Projects 1964 PONTIAC 421 HO Engine Build

Just about to begin the assembly phase of my 1964 421 HO project after collecting pieces for it for the last few years. I'm just now gathering everything up for a trip to a friend's shop. He'll transport it to a trusted local shop to get all the machine work done and after that he will carefully put it all together.

This Tri-Power 421 (370 HP factory rating with 10.75:1 compression) was only offered in the full-size Pontiacs (Bonneville, Catalina, etc.). It will be installed in a well-optioned 1964 LeMans convertible that was originally equipped with a 250 HP 2-barrel 326. This is the kind of swap that was done 'back in the day' when a Pontiac hot rodder found a wrecked 421 Bonneville in his local boneyard.

I'm looking for it to make about 350 honest horsepower for cruising and road trips, the compression will be lowered to 9:1 so the engine will be happy running 91 octane fuel. This engine will probably never need to have the valve covers removed after it's installed. Oil and spark plug changes and an occasional ignition point adjustment will be all it will ever need, just as Pontiac engineering intended.

Here are some pictures of most of the components, all taken before beginning any cleaning, machining or painting. Hopefully the pictures of the 1964 factory components will be of interest to the Pontiac fans here who are not as familiar with some of the features of the pre-1965 Pontiac engines.

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Crower forged rods, purchased over 20 years ago for a previous engine project, long before any good Pontiac rods other than factory 455 SD or BME aluminum were available. These are press-fit and will get bushings installed for floating pins.



AutoTec custom forged dished pistons, the 23cc dish will get the compression down close to 9:1.



Melling Select 60 psi oil pump and pump driveshaft.



New harmonic balancer and hub. Cheaper to buy new than to have the original rebuilt, the new hub provides an unworn surface for the front cover seal.



NOS Pontiac 9779068 'S' camshaft and new Johnson Hylift hydraulic lifters. Cam specs - 288/302 advertised duration (212/225 @ .050) .407"/.407" lift with 1.5:1 rocker arms. The '068' cam is best known as the 'Tri-Power cam' because it was used in most of the Tri-Power GTO engines.

The '068' cam has the same exact profile as the 9770543 cam originally used in the 1964 421 HO.



Note the 'S' identifier stamped on the nose of the cam.





Cam thrust plate and mechanical fuel pump eccentric. The factory thrust plate closely limits the amount the cam can walk, no need for a thrust button here.



H-O Racing VS-11 valve springs.



H-O Racing HW-51 oil gallery plug set, the brass plug is drilled .030" to positively oil the distributor drive gear. This 3/8 NPT plug set replaces the factory press-in cup plugs.



Cloyes Tru-Roller timing set.



1964 GTO 1111054 iron body points distributor, restored, rebuilt and recurved.



Factory windage tray used on 1964 and earlier engines, it fastens to the #4 and #5 main caps. The lower dipstick tube is retained by the tray.



From the top we have the lower dipstick tube, block tube and upper dipstick tube. Not at all like the common 1965 and later parts.





1964 oil pan, it has a slightly wider sump in order to accept the windage tray, 1965 and later pans are too narrow and won't fit.



Rear oil pan seal reinforcement strap and hardware.



Angled oil filter adapter to fit the A-body chassis. This 421 HO originally came with a 90-degree adapter mounted to a special spacer to angle it rearward to clear long-branch HO exhaust manifolds. This build will use the standard log manifolds.



Corrosion-free 1964 timing cover.



Water pump divider plates in surprisingly nice condition.



Rebuilt original 1964 8-bolt water pump.



Timing cover hardware and engine lifting hook.

 

The heart of the build, a code 45B 1964 421 HO 370 HP manual trans 4-bolt main block, all Pontiac 421 engines without exception had 4-bolt main caps.



Block casting # 9773157



The block is still at standard 421 bore size (4.09375") and will be bored to fit standard size forged 428 pistons (4.120").



Oil passage used on non-HO 421 engines that still oiled the rocker arms through hollow rocker studs. 1964 was the last year for rockers that oiled through the studs. The 421 HO and GTO 389 both used the 9770716 heads that oiled the rockers through the pushrods, so this oil passage was not used and was sealed off by the head gasket and the head itself.



