1967 327/300 camshaft selection

[Jim Datsko]

After owning five previous midyear coupes, I've finally purchased my sixth and last one - to be a lifetime keeper. It's a 1967 327/300 with 4 speed, and 3:08 highway economy axle.

Unfortunately the previous owner appears to have installed a more radical cam in it, which caused some driveability problems until increasing the timing to about 14 BTDC. It still gets lousy gas mileage compared to my other midyears [all small blocks]. And since it had an excessive oil consumption problem, it's in the shop being rebuilt again.

It is otherwise all stock, except that I had the heads ported and polished, which I'm not sure was the right decision. Since my priorities are first to achieve good fuel economy of at least 20 mpg easy highway driving, and only secondly to improve driving power and performance.

The big decision now is which camshaft to install?

I'm basically an OEM kind of guy, and I've been real happy with the stock cams in my previous stock Sting Rays. But I'm wondering if a more modern cam might improve fuel economy, and maybe even a little extra performance while at it? I'm not certain whether the porting and polishing is going to cost me some fuel economy since the engine will now inhale more of a fuel/air mixture unless the camshaft keeps the intake valve closed a little longer than stock.

I've been reading other postings about OEM vs. the Comp Cams "260" cam, vs the OEM replacement -929 cam, vs the -151 350 hp cam which I probably have in it right now and don't care for it's driveability, though it pulls like a jet at higher revs. Maintenance-free long-term durability is also a major factor for me.

Also been reading postings about some members who run Desktop Dymo Simulation Software, and wondering if that could factor my porting and polishing into the equation, and give fuel economy projections in addition to power projections.

I mainly use this car for long distance GT [grand touring] trips, so dragstrip type of performance is of little interest to me, though gobs of passing power is appreciated. The NCRS magazine published a two-part article about the fun involved in getting this car home by driving it across the country via Pacific Coast Highway and Route 66, called "Sting Ray Adventure". What a blast !!

Any thoughts out there?
Thanks, Jim D.

[Duke W.]

Re: 1967 327/300 camshaft selection

GO WITH THE OE 929 CAM!!! Ever wonder why it was the base Corvette engine cam from 1967 - 1980? It's a great cam! Most aftermarket cams have too much overlap and will affect idle quality and fuel economy for the worse. The 929 cam not the favorite of guys who prefer SHP engine characteristics and performance, but it's perfect for those who want an easy driving cruiser and touring car.

My '63 L-76 with 3.08 axle will achieve 20-22 MPG in highway cruising, and the 300 HP engine should do at least as well with a 3.08.

Modifying the heads by cleaning up the valve pockets, a multiangle valve job, and matching the ports to the manifold is a good idea, but the ports should not be opening up beyond just the above two operations and they should not be "polished". Pocket porting/port matching/ multiangle valve job should improve power in the upper third of the rev range by about 7 percent and allow the engine to pull strongly to 5500 without affecting low end torque or the excellent idle quality and driveability of the 300 HP engind.

Be sure the carburetor is set exactly to OE spec and the ignition map is exactly per OE specification if you want to achieve best fuel economy. Many carbs and distributors have been modified - many poorly - and the best thing to do is get back to OE spec and then go from there if you think you can beat the OE engineers on carburetor and ignition tuning for best economy and performance.

Duke

[Joe L.]

Re: 1967 327/300 camshaft selection

Jim------

I agree with Duke, too. For you application and intended use I don't think that you could do much better than a stock '929' camshaft. It's long since GM discontinued, but clones are readily available from most of the major cam manufacturers.

Another option that I could recommend to you: a Speed-Pro (Federal-Mogul) retrofit hydraulic roller camshaft of grind 1061-R. This will give you just a bit more than the stock cam, but with a stock idle and stock fuel economy. You can purchase this cam in a kit of KS-1061-R that will give you all the parts you need for the hydraulic roller conversion. The only thing you'll need to add is a Cloyes 9-3100T timing set with roller thust bearing. This is not an inexpensive cam kit, but I think it's worth it. You'll get the best of all worlds.

