# 1964 326 convert from 2 to 4 barrel?



## Pontiac-K (Mar 2, 2018)

I have questions regarding my 64 326 2 barrel engine and changing it into a 4 barrel

In 64 there was the 326 HO option which had a 4 barrel, dual exhaust, but it had higher compression. Typically to capitalize on a 4 barrel, the rest of the engine needs to be dialed in to take advantage. Some engines can't draw enough air through a bigger carb to take advantage of the larger air intake, the engine will bog down and not perform well.

I can obtain a 4 barrel Pontiac intake that's correct for the motor.

The car already has dual exhaust, which will help, BUT from what I've read, with the original pressed oiling head studs, I can't upgrade to a better breathing camshaft without the worry of pulling them loose over time. (Perhaps there's an RV cam would work in this setup, but not sure?)

I want to be able to run high octane pump gas in this car, as it will be a driver. I'm also thinking that it would be best to just keep it a two barrel, throw a new carb on it and leave it be!

Anyway, If you have any helpful tips/suggestions/info I would greatly appreciate it! There's just not a lot of information out there in regards to the 64 326, as it was different than the other years it was made.


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## PontiacJim (Dec 29, 2012)

Don't sound so discouraged. The 326CI is small, but still has potential.

The standard 326 vs 326 HO shows that the 326 has 8.6 compression and the HO has 10.5 compression.

For now, let's disregard the cubic inch differences between 326 & 389, and the compression differences of the standard vs HO engines.

Both 326CI engines use the same "441" cam. Intake duration: 269 degrees. Ex duration 277 degrees. Intake lift .374". Ex lift .406". Overlap 47 degrees.

So here is the good news. Most Pontiac street cams used the .406" lift, but changed the duration number - along with opening & closing degrees of the intake/exhaust lobes. Note the "441" cam has the .406" lift exhaust so your intakes should be able to take the same lift.

The '64 389CI used the "009" cam - Int/Ex duration: 273/289 Int/Ex Lift: .406" Overlap 54 degrees. The heads used press-in studs. But notice a little more duration on the Int/Ex but the same lift - which is not a real big increase.

What you want to look at is the Overlap. 47 degrees is pretty mild. 54 degrees is a better number for performance. More overlap means a more aggressive cam and typically means a higher RPM power range - and more overlap gives the engine that rough rumpty-rump sound all us motorheads like. As example, the Ram Air IV cam has 87 degrees of overlap and in a 400CI engine it is not a good candidate for low RPM street cruising and really likes to spin 6,000 RPM's.

As the cams got "bigger", heavier valve springs were needed and your HiPerf engines used the bottle-neck 7/16" screw-in rocker arm studs. So if you don't go crazy on a cam - which you probably won't anyway with a 326CI - you should be OK with the factory oil through studs if you plan to keep them.

That said, don't let the 8.6 compression give you much concern. An 8.6 compression engine CAN make power. The trick is, like all engines, to select the correct cam for your engine application. 

Pontiac, in general, used what is called a wide lobe separation angle (LSA) near 114 degrees. This provided a nice broad power/torque curve across the engine's RPM range providing good vacuum for accessories, smooth idle, good pull at lower RPM's and nice power as RPM's increase. But of course this was typically with the 10.5 compression of the day.

With the lower 8.6 compression, you want to tighten this up to build more cylinder pressure or Dynamic compression as it is called. Here is where (_in my opinion, bigD_) I would recommend a Competition Cams camshaft having a 110 LSA. This will take advantage of your lower 8.6 compression. The 110 LSA will build cylinder pressure and the engine will respond as if you added more compression by changing out to higher compression pistons. The power/torque will be much improved and pull real hard up to a plateau at which it will then drop off like a stone - but I can't tell you what that RPM limit is. An 8.2 400CI I used a Competition Cams 110 LSA in pulled like a freight train and dropped off about 5500-5600 RPM's and you could feel that there was no power to be had revving it any higher.

Now my car had manual drum brakes and no power robbing accessories so low intake vacuum was never an issue and/or something I ever measured. I don't think 110LSA would pose any problems. You might also consider a 112 LSA cam which would most likely give a little more manifold vacuum, but I would still look into the 110 LSA cams first.

