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my lemans has the original stock 400 two barrel im changing the cam im using a summit performance cam 268 duration 420/442 and a holley 500 cfm two barrel and sealed power timing set. and  dynomax super turbo mufflers. last summer mobile dyno at atlanta dragway said 205 horses dont remember what the tork was  i ran 16.25 88 mph   power increase from parts combo.estimated 1/4 et any answers would be awsome thank you. i named my lemans godzilla is that okay?

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How fast do you want to go? What are your goals and budget for the car?  

It sounds like you are trying to stay close to stock based on the fact that you are using 500 cfm Holly 2-barrel rather than upgrading to a 4-bbl intake and carburetor.  The cam specs you've chosen are close to stock 268 degrees intake duration with .420 intake / .442 exhaust lift. Is that at 1.50:1 or 1.65:1 lift?

The stock Rochester 2-bbl carbs run around 250-280 cfm, so you've clearly added the potential for more air with the bigger Holley carb.  I think you could break 100 mph in the quarter but that means you really have to dial in the carb to the cam. Too much air and leaning out the fuel mixture too much won't help you get down the track - the proper jetting is key here. Get all your mechanical and vacuum advance in as soon as possible too.

The 1973 motors were not considered horsepower monsters by any stretch of the imagination. GM had switched to net HP/torque ratings (meaning that engines were rated with all parasitic drag elements in place like A/C and power steering pumps, alternators, and air cleaners and filters in place. Previously, GM used gross HP/torque figures which removed all these items. In 1973, a 2-bbl 400 could expect to make 170-185 HP (at the flywheel), while a 4-bbl 400 would be rated around 200-230 HP. So don't expect any huge numbers at the rear wheels.  Also, these cars were coming into the era of (then) new unleaded fuel and emissions. So compression ratios also started coming down to handle the lack of lead (which helped manage engine knock or detonation in those days), which further helped reduced HP figures.

 

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On 3/5/2018 at 1:24 PM, Frosty said:

How fast do you want to go? What are your goals and budget for the car?  

It sounds like you are trying to stay close to stock based on the fact that you are using 500 cfm Holly 2-barrel rather than upgrading to a 4-bbl intake and carburetor.  The cam specs you've chosen are close to stock 268 degrees intake duration with .420 intake / .442 exhaust lift. Is that at 1.50:1 or 1.65:1 lift?

The stock Rochester 2-bbl carbs run around 250-280 cfm, so you've clearly added the potential for more air with the bigger Holley carb.  I think you could break 100 mph in the quarter but that means you really have to dial in the carb to the cam. Too much air and leaning out the fuel mixture too much won't help you get down the track - the proper jetting is key here. Get all your mechanical and vacuum advance in as soon as possible too.

The 1973 motors were not considered horsepower monsters by any stretch of the imagination. GM had switched to net HP/torque ratings (meaning that engines were rated with all parasitic drag elements in place like A/C and power steering pumps, alternators, and air cleaners and filters in place. Previously, GM used gross HP/torque figures which removed all these items. In 1973, a 2-bbl 400 could expect to make 170-185 HP (at the flywheel), while a 4-bbl 400 would be rated around 200-230 HP. So don't expect any huge numbers at the rear wheels.  Also, these cars were coming into the era of (then) new unleaded fuel and emissions. So compression ratios also started coming down to handle the lack of lead (which helped manage engine knock or detonation in those days), which further helped reduced HP figures.

 

 

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2 minutes ago, KACEYPERRINE said:

 

thank you  for the info. i started out with 10,500$. 1973 lemans 2500$ parts from summit 300$ slightly used firestone wide ovals 200$ at a flea market.  godzilla runs real good now. on the bottom end the holley two barrel didnt help the top end like i thought it would. what is best eldebrock and holley four barrel or iron and quadrajet. do i change the 3.08 posi the original owner had put in for 3.23 ? 3.55? the goal is go to the track an beat the snot out of my next door neighbors 1970 camaro SS396  that runs 13.60 @104

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Posted (edited)

Actually for the money, I would try to find a used iron Pontiac 4-bbl manifold. Nothing against Edelbrock since I run one but so many tests I've seen comparing the stock single plane manifolds to the aftermarket ones, the stock ones holdup extremely well. Pontiac really did a good job designing their intake manifolds back int he day. There are lots of them at the swap meets and Craigslist for around $100.  One of the biggest advantages of the Edelbrock is the weight savings - aluminium vs. cast iron. However is it going to make that much difference in the  long run?

The Quadrajet is a good carb if you know how to jet and tune it correctly. Otherwise a Holly 650/750 cfm vacuum secondary carb might be a good second choice.

As for gear ratios the taller the gear (e.g. numerically lower), the better it is for economy. So a 3:08-1 is great for highway mileage but it will be terrible out of the hole. I personally run a 3:55 rear posi gear. The smaller the gear (e.g. numerically higher), the better it is for racing and performance, but it will hurt your fuel economy, that's why a 4:56 gear is popular with drag racers - they don't care about economy. I think that 3:55 is a good compromise between performance and street. I get around 12-14 mpg with the top up running my 455/TH400. I still kick myself for not building a TH200 4R overdrive transmission given all the highway driving I do with Lucy.

Next, I'd recommend ditching your stock exhaust. Log style manifolds are very restrictive. Headers are a good choice. Alternatively Ram Air Restorations sells reproduction Ram Air IV / H.O. factory headers (cast iron). These can be connected up to a mandrel bent dual exhaust system. This should help get the air through the motor rather well and still keep it stock looking.

Lastly, look at your brakes. If you are uping the "go" factor, you need to consider the "whoa" factor. Consider upgrading your front disc to slotted and perhaps drilled rotors, look at a performance oriented brake pads. Obviously inspect your brake lines and hoses and rear brakes, and repair/replace what is needed. However, nothing that I am suggesting here should break the bank.

