# Deciphering My Motor



## MidnightAuto (May 28, 2018)

Hello - I am a couple months into my new purchase and am starting to put together the car's story - (previous owner is not around to share history). I was hoping some might give some opinions on what I have. Here is what I know - Ive got a 1964 421 block casting 35B and 9773157. The research says this is a 320 HP motor with 1X4. But the previous owner apparently made some changes that I can see externally. It looks like the previous owner found some aftermarket ram air exhaust manifolds. It is now a tri power with the intake from 66, #9782898 as well as the middle carb, #17057380 , and the two end 199 carbs, which I believe are 1959-62. The heads are 977877 which has been hard to understand (from web research) if these are the heads that came with this block. I'd love anyone's thoughts on whether or not these heads might be matched to the block or not, and their general level of expected performance? in 1964, this block with a tripower set up was rated at 350HP. I dont know what else might have been done from the factory to lift the HP from 320 to 350 - but was also curious if I should expect my HP to now be in the 350 range, all things equal? 

Thanks for any thoughts...


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## PontiacJim (Dec 29, 2012)

You have the 1965 "77" heads - closed chamber. In 1965, the intake pattern was changed so to use the 1966 tri-power, you need 1965 and up heads.

Keep in mind that the valve angle and location changed in 1967 with the introduction of the 400CI. So the 1966 and earlier 389/421 heads would have to be used to match the valve reliefs in the pistons of the 421. 

However, later heads with bigger valves can be used, by using the correct pistons. This could be easily accomplished by boring the 421 .030" over and using the 1968 and up 428 pistons which would be a match for the later 1968 and up open chamber heads and larger valves. HP would increase by use of the later 1968 and up heads with the bigger valves. Add a good cam, and you are close to the 400HP mark.

The 320HP and 350 HP used the same cams. The 320HP had 10.5 compression. 350HP had 10.75 compression. The extra HP comes from a little more compression and the 3 x 2 set-up used on the 350 HP engine. With the '66 tripower, you have the bigger center carb, so probably in the ball park of 350HP as well. Don't be too hooked on HP numbers with regards to Pontiac engines. It is the torque they make that puts them ahead of others. The 421 makes torque.


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## MidnightAuto (May 28, 2018)

Thanks Jim, very helpful. I’d been ignoring that 77 on the #7 port, thinking that was inconsequential since not the center port. But that makes sense - I had gotten the full number as it appears once I removed the valve cover. 

I’ve got this matched to an m20 4 speed and rear gears of probably 323. I’d like to have something moderately fast, low 13’s would be a great goal with some mods. would you swap these heads to something bigger/better flow, or would you make the changes u mentioned to these heads? I don’t really have plans to open up the bottom end, so have to keep that in mind...thanks


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## BearGFR (Aug 25, 2008)

That thing should run 13's without breaking a sweat. That confluence of years with the different valve angles and intake pattern can be a challenge to fit parts to, but you have a very special and unique combination there so it's worth the effort. If you're planning to beat on it any, do consider a good set of forged rods. They aren't that pricey and it would sure be a shame to have a stock rod let go and kill that one.


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## PontiacJim (Dec 29, 2012)

This may or may not be a concern. What is your oil pressure? The older engines only had 40 PSI versus the 60 PSI found on the later 1965 & up GTO's and HP engines. If you only have the 40PSI pump, then I would be a little hesitant to push the power through it - but keep in mind I am no expert on this and I would contact Butler or Kaufmann who build these engines regularly.

That said, the 421 as Bear stated should have no problem hitting the mid-to-low 13 seconds. Keep in mind that the 1964 "389" used by Jim Wangers was fitted with a disguised 421CI that was blueprinted with the "Bobcat" kit and ran 13.1 @115MPH in the 1/4 mile BUT, it was fitted with a close ratio 4-speed and 3.90 gears. So, my guess is that with your combo you could get a realistic mid 13's. Maybe fine tuning would drop this to lower 13's. The 0-100MPH times were 11.8 seconds and 0-60 was clocked at 4.6.

The above performance was with a "Bobcat" prepped engine which meant cc'ing the heads down, and thinner head gaskets to achieve more like 11.5 compression ratio - way too much today unless you are OK using racing gas only. Your compression now is probably 10-to-1 and requires a blend of race gas or an additive.

