408 Clevor Valvetrain Upgrade and Track Results

In this Tech Exchange article I'm going to share my recent decision to upgrade my valvetrain and back it up with some before and after quarter mile track results. For those who do not know, I run my 65 Ranchero in a few of the NMRA National Series events. Last year was my first time participating and I recently won the NMRA Truck & Lightning Class at the 4th Annual Nitto Tire NMRA/NMCA Super Bowl of Street Legal Drag Racing at Joliet, IL. Winning at Joliet was an awesome personal accomplishment for me and better yet, a great validation of the valvetrain combination upgrade I made to my 408 Clevor just prior to the 2009 season. The following upgrade was made possible with the expert services of Scott Gunderman Performance Engines and the techs at Comp Cams.



Engine Profile
Before we get into the valvetrain upgrade here's a run down of the critical attributes of my 408 Clevor to give you the proper perspective of what I've been using to propel the Ranchero down the quarter mile.

Block - 1972 351 Windsor
Heads - 1971 351C 4V quench chamber
Intake - Offenhauser Boss 302 Tunnel Ram with adapter plates
Carburetor - 2 x 650cfm Mighty Demons
Cam - Comp Cams Solid Roller
Ignition - All MSD Ignition, Taylor Pro Race 409 Plug wires.
Pistons - Wiseco Custom Race Pistons
Compression - 12.5:1
Rods - 6.2 Eagle H-Beam
Crank - 4340 Forged Eagle
Rockers - Comp Cams 1.7:1 Stainless Steel
Valve Diameter - 2.190" Intake, 1.710" Exhaust

2008 Season - Old valvetrain
At the end of the 2008 season I decided to dedicate my Ranchero to the strip in order to get serious about the 2009 season. During 2008 I ran an off-the-shelf Street/Strip solid roller. My 2008 combination yielded a best of time 10.18 at 128MPH, however the 2008 valvetrain was done at 6800RPM. My 408 Clevor was running 4V Cleveland heads so there was still more in this motor. Additionally, after adding a 5500 stall converter for 2009, low RPM's were no longer practical without some real heat.



2008 Cam Selection
Lift - 650/669
Duration - 264/270 at .050"
Lobe Seperation - 108 degrees

2008 Best 1/4 Mile
NMRA World Finals in Bowling Green Kentucky - 10.18 at 128MPH

2009 Season - New Valvetrain
For 2009 I again turned to Comp Cams for my cam and valvetrain needs. The Comp Cams tech line was very conscientious with regard to the cam selection for my application. I simply gave all engine and transmission information, rear gear ratios, tire size and intended use of my combination and was also advised on a proper a stall speed.

My engine builder, Scott Gunderman, removed the old cam and replaced it with a custom grind. We added new rockers, valve springs, moly push rods, stud girdles, and timing chain. The intention here was to hang the valves open 100 thousandths more and to add more duration in order to utilize the canted valve heads. This new valvetrain opened up my power range from
5500RPM to approximately 7400RPM. At Joliet, IL on July 16-17, 2009, I reaped great results after completing this cam and valvetrain upgrade with a personal best of 9.64 at 137MPH



2009 Cam Selection
Lift - 759/762
Duration - 275/287 at .050
Lobe Seperation - 112 degrees

2009 Best 1/4 Mile
4th Annual Nitto Tire NMRA/NMCA Super Bowl of Street Legal Drag Racing at Joliet, IL - 9.64 at 137MPH

2009 Valvetrain Parts List
Comp Cams PN 35-000-9 (Camshaft)
Comp Cams PN 838-16 (Lifters)
Comp Cams PN 998-16 (Springs)
Comp Cams PN 733 (Retainers)
Comp Cams PN 614-16 (Keepers)
Comp Cams PN 4016 (Stud Girdle)
Comp Cams PN 1130-16 (Rockers)
Comp Cams PN 3135KT (Timing Chain)
Comp Cams PN 4512-16 (Rocker Studs)

Piston-to-Valve Clearance
When re-assembling the engine with the new valvetrain, there was no need to make room for the extra lift, the valve-to-piston clearance was set to be able to upgrade initially.

Addressing Nitrous
With the new cam & valvetrain upgrade, I still spray a 175 shot of
Nitrous Oxide. At this time, I have added a NGK o2 sensor that will be used to calibrate and monitor the air fuel mixture.



Air/Fuel mixture is very critical to the operation of a high compression engine using Nitrous Oxide. I am using Autolite AR133 sparkplugs as my Nitrous Plug. The AR133 Autolite Racing plug features a cut-back electrode and is the same heat range the NGK#8, but $1.00 less on the price of each plug. Remember, when using Nitrous Oxide you must decrease the heat range of your plugs at least 2 steps.

In the Shop
Here are a few shots of the 408 Clevor getting redressed with the new valvetrain parts. Starting off with the big ol' solid roller.


Cam Degree Wheel


Valve Spring Micrometer


Double Roller Timing Chain


Piston-to-Valve Cearance is good to go


Stud Girdles and 1.7 Stainless Steel Roller Rockers











The Notorious Heavy Breathing 4V Intake Ports








Conclusions and Concerns
I have attained great results in completing this cam and valvetrain upgrade. This combo was a homerun! However, the increased lift of this cam has also increased my valve spring pressure. The valve spring pressure will need to be monitored. If one spring pressure reading drops below pre-determined measurement, I will replace all springs. After all I have acheived with this motor, it would be ignorant on my part to not attempt to prevent the dropping of a valve.

thanks, great post.

This shows how far these iron 4v heads can take you.

Good info and pics Rick.

I love how you make that Ranchero fly!

Nice results and very nice write up.

Are the port plates home made or purchased?

Thanks Guys. The port plates were purchased through Price Motorsport .
Also, the their distributor adapter was used. Unbelievable port match right out of the box on the plates!

a 175 shot ? what does she run NA ?

Last time I ran it NA before the O2 sensor, it ran 10.80's. I'm running 35 degrees instead of 32 advised by NOS. It may Possibly be a 180 shot. NOS charts are very inaccurate. The only way for me to truly identify my shot were to be a chassis dyno. Which I would like to do very soon!