300hp 307

[john87442]

Regarding the Oldsmobile 307 and horsepower, earlier this year I visited with the good folks at Mondello Performance in California. The 307 can easily achieve the magical threshold of 1 hp per cubic inch, with the following:

• High compression pistons
• Edelbrock Aluminum Cylinder Heads
• Edelbrock Aluminum Intake Manifold
• Hotter Camshaft
• Holley or Edelbrock higher CFM Carburetor
• Tubular Exhaust Headers

So, that gets you to 300+ hp. However, for my 1984 Hurst/Olds, I would dial this back to 230 hp to 250 hp, due to keeping the following:

• Stock Air Cleaner
• Stock Quadrajet Carburetor
• Stock (Aluminum) Intake Manifold (to maintain provision and placement for Cruise Control, etc.)
• Exhaust Manifolds
• Air Pump, EGR, and O2 Sensor
• Single Catalytic Converter
• "Computer"

I have looked into Extrusion Honing the Exhaust Manifolds and the Intake Manifold, which should get back a small amount of horsepower from 100% stock.

A wise sage on this forum admonished me to be "circumspect" about modifying a nearly bone stock and original 1984 Hurst/Olds. Even getting to 230 hp would be a big jump from the stock 180 hp. This would set me back around $ 10k. Worth it to keep this car with a "numbers matching" engine.

Not that I even find the stock 307 all that bad. It starts easily in cold, runs well, smooth and reliable, barely burning oil at 65,000 miles. With the 3.73:1 Rear Axle and the 4-speed automatic, it runs great around town and effortlessly cruises with the 85 mph speedometer pinned.

I own and have owned much higher horsepower cars, yet I find driving the 1984 Olds a delightful experience.

From personal experience I will say unless you’re dealing with Barnard Mondello I wouldn’t recommend anything from Mondello performance…. Although Lynn is no longer with us I will refrain from saying anything about him. It’s a shame Joe Mondellos hard work and reputation is attached to that place. They will say anything and their work is sub par … ok I’m done

 

[scoti]

I see where people aren't considering the "while also passing emissions" along with those 300+ HP numbers anymore. Because it WON'T happen. Be thankful if you don't have emissions testing for old cars in your area. Mods are great, but you gotta watch out if you have to pass emission testing as well.

I've watched this thread but since I'm not an Olds guy I never commented.

I see the recurring sentiment about wanting to keep the cars 'clean' but the struggle is maintaining them (or trying to build them up) EXACTLY as the OE spec was in any given year the regulations/spec were set. I went through this w/former El Camino's & Malibu's so I thought I'd comment (gets the step stool out).

I wanted to run better exhaust systems vs the OE for 350ci vs 305ci motors. Dual cats = auto fail because they weren't certified by the GOV. So, it would have been illegal to build a true dual exhaust w/dual cats & keeping within the spirit of the rules while trying to be as clean as possible emission wise.

So.... Spending $$ trying to keep it emissions compliant in spirit (actually wanting their cars to be clean), but not as it was technically certified...... was 'against the law', ya 'gotta wonder how many said 'F-It' & just ran true duals, no Cats, & stopped caring about the air quality everyone shares? I know many that did. It was just as illegal to not run cats @ all & less expensive.

I truly was in favor of the stricter emissions testing for TX back in the day (loaded/dyno roller style testing)....... but only if the testing could be done w/o the 'all OE certified parts were in place' stipulation. The end goal should be cleaner air & we all know that it can easily be done w/o having to utilize the technical/parts limitations of the late 70's - 80's era. "Here's the set-point/standard for said vehicle, meet it or beat it & you're good to go." Instead, many just cheated. But I guess the powers that be & GOV still cashed in somehow chasing all the scofflaws & derelicts.

Car enthusiasts are a crafty group. Always seemed dumb that the powers that be couldn't see the logic in the 'as long as it beats the original target' philosophy.

 

[Clone TIE Pilot]

I've watched this thread but since I'm not an Olds guy I never commented.

I see the recurring sentiment about wanting to keep the cars 'clean' but the struggle is maintaining them (or trying to build them up) EXACTLY as the OE spec was in any given year the regulations/spec were set. I went through this w/former El Camino's & Malibu's so I thought I'd comment (gets the step stool out).

I wanted to run better exhaust systems vs the OE for 350ci vs 305ci motors. Dual cats = auto fail because they weren't certified by the GOV. So, it would have been illegal to build a true dual exhaust w/dual cats & keeping within the spirit of the rules while trying to be as clean as possible emission wise.

