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

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.

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

I forgot to say, it is a factory 4 speed. Steve

Stroker crank would be a HUGE help!!!

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

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.

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.

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.

I forgot about the first gen Firebird RA manifolds!!

The best factory manifolds, and you can run them!

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

Take out the original GTO 350 and store it.

Put in a lightly warmed over 455.

Great street manners and no exotic parts needed.

Yup, open ended questions, start getting open ended responses.

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.

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

Have to agree with B-Man on this one. Lots of 455 engines are still out there
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.

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 !

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

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

X2 with the above!

A good friends 74 GTO runs 10.60 in NHRA legal trim. That means stock engine size and stock head castings. Wallace calculator says that's 562 flywheel HP. So yes, 400 HP can be done without too much trouble. 350 Pontiac engines are not near as popular as the larger cousins so parts are more expensive and less bang for the buck because "there is no replacement for displacement" You can make 400 HP with a 400 Pontiac junk yard core and $1000.00. You will be many times that coaxing 400 HP from a 350. It depends how much you want to save that original engine?