So, my recommendation would be to email or contact Competition Cams, Butler Performance, KRE, TinIndian, or anyone else who specializes in Pontiac engine cams/builds and get their recommendation on a kit that includes a matched cam/lifters/springs for your engine.

You should have no problem adding a 4Bbl intake/carb. The original carbs are about 500CFM's which is not very big per say, but just what you will want for the smaller 326CI. :thumbsup:


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## Nicholas (Jan 16, 2017)

Not even my thread, but I want to thank you for taking the time to share your thoughts and experiences with us. I enjoyed reading it. You are certainly a wealth of knowledge, Nicholas.


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## 1968gto421 (Mar 28, 2014)

You might also consider Lunati Voodoo cams. ( Voodoo - Hydraulic Flat Tappet - Lunati Power ) Like the Comp Cams cams, they have 110 LSAs and build good cylinder pressure. They were designed by famous (but now deceased) cam designer Harold Brookshire. Comp has a reputation for steep closing ramps on their cams causing valves to bonce on the valve seat despite valve springs used. Harold designed the Voodoo's to have closing ramps like the GM designed cams so the valves have a slower, gentler landing. Like Jim, I have used Comp cams but did have that valve seating problem. Anyway, IMHO.

And best of luck with your 326!


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## Pontiac-K (Mar 2, 2018)

Nicholas said:


> Not even my thread, but I want to thank you for taking the time to share your thoughts and experiences with us. I enjoyed reading it. You are certainly a wealth of knowledge, Nicholas.


100% couldn't agree more! This forum is fantastic!


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## Pontiac-K (Mar 2, 2018)

1968gto421 said:


> You might also consider Lunati Voodoo cams. ( Voodoo - Hydraulic Flat Tappet - Lunati Power ) Like the Comp Cams cams, they have 110 LSAs and build good cylinder pressure. They were designed by famous (but now deceased) cam designer Harold Brookshire. Comp has a reputation for steep closing ramps on their cams causing valves to bonce on the valve seat despite valve springs used. Harold designed the Voodoo's to have closing ramps like the GM designed cams so the valves have a slower, gentler landing. Like Jim, I have used Comp cams but did have that valve seating problem. Anyway, IMHO.
> 
> And best of luck with your 326!


Thanks for the information. I'll look into those as well. Back on track with the motor. Should be getting it back by the end of the month. I'll definitely be sharing photos and also what I ended up doing for the build.


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## Pontiac-K (Mar 2, 2018)

PontiacJim said:


> Don't sound so discouraged. The 326CI is small, but still has potential.
> 
> The standard 326 vs 326 HO shows that the 326 has 8.6 compression and the HO has 10.5 compression.
> 
> ...


I appreciate all of your info PontiacJim. I have been doing my homework since this post I have some things to share with everyone below.

I’ve labeled the different cam options that 1 thru 3 (Pick a winner!)


#1 Greg and Steve at Butler performance said that this was the ONLY cam they could recommend to me. It’s the Melling SPC-5… “stock replacement” which appears to be close to the 389 cam specs you gave above Pontiac Jim.

Melling SPC-5
Description: OE stock replacement grind

Intake duration: 272°
Exhaust duration: 280°
Intake lift: .407
Exhaust lift: .411
LSA: 112
Overlap: I believe would be 52°



#2 Mellings part lookup gave me MTP-1 as an option as well, but there’s mention of a specific valve spring. *(This is the one that I am considering for the rebuild)*

Melling MTP-1
Descriptions: Excellent low end torque and horsepower, use with VS-310 valve spring. Installed height 1.57”

Intake duration: 278°
Exhaust duration: 288°
Intake lift: .420
Exhaust lift: .443
LSA: 112
Overlap: I believe would be 59°





#3 Here is another Mellings RV/Performance cam that was stated as compatible on their site

Mellings 26204
Description:Fair idle quality. Good low to mid range torque and horsepower. Will work with stock or modified engine. Possibly lower vacuum than stock

Intake duration: 288°
Exhaust duration: 289°
Intake lift: .443
Exhaust lift: .466
LSA: 112
Overlap: I believe would be 69°



Pontiac Jim, could you clarify how you calculate overlap? I’m not able to get the same overlap numbers that you gave for the 326 and 389 above. I found 4 different ways to calculate overlap and they all come out with different numbers. 
Wallace racing also has a calculator as well which comes out to this equation here I think:
(Intake Duration+Exhaust Duration)/2 - (LSAx2) = Overlap



On another note regarding cams..I’ve also seen a couple places online that give the target range of 30-55 degree overlap for a daily driven low rpm performance. If that's the case, then #3 would probably be too outside the window we want to stay in? Seems like that one would fall under a rougher idle category?


