300hp 307

scoti

Royal Smart Person
Sep 5, 2019
1,979
3,404
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Texas
It's your car, so obviously do with it what you want but my perspective is either modify it or don't. It's either original or it's not. I don't understand why it's ok to put aftermarket suspension and brakes on it but the engine has to look original and has to be the original 307.🤔
This is my logic/perspective as well.
 
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Maryland G-man

Not-quite-so-new-guy
Supporting Member
May 12, 2023
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Great stuff, G-body forum contributors. Here is a "stream of consciousness" reply to all of the recent comments:

  • Regarding originality in the most holistic sense, I plan to DRIVE this car, for lots of miles. Therefore, it will perpetually be on a Degradation Continuum. I will have to replace or repair wear-item parts frequently. So, the car will never be truly "original".
  • I just replaced the shocks with Bilsteins. I am currently lining the insides of the doors and the trunk with Dynamat sound insulation. There will be a whole host of minor, "bolt on" mods that this car will receive, and already has. So what?
  • I am just in a "you will take my original 307 out of my cold, dead hands" mode for now. I deliberately plan to not increase horsepower significantly, only moderately. That would avoid me from having to significantly upgrade the brakes and suspension, to match any sizable increase in power.
  • On Mondello, yes I have heard lots of negative information about their business practices. But I spoke face-to-face with their Master Engine Builder (Rick), and he has built like over a hundred Oldsmobile V-8 engine; I have built ZERO. He knows what he is talking about, technically, or at least WAYYY more than I do.
  • I still have mild PTSD from getting heckled, shamed, and mocked for bringing my 1971 Plymouth Duster 340 to the Carlisle, PA MOPAR Nationals. Lots of people would confront me, "Gee, that doesn't look correct, nor original". I actually came up with a "backronym" for MOPAR: Misguided Obsessive Preoccupation with Authenticity of Restoration".
Looking forward to the July, 2024 G-body event in Medina, OH. I will be driving from Maryland to there, a nice road trip...in a comfortable, quiet, reliable, and fuel economical G-body. ;)
 

Maryland G-man

Not-quite-so-new-guy
Supporting Member
May 12, 2023
26
28
13
The work "Original" seems to come up a lot. Here is how the Carlisle Events defines vehicle modifications for its car shows:

GM Vehicle Modifications
Stock (3 or less modifications)
Street (minor performance modification)
Modified (4+ modifications)
Pro-Street/Race (Tubs, Induction thru Hood, Roll Cage, etc)

That's their wording. I think these could be further "dissected" as follows:

  • Original (as it left the factory, with 1980's tires, belts, etc.; perhaps a few GNX cars are sitting in a garage or museum like this...so would I with a $ 250 k car)
  • Correct (parts have been changed, but it remains a "Keep Your GM Vehicle All GM" situation)
  • Stock (meaning, you could have generic or aftermarket parts from like Autozone, Pep Boys, Rock Auto, etc., but they fit and look like the same as OEM parts, even if they are not marked "AC Delco")
  • Customized, especially visually (non-factory paint job, airbrushed graphics, bulged hood
  • Restomod (L3 engine conversion, digital gauges, modern seats, low profile tires on larger diameter wheels, etc.)
 

565bbchevy

Geezer
Aug 8, 2011
9,614
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Michigan
I still have mild PTSD from getting heckled, shamed, and mocked for bringing my 1971 Plymouth Duster 340 to the Carlisle, PA MOPAR Nationals. Lots of people would confront me, "Gee, that doesn't look correct, nor original".
With a 350 Olds in place of your 307 and dressed with everything from your 307 , I doubt this would ever happen and even if someone noticed the swap they would most likely compliment you for adding some much needed power under the hood of a great looking car and for going through the effort to make it look factory and keeping it Olds powered.
 
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Rocknrod

All Around Good Egg
Supporting Member
Jan 7, 2024
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Is there an Olds specific car show around that does this?
"Stock (3 or less modifications)
Street (minor performance modification)
Modified (4+ modifications)
Pro-Street/Race (Tubs, Induction thru Hood, Roll Cage, etc)"
I wouldn't go.
 

Maryland G-man

Not-quite-so-new-guy
Supporting Member
May 12, 2023
26
28
13
All that I can say, is when I brought my 1971 Plymouth Duster 340 to the Carlisle Mopar Nationals, the "incorrectitude" of my engine was viewed as a B.F.D. (Big Friggin' Deal) amongst the spectators.

It didn't matter that it still was a 340 cubic inch engine. The car came from the factory with the 340, and my car was still a 340 (or close to it, after being slightly bored out from its 400+ hp rebuild).

It was just that it was a "N.O.M." (Non-Original Motor), or not "Numbers-matching". Furthermore, the 340 engine block was a 1969 casting, not a 1971 casting that would match the year of the car. Even though the castings between those years was very similar.

Sooo...this was all viewed very badly. Even the person who eventually bought the car from me noted the engine "incorrectitude".
 

DRIVEN

Geezer
Apr 25, 2009
8,075
14,536
113
*CENSORED*
Cool. I'll just be over here counting the money I didn't spend trying to get strangers to like my toys.

Start that build thread yet?
 
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64nailhead

Goat Herder
Dec 1, 2014
5,710
1
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Upstate NY
I haven’t read every post after seeing several repetitive posts.

If you want maximum HP from a 300-350 ci engine, then the formula is really quite simple :
1st - pistons to increase compression
2nd - stock heads reworked by someone ‘in the know’ about the heads
3rd - camshaft to work with compression, head flow in the intended rpm range
4th - ported factory exhaust manifolds
5th - *most important* someone to tune it that knows more than ‘put in a bigger jet’

The tune will make it all work once the supporting modifications are complete. Or a bad tune will blow it up in about 50-100miles.

Personally, I wouldn’t try it. Either car is a true survivor and it should be left along be for value, or it should be treated as a race car. You have to pick.

Where there is a will, and bank account, there is a way.
 
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