Poncho Revival -- Building a Stroker Pontiac (Secret EFI!)

Pontiac is widely credited with giving rise to the muscle car movement when it introduced its famous 389 v8 into the GTO in 1964. Automotive Specialists owner Keith Dorton is

building

a classic 389 with some modern upgrades that should help you produce much more than advertised. 215 to 360 max horsepower from the original engines and that's good because this engine is not going into a light gto but rather a 1955 Pontiac Safari truck so it will need some mass. This engine will be bored and knocked over the two original 4.0625s. inches diameter and three inches seven hundred and fifty thousand strokes to four inches one hundred fifty-five thousand spores and four and a quarter inches stroke, bringing the total displacement to four hundred and sixty-one cubic inches to fill those large cylindrical boards Dorton is using a Molly Piston set with a flat top and a generous valve pocket.

He remembers that these are profitable pistons. The compression ratio will be a relatively mild 9.71, which will help keep the engine safe from detonation while hauling a relatively heavy car and burning it out. gas pump rings are a lightweight low tension package from molly and measure one millimeter for the top and second rings and two millimeters for the oil ring these pistons use a low resistance floating pin design and there is sufficient compression distance in pistons that the pegboard does not interfere with the oil ring groove, meaning the support rail is not required. Those eight pistons are attached to a set of monar H-beam connecting rods.

They are six inches eight hundred thousand long and two inches two hundred. thousandths of a big block size chevy big end and then the entire assembly is installed in the block where the crank has already been placed in place. The block is an original 389 small journal casting that Dorton acquired, unfortunately the previous owner had managed to lose the main caps, so Dorton did the necessary machine work to install a set of new billet steel four bolt main caps. Billet Speed ​​Works. This engine will end up in a show car, so all that roughness and casting dross has already been painstakingly polished away by God knows how many. sanding rollers and gallons of elbow grease, Johnson automaker's hot rod shop will apply a multi-stage paint job to the engine to suit the car, so it remains bare metal for the build session and test bench in the old days, the biggest 400. and Pontiac cubic inch blocks were more sought after because they were easier to generate power, but these days a modern aftermarket crank makes the small 389 journal a better choice.

The 389 uses a smaller three-inch diameter main journal compared to the three-and-a-quarter-inch mains. which reduces parasitic losses, so dirt uses a monar forged crank that uses the smaller main journals while increasing the stroke to the aforementioned four and a quarter inches. A 10.24-inch deck height allows for easy matching of that stroke along with a six-inch, eight-thousandths-long tall connecting rod that helps maintain a good rod stroke ratio, by the way, look at the fuel pump pickup. oil bolted to the milling oil pump. This design moves the pickup directly over the oil pump to tighten it a bit. closer to the back of the pan which helps ensure the truck is not uncovered during hard launches, the camshaft is from the crane, it is a hydraulic roller that has been ground to match well with the truck heads. highest flow rates we will use at 50,000 tap it lift has 247 degrees of duration for the intakes and 255 for the exhaust lobe lift is 360 mils for the intakes and 372 mils for the exhaust combined with the crane rockers with a ratio of 1.65 to 1 that we will use and that makes total valve lift 594 and 614 thousandths respectively, the crankshaft rotates the cam through a double roller timing chain.

You will notice that the front of the engine does not have pins to help locate the front cover, so some precautions must be taken if the front of the cover is not positioned correctly, that means the front seal will not be centered around the mouth. of the crankshaft and damper hub and that extra pressure on one side or the other of the seal means it will fail prematurely to prevent that from happening. Dorton uses only a couple of bolts to hold the front cover to the block, but leaves them loose. He then partially installs the Ati shock hub that he will use on the crank.

If he is using an original shock absorber, it is not necessary to disassemble it. press it in enough so that it extends past the seal then make sure nothing is tied down and the front seal rests lightly on the nose of the shock and you can finish screwing on the front cover and here is a shot with the shock ati put and secured the crank, the old tray has also been screwed on. This is a Pontiac Pro Touring Tray by Milodon. I'm too late to show you the interior, but it's completely stumped with flaps to retain oil around the truck, no matter how hard it is to drive.

The pan can handle a stroke of up to four and a half inches and holds seven quarts of oil. A pair of Kimetic multi-layer steel head gaskets are used to provide a proper seal between the block deck and the Edelbrock Performer rpm cylinder heads. I'll use edelbrock says their high performance rpm heads for

pontiac

are based on the

pontiac

ram air 4 head between 1969 and '70. These particular heads have 72cc combustion chambers combined with 215cc intake runners, but it's worth the It is worth noting that automotive specialists have adapted them manually. these heads for more airflow and that means the chamber size will be a few cc larger.

These 14 degree heads are designed to produce the best power from 1500 to 6500 rpm. The stainless steel valves are foreign and are sized two-hundred-ten-thousand inches for the intakes and one six-hundred-sixty-thousand inches for the exhaust, both with an eleven-thirty-32-inch valve stem. Pontiac's block design has a very thick deck for great strength. Only 10 bolts are used to attach each head to the block, but each one measures half an inch. harp bolt that is torqued to 100 foot-pounds, so the clamping load is quite high. Also, all the bolt holes are blind so none encroach on the water jackets, which is always a good thing.

