1969 Pontiac Royal Bobcat Engine Build and Dyno - 2008

When Pontiac guys think of building an engine the first thing that comes to mind is how lucky the Chevy guys have it. Order a crate engine have it delivered a few days later, paint it, bolt on the goodies and get ready to drop it in the car. The best part is the engine specs are already proven, the horse power published and the price is established, if that was not enough the warranty is 3 years 36,000 miles. Of course this practice is not going to work on the numbers matching show car or the all original car that needs just to be freshened up but if you are planning an upgrade and yanking out that old 2 barrel or straight 6 this makes good sense.  We can stop right here because Pontiac does not offer a crate engine so we are in for more work. We have to find a machine shop, nail down a price and wait. I don’t know which is worse the price or the waiting.

There are a number of bigger engine builders that offer “crate engines” with combo’s they have tested, they can use your block and heads or their core which means a 400 block and common head but you still have to wait. The wait could be 4 months to a year. So before you start your project you should know there is nothing fast about building or rebuilding an engine.

Most builders will use new pistons, rods, and maybe even a crank. These items take time to make and the manufacture usually wants to have a few orders built up so they can be made all at once. This saves the manufacture time and money which lowers your retail price. The engine shop is usually doing all sorts of makes and model engines so you have to wait in line. To set up all these different types of engines takes time. Next you have to find the right builder for your engine. All the shops can do the basic machining but picking the parts for the compression and Horse Power is the hard part. If you pick the race engine builder chances are you will have a full blown race engine that you will not be happy with in a street car. If the compression is too high now you have to run race fuel.

While we all want a few more horses out of our poncho, be careful what you ask for. Most GTO’s in the late 60’s and early 70’s were packing 350-370 hp off the dealer ship floor and this was plenty to roast the tires and impress your friends but not enough to be the top dog at the track. But how many of us actually made it to the track. These cars are nearly 40 years old and the trend is more to cruse and show and go for a drive on a Sunday afternoon and maybe a few will make it to the track.  Building an engine is all about knowing what you want and finding the shop that specializes in the type of engine build you want. This can make all the difference in the final outcome and your happiness.

We started our project with a car in mind that the engine was going in. The car was going to look stock but had to be faster than most. We mainly wanted to cruse but did not want to be embarrassed at the track and knew were going to run stock tires so we called Butler and ordered an engine with the instructions: do all you can on pump gas. One year later the engine arrived.  It was the popular 461-467 cu. in. for the 400 that included 4 bolt main, 10.5:1 compression, crank 4.250, stroke 2.200 rod, eagle rods 6.800”, Ross pistons, Ferrea pins, total seal rings, BP Billet gears and chains, Melling oil pump, solid roller cam, BP roller rockers, Edelbrock 87cc Heads, MSD distributor and boasted well over 600 hp with the right carburetor, intake manifold, and headers.

The engine from Butler was built for a high rise intake, demon carb, and headers and the performance would suffer with the stock parts. Dan Jensen of the pure stock drag races has built tons of stock engines and was called to help. Dan looked at all the specs and proposed the strong points and the weak and made combination changes in desk top dyno until we got what we wanted.
Just to see the comparison we would run the Butler setup first and tear down at lunch and run the new picked combo.

The day the engine arrived we eagerly bolted on all the pieces to see how it would look in the car. We had to swap to a stock valley pan and oil pan. And the rocker girdle was making it impossible to have any stock valve cover fit so it was removed. Even with the added clearance the valve covers needed metal spacers.

We knew this was going in a stock looking car and the aluminum heads would stick out and with a stock Ram Air IV intake, exhaust manifolds and Q-jet carb, something would have to be done with the heads. The heads were taken apart and the ends were milled to look like the ram air head, a few wire loom bosses were added and the numbers were put on with a bead of weld and ground with a dremel tool. After hours of grinding and finishing smooth the heads were taped off and shot blasted to get the texture back into the aluminum.

This is the Butler specs but with the stock intake, carb, and exhaust manifolds, we know the numbers are going to be much lower than the advertised 600 hp. The engine has already been run off site on Dan’s engine stand to break in the cam and make sure there are no other major problems. Dyno time is limited and expensive so any problem that can be worked in advance can save hours of time. The engine is hooked to the dyno and all the probes installed. The computer will read water temp, oil pressure, spark, engine fuel and exhaust gases. The dyno can control fuel pressure, water temp and uses clean air pumped from outside. We are also hooked to a 2 ½” exhaust and ready for the first run.

We have problems right from the start. At RPM’s higher than 4000 on the first run we are getting a loss of oil pressure. So run one is aborted and the problem must be addressed. After a few minutes of brain storming we determine that with a deeper pan a windage tray in the lower end is not as big an issue but with a stock pan it is our source of low oil pressure. The oil is being wiped around in a tornado from the crank and is forcing the dip stick out of the hole. The oil pan was removed and a windage tray installed. 1 hour is down with no runs yet.

The next few runs will be all tuning runs, we would like to have the dyno curve as smooth as we can get it. We first try 34 degrees of advance, then 36, 37, 38 and find Pontiacs like 36 degrees of full advance. We do not worry about initial advance as long as the engine starts it is what it is. Second is the carb jetting, first the primary then the secondary. Jet sizes can vary a few thousands .002 and make a sizable difference. The metering rod hanger can also make a difference. This can clean a bumpy curve into a smooth one. You can hear and feel in the floor every bobal of engine noise and make adjustments until it is gone.
We have now got all that we can out of the tuned engine after 23 passes and we are right at 500 H.P with 563 lbs of toque at 3800 rpm. The next few passes we try a few experiments. With the air cleaner base we lost 5 HP, with the exhaust off we gained 15 HP, with a breather in both air cleaners we gained 5 hp. With the air cleaner tube from the valve cover pointing towards the engine and directing dirty air towards the engine we lost 5 hp.

Engine Specs:

400 - 461-474 CU in
up to 660 HP 625 Ft Lbs Torque on pump gas
400 block 4 bolt main with studs
crank 4.250 Stroke 2.200 Rod - Forged
Eagle rods CRS 6800 BBC H Beam w/8740 bolts
BP Ross Pistons 4.155x1.295
Ferrea Pins. 990x2.930 Tapered
MSD Pro Billet Pontiac Distributor
Fuel Pump - Stock AC delco
Wires - stock aftermarket
Total Seal Rings
RM Race Bearings
BP Billet Gears and Chains
eagle 400 Pontiac Crank 3" mains 4.250 stroke 2.2 rod journals
455 crankshaft oil scraper
NGK-R5672A-8 Spark Plug
Melling SD M54 Oil Pump 60 psi
Solid Roller cam
Duration@.050 intake 272 exhaust 276
lobe lift intake .4400 exhaust .4410
lobe seperation 108.0
1.5 roller rockers stock ram air 3
edelbrock 87cc heads
ferrea valves 2.11in 1.77 ex
springs - titanium retainers 10 degree

Changes made to engine
Hydralic Roller cam
Duration@.050 intake 236 exhaust 242
lobe lift intake .3770 exhaust .3810
lobe separation 110.0
1.65 roller rockers Stock Ram Air 4