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## Pontiac-K (Mar 2, 2018)

PontiacJim said:


> Don't sound so discouraged. The 326CI is small, but still has potential.
> 
> The standard 326 vs 326 HO shows that the 326 has 8.6 compression
> 
> You should have no problem adding a 4Bbl intake/carb. The original carbs are about 500CFM's which is not very big per say, but just what you will want for the smaller 326CI. :thumbsup:


I also did homework on different carb options. Thus far I have found a couple of Holley options.

If I go with the 2 barrel intake:

Holley Street Avenger 2bbl Carburetor 0-80350 350 cfm 

There's also a 500 CFM offering with the 2 barrel as well

My thinking is that the factory Rochester 2 barrel was 500, so I should go with the 500. I've also read on here that some have had success with the 350 CFM...my thinking is that it would be under fed with this? Thoughts?

If I go with the 4 barrel intake:

Holley street avenger 4 barrel 0-85570 570 cfm

Thoughts on how this 570 will mate up with my 326??

I have both the correct 1964 Pontiac 2 and 4 barrel intakes for this motor. Just need to make up my mind on which intake to roll with and see if there are any other carb options to look at. Anyone with thoughts please chime in!


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## PontiacJim (Dec 29, 2012)

Pontiac-K said:


> I appreciate all of your info PontiacJim. I have been doing my homework since this post I have some things to share with everyone below.
> 
> I’ve labeled the different cam options that 1 thru 3 (Pick a winner!)
> 
> ...



Looks like I missed this one, so here is my answer. Keep in mind that you have press-in 3/8" rocker arm studs and going to a higher lift cam could pull them out and/or put additional pressure on them to cause breakage. Going with a higher lift cam generally requires a stiffer valve spring which aggravates both previous conditions.......and why Butler could only recommend the one grind. So the SPC-5 would be my choice. Keep in mind that the smaller 326 cubic inches will respond well to a _seemingly smaller_ grind as compared to the larger 389. 

Overlap can be different from cam to cam even though the same general grind. The difference can be in how the cam was measured. There are several ways to claculate overlap - this comes from Lunati - Overlap can be calculated by adding the exhaust closing and the intake opening points. Another way I found on the net says you can measure it this way - Add the intake and exhaust adv durations, then divide the results by 4, then subtract the lobe separation angle, then multiply the results by 2. Keep in mind that most cam timing figures are at 0.050" of valve lift, this therefore is overlap at 0.050". Another cam might use the opening and closing figures at 0.006" or even seat-to-seat, and overlap would be calculated differently.

Overlap is what gives the engine that nice sound, but also is what determines engine vacuum. For the street, you want good vacuum over the nice sound we all like. Sometimes, going for "that sound" is not a good choice for your engine and you actually give up power that your engine could be using. So never choose a cam based on sound. :thumbsup:


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## PontiacJim (Dec 29, 2012)

Pontiac-K said:


> I also did homework on different carb options. Thus far I have found a couple of Holley options.
> 
> If I go with the 2 barrel intake:
> 
> ...



Go with the factory 4-Bbl. The factory 2 Bbl was not 500CFM's. The 2 Bbl is more like 250 CFM's. The factory 4 Bbl was 575 CFM's. Look up info on the 326 HO engine. It used the 4-Bbl which was 575 CFM's. You don't want big bores as found on a 500CFM 2-Bbl as it will be horrible on gas and velocity speed of the air/fuel mixture might be sluggish on the bottom end and this could lead to problems. 

The thing to note is the base of the Holley as to how it mates to the 4-Bbl manifold. Might have a different bolt-on pattern. You want to steer away from an adapter, but it is not out of the question either. You might also have linkage problems that you may have to solve for in using the Holley. The factory 4-Bbl is a good choice and can be found on Ebay or through a carb rebuild service. I have not had experience with Holleys so I cannot give a qualified answer on its use should you go that route. You might want to actually get a carb gasket for the Holley and a carb gasket for the factory 4-Bbl and overlay them to see if there might be any issues before you make your choice.........but definitely go with the 4-Bbl intake.


