# 66 GTO original with mild cam. What is the best carb?



## tonyli (Aug 14, 2013)

Hi guys i have had my GTO for 2 years. I drive every chance I get. The gas mileage is not so great. I purchased a 200R4 from a Grand national to go in the car. However I am thinking about changing the carburetor. Before I do the swap.
The engine has all the stock components from the original carb, intake manifold , distributor point ignition set up as well has the pollution pump. Factory A/C car with with a 323 rear which will be changed after the transmission swap.

The previous owner rebuilt the motor and as far has know the only thing he did out of specifications is the cam. He installed a mild Comp cam Grind number 275DEH-10 GROSS VALVE LIFT INTAKE HYD.462 EXHAUST HYD.480 DURATION AT .006 TAPPET LIFT 275 INTAKE, 277 EXHAUST

I went to local speed shop and they recommend installing a an Eldelbrock Performer manifold and a 650 billet double pumper carb and recommends and removing the points and going with the electronic conversion.

The car runs good, but there is room for improvement has far as fuel efficiency and overall performance. Like a couple of burnouts here and there

What is your opinion and is a double pumper too much for this motor.
whats your set up?


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## ALKYGTO (Mar 29, 2010)

Let me be the first to say....don't you even think about switching out the original carb and intake. 

I would suggest a good tune first. Is there a chassis dyno close to you?


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## Bensjammin66 (May 12, 2009)

ALKYGTO said:


> Let me be the first to say....don't you even think about switching out the original carb and intake.


Hahaha!! You knew that was coming! 

Speaking from an unbiased point of view on originality here: The performer RPM is a great light weight manifold when coupled with like a 2000 stall convertor, mild cam and mild (323-373) gearing. By no means imaginable is a double pumper carb going to improve your fuel economy so forget that if MPG is your goal.. I may offend someone but edlebrock carbs are junk. Q-jet or Holley. 
I would suggest a well tuned vacuum secondary 650cfm carb and yes an electronic ignition. Make sure your base line and max timing are where they should be. Try 36 degrees total from an HEI and use an adjustable vacuum advance can to add another 15-20 degrees when cruising. Use the gold springs from Mr Gasket kit 928G in an HEI to bring that timing in a little earlier like by 2800rpm. Hot perfectly timed electronic ignition with fresh plugs, a tuned vac secondary carb and a gentle right foot is going to go the furthest for you mpg wise in my opinion.


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## rickm (Feb 8, 2012)

tonyli said:


> Hi guys i have had my GTO for 2 years. I drive every chance I get. The gas mileage is not so great. I purchased a 200R4 from a Grand national to go in the car. However I am thinking about changing the carburetor. Before I do the swap.
> The engine has all the stock components from the original carb, intake manifold , distributor point ignition set up as well has the pollution pump. Factory A/C car with with a 323 rear which will be changed after the transmission swap.
> 
> The previous owner rebuilt the motor and as far has know the only thing he did out of specifications is the cam. He installed a mild Comp cam Grind number 275DEH-10 GROSS VALVE LIFT INTAKE HYD.462 EXHAUST HYD.480 DURATION AT .006 TAPPET LIFT 275 INTAKE, 277 EXHAUST
> ...


they just want to sell you a bunch of parts. edelbrock my ass. someone explain to me what a " billet" carb. is.


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## Bensjammin66 (May 12, 2009)

rickm said:


> they just want to sell you a bunch of parts. edelbrock my ass. someone explain to me what a " billet" carb. is.


Lmao!! Great point. Step one, NEVER return to that shop!!


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## PontiacJim (Dec 29, 2012)

rickm said:


> they just want to sell you a bunch of parts. edelbrock my ass. someone explain to me what a " billet" carb. is.



"billet" - machined, not cast as most carbs are. Carb Class: The Benefits of Billet


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## rickm (Feb 8, 2012)

PontiacJim said:


> "billet" - machined, not cast as most carbs are. Carb Class: The Benefits of Billet


don't mean s**t to me. just a fancy name that you hear on those sat. morning automotive tv shows to try n sell you something. billet this n billet that, a selling ploy.


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## ALKYGTO (Mar 29, 2010)

No reason to change out the carb and manifold....they've been doing there job almost 50 years. Same with the points, the distributor might need rebuilt but if it's just a weekend toy I'd stay with the points. If it needs it get the carb rebuilt, just make sure you get your original back.