4-bolt mains.



4" stroke 421 crankshaft, still at standard size on all of the journals.



Armasteel was just a fancy name for a high grade of cast iron.



1964 421 HO head casting # 9770716 was shared with the GTO 389 that year. These big-valve (1.92/1.66) heads were the best Pontiac production passenger car heads available at the time. The standard 326/389/421 heads had 1.88/1.60 valves.



These heads have press-in rocker studs and no pushrod guideplates, two things I will need to address on this build for the sake of long-term reliability.



Closed 72cc combustion chambers. They will be treated to some rework to remove any sharp edges (to avoid creating any hot spots) and to gain a few extra ccs of volume to help get it down to my 9:1 compression target.



Along with the bigger valves these heads had bigger ports than the standard 326/389/421 heads.



Factory head bolt set.



Stamped steel factory replacement 1.5:1 rockers.



1964 GTO 389 chrome valve covers, still in excellent driver-condition after all these years.



1964 Tri-Power intake manifold, this design was the first of the high-rise Tri-Power intakes.



Restored correct Rochester Tri-Power carburetors. The center carb is a 1964 GTO auto trans unit that still has provisions for use with vacuum secondary carb linkage. The two end carbs were taken from a 1966 setup I used to drive daily. Wide-open all 3 carbs will supply right around 700 cfm of air flow to feed the 421.





1964 GTO Tri-Power throttle linkage bracket. This hard to find bracket was used early in GTO production, it was cut in half at the factory and then welded back together to change the configuration.





1964 Tri-Power thermostat housings both OEM and repro, the upper one with the raised pad under the casting number is the original piece. The repro piece is actually about 1/4" shorter than the original.



Thermostatic vacuum valve used for the factory vacuum actuated secondary system.



1962 big Pontiac Tri-Power air cleaner in excellent original condition. The 1964 units had both snorkels shifted off to the passenger side, this one is more pleasing to the eye with both facing forward.

All of the 1964 big Pontiac 421 HO and 389 Tri-Power engines came with these huge air cleaners, not at all like the 3 small chrome ones that the Tri-Power GTO 389 used.









The lucky recipient of the 421, it currently has a 325 HP 1964 GTO 389 4-barrel engine residing under the hood.

 

Great pics! My buddy has a tri powered 421/4 speed Catalina convert. I really don't pay too much attention to it but these pics remind me to. I know he brought over the intake and carbs one Friday night 'shop night' to install and set up.

Thanks for sharing.

 

What a great collection of old poncho parts! That air cleaner was new to me..never saw one but I love it. Are those chrome plated Ralleye 1s on the car?
Wish I'd used forged pistons in my 370. [1957 347 punched 0.125"] but at least I got the early forged crank/rods.

 

They're Tempest/LeMans/GTO Custom Spinner wheelcovers available in 1964 only.



Will swap back and forth between the 14X6" steel wheels/spinners and a set of 14X6" Hurst wheels (the only size they were produced), all on narrow whitewalls. The 45 year-old bias-ply General triple-stripe tires in the picture have since been dismounted and sold off.

 

Wow, you really have been collecting up all the good stuff for this build. I'll be watching. I've got a '64 3x2 GTO.
Mike T - Prescott AZ

 

Head teardown revealed some rust buildup inside some of the intake ports near the valve seats.

Should clean up no problem after the machine shop finishes baking and blasting the heads.

 

Nice project, reminds me of my 65 GTO with a 66 421HO. I pulled the 421 out of a 66 ventura that was rusted to death. Never new the ventura had a 421 in it. Owner lived behind the grammer school i went to. Always saw the car around town. When i saw it laying in his driveway i inquired. He said he wouldnt sell the car but would let me part it out in his driveway and then he would scrap it. I paid $250 for the running engine.

 

Making some progress while waiting for the block, crank and heads to make their way through the machine shop.

