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Discussion Starter #1
Hello,

Anyone knows here what is the maximum flow rate of the two barrel intake manifold?
Worth to put bigger valve in the 327 210 HP head while keeping the stock two barrel intake manifold? Can the 2 barrel manifold / carb setup flow enough to the bigger valves?
Thanks.
 

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Hello,

Anyone knows here what is the maximum flow rate of the two barrel intake manifold?
Worth to put bigger valve in the 327 210 HP head while keeping the stock two barrel intake manifold? Can the 2 barrel manifold / carb setup flow enough to the bigger valves?
Thanks.
You can install the bigger valves and upgrade later to a 4 barrel.

Otherwise you're just throwing money away. The 2 barrel is probably done by 4000 rpm.
 

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Discussion Starter #3
Damn it. :)
I want to keep the car all original by looking at it. But hop up the internals for a bit more power. I am afraid the car will lose its value if I put a 4-Barrel manifold and a bigger carb.
I thought put a bit more compression, and bigger valves will add some power keeping the original manifold.

You can install the bigger valves and upgrade later to a 4 barrel.

Otherwise you're just throwing money away. The 2 barrel is probably done by 4000 rpm.
 

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All is not lost. Here's an article from carb guru Sean Murphy on 2 bbl. Circle track classes use these carbs. Nascar runs 390 cfm carbs.

I don't know what the six banger manifold flows but you could have it opened up by Extrude Hone to give you more flow. Expensive but very effective. Nobody would ever be able to tell from the outside.
 

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Discussion Starter #5
You have the link for the article?
All is not lost. Here's an article from carb guru Sean Murphy on 2 bbl. Circle track classes use these carbs. Nascar runs 390 cfm carbs.

I don't know what the six banger manifold flows but you could have it opened up by Extrude Hone to give you more flow. Expensive but very effective. Nobody would ever be able to tell from the outside.
 

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The limiting factor in dry flow rate will be the carb itself which flows between 352 to 435cfm depending upon the venturi size (most likely it is the 423 cfm version). Just keep in mind that two barrels are rated at twice the intake vacuum drop that a four barrel is rated for so that a 500 cfm Holley actually flows the same as a 350 cfm four barrel. You can not directly compare them you have to multiply the two barrel rate by 0.70 to compare it to a four barrel.

I mention dry flow because we run gas as an aerosol suspended in the air column. This is where the old hand cast manifold that were made by hand rolling green sand on a desk top to form the runners has a lot of very sharp bends inside because that was the cheapest way to make the manifold. Today's wet flow manifolds that were designed by a computer that are now made by a computer controlled robotic arm cutting out foam (lost wax casting) has smoother transitions that maintain or even increase the port velocity inside the manifold. This allows a dual plane manifold to flow at the same rate as a single plane while retaining the advantages of the dual plane without having the fuel fall out of suspension.

Larger valves and head porting your original "Power Pack" heads will improve the horsepower potential, but the combustion chamber is the biggest improvement to head design that has resulted in every one with a SBC having the potential for a 500 horse engine. You can run a modern raised port aluminum head with a heart shaped fast burn combustion chamber and have the ends of the aluminum head machined to look like your old head. Once painted orange it could pass for the original.

Here is a set of AFR heads CNC'd to look like stock Chevy Fuelie heads:



The Power Pack head was introduced in 1956 as the first small block horsepower improvement. But even by 1968 they were long in the tooth and long since surpassed by the 1957 283 horsepower 283 fuel injected engine heads that have been steadily improved year after year up to 1969.

The Power Pack casting mark:



Compared to the Fuel Injected head:



What you could do is to grind off the identifying aftermarket brand name sand blast the grinding marks and then paint orange a cast aluminum modern aftermarket intake manifold (that doesn't have an air gap) with raised intake ports to match the heads. You could then have a stealth stock looking motor which is the first step in building a sleeper.

Big Dave
 

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If you want to keep it 2 bbl stock looking check on a 350 or 400 sb intake for 2bbl set up. The 350/400
carb is bigger and would still give a stock look.
 

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My stock 2 barrel and manifold have been in a bag collecting dust since 1980. Just get a nice stock looking intake and a 600 vac. sec. holley 4 barrel and a 14" chrome air cleaner and youll be good to go. It will still look somewhat stock. If your motor is the one from the other thread then I assume your car is not a concourse correct restoration. Improvements made to a low hp car do not hurt the value. Just keep the old parts.
 

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My stock 2 barrel and manifold have been in a bag collecting dust since 1980. Just get a nice stock looking intake and a 600 vac. sec. holley 4 barrel and a 14" chrome air cleaner and youll be good to go. It will still look somewhat stock. If your motor is the one from the other thread then I assume your car is not a concourse correct restoration. Improvements made to a low hp car do not hurt the value. Just keep the old parts.
Agree. Mods to up the horsepower without affecting the smoothness/drivability will improve the resale value.

People don't buy first-gen Camaros to get beat by a Ford Focus. :D

Just use the right combo of parts. If you go to a 4 barrel (which you should), go with a Q-jet type carb like the street demon.
https://www.youtube.com/watch?v=IHWJpZCmUAk

Use a Corvette style drop base air cleaner or stock 4 barrel intake if you can find one.

You will need to upgrade the exhaust and cam to reach 300 hp.

