140 camshaft selection for Street/Driver

[carolinefx]

Looking for recommendations on Camshaft selection for a 1969 140 (factory 140).

I've decided to bite the bullet and build a reliable engine once and for all. This is a fun driver - not a show car or a racer.

I'm working with a very knowledgeable engine builder who's default choice (wisely) is "STOCK"

However, this is going to be the only engine I'll ever build and I hate to leave something on the table, especially with the camshaft.
I can change carbs, perhaps even modify heads later - I don't want to ever split the block again.

So, leaning toward A) stock, B) OT-10, C) OT-20 or ?????. This is a ground up build with new Wolf carbs, complete head work,etc., but nothing exotic like slanted exhaust ports. I don't have the skill to build an engine myself, and I understand that swapping a cam is just part of a larger system, and that the engineers at Chevy were smarter than I am.

So - THOUGHTS???? - let the debate begin. Thank you for your advice

Caroline
Keene NH

[cnicol]

Please check or have your builder check the cam gear on the crankshaft. As you probably know, there were two versions; standard timing and retarded timing. Many, if not all, 69 140 engines had retarded cam timing crank gears which "steps up" a given camshaft to higher RPM range. This worked well to wake-up the flaccid 889 cam for PG and smog applications but might be too much for a "standard" 140 cam. Also need to know what transmission your car has. I have a ready recommendation if your car has a 4-speed and standard timing on the crank but I'm reluctant to say before knowing about the crank gear and transmission.

[carolinefx]

Hello,
Thanks for your note Craig. Yes, new Cam Gear is absolutely part of the mix. Transmission is 4 spd with 3.27 diff.
Sadly the original engine for the the car was toasted (I got it with the car, but was not usable). So, the build is based on an RB Block, standard 140 crankshaft, and very probably stock size pistons with no overbore.

Much appreciated,
Caroline

[66vairguy]

You will get many suggestions on cams.

I can suggest the OT-10 or Isky 260. They are close to 140 stock cam profiles if you want a nice driver. The four carb's will give you better top end than a 110HP engine. So you get nice low end torque and some go at the top end.

If you like to rev the engine to go and want some more power at the top end then the Isky 270 or OT-20 are nice, but you will have to use a stronger valve spring to take advantage of the higher RPM power or you'll end up with valve bounce above about 4,800 RPM. Of course there is always concern about flat tappet cams and higher valve spring tension.

I have nothing against going racing, but you typically trade long term reliability for more short term go with hotter cams.

As mentioned it has been reported the 140HP manual transmission engines had the retard crank gear originally used for the PG cars. Replacing that is good. Also the distributor needs to be changed from the 69 smog curve to the 65-66 curve - that will make a big difference in off the line throttle response.

Another issue is the 66 and later primary carburetors They used a revised idle circuit for a smoother idle with a leaner mix that worked great until they don't. I've had a few with corrosion in the body idle circuit paths and the carburetors would not hold an idle - the problem is NOT repairable. The only fix is another carburetor or use a 65 carburetor base (and cluster) with the old simpler idle circuit.

A lot of folks will say to go with bigger "richer" carburetor jets. I find the stock jets work just fine. The bigger jets do reduce head temperatures and increase power slightly, they also lead to a lot of carbon on the pistons and heads based on engines I've taken apart. In 69 the primaries had a 52 jet to make the A.I.R. (smog) air injection system work. I'd go with a 50 jet. I recommend Bob Helts Rochester carburetor book as it explains the 65 - 69 differences.

The late 65 - 69 lockout four carburetor linkage is difficult to get working. Many go with the early 65 style that is easier to set up, but the driver must remember to not open the secondaries until the engine is warmed up. Roger Parent out of San Diego CA. makes a great, and handsome, linkage in either early 65 or later 65-69 style.

Just my opinions and as always it's best to ask around.

[cnicol]

Given the straight cam timing and manual transmission, I agree with 66vairguy's camshaft recommendations, leaning slightly toward the "OT" versions because they have different lobe shapes for the intake and exhaust cams (aka "dual pattern"). Dual pattern cams make sense to me and are shown to work a bit better than camshafts that have the same lobe shape for intake and exhaust. Why wouldn't they be different, they're handling completely different gaseous animals.