Best OEM style replacement cam 427/390

[Gary H.]

I have been told to look at comp cams for a OEM style replacement cam with modern specs. Any suggestions?

I have a 69 427/390 4 speed with M20 and 3.08. I want to keep it sounding stock, but want a little added performance, so this might be a great fit.

[Joe L.]

Re: Best OEM style replacement cam 427/390

I have been told to look at comp cams for a OEM style replacement cam with modern specs. Any suggestions?

I have a 69 427/390 4 speed with M20 and 3.08. I want to keep it sounding stock, but want a little added performance, so this might be a great fit.

Gary------



The L-36 camshaft was one of the, if not the, best street big block camshafts EVER. Overall, it's hard to beat.

However, I like hydraulic roller cams. They offer performance potential that just was not available in the 60's. So, if you want to get away from stock, I'd look towards an hydraulic roller. However, not one with "wild" specs.

[Duke W.]

Re: Best OEM style replacement cam 427/390

Comp Cams is the absolute last place I would look for ANY camshaft. The OE vintage cams are all available from Federal Mogul and Dana Corp. in their house brands, Sealed Power and Clevite, respecitively, and you can buy them through virtually any parts house.

Go to napaonline.com and just type the OE camshaft number into the parts interchange box on the home page. That will get you the Sealed Power number, which is built exactly to the GM specs.

Some aftermarket companies offer "OE replacement" cams, but they are NOT always built to GM specs. They often have more aggressive flanks, which require higher than OE rate springs, which increase valve train loading. A true OE replacement cam is built exactly to the GM specs. An OE replacement cam with "modern specs" is a different design. Don't get sucked in to this marketing BS.

The OE 427/390 cam is an excellent all around design for a high performance road engine with lots of low end torque. If you want "more power" simply massage the heads.

In not a fan of roller cam conversions - not worth the money IMO. It's better spent on head massaging. Roller cams require higher rate valve springs and most have too much overlap, which will roughen the idle and hurt low end torque and fuel economy. OE equivalent cams mean OE idle behavior, low end torque, fuel economy, and valve train durabililty.

How much more power you can get in the upper third of the rev range is a function of how well the heads are massaged for increased flow. Eight to twelve percent and another 500-1000 useable revs is typical. The additional useable revs are due to the power peaking a few hundred revs higher with slower rolloff past the peak.

If you want maximum torque/power across the rev range and maximum fuel economy it's also very important to properly manage the compression ratio and optimize the spark advance map.

The TDB and other automotive Web sites are full or horror stories about owners who handed their engine over to some "engine builder" who filled it up with expensive aftermarket parts that yielded poor idle quality, loss of low end torque, poor fuel economy and driveability, and high oil consumption, and it's debatable whether they made more top end power.

Do your homework. Understand your objective. Pick the part manufacturers/part numbers for all parts that might need replacement up front as part of your plan. Pick an appropriate target compression ratio and manage the process to achieve it and only authorize machining operations that are absolutely necessary.

In most cases the only necessary block machining process is boring/honing for oversize pistons, and the only necessary head machining is what is required to rebuild the valve guides.

Duke

[David P.]

Re: Best OEM style replacement cam 427/390

Thought I'd throw a quick reminder out there to pay close attention to the cam's effects of idle quality and the impact on manifold vacuum which is critical to the OE performance of a C3. Getting the headlights and wiper door to snap into position with low vacuum is going to be disappointing. You can always go the route of hiding an electric vacuum booster pump somewhere, but that brings its own set of new challenges...