These valves are actuated by a set of package springs. They are a double nested spring. with a shock in the middle and have an installed height of one inch 900 mil with the valves against the seat they produce 145 pounds of pressure and at maximum valve lift they will spring back with a force of 435 pounds those valve spring retainers Unique looking Titanium Manly Super Sevens are no longer made by Manly and were primarily used for Nascar Cup racing, but these are the kind of things you never know when Dorton will pull out of his bag of tricks, like the camshaft from which lifters also come.

Crane These are hydraulic rollers designed to directly fit the Pontiac block which originally never came with rollers. The tall bodies of these lifts mean that they can handle a lot of lifting without hitting one of the steel bars in the lift hole. Dorton then installs the two pieces. pushrod guide plates and 7 16-inch rocker bolts Before tightening the rocker bolts that secure the guide plates in place, you mock up everything including the pushrods and rocker arms, then you can adjust the position of the guide plate so that the pushrod does not rub against the pushrod holes in the cylinder heads and the tip of the rocker arm is centered over the top of the valve stem as much as possible.

This is possible because the hardened guide plates come in two pieces and the bolt holes are slotted, allowing a little movement for adjustment as part of the checking process. He also checked the proper pushrod length to ensure the rocker arm sweep is centered over the top of the valve stem. We ended up using 5 16-inch hardened pushrods that measure 750 thousandths of an eight inch. With everything checked, aluminum crane rockers can be installed in place of the usual 1.5 to 1 ratio rockers. These are a more aggressive 1.65 ratio for both the intakes and exhaust, so net lift will be 594k for intakes and 614k for exhaust Thorton sets the valves by tightening the adjuster nut until the entire latch is removed and then lowers it an additional three-quarter turn, which depresses the hydraulic cup and the lift approximately 40 mils and then locks everything when Doran began to plant this construction.

The idea was to build a very high horsepower Pontiac with lots of cubic inches and a single plane intake manifold with dual four cylinder carbs to feed it lots of air and fuel, but along the way the owner had a change. he from heart and he decided that he wanted a more retro look, even if it cost him some horsepower, so this shot will be used instead. The pontiac tripower aluminum casting is based on a 1966 pontiac intake for a two barrel triple carburetor setup, except in this build. We'll be using fuel injection, this dual-plane intake is an old design and certainly won't be able to flow as much air as the setup Dorton had originally planned, but you have to admit it's still pretty cool that the fuel injection setup is from Auto Trend . efi and has obviously been designed for the throttle bodies to mimic the look of the old school Rochester.

Two barrels. All three throttle bodies are completely CNC cut and each is rated at 350 cfm, which is much better than the stock Rochester that flowed just around. 278. Each unit is equipped with a pair of 42-pound injectors; however, the system has a unique method of mounting it. It turns out that the base plates and their corresponding bolt holes are narrower than the carburetor mounting flanges on the intake manifold in order to move around. If the Auto Trend EFI system uses these offset bolts, the bolts thread into the manifold, but do not have to be tightened once they are in place, a set of spacers come down, the spacers have slotted bolt holes that are machined to fit exactly over the shoulders of the offset bolts so they can fit flat against the intake manifold and not be held in place after another gasket falls into place.

Fuel injection bodies can be mounted up because the spacer plate fits over the shoulder of the offset bolts once the throttle bodies are bolted on, sealing the plates and gaskets and creating a leak free system and because everything will be computer controlled, we are actually using a Holley ecu specifically, there is no need for complex progressive throttle linkages like you would normally see with a carburetor. system, it's actually a pretty good setup and with that it's time to take this

poncho

to the dyno and see what it's capable of, as you can see all three throttle bodies are fed through a common fuel register, although small, we gave them a constant 60. pounds of fuel pressure and were happy that the car's manufacturer and owner were working on machining some custom valve covers for this engine and they weren't ready yet, so Dorton pulled these seal pieces off a shelf.

They are not pretty, but for now all of them. What we need them to do is keep the oil inside the engine. Also not very pretty are the headers and their peculiar manifold arrangement that we are using, but these are just dyno headers, they have a two inch pipe diameter and while the manifold design may not be the most efficient on the market. world, it won't hurt much, if at all, so how did it do it? Not too bad, this 461 makes enough torque to get the 55 Safari truck moving down Dorton Highway. Pulled from 3,800 rpm to 5,500, torque comes on strong right off the bat with a peak of 544.2 pound-feet at 3,900 rpm and never drops below 500 until 5,100 rpm due to the intake manifold we knew this engine had. was not.

It's going to be a tall river, but that's not what it was intended to be anyway, we almost broke the 500 horsepower mark with a peak of 487.9 horsepower at 5400 rpm and the average horsepower across the group was a healthy 454.7 with plenty of torque on demand at all times. rpm range and a highly controlled fuel injection system that should make this enginestart on first shot any time of year this mill will be a lot of fun and hey i can support anyone who wants to keep classic pontiac v8s alive if you've made it this far my sincere thanks for watching please like and subscribe because we have tons of cool builds coming up.