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## Pontiac-K (Mar 2, 2018)

PontiacJim said:


> Looks like I missed this one, so here is my answer. Keep in mind that you have press-in 3/8" rocker arm studs and going to a higher lift cam could pull them out and/or put additional pressure on them to cause breakage. Going with a higher lift cam generally requires a stiffer valve spring which aggravates both previous conditions.......and why Butler could only recommend the one grind. So the SPC-5 would be my choice. Keep in mind that the smaller 326 cubic inches will respond well to a _seemingly smaller_ grind as compared to the larger 389. :thumbsup:


Thanks for your input! Interesting....I wasn't that concerned about the minor lift differences between the SPC-5 and the MTP-1. I figured that the 13 thousandths difference between the Intake lift and the 32 thousandths difference between the exhaust lift wouldn’t be that big of a deal. On paper it's looks very minimal. What raised a red flag was that Mellings suggested a different valve spring (VS-310) along with the fact that Butler only could suggest the SPC-5.


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## Pontiac-K (Mar 2, 2018)

PontiacJim said:


> Go with the factory 4-Bbl. The factory 2 Bbl was not 500CFM's. The 2 Bbl is more like 250 CFM's. The factory 4 Bbl was 575 CFM's. Look up info on the 326 HO engine. It used the 4-Bbl which was 575 CFM's. You don't want big bores as found on a 500CFM 2-Bbl as it will be horrible on gas and velocity speed of the air/fuel mixture might be sluggish on the bottom end and this could lead to problems.
> 
> The thing to note is the base of the Holley as to how it mates to the 4-Bbl manifold. Might have a different bolt-on pattern. You want to steer away from an adapter, but it is not out of the question either. You might also have linkage problems that you may have to solve for in using the Holley. The factory 4-Bbl is a good choice and can be found on Ebay or through a carb rebuild service. I have not had experience with Holleys so I cannot give a qualified answer on its use should you go that route. You might want to actually get a carb gasket for the Holley and a carb gasket for the factory 4-Bbl and overlay them to see if there might be any issues before you make your choice.........but definitely go with the 4-Bbl intake.


Thanks for the clarification on the CFM’s for the 2 vs 4 barrel. I like the idea you proposed regarding picking up a carb gasket for the Holley and the Factory carb and seeing how they line up. 

As far as the “factory” carb. I am assuming that you are referring to a Carter? If so, does it matter what year I pick up and/or is there a range of years for that carb build that would just bolt right on with the proper 575 CFM?


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## PontiacJim (Dec 29, 2012)

Pontiac-K said:


> Thanks for your input! Interesting....I wasn't that concerned about the minor lift differences between the SPC-5 and the MTP-1. I figured that the 13 thousandths difference between the Intake lift and the 32 thousandths difference between the exhaust lift wouldn’t be that big of a deal. On paper it's looks very minimal. What raised a red flag was that Mellings suggested a different valve spring (VS-310) along with the fact that Butler only could suggest the SPC-5.



The difference in lift may not seem like a lot, but it is. That is why a stronger spring is recommended. The valves could bounce off the seats as they close because of improper pressure - so this is a bad thing & valves can break. The higher load of the springs may pull out the pressed-in rocker arm studs - so this is a bad thing. Valves kissing pistons because lift was a little too much is a bad thing. Head flow is also something to consider. Why go higher with lift if the heads won't flow past a certain lift. Notice how Pontiac increases duration versus going higher on the lift. Now if you go more duration, you raise the RPM range at which the engine will run and sacrifice bottom end. 

Do you plan on spinning 6,000-6,500 RPM's on a regular basis? The most important key with a Pontiac is to match all your parts so they work together. When you use the "bigger is better" mentality you can wind up with a dog of an engine rather than one that performs as hoped. You have a 326, not a 400 or 455 you are building. So you have to tailor any add-ons or even a complete rebuild based on a 326CI. You will only get so much HP out of it without doing a high performance rebuild and using all the techniques/upgrades needed - even then you could build a good 400 that would outperform a hopped up 326. 

