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#1
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74 GTO 350 motor question
Hi, I have a 74 GTO with the original 350. Can that motor be juiced up the get 400 HP ? Thanks Steve
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#2
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Yes, and if you want to get that 400 hp ( 1.12 hp per cid) in NA form you will have to do a good amount of work to it.
The first thing will be getting the compression up to 9.5 if you stay with iron heads, or 10.7 comp with Aluminum heads.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#3
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Even though they have smaller valves the 1969 era 2bbl 350 heads will provide more power than your originals
It will be hard to set the world on fire with a 74 350 but you can easily make it much more fun 1969 2bbl heads ports blended nice valve job a 2801 summit camshaft and headers it will feel much different Or small chamber and then milled a touch KRE d'ports with a nice little cam it's easy to over cam a 350 unless new gears and torque converter are installed |
#4
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I forgot to say, it is a factory 4 speed. Steve
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#5
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Stroker crank would be a HUGE help!!!
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... |
The Following User Says Thank You to 77 TRASHCAN For This Useful Post: | ||
#6
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Regarding increasing the stroke on a 350........
Small-Bore Pontiac Engine Build - Revenge Of The 350 Dust off Your Small-Bore Pontiac, Stroke it to 383 Cubes and Make 460+ HP https://www.google.com/url?sa=t&sour...jcYlMcrW64EFyE
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
#7
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See if it still has the #46 heads with screw-in rocker studs.
That is what would have been original issue - and they are pretty good heads - but low compression ratio on a 350cid. Don't toss them outdoors behind the barn if you don't use them on this build. |
#8
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if you did a sizable jump in power, please remove your original four speed before it grenades;
1974 GTO four speeds were saginaw units, and are probably already at their upper threshold for torque capactiy BEFORE you do any upgrades. Look into 1968-1969 Firebird/Tempest/Lemans "350HO" engines, and you should get a pretty good idea as to the kind of easy to attain power levels that a Pontiac 350 can get to.
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1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
The Following User Says Thank You to unruhjonny For This Useful Post: | ||
#9
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Yes
48 heads RA IV cam (others will punch holes at this one, but works for me) RA IV aluminum intake with Q-Jet (I am using an 850 CFM TQ, instead of the Q-Jet) RA exhaust manifolds (Firebird maybe, from the late 1960's???) And if you really want to kill city driveability, but run like a banshee above 2500 RPM, an aluminum flywheel And if you are putting this in a '74 GTO, put the car on a diet!!!!! LOTS of surplus weight on that car! I removed several hundred pounds from mine. Jon.
__________________
"Good carburetion is fuelish hot air". "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
#10
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I forgot about the first gen Firebird RA manifolds!!
The best factory manifolds, and you can run them!
__________________
1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
#11
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In reality you need to state budgetary concerns, willingness to take the car to what level, your personal mechanical abilities, real expectations, or in a few days there will be no replacement for displacement 535 aftermarket block forged crankshaft trans brake narrowed 9inch Alston chassis 74 GTO in your future
It's not to hard to get your 74 up to the performance level of a 60's GTO |
#12
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Quote:
Based on cost and ease of making 400 hp on a low comp 350P, I'd get one of these. https://torqstorm.com/product/kits_s...ntiac_326-455/ If the engine is in otherwise good condition, it'll probably run forever right near 400 hp without having to open anything up.
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-Jason 1969 Pontiac Firebird |
#13
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Take out the original GTO 350 and store it.
Put in a lightly warmed over 455. Great street manners and no exotic parts needed.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
The Following 4 Users Say Thank You to b-man For This Useful Post: | ||
#14
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Quote:
and just put the original engine on a stand somewhere. At the end of the day you will make more power, have better torque, and be easier on the parts vs trying to stroke the little 350 engine. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#15
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I do have a couple spare engines, a 70 400 with #12 heads and a 70 455 with #64 heads. So the best thing is pull the original 350 and set it back. I also have a 70, 4speed M20 that came with the 70 400 I have. Steve
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#16
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The price of rebuilding either of those two more powerful motors that you have will be the same as doing up the 350 and puts you at a hp advantage right from the start !
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#17
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Having done the 350, I can agree (from experience) with those stating the 455 is cheaper.
However, I had a reason for doing the 350, and would do the same again for my reason. If I could subtract about 20 years, there is still about 200 pounds of excess weight on the car; but it is scary fast now, another 200 pounds less and it would be more of a hand-full. First gear is virtually useless now for driving in anger, and I refuse to tub the rear fenders. Jon
__________________
"Good carburetion is fuelish hot air". "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
#18
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Now that you have disclosed options if keeping 4speed I would build the 400 for it,
In my opinion 4speeds are more fun with a engine that RPMs a bit vrs fry the tires on the hit then wonder where the rest of the engine is plus to much torque and traction or wheel hop and you will be repairing the trans |
#19
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Were some 1970 445s (particularity early ones) that had 2 bolt mains and were many in for warranty work.
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#20
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X2 with the above!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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