[Clem Z.]

joe 1 thing i would add to your suggestion

since roller cams do not have the taper ground into the lobe face that causes flat tappet cams to be forced to the rear of the engine,you must have some type of positive stop in the timing gear cover to prevent "cam walk". there are several different "cam buttons" that go into the hole in the cam gear and ride against the timing cover BUT you need to renforce the the cover to prevent the cam button from bending the cover outward. most engine builders braze a 1/8" steel plate inside the cover to do this if you use the stock cover. some after market water pumps have a adjustable bolt that can be used to rest against the cover from the outside to prevent the cover from bending outward.

[Jim Datsko]

Re: 1967 327/300 camshaft selection

Duke,

Thanks for the information. I'm leaning towards the OE 929 cam at this time.

Next question is where to buy it?

The $99 replacement OE style cams available from Comp Cams, and Crane refer to it being the 1965-68 style cam, which leads me to believe it may have been the cam used by GM for 1965-66 Corvettes, not the new improved cam GM cam out with for 1967.

I have purchased genuine GM parts through The Final Detail in the past, and they show a replacement part available #1408839, having an id# ending in 930. Available for about $250

I called the local Chevrolet parts department, and the kid there had trouble telling his Chevettes from his Corvettes, and was no help at all.

I checked a great resource I was able to purchase through NCRS Drivetrain from another member: A near mint condition "1953-70 Corvette Parts Manual" from an actual Chevrolet Dealership. It shows:
67-70 Corvette (327,350) (exc. H/Per., Sp. H/Per).. 3896929 standard (Ident No. 3896930)

What are good sources to buy the 929 cam? And how do I know I'm getting the right part number?

Too late to cancel out the porting and polishing of the heads, as I was talked into doing that by the local machine shop a couple of years ago; and hope that doesn't interfere with the economical touring provided by the 929 cam. As your 20-22 mph is enticing.

Jim D.

[Duke W.]

Re: 1967 327/300 camshaft selection

Federal Mogul should have an exact replacement for the 929 cam. It's not listed in their performance parts catalog, but it should be in the standard replacement parts catalog. Given that it was used in millions of engines any other major replacement parts manufacturer that supplies camshafts should also make it. I prefer to go with "Tier 1" OE suppliers for parts rather than the aftermarket "hot rod" parts vendors.

I trust the QA programs in place and required to achieve Tier 1 OE certification.

Duke

[Joe L.]

Re: 1967 327/300 camshaft selection

Jim------

The GM #3896929 camshaft has been superceded several times. Currently, it's known as GM #14088839. The profile of this camshaft is very similar, but not identical, to the GM #3896929. The camshaft part numbers that were supercessive to the 3896929 were used on many PRODUCTION applications in the 80s and 90s for Z-28s and other cars. I believe that the slight changes in the profile were done for emissions control reasons. You might be better off with the original profile. Plus, the GM #14088839 currently GM lists for $288.78.

In addition to sources like Federal-Mogul, you can obtain a Crane-manufactured clone of the '929' camshaft and lifter kit from GM under GM #12364051.

[Joe L.]

Re: 1967 327/300 camshaft selection

Duke-----

The problem is that there is no guarantee that the Federal-Mogul aftermarket cams are manufactured to the same standards as their OEM pieces. Very often, big automotive parts manufacturers like Federal-Mogul will have "OEM Divisions" and "Aftermarket Divisions" and the parts for each will be manufactured in completely different plants. In some cases, the "Aftermarket Division" will obtain their parts from another manufacturing source and they will be packaged in the "colors" of the major manufacturer involved.

The reason for this is that the aftermarket is a FAR more competitive pricing environment than OEM and quality is less of an issue. Also, the purchaser in the vast majority of cases isn't concerned about getting a piece that's up to original quality standards----just one that will last them another 50,000 miles, or so.

[Duke W.]

Re: 1967 327/300 camshaft selection

Joe - do you have the basic specs for the 140888839 - duration at .010" lifter rise and centerlines?

There was a seeming proliferation of SB cams in the eighties, and like Joe said, a lot of them were specifically designed for emissions. Some had "excess overlap" to act as a built in EGR system to control NOx.

The conbination of excess overlap and short duration killed low end torque and top end power - the reasons why most SBs from the eighties are not loved.

Duke

[Duke W.]

I meant .050" lifter rise *NM*

[Joe L.]

Re: 1967 327/300 camshaft selection

Duke-----

No, I don't have them. I saw them somewhere once-upon-a-time but I've forgotten where. All I recall is that they're close to the '929', but not the same.