So.... Spending $$ trying to keep it emissions compliant in spirit (actually wanting their cars to be clean), but not as it was technically certified...... was 'against the law', ya 'gotta wonder how many said 'F-It' & just ran true duals, no Cats, & stopped caring about the air quality everyone shares? I know many that did. It was just as illegal to not run cats @ all & less expensive.

I truly was in favor of the stricter emissions testing for TX back in the day (loaded/dyno roller style testing)....... but only if the testing could be done w/o the 'all OE certified parts were in place' stipulation. The end goal should be cleaner air & we all know that it can easily be done w/o having to utilize the technical/parts limitations of the late 70's - 80's era. "Here's the set-point/standard for said vehicle, meet it or beat it & you're good to go." Instead, many just cheated. But I guess the powers that be & GOV still cashed in somehow chasing all the scofflaws & derelicts.

Car enthusiasts are a crafty group. Always seemed dumb that the powers that be couldn't see the logic in the 'as long as it beats the original target' philosophy.

Emissions are a complex subject that combines physics with legalese which are both already quite complex topics on their own. Tailpipe emissions are one aspect of emission control. The other two major sources of pollutants from cars are emissions from the crankcase and emissions from the fuel tank which is pretty overlooked by most gearheads. The PCV system easily takes care of crankcase blowby gasses with a simple system that is often still poorly understood. The fuel tank requires a fairly complex EVAP system to control all the evaporative polluants emitted from the fuel. The fuel tank polluates whenever it has fuel in it regardless if the engine is running or not. If you modify a engine it is possible to reduce tailpipe emissions while making evaporative emissions worse.


As smog testing goes, most inspection stations only have the capability of testing stock emission systems against factory specs. Most cannot test custom setups, even CA's referee stations have limited capacity to test custom setups. Think of it like alignment shops, most can do stock alignments but most can't align custom suspensions. The emission certification tests that car manufacturers submit their cars to costs millions of dollars per model and requires racking up 50k to 100k miles on the cars being tested to ensure their emissions control does't degrade below acceptable levels for a long time. So getting custom emission controls certified is beyond what most of us hear could afford. In short, to get certified the govt tests cars for tailpipe, crankcase, fuel tank emissions and longevity of those systems. Low emission legal performance parts are also tested to get certitication.

Moreover, not all modern emission systems are backwards compatible with older cars. Modern OBD2 powertrains for example use enhanced EVAP systems that are not compatible with older fuel tanks and its illegal to downgrade a powertrain with enhanced EVAP to older non enhanced EVAP, regardless if the tailpipe is cleaner because you made the gas tank worse.

Now with dual cats, part of the problem is that dual cats each only receives half the exhaust heat a single cat would receive. Cat convertors require heat to operate. In turn a dual cat system would require smaller cats than a single cat system. Even after being properly sized such a custom system would still need to be submitted to govt certification.

 

[Clone TIE Pilot]

Regarding the Oldsmobile 307 and horsepower, earlier this year I visited with the good folks at Mondello Performance in California. The 307 can easily achieve the magical threshold of 1 hp per cubic inch, with the following:

• High compression pistons
• Edelbrock Aluminum Cylinder Heads
• Edelbrock Aluminum Intake Manifold
• Hotter Camshaft
• Holley or Edelbrock higher CFM Carburetor
• Tubular Exhaust Headers

So, that gets you to 300+ hp. However, for my 1984 Hurst/Olds, I would dial this back to 230 hp to 250 hp, due to keeping the following:

• Stock Air Cleaner
• Stock Quadrajet Carburetor
• Stock (Aluminum) Intake Manifold (to maintain provision and placement for Cruise Control, etc.)
• Exhaust Manifolds
• Air Pump, EGR, and O2 Sensor
• Single Catalytic Converter
• "Computer"

I have looked into Extrusion Honing the Exhaust Manifolds and the Intake Manifold, which should get back a small amount of horsepower from 100% stock.

A wise sage on this forum admonished me to be "circumspect" about modifying a nearly bone stock and original 1984 Hurst/Olds. Even getting to 230 hp would be a big jump from the stock 180 hp. This would set me back around $ 10k. Worth it to keep this car with a "numbers matching" engine.

Not that I even find the stock 307 all that bad. It starts easily in cold, runs well, smooth and reliable, barely burning oil at 65,000 miles. With the 3.73:1 Rear Axle and the 4-speed automatic, it runs great around town and effortlessly cruises with the 85 mph speedometer pinned.

I own and have owned much higher horsepower cars, yet I find driving the 1984 Olds a delightful experience.

