outboards but won’t work here. It won’t stay running if I do that.

Started with the outer carbs 1/4 out. Cranked but wouldn’t stay running. Before messing with anything as it was in a running but rich state, the mixture screws on the outboard carbs were between 1.5 and 2.5 turns out.

With this setting, The Autolite 65s were carbon fowled and wet on the outers. 1,2,7,8.

The one 66 in it was good with the rich mixture. That’s why I went with 66s.

Too hot of a plug? Any ideas?

Got it running with center 2 turns out, outboards 1 turn out and Autolite 66s. Exhaust smell is rich with 2, 1, and 1 but cranks right up and runs. Just stinks.

The stewart number is on the post...................................
No temp freaks here, just engineering geek types using modern tech devices, wide band A/F meters, IR temp gun, digital readout tach/timing light by snap no, Fluke DVM etc no need for thermocouples...lol No six pak tune up has been too tough to tame yet. Many have been tamed.

What does the guide say? Read it again.

OP you are over- jetted - Center carb jets at 62 or lower.
180 is the wrong thermostat temperature. 195! Pay attention! Stop wasting everyone's time with the 180 operating temp- it will not run properly at that min operating temp- it's in the guide!!!. 195 thermostat - at this pt just buy one from Napa, or look on line for a oem nos 195 temp
the temp change alone to 195 will affect how it runs.............
Float levels
initial timing 16-18 btdc
coolant mix
Firecore spark plug wires
plug gap 0.040
please read the guide

You may have mis read that about the outboards being set at 1/8 to 1/4 turn out. From the factory they are set about 3/4 to 7/8 turn out, which is usually a little lean. If you want know how a six pack works, install O2 bungs and get a wide band sensor. It really helps.

What the factory did 50 yrs ago has no bearing on what needs to be done here.

Set the carb/engine up per the document - It's called the baseline - that where you start the process. Works every time on this end.

What document

I know about the t-stat it’s on my list of to do things. I’ll probably just get a Murray from Oreilys.

I’m going by the document. Maybe I wasn’t clear enough. It WILL NOT stay running at 1/8, 1/4 or even 1/2 turn out on outboards regardless as to what the guide says it DOES NOT work here and I seriously doubt going up 15 degrees in temp will change that but we’ll see. It wants at least 1 turn out to keep running. Now if it had a 160 and I was going to 195 that would be significant.

What about the Autolite 66s in combo with 195 t-stat is that likely to lead to running too lean? Is the 66 ok to use?

It is called " the six pak tuning guide" ....it's been posted here too many times, no one wants read it let alone to do the work required

look on the lift off hood playground for it

I have a much better latest revision - but i don't see any good reason to post it. I am the copy editor & collector of the information. We test six paks weekly over here. It works! Send money i will send a copy of the latest - it is pretty good. lol

Same old posts, wrong thermostat, over jetted, same ole $#%^, no patience on the user end, no instrumentation, no documentation, reach thru the computer and turn the screwdriver, set my float levels.... and there is no app for your phone.

Thermostat/temp is irrelevant if it won’t stay running cause it won’t get up to 160, 180, 195. It won’t stay running with outboards less than 1 turn out. How am I over-jetted with everything stock??

What about the Autolite 66s? Are they too hot? Especially in combination with a 195 T-Stat?

Where is that quoted from? Contrary to everything I've heard and done for 50 years. High temps came about in the emission era in an attempt to reduce tailpipe emissions.

Everyone, I've ever heard, and who knows anything, said cooler is better in a performance application. The 40% coolant is also strange as straight water, or something like the Evans stuff, with a bottle of Water Wetter or equivalent, is also supposed to work best.

Just asking

ETA...66s are too hot, unless this thing mopes around in city traffic all day.

ETA... not sure why a 340 6 pac would require tuning in contrast to every other pushrod V8, but I'm all ears.

Been running 6 packs on a multitude of vehicles for over 45 years, no issues here BTW you may want to read IR Gun Accuracy

My 2-cents
1. Are the carbs used? We used to drill out a lot of orifices back in the day per Direct Connection engine guide
2. Is your power valve possibly bad?

Only by me. They were rebuilt a few years back to stock and concourse appearance. Power valve I can easily switch out and try a new one. Why do you ask? Usually with a bad power valve you have to turn the mixture screws way in. Idle and drivability are fine. Just stinks/rich.

How old is this fuel now?

One week this Sunday

I have seen many hotrodders leave their gas tanks have empty in the winter and summer for over 90 days and wonder why the engine doesn't run like normal, all pump fuel that I have heard has a limited shelf life of 90 days or less depending on how long that gas was in the tank at the station

That’s basically what I have heard. I ALWAYS use stabil 360 in every tank for both toys and small power equipment.

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/927165/re-6-pack.html#Post927165


^the guide that has been referenced. Mods could it get added to the tech archives? Its actually not THAT easy to find with a search.

I can't help moparts with retaining documentation and the spoon feeding is over

If you finally read the guide, it will tell you all about why you need a 195 degree thermostat. I am not repeating what is already well documented. Read the guide . We [there is 2 of us] work six pak carb set ups typically weekly and we are very successful.

– if the op wants to work this offline he should pm me.

The new guide is greatly improved but I see no reason to publish it. Convince me otherwise in a PM or just send money.

I don't buy or use any gas additives, none :twocents
Fresh gas only
I do buy aviation 100 Low lead gasoline at the local airport for one of my cars that sits a lot between uses because it has a 18-month shelf life
I do need to warn everyone about using any leaded fuel on highways, the Feds have a law that they can charge you with, if caught and convicted, violating it that has a ten-year jail sentence max Race or aviation gas

I am having way too much fun with this

We get paid for fixing/tuning six paks and debunking the ignorance that surrounds the fuel system.
Most six pak cars run like turds but the owner will tell me it runs great

Again: Convince me why i should post the latest version of a well written/researched technical document, with a previous published version not as well written [that works if you can read] for free? Send money i will provide you a printed copy

I offered [free] offline help to the OP, should i charge him instead?

This board IMO is about helping each other not making money unless you advertise on it. I have been here since 1998 or so, have 5.5 times as many posts (mostly trying to help another that I don't know), and have never asked for a red cent.
And yes I run a business too

Well another potentially good six pack post run off course
Excuse Thermoquad - hes just old and grumpy with poor
internet charisma. Doesnt make him completely a bad person.
But …….


.op just wanted to know about plugs and stat

Then he posts it runs like crap ..or idles like crap.
Who knows

I was screwing with some carbs last night
1/8 turn on outboard baseplate changed my af by 1 point.

You have six screws to adjust to get it right and a Pv
which means you need to know engine vacuum and then
you have to play with timing

Its not take out of box and bolt on .

Unless you can get the basics running right at 190-195
All bets are off .

If youre going a 1/4 mile at a time then you can worry about
Low temps - AFTER you get it idling and performing at temp ..

lol, there is sogtx giving away our secrets, not old n cranky...lol, no more patience for the bs. None. You all can't remember $hit and it's not my job to prop up the lost and lazy.

Read the old guide, someday i might publish the latest and greatest guide. In the meantime if some one would send me money for the latest version i would let the cat out of the bag.



I offered the OP free help and i get crickets.......

Have a gofundme started for you... up to 22 cent, some pocket lint and old receipt.

I'll up it to 23 cents but he'll have to pay my transaction fee

Did the OP fig out his🤔 issue ?