235 vs 261 6 Cylinder

Halfbreed · Addicted!

235 vs 261 6 Cylinder

eeluddy · Uber Guru

The 261 is the same as a 235 except the bore & stroke, and colour of course. It was done so as to put the Pontiac in a higher price bracket than the Chevrolet and offered better torque & hp.
Lot's of folks on here know a great deal more about them than me so hopefully they will chime in.

seventy2plus2 · Canadian Poncho Superstar!

If I recall, the 261 was basically a truck engine, built on the same platform as the 235. The 235 had been around for years.

58 poncho fan · Addicted!

The way I have been informed thru brochures, etc. all six cylinder Canadian Pontiacs from 1955-1962 should have the GMC 261 truck engines from the factory! However I do recall one of those years, (it could have been the 1957) did have the 235 engine if it was stick shift! Does anyone else out there have a 1957 Canadian Sales Brochure, as perhaps it will give more details, if it is an updated issue!

davelacourse · Poncho Master!

Glad to have you on board!

The Canadian Pontiac 6 was based on the truck engine but had significant differences.

Most important was the fact that the Pontiac was 'a step above' the Chevy so the common 235 would not do, hence the bigger better 261.

"Basically, this larger engine was a 235 with the same crankshaft but GM engineers made various modifications to give it extra strength and horsepower.Its standard bore diameter increased from 3-9/16 inches to 3-3/4 inches. The connecting rods were heavier and attached to increased diameter piston wrist pins."

So same stroke, bigger bore.

Also, "Its higher lift cam shaft, for better breathing, was shared only with the early 235 six cylinder Corvette. A modified larger Rochester carburetor was also a 261 only feature. Unfortunately most of these larger sixes have long since had their original Rochesters replaced with 235's and therefore do not perform to their full potential."

Keep in mind: "the 261 truck engine came standard with solid valve lifters and an aluminum camshaft timing gear. The Chevy passenger car's 235 was equipped with hydraulic valve lifters and a fiber timing gear for quieter operation.

During the 1955-62 Canadian Pontiac application the lifters were the hydraulic type, the cam gear was fiber not aluminum, and it did not have the full flow oil filter. These Canadian made 261's did not add the full flow filter in 1958 as in the U.S."

I have more info, PM me with your email address and I will pass it along.

Dave

omp60 · Addicted!

http://www.oldchevytrucks.com/Tips/261_six.htm

the forgotten 261 six cylinder

ylinder

-- Edited by omp60 on Wednesday 2nd of September 2009 07:58:21 PM

Oracle · Addicted!

The 261 Astro-Six as it was called had a higher compression ratio than the Jobmaster Six 261. I think the heads were changed in 1959 and the bhp dropped officially from 150 to 148. Right-hand drive versions were produced, with Powerglide available as an option in rhd and lhd. All Canadian 261s were built by Windsor Transmission Plant using castings from The McKinnon Industries Ltd of St Catherines, Ontario, with the P/Gs built by McKinnons as well...manual trans by Windsor.

68sd · Canadian Poncho Superstar!

http://canadianponcho.activeboard.com/forum.spark?forumID=118110&p=3&topicID=24380208

brochure

davelacourse · Poncho Master!

omp60 wrote:

http://www.oldchevytrucks.com/Tips/261_six.htm

the forgotten 261 six cylinder

Yup, that was my source.

Dave

Stephenzone · Canadian Poncho Superstar!

never knew of this engine, you guys are great. checked my 55 chev/gmc maintence manual (can vers) and it lists the 261 as a option for the 1600/9600 series truck. next time i'm in jacksons i'll have to see if any of those big boys have a 261

73SC · A Poncho Legend!

So what is the answer to Halfbreed's question ? I always though it was the 261 in '57 never realized there was a possibility of the 235.

davelacourse · Poncho Master!

Well I'll be danged, in fact the ONLY 6-cylinder motor offered in the 1957 Canadian Pontiac was 235 c.i.d.!

My Canadian Pontiac Parts Book shows 1957 bore = 3-9/16 x stroke = 3-15/16 which is 235! For 55 and 56, it was 3-3/4 x 3-15/16 which is of course our old pal the 261.

