In this Tech Exchange article I’m going to share my recent decision to upgrade my valve train 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 valve train 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.
Before we get into the valve train 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 Valve Train
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 valve train 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 were no longer practical without some real heat.
2008 Cam Selection
Lift – 650/669
Duration – 264/270 at .050″
Lobe Separation – 108 degrees
2008 Best 1/4 Mile
NMRA World Finals in Bowling Green Kentucky – 10.18 at 128mph
2009 Season – New Valve Train
For 2009, I again turned to COMP Cams for my cam and valve train 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 valve train 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 valve train upgrade with a personal best of 9.64 at 137mph.
2009 Cam Selection
Lift – 759/762
Duration – 275/287 at .050
Lobe Separation – 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 Valve Train 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)
When re-assembling the engine with the new valve train, there was no need to make room for the extra lift, the valve-to-piston clearance was set to be able to upgrade initially.
With the new cam & valve train 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 valve train 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 valve train 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 achieved with this motor, it would be ignorant on my part to not attempt to prevent the dropping of a valve.