how to turn my 72 stock 402 BB 240hp into a respectable 400hp motor?

I recently bought a 72 Monte, frame-off restoration, #s matching car. beautiful, done right. Bone stock which I can really appreciate. HOWEVER... this paltry 240hp is not fun, pretty... but not fun. EVERYthing is bone stock & with air. I don't feel it's unreasonable to think as long as my mpg is god-awful I may as well have horses to go with it.

That stated, I've dropped... a few... dollars on this car so I'm looking to get to that 400 number as efficiently as possible.

BUT

I'm confused with what I've read to this point about it here and there.

This has less than 300 miles on it to date. It is for street only.

HEADS are large oval, open chamber

Cam is the stock flat tappet.

I am under the impression that if I put in a 10.5:1 piston it will take me to 325 horse in one fell swoop. ???

If I ad a SEMI-CLOSED head it takes me up 60-80 more horse. ??

I would think a different cam would be necessary too. ??

How far led astray am I? ....or am I?

Any knowledgeable input is greatly appreciated.

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Originally Posted by ital-rich

I'm confused with what I've read to this point about it here and there.

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Well, I can understand that, there is so much bogus information out there on the web. But have no fear, you have landed squarely in the middle of a bunch of good-guy hotrodders who can and will help you out of your dilemma.

First thing you need to understand is that you will need more cubic inches. That sniveling little 402 might have been fine for hauling grandma to Bingo once a week, but it will fail miserably at hauling your butt on a fast street ride. I would begin advertising on craigslist and other venues for a 454 block or short block, stock bore or +0.030" oversize so that we can bore it to +0.060".

Hot Rod magazine penned a story back in 2013 that I still refer to, because the results are timeless for a good, strong 460 or 466 cubic inch big block that will take that Monte for a ride. Here's the story.......570 horsepower and 587 ft/lbs of torque in a streetable package......
https://www.hotrod.com/articles/crane-cams-dyno/
There are a few things that can be tweaked from the original story, but it is pretty much "as good as it gets" for a street motor as it is written. I would limit static compression ratio to 10.0:1 or somewhere close to that, depending on piston availability and might lighten up on the cam a tad, to help improve intake manifold vacuum for power brake function. Read through the article and then come back and ask questions. In the meantime, I'll be looking for a good set of forged pistons for you, as well as an aftermarket roller tappet camshaft and lifters. That flat tappet cam won't last long in a Big Block Chevy. They are famous for eating flat tappets.

Have no fear, jump in with both feet and enjoy yourself.

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Thanks for the input. That all sounds great but unfortunately at this time I'm on a tight budget for the car money after just paying for it. I'm just hoping to get to a respectable 400 hp with this engine if it's at all possible. Doing it properly, but still on a budget. I figured with this all stock 72 402 being a .030 over 396 that it might be a good enough lump to get me to that point some how. Also, I'd like to keep the car the #s matching car it currently is. Frame off resto and it's completely finished, just a dog of an engine is all. I figure as long as my gas mileage is already horrible, this anchor may as well grow a pair and do justice to the car. I also plan on using the A/C. lol.

Welcome to CHR!

Sounds like you’ve found a real gem in the Monte Carlo. My father had a ’72 – blue with a white landau top and white interior. It was a beautiful car and to find one with a correct frame off is rare. You can certainly get 400 HP out of the 402 but you will spend a lot of cash and still have a 47 year old base.

A suggestion would be to drive that beauty as-is while saving the money to purchase a 454 crate motor. A complete 400+ HP engine with a roller cam and a warranty can be had for around $5K. You didn’t say if you are equipped to do the work yourself. If not, you’ll need to enlist or buy the services of someone who has the skill set and tools to install a new engine. While not difficult to perform, the first one is time consuming and if not done correctly can be a disaster. The only reason to keep “numbers matching” is for resale or concours d'elegance shows. When you do sell the car, advertise the original engine as part of the package.

You bought it to drive it and love it. A hot rod is never really done and it’s expected that you will always be saving to buy some kind of upgrade.

Post some pictures - we're a visual bunch here..

Regards,
Glenn

I'm with Glenn on your dilemma! Run the engine and enjoy the car as is while saving up some $$$$ for a big snorting 496" stroker motor with a good set of aluminum heads, then turn it into a beast and have some way big fun with the car!

Well I agree with that. I've been expecting this plan will come out of necessity, if I'm being prudent. The 402 is a fresh rebuild so it's not like I'm sitting on an about-to-blow motor. When the time comes to remove this engine I'll pick up a decent stand for it to rest on until I sell the car... or need it for something else. I don't PLAN to sell this car anyway. But then we all know how that plan can change. If I'm being honest I want the 454 and a muncie m22 Rock crusher. I had one of those in my 67 Chevy II and I miss the whine from it more than the car almost. thanks for the input.

Yes, I am too at this point.

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Originally Posted by ital-rich

Well I agree with that. I've been expecting this plan will come out of necessity, if I'm being prudent. The 402 is a fresh rebuild so it's not like I'm sitting on an about-to-blow motor. When the time comes to remove this engine I'll pick up a decent stand for it to rest on until I sell the car... or need it for something else. I don't PLAN to sell this car anyway. But then we all know how that plan can change. If I'm being honest I want the 454 and a muncie m22 Rock crusher. I had one of those in my 67 Chevy II and I miss the whine from it more than the car almost. thanks for the input.

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Sounds like a great plan! Friend of mine has a '64 Nova SS, he has all the original engine and transmission pieces wrapped up in plastic put away on shelves while he enjoys the car with a real butt kicking 427" small block and 700R4 trans. The original 283" and glide will be there should he ever want to go back original.