The people over at Butler's know what they are doing and I would use their recommendation IF you plan on keeping the heads/short block stock. BUT, it is your engine and you can indeed build it the way you see best. You may never have an issue, but then again..........:thumbsup: Just my opinion on it.


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## PontiacJim (Dec 29, 2012)

Pontiac-K said:


> Thanks for the clarification on the CFM’s for the 2 vs 4 barrel. I like the idea you proposed regarding picking up a carb gasket for the Holley and the Factory carb and seeing how they line up.
> 
> As far as the “factory” carb. I am assuming that you are referring to a Carter? If so, does it matter what year I pick up and/or is there a range of years for that carb build that would just bolt right on with the proper 575 CFM?


I would try to get another Pontiac carb to make sure you have the correct throttle linkage holes and fuel inlet. I believe the 1964-1967 Carter will all be the same. Check this out, should give you a pretty good idea: The Carburetor Shop / Pontiac AFB carburetors


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## Pontiac-K (Mar 2, 2018)

PontiacJim said:


> I would try to get another Pontiac carb to make sure you have the correct throttle linkage holes and fuel inlet. I believe the 1964-1967 Carter will all be the same. Check this out, should give you a pretty good idea: The Carburetor Shop / Pontiac AFB carburetors


I'll start the final hunt this week. Things are a couple weeks out, so should be ready to put back together soon.


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## 326user (May 8, 2018)

Keep in mind 64 heads have a shorter valve spring assembled height. You would have to alter that somehow to use the cam/springs you are looking at that are above .411" lift. Valve spring seats can be machined, the metal umbrella can be removed, and/or offset valve keepers can be used. Plus you may already have some additional clearance from valve/seat grinding. Then also you need adequate valve retainer to guide (or seal) clearance.


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## Pontiac-K (Mar 2, 2018)

326user said:


> Keep in mind 64 heads have a shorter valve spring assembled height. You would have to alter that somehow to use the cam/springs you are looking at that are above .411" lift. Valve spring seats can be machined, the metal umbrella can be removed, and/or offset valve keepers can be used. Plus you may already have some additional clearance from valve/seat grinding. Then also you need adequate valve retainer to guide (or seal) clearance.


Understood! I went ahead with the stock setup. Motor should be coming home this week and it will be reassembly time! Looking forward to sharing photos


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## RunninLeMans (Apr 3, 2014)

Probably too late for this input, but I have the Lunati voodoo 213/219 cam in my 326 and love it. Broad torque from off-idle through about 4,500 rpm, peak hp at 5,000. 

Regarding the stock heads, the '64 326 used the 3345 heads, same as the 389 and 421 for that year. When I built the '67 326 for my car, I measured the intake ports on those originals and the 140's that came with the '67 before I ported the heads. Intake ports on the '64 ran about 150 cc's, but only ~120 cc's on the '67. The story is that Pontiac wanted more low-end torque and responsiveness for the later 326, but the point is those '64 heads probably flow enough to handle a pretty good cam increase on a 326.

Good luck, keep us posted!


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## Arlo Vonstalvick (Jan 1, 2021)

Has anyone used the Holley Sniper EFI on their 326. I am considering adding this EFI option to my 67 Firebird 326. Holley has a 2 barrel and 4 barrel option. The engine is stock and it looks like the 2 barrel 550 cfm might be the best option . Does anyone see a benefit going to the 800cfm 4 barrel model?


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## PontiacJim (Dec 29, 2012)

Arlo Vonstalvick said:


> Has anyone used the Holley Sniper EFI on their 326. I am considering adding this EFI option to my 67 Firebird 326. Holley has a 2 barrel and 4 barrel option. The engine is stock and it looks like the 2 barrel 550 cfm might be the best option . Does anyone see a benefit going to the 800cfm 4 barrel model?


Never used one, but in today's world, the EFI is probably a good choice. The 800 CFM would be too big in my opinion seeing the 2 bbl carb is probably rated at 250CFM or less.

I did not find an application for the 326 2 bbl, just the Ford 2 bbl. You may need a carb adapter to mount the EFI. Just make sure you get all the matching components like a complete kit rather than piece meal the set-up together.


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