300hp 307

[Maryland G-man]

Problem is you have at best 8.5 to 1, restrictive heads and very restrictive exhaust. A chassis dyno would be handy for a starting and where it ends up after mods. Extrude hone and hand port the openings on the exhaust manifolds. The largest crossover, maybe a 2.25" versus 2" or at least mandrel bent and maybe a 3" down pipe and into either a custom, Hooker or Pypes 2.5" catback to remain visual and emissions complaint. Internally milled 5A heads with 350's valves and porting, a hotter cam would get you a nice boost. The dyno before and after would tell you how much.

Yes, agree on the Compression Ratio and Heads. As I wrote earlier on this Thread, I plan to Extrusion Hone both the Exhaust Manifolds, and even in stock Aluminum intake manifold. I will replace the cylinder heads with Edelbrock Aluminum cylinder heads. And I will bump up the Compression Ratio to 9.5:1. And yes, a hotter camshaft as well.

I have a high-flow Magnaflow Catalytic Converter, which is less restrictive than stock. I also have the Pypes mufflers, which flow better than stock. And the Pypes tubing has a larger diameter than stock.

I will also try to do a before and after dyno run.

 

[Maryland G-man]

Keep in mind that even Chevy 305s have higher airflow than Olds 307s. Its why 305 Qjets have idle air bypass to prevent nozzle drip and Olds 307 Qjets don't. So its comparing apples to oranges.

I simply comparing Engine Displacements here. Chevrolet also made a 305 called the LG4. It put out 165 hp. Does it have a higher flow than the Olds 307 "9" ?

 

[Maryland G-man]

If your looking to stay Oldsmobile why not install a 350 Olds engine with FI and be done with it? - https://www.sandjengines.com/product/1970~~~3309

Yes, but part of the allure (for me) of these GM G-body cars is that they are the last of the CARBURETOR equipped V-8 engines. That is why I did not go the Grand National route. If I was looking to do a Crate Engine, which I am trying to avoid the NOM (Non-Original Motor) situation, then here are some Oldsmobile Crate Engine suppliers:

https://mondelloperformance.com/engines/

Oldsmobile Performance Crate Engines

Oldsmobile Crate Engines: Eddies Performance Motors-High Performance Engines, Crate Engine, Racing Engine Builder, Rebuilt Motor; Raritan Street, Sayreville, NJ 08872

 

[olds307 and 403]

The current Edelbrock heads won't work, a minimum 4.125" bore and huge ports. Suppisedly the mid 60's chamber CC with smaller 2.07" intake valve is supposedly getting released in Spring, hearing that for a year or more. Get the Procomp heads mill them from the 81cc chamber size, not 77cc as advertised to 60cc along with the intake face or intake cut to fit. You will have to get it aligned just right to cover the bigger BBO ports. Also an electric fuel pump or heavy modification to the pump arm or grinding and welding the end of the head for a mechanical fuel pump. Good luck.

 

[Maryland G-man]

The current Edelbrock heads won't work, a minimum 4.125" bore and huge ports. Suppisedly the mid 60's chamber CC with smaller 2.07" intake valve is supposedly getting released in Spring, hearing that for a year or more. Get the Procomp heads mill them from the 81cc chamber size, not 77cc as advertised to 60cc along with the intake face or intake cut to fit. You will have to get it aligned just right to cover the bigger BBO ports. Also an electric fuel pump or heavy modification to the pump arm or grinding and welding the end of the head for a mechanical fuel pump. Good luck.

Thanks for the advice on the Cylinder Heads. When I spoke to the folks at Mondello, they mentioned they take the Edelbrock Aluminum Cylinder Head, perform their own in-house modifications to it, and then it is ready to be installed on the Oldsmobile 307.

https://mondelloperformance.com/shop/cylinder-heads/mondello-aluminum-cylinder-heads-pair/

But if that is not an option, I will look at the Procomp Cylinder Heads.

I hope to avoid switching from a mechanical to electric fuel pump. That 400+ hp Mopar engine in my Plymouth Duster ran fine with the stock, mechanical fuel pump. I just find most electric fuel pumps make an annoying sound. I think the Grand national has a stock electric fuel pump, and it is often noisy.

Keeping the stock mechanical fuel pump is all the more reason why I am quite happy to pursue this "mild" rebuild on the 307.

 

[CopperNick]

My vote goes to the 350 Olds version. "No replacement for displacement" as the saying goes. You don't need to automatically go to FI with it. A good carb along the lines of what you seem to thinking about for the 07 would work just as well. Among themselves here on the board, the Olds coalition ought to know of someone who has an Olds 350 take out that would work for you.



Nick

 

[Maryland G-man]

My vote goes to the 350 Olds version. "No replacement for displacement" as the saying goes. You don't need to automatically go to FI with it. A good carb along the lines of what you seem to thinking about for the 07 would work just as well. Among themselves here on the board, the Olds coalition ought to know of someone who has an Olds 350 take out that would work for you.



Nick

Nick,

Thanks for your advice. Well, if you feel THAT strongly about it, I will be glad to setup a GoFundMe website, where you and other interested parties can contribute $ to my car. Your generosity will be appreciated. Ha-ha, I am 100% kidding on that.

I plan to also keep the stock "electronic" Carburetor as well. I will get the "Performance Rebuild" from these folks:

Quadrajet Power, Your One Stop Quadrajet Shop

Quadrajet service, parts, kits, restored originals

quadrajetpower.com

 

[Clone TIE Pilot]

I simply comparing Engine Displacements here. Chevrolet also made a 305 called the LG4. It put out 165 hp. Does it have a higher flow than the Olds 307 "9" ?

Yes, even LG4s have idle air bypass for higher airflow. Olds 307s are optimized for low end torque and a range of 500 to 3,500 RPMs. So any typical hot rodding tricks will hurt power unless you change everything about the 307 engine. Depending on which version, the 305 does not suffer as many limitations untill 6K RPMs. A 305 with stock heads can be bumped up to 250 HP fairly easy with just bolt ons. But both are designed to be 55 MPH cruisers. A major issue Olds 307 blocks have are windowed mains that limit safe RPM levels for it. Chevy 305s on the other hand have normal SBC mains.

 

[olds307 and 403]

Those Mondello heads in your link are Procomp heads with their engraving. You need make sure the 307 gasket will seal the combustion chamber properly. The windowed mains only come into play well above the factory high 4000 rpm shift points. It helps the 307 H.O has a real balancer, the Y doesn't. Yeah the 350 and 403 are massive improvements due to the much larger bores and bigger cubic inches. They would both easily hit 250 HP with stock exhaust. Find some rare 350 5A heads from 68 and 69, paint tge 350 or 403 semi gloss black and no one will know the difference. With the value in these cars now, I would probably do what you are doing.

 

[DRIVEN]

In the last 8 pages we've covered a lot and gone nowhere. OP hasn't been around in over a month.

As for Maryland G-man's project, if you're chasing pristine originality points, I wouldn't lift a finger. If you want to fool 97% of the people 100% of the time, corporate black paint on an otherwise stock 350 or 403. If you really want to let your 307 freak flag fly, pull the numbers matching original and store it in the corner. Then build another 307 based stroker with a roller conversion and aim to maximize low-mid RPM torque. It's an Oldsmobile -- forget all about HP.