Idle problem on C15 261 CU IN

[Bob Carriere]

Hi Terry

Survived another Xmas........ came back from TO today...... in freezing rain.... 401 was shut down on the East side and a parking lot for us heading East bound...... in a section that dips and curves near Brighton over 9 or 10 transport we all smashed up.... I mean broken up with cargo spewed all over.... more large and extra large two trucks and cranes trying to unload steel coils off the wrecks onto safe flatbeds.....

Back to reality..... I suspect that that your vacuum connection to the carb port is/may be to blame for such a low reading and the engine still running good. That vaccum port is only intended for the dizzy vacuum pot I beleive.

But you are on to solution when you say you will need a spacer for a proper vaccum and wiper connection. Originally my 1959 Chev 261 had a vaccum port on the square chamber just below the carb phenolic insulator. But when I went to install the engince cover there was not sufficient space for that original fitting so it was removed and plugged.

I had a local metal fabricator cut out a spacer from 7/8 flat stock based on the outline of the phenolic insulator. Had him drill and tap three 3/8 holes for future vacuum connections. I used thin paper gasket between all surfaces and the thick gasket with the groves immediately below the carburator. My centre hole matches the 2 15/16 in. bore of the carburator. One hole is currently used for the wipers..... which work quite well.... and the other for my permanently mounted vaccum gauge.... mounted below the dash left of the steering wheel.... the 3rd hole is used for the PCV.

Are you saying that you do not have a PCV or it is not connected??? or are you using just a open draft tube...?

now for the photos.

I really think that if you were connected to the full vacuum of the manifold you would be getting a different reading.

Coil wise I am running a Pertronix 40K coil and no resistor.... runs fine. This is my second Pertronix..... the first one was installed in the original 1959 tall dizzy cap distributor..... which I found did not have sufficient clearance for the darn engine cover panels.... so I used a NOS 216 low cap dizzy with a new PErtronix as the old one from the later tall dizzy did not fit inside the older 216 distributor.

Cheers

PS.... first picture shows the Rochester B second shows the Carter YF.

Also elected to make use of the steam vent line on the head. We originally installed it with a valve in the system. We would run the engine until well hot than open the valve and see all the foam and bubbles vent to the radiator through the clear vinyl line. We concluded that it was worth while to have it connected permanently and replaced it with a repro steel brake line, covered in fabric as per the original, and it has served us well so far.

[TCLARK]

Funny , I today was working on the truck and thought I should replace the
phenolic spacer on my truck,as I mentioned earlier. I have the original vacuum hole on the manifold closed off, so this makes sense. I will pursue this tommorrow, as I need
a vacuum port for the wipers. I may also tap another 2 ports as you have
done,Bob! Can't wait to see if the vac is better! I do have an open draft tube. I may not meet California emissions standard!


Anouther little problem I have is with the heat gauge on the dash . I have tested my original gauge on the bench and it worked. I hooked a new sender
to it and get no response. I do have that 12 to 6v electronic voltage reducer
on my truck and am taking 6 volts off that to power up the heat gauge. Now
I'm wondering if there is a difference between a 6v sender and a 12v sender.
I have a 12v sender on a 6v gauge?? Probably an issue

Your engine looks great Bob, very lucky to have you to do my homework for me,ha ha
Cheers
Terry

[Phil Waterman]

Hi Guys

Wondering what are you using for a manual on the 235 & 261 engines? Are there significant differences between any of the timing or carb specifications? Particulaly are there differences between the US and Canadian versions.

I've had sectons of the 1960 Truck Manual covering the 235 and 261 truck engines http://canadianmilitarypattern.com/1...e%20Manual.htm if there are other sections of that manual that anybody needs let me know.

I remember that some of the vacuum advance systems have a special fitting that looks like a regular fitting but has a very small passage through it, purpose to dampen sudden changes in vacuum. Can not find my notes on which engine or carb I found this.

Cheers Phil

[Bob Carriere]

Hi Terry

................ Hi Phil

My truck has a GMC civilain rectangular dash. Only the gas gauge and the amp meter are connected and working. I used a voltage reducer on the gas guage and the amp meter as is.

I am using an after market mechanical heat guage with the bulb installed on top of the steam outlet on the original 216. I also have a mechanical oil pressure and a vacuum gauge. I later installed a tachometer......all in the interest of better monitoring the performance of the engine..... they may be removed at a later date not sure when as I now depend on them.

Nice to know you are doing 2000 rpm at 30 some mph even though the engine is screaming and the gears whining all is good. Gets close to 2900 at 44 mph flat out..... with me holding on tight. Nicer to drive at 30 - 35 mph just relaxing.

Really curious to see what kind of readings you get when you have a proper manifold connection.

Phil........ any tips or tricks you want to share....?

On a 248 GMC fire truck engine they actually add a 5 to 6 inch adapter/spacer for clearance purposes with other do-dads installed on the engine. I have read somewhere, from hot rod sources, that increasing the length of the air flow and increasing the size of the vaccum plenum is beneficial to engine performance...... so an extra inch spacer certainly will not hurt. Just make sure that you have a good seal on all joints..... paper gasket smeared very lightly with silicone sealer works great for me. Just apply the silicone to index and thumb and smear the paper...... gets tacky and compresses well with no overkill silicone getting inside parts.

Phil are you using a NOS spacer or a homemade one??? they do come up on Ebay once in a while.

Cheers

[TCLARK]

Hi Phil and Bob
Phil you were right just a small hole to suck vaccuum thru for the
distributor. I would guess for dampening also.

Bob I just got the spacer made ,it took about an hour but visiting neighbors
for a piece of 5/8 flat took half the day.
I put it all together and voila about 20 inces at 475 rpm idle. I'm
so happy, this engine purrs like never before.

Now I have to hook up the wipers does anyone know where to get the proper Blades?? I have one new nos wiper arm I got at a swap meet (even orig. OD) and one not
so good but usable. How does the blade attach to the arm?

Cheers and thanks for the great advice!
Terry

[Bob Carriere]

Good show.....

Now how about a picture of the spacer???? and your wiper arms......

.........will Photo some of my wiper arms and wipers... and post later tomorrow....usually available from most Jeep repro sellers.

so glad it worked out for you.

Now that you are getting a better reading...... try getting a higher reading first with the dizzy then with the mixture screw on the carb try for 21 near 22.....

Cheers

[rob love]

The old trico wiper blades were/are still used on the MLVW. I believe they are 11 or 12" long. You can find the same design bladfes as short as 4-1/2" long. Have a look on ebay for M35 wiper blade, or M38A1 wiper blade. If the blades you get are too long, you can cut them down with a dremel tool with cut-off wheel.


http://www.ebay.com/itm/Wiper-Blade-...5R6DvU&vxp=mtr

http://www.ebay.com/itm/Jeep-Willys-...5X0xFj&vxp=mtr