Freshly blasted factory iron Tri-Power intake, shown sitting on a postal scale weighing in at a little over 46 pounds. Heaving one of these around inside a blasting cabinet is a chore.



The timing cover came out looking almost new.



Valley pan or pushrod cover before going into the blaster. This thing was clogged up pretty well with crud so before taking this piece to the builder I knocked all the loose stuff out by tapping around it with a soft hammer. Next I soaked it in solvent for a few days, then rinsed it with high pressure water. This removed probably 75% of the crud. Then I soaked it in Simple Green for a few days and gave it another good high pressure water rinse.

The inside came out as clean as a whistle, no need to drill out the spot welds and cut it apart for cleaning. Between the solvent and Simple Green most of the paint came off. The Simple Green etched the metal too, I don't ever clean finished painted surfaces with this stuff.



Bask side carefully masked off with duct tape to prevent any glass beads from finding their way inside, this would be the kiss of death for a Pontiac engine. Rubber stoppers were used to close off the PCV grommet hole and two bolt holes on the top side, no evil blasting media made it inside.



Freshly blasted pan, it has a couple of small dents near the front that will never be seen with the intake in place.

 

Made a little more progress while waiting on the machine shop. Nothing earth-shattering to show at this early stage but nonetheless work is progressing. We did receive some good news, the block and heads passed Magnaflux testing after cleaning.

Freshly painted intake.



Timing cover is looking good.



Valley cover ready to go.

 

Very cool.
I have a OT '69 GTO 'vert. I spent more time welding in floors, trunk and quarters than building the
400 cid motor. I went with the same route on reducing the compression to 9:1.
I'll be watching this build.

 

This should be an interesting build. Subscribed

 

Good stuff really like the 421s.

 

I have a '63 421 Tri Power that has been in several of my vehicles over the years, long story there. Anyways it has 10.1 CR (actual measured) and has not had a problem with detonation.

For a long time I ran it with an Engle solid lifter cam that is a beast. Later I was talked into putting in the factory spec hydraulic cam to help the auto transmission that I was running at the time. Next trip the Engle is going back in along with a manual transmission.

I am loving your thread especially the pictures. I may be biased but the 421 is IMHO about the best thing that has happened engine wise.

 

More progress on a couple of items. The oil pan went through the bead blaster and got some Pontiac Light Blue paint applied along with the newly rebuilt water pump.

Best of all we received some very good news from the machine shop, the block mains checked out good and will not require a line hone.

 

Great news...line honing costs money best used elsewhere.
I built a 69, 428 + 0.030 for my buddy's 40 Pontiac sedan. He LOVES it!
Maybe I missed it........are you planning on a balance job?

 

A top-quality balancing job will most definitely be part of this build. We will be boring and honing the block with a torque plate and cutting the deck to put the pistons at zero deck for a tight quench distance, the objective being good combustion efficiency and octane tolerance.

Trying to cover all the bases here, nothing will be done half-assed on this. Not throwing the budget out the window, but not cheaping out on any of the necessary things to do 'er up right.

 

draggin'GTO, here is something you might find interesting. In the 60's I was into Pontiacs heavy. I had a 57 Bonneville, a 63 Bonneville convertible (tripower), and two 66 GTO', one a tripower and one a four barrel. Any way, one of my best friends Dad owned a Pontiac Cadillac dealership and my buddy got a brand new Pontiac every other year.

In 1963 he got a tripower 421 Gran Prix, and in 1965 he got a tripower GTO convertible. The GTO was black with a white top and all white interior, four speed, 4.30 gears, and a lot of options. But it was a lot quicker than the other GTO's he raced on the street and at the drags, about a second faster on cheater slicks. At 60 mph he could open up the trips and the tires would light up, it was a beast, but this wasn't unusual for him because he always had some fast cars. My tripower Goat was quick, but his was brutal, and it was a heavy convertible !

One day we were talking and he said " I want to show you something." and he pulled out the window sticker that listed all the specs on the car. Now, the window sticker on my GTO listed the engine as "389 tripower, etc, etc.", but in the block where mine said that his sheet only had a big X across that area. It did not say what motor was in the car or any of the specs on the motor.