Whatever you do don't lose those original parts!!! They are near impossible to find.


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## ALKYGTO (Mar 29, 2010)

Curious why you are going to put an overdrive in such an original car?


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## tonyli (Aug 14, 2013)

I go to shows but do not stay long enough to get judge. I would rather being cruising then sitting on chair beside my car, not that there is anything wrong with that. I take most it out weeks as long as it is nice out Saturday, Sunday, Monday and Tuesday. I fill the car car at least twice a week. The two speed transmission has a weak first gear and I would like improve that as well as the fourth gear for highway cruising is a bonus. I will save every part, nut and bolt. So if I ever do sell it I will bring back to its original parts. It is not some much the gas i am trying to improve overall performance. Believe me I know it is only original once.


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## geeteeohguy (Feb 2, 2008)

Just swapping the 2 speed trans for a TH350 or your present overdrive unit will net you all the performance and economy you'll need. Trust me on this. The car will feel like you picked up 100 horsepower, and fuel economy will improve. Leave the carb, intake, and distributor alone. Been driving these cars 40 years and have owned a bunch of them. The factory engineered stuff trumps the aftermarket stuff every time for a street driven car. Period. I run a stock Q-jet and distributor on my '67 and a stock tripower and distributor on my '65. Plenty of power, and have ran these combos for decades.


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## Bensjammin66 (May 12, 2009)

geeteeohguy said:


> Just swapping the 2 speed trans for a TH350 or your present overdrive unit will net you all the performance and economy you'll need. Trust me on this.


The OD ok, but a TH350 has a near useless final gear of 1:1. Even with a relatively high 3.23 rear you're on the edge of being able to keep up on long distance trips at turnpike/interstate speed. We live right near and use the turnpike here in Ohio daily where 80mph past cops is the norm. Without my .64 overdrive the 373 rear in my car would have me around 3500rpm instead of my current 2100rpm trying to keep up in traffic @ 75-80mph. Going from a 2 speed to a 3 speed isnt going to get you what you want. 

1:1 finals are non existant in the last 30 years for good reason. Keep the original trans in the garage in a garbage bag but if you want to drive your car long freeway distances and extend the life of the motor a 700R4 or 200R4 are both great choices behind any mild V8. Itll be the best money youve spent on the car.


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## geeteeohguy (Feb 2, 2008)

Agreed, Benjamin, but the OP could install a TH350 for less cash than an intake and carb swap, and come out way ahead. A 700 or 200 would be more coin, but, yes, a much better choice in today's world. A 3.23 isn't a bad final drive ratio, IMO. Not the best for post-80mph cruising, but not bad at all at 70-75 mph.


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## leeklm (Mar 11, 2012)

"Agreed, Benjamin, but the OP could install a TH350 for less cash than an intake and carb swap, and come out way ahead. A 700 or 200 would be more coin, but, yes, a much better choice in today's world. A 3.23 isn't a bad final drive ratio, IMO. Not the best for post-80mph cruising, but not bad at all at 70-75 mph. "

x2. A lot of the decision comes down to $$$. Nice thing about the T350 or T400 is relatively low cost and simplicity. 

Regarding carb & manifold... As many here have said, it is difficult to beat a well tuned Qjet for most street cars. I have used the factory iron manifold and the Performer RPM, and really cannot notice any seat-of-the pants difference in a street build. You do lose a little air cleaner/hood clearance with the RPM (which I am dealing with now). I have used Holleys on my circle track cars years back, so generally know the basics in tuning them. While an experienced Holley guy could do a much better job at tuning, I cannot get them to run as smooth as my Qjets on the street!!!


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## geeteeohguy (Feb 2, 2008)

Holleys run very strong, but lack the fine metering of a Q-jet and as a result, drink a lot more gas to do the same job.


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## tonyli (Aug 14, 2013)

I agree with you guys on not going back to that shop. I thought that was not the right application for car. That is why I posted the topic to get your opinion. The 200R4 is going in soon. I thought the transmission swap might go in easier with a new carburetor because the carburetor comes with the linkage for the TV cable. I also thought a 650 CFM carburetor would increase the performance a little. I know it is not going to be dramatic difference. I appreciate all the replies and technical information. Bensjammin66 thanks for all you input


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