Edited by Frosty

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On 3/8/2018 at 8:57 AM, Frosty said:

Actually for the money, I would try to find a used iron Pontiac 4-bbl manifold. Nothing against Edelbrock since I run one but so many tests I've seen comparing the stock single plane manifolds to the aftermarket ones, the stock ones holdup extremely well. Pontiac really did a good job designing their intake manifolds back int he day. There are lots of them at the swap meets and Craigslist for around $100.  One of the biggest advantages of the Edelbrock is the weight savings - aluminium vs. cast iron. However is it going to make that much difference in the  long run?

The Quadrajet is a good carb if you know how to jet and tune it correctly. Otherwise a Holly 650/750 cfm vacuum secondary carb might be a good second choice.

As for gear ratios the taller the gear (e.g. numerically lower), the better it is for economy. So a 3:08-1 is great for highway mileage but it will be terrible out of the hole. I personally run a 3:55 rear posi gear. The smaller the gear (e.g. numerically higher), the better it is for racing and performance, but it will hurt your fuel economy, that's why a 4:56 gear is popular with drag racers - they don't care about economy. I think that 3:55 is a good compromise between performance and street. I get around 12-14 mpg with the top up running my 455/TH400. I still kick myself for not building a TH200 4R overdrive transmission given all the highway driving I do with Lucy.

Next, I'd recommend ditching your stock exhaust. Log style manifolds are very restrictive. Headers are a good choice. Alternatively Ram Air Restorations sells reproduction Ram Air IV / H.O. factory headers (cast iron). These can be connected up to a mandrel bent dual exhaust system. This should help get the air through the motor rather well and still keep it stock looking.

Lastly, look at your brakes. If you are uping the "go" factor, you need to consider the "whoa" factor. Consider upgrading your front disc to slotted and perhaps drilled rotors, look at a performance oriented brake pads. Obviously inspect your brake lines and hoses and rear brakes, and repair/replace what is needed. However, nothing that I am suggesting here should break the bank.

where ar these swap meets here in georgia all the swap meets are full of chevy parts when you find some pontiac parts you need the price doesnt include a reach around. i heard about a all second gen firebird junkyard in tennese. 300 miles from atlanta.

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15 hours ago, KACEYPERRINE said:

where ar these swap meets here in georgia all the swap meets are full of chevy parts when you find some pontiac parts you need the price doesnt include a reach around. i heard about a all second gen firebird junkyard in tennese. 300 miles from atlanta.

There are a couple of Tennessee chapters  and an Alabama chapter of POCI, but no Georgia chapters. If you want, I can give you contacts for those chapters.

There is the Southeastern GTO Association in Marietta, GA.   http://www.segtoa.org/

Finally, there is the Pontiac in Pigeon Forge (TN) show - May 31- June 3. It has a swap meet.  http://www.pontiacsinpigeonforge.com/

 

Here are a couple of ads I found on craigslist in your area. eBay is always an option too.

https://atlanta.craigslist.org/atl/pts/d/pontiac-motors-and-parts/6510066939.html    - Offer to buy a manifold and a 4-bbl carb for say $150. That's a little less stuff he has to sell.

https://atlanta.craigslist.org/atl/pts/d/pontiac-parts-1960s-70s/6443763017.html

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On 3/13/2018 at 9:49 AM, Frosty said:

There are a couple of Tennessee chapters  and an Alabama chapter of POCI, but no Georgia chapters. If you want, I can give you contacts for those chapters.

There is the Southeastern GTO Association in Marietta, GA.   http://www.segtoa.org/

Finally, there is the Pontiac in Pigeon Forge (TN) show - May 31- June 3. It has a swap meet.  http://www.pontiacsinpigeonforge.com/

 

Here are a couple of ads I found on craigslist in your area. eBay is always an option too.

https://atlanta.craigslist.org/atl/pts/d/pontiac-motors-and-parts/6510066939.html    - Offer to buy a manifold and a 4-bbl carb for say $150. That's a little less stuff he has to sell.

https://atlanta.craigslist.org/atl/pts/d/pontiac-parts-1960s-70s/6443763017.html

i bought the intake and carb  thanks for the homework you did for me.when i pulled the intake off i thought about headers like you said i got hedman block huggers they look somewhat stock then  then the bad thought more cam i swiched to  304 duration 480 480 this time idid somthing wrong with the timing both gears are at 12 and godzilla will not start. what steps did i miss?? the first time i borrowed a haynes manual that covered 73 lemans. i didnt think i needed it this time. i dont want to be the guy who killed a 73 lemans. i f@cked up the timing

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Posted (edited)

Don’t panic. A couple of quick things to check.

Pull your drivers side valve cover off. Rotate the engine to top dead center. Now pull you distributor cap. It should be firing on the number one cylinder. If it’s not, then the distributor is probably 180 degrees out.

Next thing to look at is your firing order. Is it in the proper 1-8-4-3-6-5-7-2 order. Now remember that Pontiac distributors rotate counter clockwise! Chevys, Olds, and Buick’s rotate clockwise! So if your wiring is setup for a clockwise firing order, that’s your problem.

Lastly double check  your timing gear marks. I suspect they are suppose to be at 12 and 6 o’clock. I will have to check the manual on that.

Edited by Frosty

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If I think about it, timing at both 12s won’t matter that much since the crank spins twice for every cam revolution. So making sure you are at top dead center when you set up your distributor is the key take away here.

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Posted (edited)

Once you are certain your timing is set correctly, check to see if you are getting fuel to the carb, and spark to the plugs. A faulty coil, or a dirty fuel filter are sometimes the simple fix.

Edited by Frosty

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