Then he confided to me that he ordered the car with the tripower 421 HO motor because his Dad was able to check the right boxes on the order form. He didn't want anyone to know because he was making too much money street racing it. Two years later he sold the car and I became friends with the new owner, and he also continued to street race and drag race it and it continued to win.

Just thought you would enjoy this little piece of little known Pontiac history.

Don

 

The last small detail items I needed have arrived so my search for old Pontiac parts to finish up assembling the 421 HO is pretty much over now.

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Reproduction chrome breather cap, original caps in good shape are like hens teeth. I need this little beauty to cap off the tall stack on the passenger side valve cover.



Original plug wire brackets, replated and dipped in black insulating material just like when they were new.



OEM brass 45-degree heater fitting elbow that screws into the front intake manifold water crossover, the 90-degree elbow made from steel tubing (shown in the first intake photos) screws into this piece. This is a GTO Tri-Power part that was not used on the big Pontiac Tri-Power setups.



Replated OEM air cleaner studs used to secure that huge Tri-Power air cleaner to the carbs, with 3 reproduction wing nuts. Note the tips of the studs are turned down to remove the last few threads, presumably to keep a loose wingnut from easily coming off the stud and getting into one of the carb throats.



OEM heavy-duty 6550 fuel pump originally used to feed the 421 HO and various other engines that required a better pump than the standard 4512 pump. The finish on the pump casting looks nice for a 50 year-old part so I'll just give it a good cleaning and install an ethanol-compatible rebuild kit before using it.

 

Making some more progress.....

While the block machining is still being finished up the heads were gathered up from the machine shop after cleaning and crack checking for some work on the combustion chambers.

Found some dings along the edge of some of the chambers on the spark plug side, likely from being mishandled during a previous valve job long ago. These will be eliminated during the chamber work so they are of no consequence.



Some of the intake seats do exhibit some pitting that we are concerned about. After looking for some replacement stainless intake valves in the correct lengths and coming up empty we have decided to cut down some larger diameter valves to around 1.96" (stock size is 1.92") to try to find some fresh intake seat material.

Before finding the seat pitting we were going to up the valve size a bit to 1.94" to attempt to use a common Chevy stainless valve, but none were available in the length we need. We're keeping the valve spring installed height at or very close to stock 1.53" specs so we don't want to use a very long valve stem. I'm thinking we won't go for more than a 1.56" installed height, attempting to keep the valvetrain geometry as close to stock as possible.

Cutting down the larger intake valves also gives us the ability to put a nice back cut on them, we will be keeping the factory 30-degree intake seat angle that works best with the .407" lift factory cam. The 1.66" exhaust valves will be trimmed down a bit to make room for the slightly larger intakes after making the final decision on the the intake valve diameter.

Any factory casting flash or irregularities inside the valve bowls will be smoothed out with a sanding roll before any seat work begins.



The chamber work is shown here in the beginning stages, one of the smaller chambers was roughed out to 77ccs to establish a baseline to work from. As you can see most of the work is taking place on the spark plug side of the chamber, leaving the full quench pad on the opposite side intact.

Chamber ccs before starting any work, with the original valves popped back in. The factory lists the spec for these chambers at 72ccs. Pretty close in size with only a .6cc volume variance, attesting to the excellent cylinder to cylinder compression ratio control provided by the fully machined chambers that were a quality feature built into all Pontiac V8s:

1. 74.2
3. 74.0
5. 73.8
7. 73.8
2. 74.0
4. 74.0
6. 73.6
8. 73.8



After working all the chambers and rechecking the volumes as the final size was carefully established we ended up just shy of 78ccs, so to account for any small measuring errors and be safe we'll say 77.5ccs.

This is all being done before the hardened exhaust seats are installed, the valve job and the head deck resurfacing. After all the head machine work is done we'll measure one final time to find out the actual finished chamber volumes. My guess is they'll end up close to 76ccs with the minimum surface cut needed to true up the decks.



We had several different sets of head gaskets to choose from so they were all measured to find the ones that were closest to matching our finished bore size.