You cannot use the later heads IF you are not going to do a rebuild and 1.) install matching pistons for the later heads, 2.) bore the cylinder over to the 428 size so the larger valves do not hit the cylinder wall or get shrouded.

To improve performance, I would increase the valve sizes to that of the Super Duty 421 if they can be fitted. The #77 's have 1.92" intakes and 1.60" exhaust. SD heads used 2.02" intakes and 1.76" exhaust. I might go with the more readily available Pontiac 1.66" exhaust and use more cam duration on the exhaust. Some will install hardened seats on the exhaust at this time, but that is often a personal opinion as to the need. Use a good 3-angle valve job and port match & clean up the ports of any rough castings or casting bulges.

Install screw-in studs and matching springs/retainers to go along with your cam specs. If going with screw-in studs, you will want to use poly locks to hold the rockers in place. You can go with stock stamped steel 1.5 ratio rockers or roller's, but make sure you have the rocker arm balls with the oil grooves - not the smooth style. I would have the valve-to-head clearance measured so you know exactly what the limits of the cam lift will be should you choose to go higher on the lift than the factory .406" used in most instances.

Ram Air exhaust manifolds are good, but I bet you have the 2.25" diameter outlets and pipes? The 2.5" outlets would be better as would be 2.5" pipes and free flowing mufflers. You want the exhaust to breathe easily and not be restricted.

Dial in your distributor curve. 

Now all this is food for thought and is something you can use as a baseline and go from there. I would do a little more research and find a machine shop I could discuss my options/work with. If cost is not a big concern, then you might want to contact SD Performance as they have a package that will rebuild your heads for big improvements in flow and HP: SD Performance- Pontiac Performance Specialists Others to contact would be Butler https://butlerperformance.com/ , Kauffman Kauffman Racing Equipment , and Nightmare Performance Nitemare Performance | Custom-Ported Pontiac Cylinder Heads depending on where you live.


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## MidnightAuto (May 28, 2018)

Thanks for both your thoughts. I am anxious to get to the track at some point to get a baseline. The car is very clean, almost to clean for racingand screwing around. The previous owner did a lot of improvements and I have yet to find shoddy work or bad decisions in what was done so far. I honestly have not stomped on it a bunch, but it does seem to move out when those end carbs kick in. Is the actual diameter of exhaust true? So 2.5 inch really is 2.5? I can check if so. It has thrush free flowing mufflers, it’s pretty loud, maybe even too much for the neighbors. But what can you do. 

I am not really set up with tools/garage to do bottom end work (No engine hoist, etc) but point taken bear, I don’t need to get crazy. It would be a tragedy to blow this one. 

Jim I’ve got few of those mods on to do list already, will keep you posted!


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## MidnightAuto (May 28, 2018)

On the oil pressure question, I don’t know yet. In the process of installing gauges, only idiot lights at this point. 

I did buy a curve kit, should I automatically go to the lightest springs?

Thanks for thoughts on the heads, I’ll see who I have local. Will probably enjoy car for a bit this summer before taking the heads off and taking out of commission for awhile


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## MidnightAuto (May 28, 2018)

I just noticed that nitemare shop is pretty close to me. Have either of you guys used them for anything or heard any opinions? Geographically a good option for me.


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## PontiacJim (Dec 29, 2012)

MidnightAuto said:


> I just noticed that nitemare shop is pretty close to me. Have either of you guys used them for anything or heard any opinions? Geographically a good option for me.


Nitemare Performance is featured in Don Keefe's _Poncho Perfection_ monthly magazine. Nitemare is presently building a contest give-away engine. The build covers the replacement parts and how clearances & tolerances are measured. The June issue (60 pages in this issue) covers head porting & flow. He has his advertisements listed as well. I don't think he would be in the magazine if he was not reputable.

My brother got me this subscription to the magazine and it is exclusively Pontiac. I don't know why it isn't advertised more? Most magazine racks don't seem to carry it. I like it and the engine build series is pretty good with photos showing what the text is talking of. :thumbsup:


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## MidnightAuto (May 28, 2018)

Ok got it. I’ll check out the magazine too...


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