The Stovebolt Site Forums The Shop Area Engine Shop 261 CAM

I have a '51 3100 with a '58 235, solid lifters, Fenton headers, two 2bbl Carter/Webers on an Offy intake, Langdon's mini HEI and running 3:55 rear.

I spent quite a bit of time in search mode but can't find a thing that tells me the pluses of installing a 261 cam in my engine. Everything says..."yep, install it..best thing for my truck...very good". I don't see a thing about what it actually does for my engine.

Will someone please help me? I have a NEW 261 cam that was given to me and don't want to install it unless I know what the advantages are.

Thanks in advance

Thruwurkin

The 261 cam is a high lift cam (higher lift cam). Someone else will have to tell you what this gives you, but Chevrolet stated that this not only maintains higher horsepower at higher speeds but it also maintains increased torque over a wider speed range.

Maybe someone who has done the upgrade will respond. The 1954 Engineering Features Manual indicates that larger journals (?) were used for cam lobe clearance .

One aspect of this upgrade is the "cool factor" - the 235 engines in early Corvettes used this cam (1953, 1954 and supposedly into 1955 until the 235s ran out).

Tim

I just went thru that and in my case the difference was huge as the old cam was severely worn probably due to an improper break in. I can tell you that a new 261 solid lifter cam will raise the pushrod vertically .275" when open. If you put a dial indicator on top of a rocker adjuster and rotate until it's fully open you can determine how much less you are than that value and how much you will gain. The higher the valve lift the more gas gets in, more exhaust gets out and more power is generated. The "bark" that it makes at higher rpm and the quicker throttle response are what really makes that modification worth while though. Hope this helps.

Curt B.

A cam with more lift and duration will move the power band up on the rpm range, while sacrificing power/torque at lower rpm.

In an early 235s with multiple carbs and headers, the 261 cam gives noticeable gains in power, especially above 2000 rpm.
That worked well for the early Corvette which was light and more about high rpm than hauling or cruising. It also had the 'new' 848 head with higher compression.

235s starting in 1956 came from the factory with 848 heads and 261 cams.
Hydraulic cams starting in 1954 had virtually the same duration and lift as the 261 solid cam.

Under 3500 rpm the stock cam in late 235s is all you ever need.
More would give a loss of power and torque at typical street rpm.

If you are going to go through the trouble of installing a new cam, I would get one of the performance 235 grinds instead of a 261 cam. The there is not much of a performance improvement between the two, a stock 261 was only rated for 10 more horsepower than a 235.

In 1954, the 261 supposedly produced 135 hp and the 235 supposedly produced 112 hp (about a 20% increase). However, it is hard to say how much of the increased horsepower was due to increased displacement.

Many Thanks to all that replied. After reading all of the replies carefully and considering that my engine only has 5000 miles on it, I have come to the conclusion that replacing my cam with a 261 cam would not be a big gain for me...certainly not worth the labor and cost involved.

Again, many Thanks

Thruwurkin

I think you hqve come to the right conclusion. Leave it alone.
Cleon

Are you familiar with Racer Brown's May 1955 HRM about Frank McGurk's 261 engine modifications? The article give the basic specs on the stock 261 cam and compares the performance with the stock cam to a couple of of McGurk's cams.

I do not recall ever seeing a direct comparison between a typical 235 cam and the Corvette six/261 cam. Based on my experience wirh several 235s and 261s, I would not take apart an engine, otherwise running ok, just to put in a 261 cam. If the engine was already apart and the cam was free, yes. Otherwise, get a cam from Patrick's, Tom Langdon, Delta Cams, etc.

The link to the article about the 261 was originally posted by "Old Fart Ed" in the Inliners BB, 1 November 2005. I still have my original copy of that HRM.

Hoyt

I have heard that you can use GMC rockers from a 270 that have a different ratio to increase performance? Does anyone have info on this? OldWolf