We learned something on the head gasket sizes. Measured the FelPro 1016's, Butler style, and ROL HD's. The ROL was the largest at 4.34" X 4.32", FelPro next with a 4.34" by 4.30", and then the Butler's at 4.34" X 4.17". Interesting that they were all the same width front to back and only varied in bore width.

Here we have one of the FelPro 1016 teflon coated gaskets sitting on top of one of the Butler composition gaskets, showing the smaller diameter and closer fit of the Butler gasket that we will most likely end up using.

 

Head gasket and chamber are matching up nicely. Took a quick shot just before running the heads back to the machine shop. The machinist commented that it may take only a .005" to .006" cut to clean up the deck surfaces.

It's looking like we may need at least one new intake valve seat, the machinist thinks the deep pitting may not clean up even going up to a 1.96" valve size. Either way we'll know before too long and do whatever it takes to get these cast iron beauties back into top form.

 

In 72, I had a 64 Gran Prix with the 421 TriPower 4 speed powertrain. It was an absolute wore out piece of junk, but that engine pulled like a locomotive. Glad to see someone putting one together the right way.

 

A minor but important issue has reared its ugly head.

Unfortunately there was an issue with one of the cylinder banks on my block. It seems at one time the engine was rebuilt still keeping the original pistons. It looks like whoever was doing the work may have used a ridge reamer and gouged into the bores about 1/2" down from the top, again on only one bank of cylinders.

One side of the block cleaned up just fine at 4.120" which is about .027" over standard. However the other bank needed to go 4.135" to clean up, so I will be purchasing a new set of custom pistons at the new 4.135" bore size. I will be looking to sell off the RaceTec 23cc dished 4.120" bore 4" stroke pistons or perhaps keep them for a future 389 build with a 4" stroker crank. A 389 block would be a good home for these pistons, bored about .057" over.

Not sure at this point yet if I will be using RaceTec or Ross pistons, and likely will add one or two additional ccs to the dish volume to make up for the added bore size and to get closer to 9:1 rather than the originally planned 9.3:1 compression ratio.

Since my car is air-conditioned and equipped with a TH400 and tall 2.56 highway gears I think it is wise to go just a bit lower on compression. Our ethanol-laced 91-octane premium isn't likely to get any better in the future and I don't want to worry about detonation on hot summer days while running the A/C.

Use care if using a ridge reamer, in fact most of the time you really don't need to use one to get those pistons free of the bores during a rebuild. In the hands of a novice they can easily do more damage than good.

 

Well that certainly put a gouge in the works.

 

As the owner of a maybe ... never on the road again, deer damaged '65 GTO, I am very happy to stumble upon this thread. Very nice information here. Thanks for sharing ... definitely.

 

why not sleeve the bores? cheaper than a set of custom pistons.

 

If the block was worn to the point where it needed sleeves to make it serviceable I'd do that in a heartbeat, but I see putting sleeves in all 4 holes of one bank as compromising the integrity of an otherwise very good block. The new bore size amounts to boring the block .041" oversize (from 4.094" to 4.135"), a pretty happy situation for any block that's more than 50 years old.

In my opinion buying a new set of pistons is the most solid approach, even if it costs me a little more cash. Putting 4 sleeves in a rare 421 HO block unfortunately would serve to devalue it as well.

 

Damn! Sorry to hear that... I have a '59, 389 and a pair of '64 heads like yours. Will a 4 inch crank fit the earlier [59-60] engines? Main saddles around the oil pump are a little different than the 61-up block..Makes it tough to find an aftermarket oil pump.

 

You can turn down the 3.250" mains on a 4.00" stroke 421 or 428 crank down to 3.00" and use an Olds thrust bearing with shims. Contact Pontiac Dude on the PY forums, he may still sell the kit to do this conversion:http://forums.maxperformanceinc.com/forums/showthread.php?t=450861&highlight=thrust

There are also some 3.00" main 4.00" stroke aftermarket cranks floating around that are a direct bolt-in.

 

Thanks...sorry for the hijack