(My parts book stops at 57 so I cannot use this reference for later years.)

Just to add to the 1957 history mystery, the Parts Books shows the same cylinder head for 56 & 57 6-cylinder motor and the same cylinder head gasket for 55-57 - and as we know that means with steam holes not found on Chevy 235's.

Seems like the 57 Canadian Pontica 6 was unique - smaller bore 235 but otherwise "upgraded" from the Chevy.

Dave

davelacourse · Poncho Master!

Stephenzone wrote:

never knew of this engine, you guys are great. checked my 55 chev/gmc maintence manual (can vers) and it lists the 261 as a option for the 1600/9600 series truck. next time i'm in jacksons i'll have to see if any of those big boys have a 261

Look for the "Captain's Bars" on the block above the starter.

Dave

Oracle · Addicted!

My Sanford-Evans Statistical Service book for 1957-58 states clearly that the engines available were just the 261 and 283..what about the 265 then?

73SC · A Poncho Legend!

265 is 55 & 56 only. 283 debut in 57's.

Stephenzone · Canadian Poncho Superstar!

while shooting the breeze today about the truck version 261. he said they used to change the lifters so who ever was buying the engine would think they were getting the car one.

Beaumont4008 · Uber Guru

Halfbreed, any way of posting the page with the engine data from your brochure. We have one on file but can not read the printed details. Does this mean that some folks with 57's think they have a 261 when they have a 235 ? I see some cars in the 57 regestry that are listed as 261's.

davelacourse · Poncho Master!

73SC wrote:

265 is 55 & 56 only. 283 debut in 57's.

I think early 57's were still available with 265, but basically the 55-56 265 was replaced with the 283 in 57.

However this is for Chevy's, not sure about our dear Canadian Pontiacs

Dave

davelacourse · Poncho Master!

Beaumont4008 wrote:

Halfbreed, any way of posting the page with the engine data from your brochure. We have one on file but can not read the printed details. Does this mean that some folks with 57's think they have a 261 when they have a 235 ? I see some cars in the 57 regestry that are listed as 261's.

57Poncho is going to email me full-size version of his brochure so I will work to make it available for all to see with legible print.

Dave

73SC · A Poncho Legend!

davelacourse wrote:

57Poncho is going to email me full-size version of his brochure so I will work to make it available for all to see with legible print.

Dave

Nice

Halfbreed · Addicted!

Dave, I have been trying to reproduce a copy of the spec sheet. I have it in a PDF file but can't seem to make it function properly. I gaurantee you the Specification Chart states Strato Six - 148 hp - 235 cubic inches with no mention of a 261 engine.

Also noted in the list of engine combinations is a 283hp - 283 engine with fuel injection. Anyone have or ever seen one of those rare critters.

Halfbreed

73SC · A Poncho Legend!

The fuelie was an option for 58 as well, it's known as the Power Chief. I have never seen one in a Canadian Pontiac

davelacourse · Poncho Master!

Halfbreed wrote:

Dave, I have been trying to reproduce a copy of the spec sheet. I have it in a PDF file but can't seem to make it function properly. I gaurantee you the Specification Chart states Strato Six - 148 hp - 235 cubic inches with no mention of a 261 engine.

Halfbreed

John, I am with you 100%, the 57 was a 235, not a 261 - if you will send me the pdf I will try to make it readable (I will send you my email address so you can send it to me).

Thanks,
Dave

eeluddy · Uber Guru

Years ago I was trying to buy a 54 Corvette that was missing its original engine. My plan was to do up a 261 with a dual carb intake, worked Corvair carbs, and a Clifford header system with a 3 speed stick set up out of a 56 Corvette. Like a mid 50's hot rod. I just couldn't make a deal on the car. Still PO'd at myself!

Halfbreed · Addicted!

davelacourse - I have sent you the PDF file you requested. Hope you can enlighten us. Thanks to all for your efforts.

I'm stll wondering how many 1957 CPs had fuel injection. I know of some in Chevrolets in our area over the years. One friend of mine inherited his brothers original a few years ago. What a beauty!