Have fun ! :beers:
 

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Hello,

Anyone knows here what is the maximum flow rate of the two barrel intake manifold?
Worth to put bigger valve in the 327 210 HP head while keeping the stock two barrel intake manifold? Can the 2 barrel manifold / carb setup flow enough to the bigger valves?
Thanks.
The only difference between a 210 horse 69 327 engine and a 275 horse 67 or 68 327 is the heads, intake manifold and carburetor. Swapping from the heads up will give you more compression (approximately 10.25 to 1), larger valves and more power. No need to change the cam since they were the same between the 210 and the 275. Just as a comparison, the basic 275 horse engine was rated at 300 hp in 63, 64 and 65. It will still appear to look like a stock engine as long as you stay with the factory cast iron intake and a quadrajet. One other thing, use 69 or later heads if you do a swap. The 67 and 68 heads would most likely not have the proper holes in the ends of the heads to attach your 69 brackets.
 

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Discussion Starter #13
My only problem, I started this project as a full original restoration. Didn't wanted to change anything from original. I already got the original single exhaust system. just have it custom made a bit bigger 2.25" diameter. So I need to make the maximum out of the engine without making big changes. The 500 cfm 2BBL carb could be good Idea I believe. I put a higher compression piston, port the intake manifold. And keeping the original cam, since its good for 275-300 HP.
You guys think its doable? I will not buy a different exhaust. This one cost me a lots of money to have custom made in stainless steel, so I want to keep it.
 

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My only problem, I started this project as a full original restoration. Didn't wanted to change anything from original. I already got the original single exhaust system. just have it custom made a bit bigger 2.25" diameter. So I need to make the maximum out of the engine without making big changes. The 500 cfm 2BBL carb could be good Idea I believe. I put a higher compression piston, port the intake manifold. And keeping the original cam, since its good for 275-300 HP.
You guys think its doable? I will not buy a different exhaust. This one cost me a lots of money to have custom made in stainless steel, so I want to keep it.
Anything is doable. Just depends on your skill level and amount of money in your bank account. If you want to have more power but with the stock look, I'd say your plan is a good one. Good luck.
 

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Anything is doable. Just depends on your skill level and amount of money in your bank account. If you want to have more power but with the stock look, I'd say your plan is a good one. Good luck.
Skill level is pretty much good enough, i build road race motorcycles for living. ;)
Money can be an issue after a certain level of mods...
But i think with the 500CFM SMI 2BBL carb, ported 2BBL manifold, oversized valves, raised compression ratio, I should be a happy camper. With stock look. Most of the work I can do myself.
 

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The problem with that intake is it has no provision for an oil filler tube or the upper bolt for the alternator bracket. You will be forced to use a single bolt alternator arm. You will also then be forced to use valve covers with the oil fill cap. You will also be eliminating the breather for the pcv system with no vented oil filler tube cap. In other words this will open up a whole new can of worms for you trying to keep the stock look of your engine. At that point, you might as well do the 4 barrel conversion. Other issues with that manifold are no port to screw in your temp sending unit, you will need to find a choke coil that will bolt onto that manifold, if that hole is even tapped. Like I said a whole can of worms. You can easily find an aftermarket 4 barrel manifold that will solve all of those problems. Or even the stock era cast iron 4 barrel manifold is fine for up to 5500 rpm. It will bolt right in without any of those issues and give you that extra power youre looking for.
 

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Discussion Starter #18
The problem with that intake is it has no provision for an oil filler tube or the upper bolt for the alternator bracket. You will be forced to use a single bolt alternator arm. You will also then be forced to use valve covers with the oil fill cap. You will also be eliminating the breather for the pcv system with no vented oil filler tube cap. In other words this will open up a whole new can of worms for you trying to keep the stock look of your engine. At that point, you might as well do the 4 barrel conversion. Other issues with that manifold are no port to screw in your temp sending unit, you will need to find a choke coil that will bolt onto that manifold, if that hole is even tapped. Like I said a whole can of worms. You can easily find an aftermarket 4 barrel manifold that will solve all of those problems. Or even the stock era cast iron 4 barrel manifold is fine for up to 5500 rpm. It will bolt right in without any of those issues and give you that extra power youre looking for.
Yeah, I didn't pay enough attention to those details. Thanks for opening my eyes! :) Keep looking :)
 

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Yeah, I didn't pay enough attention to those details. Thanks for opening my eyes! :) Keep looking :)
Yeah, I did a similar thing in the past and ran into all those little problems. It stinks when you try to do something simple and there ends up being so many little complications. I was thinking of something like this.

http://www.ebay.com/itm/vintage-che...ase-/252042517292?hash=item3aaee79b2c&vxp=mtr

It would solve all those little problems, look totally stock, and allow you to use an easily sourced holly 600 cfm carb for that extra power. That one is probably overpriced and IDK if ebay works for you, being in Hungary.
 

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Discussion Starter #20
Yeah, could be this is the way i should go...
Ebay is my big friend, i can have shipped here to Hungary any parts no problem 2 weeks, shipping is reasonable.
Yeah, I did a similar thing in the past and ran into all those little problems. It stinks when you try to do something simple and there ends up being so many little complications. I was thinking of something like this.

http://www.ebay.com/itm/vintage-che...ase-/252042517292?hash=item3aaee79b2c&vxp=mtr

It would solve all those little problems, look totally stock, and allow you to use an easily sourced holly 600 cfm carb for that extra power. That one is probably overpriced and IDK if ebay works for you, being in Hungary.
 
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