With the aircleaners I would build a dual snorkel Thermac aircleaner out of two aircleaners to improve airflow. With the HO Chevy 305s, the Camero version got an extra 10 HP (190 hp) just from using a dual snorkel aircleaner vs Monte Carlo 305s (180 hp), which just had single snorkel aircleaners.

 

[scoti]

Emissions are a complex subject that combines physics with legalese which are both already quite complex topics on their own. Tailpipe emissions are one aspect of emission control. The other two major sources of pollutants from cars are emissions from the crankcase and emissions from the fuel tank which is pretty overlooked by most gearheads. The PCV system easily takes care of crankcase blowby gasses with a simple system that is often still poorly understood. The fuel tank requires a fairly complex EVAP system to control all the evaporative polluants emitted from the fuel. The fuel tank polluates whenever it has fuel in it regardless if the engine is running or not. If you modify a engine it is possible to reduce tailpipe emissions while making evaporative emissions worse.


As smog testing goes, most inspection stations only have the capability of testing stock emission systems against factory specs. Most cannot test custom setups, even CA's referee stations have limited capacity to test custom setups. Think of it like alignment shops, most can do stock alignments but most can't align custom suspensions. The emission certification tests that car manufacturers submit their cars to costs millions of dollars per model and requires racking up 50k to 100k miles on the cars being tested to ensure their emissions control does't degrade below acceptable levels for a long time. So getting custom emission controls certified is beyond what most of us hear could afford. In short, to get certified the govt tests cars for tailpipe, crankcase, fuel tank emissions and longevity of those systems. Low emission legal performance parts are also tested to get certitication.

Moreover, not all modern emission systems are backwards compatible with older cars. Modern OBD2 powertrains for example use enhanced EVAP systems that are not compatible with older fuel tanks and its illegal to downgrade a powertrain with enhanced EVAP to older non enhanced EVAP, regardless if the tailpipe is cleaner because you made the gas tank worse.

Now with dual cats, part of the problem is that dual cats each only receives half the exhaust heat a single cat would receive. Cat convertors require heat to operate. In turn a dual cat system would require smaller cats than a single cat system. Even after being properly sized such a custom system would still need to be submitted to govt certification.

I get it.

My thoughts were always how did the 'powers that be' test the PCV + EVAP emissions quality? "Ok, all OE equipment is in place" = PASS? So just a visual (@ least that's all it was in TX).

Built 350's I knew about w/non-legal set-ups both tested cleaner vs the previous 305's w/their legal set-ups. Cleaner tail-pipe emissions. Pass or Fail on the PCV/EVAP was only a visual here so no parts, no pass. Thus my let the car 'crafters' see what they could do to make things better for the environment vs just a Pass/Fail on a visual. *Again not sure how other states 'tested' for them.

 

[Clone TIE Pilot]

I get it.

My thoughts were always how did the 'powers that be' test the PCV + EVAP emissions quality? "Ok, all OE equipment is in place" = PASS? So just a visual (@ least that's all it was in TX).

Built 350's I knew about w/non-legal set-ups both tested cleaner vs the previous 305's w/their legal set-ups. Cleaner tail-pipe emissions. Pass or Fail on the PCV/EVAP was only a visual here so no parts, no pass. Thus my let the car 'crafters' see what they could do to make things better for the environment vs just a Pass/Fail on a visual. *Again not sure how other states 'tested' for them.

Supposedly the only way to test the effectiveness of an EVAP system is to lock the car in an airtight chamber for 2 weeks and measure HCs levels. This is a test most inspection stations can't perform, not even CA is crazy enough to force all cars to go through such a test at every inspection period. So in the old days it was just a visual inspection of EVAP systems. With modern OBD2 enhanced EVAP, the inspectors just plug into the OBD2 ALDL and use the car's onboard sensors to test the EVAP for proper operation. The main difference between non ehanced and enhanced EVAP is that the latter has built in self dianostics which inspectors are supposed to use. But how well any individual inspector looks will vary. Moreover, the newer the car or powertrain, the more strict emission regulations it must meet.

I am not sure how PCV systems are tested. However, a PCV system must be tight to avoid inducing vacuum leaks. Valve cover, intake China walls, timing cover, PCV and breather grommets, and oil pan leaks can leak air into the crankcase and cause a vacuum leak through the PCV system.

 

[olds307 and 403]

With the aircleaners I would build a dual snorkel Thermac aircleaner out of two aircleaners to improve airflow. With the HO Chevy 305s, the Camero version got an extra 10 HP (190 hp) just from using a dual snorkel aircleaner vs Monte Carlo 305s (180 hp), which just had single snorkel aircleaners.

Olds did use the dual snorkel on the 307 HO. I did build my own for my 70S. Unfortunately Olds not using a real Y pipe really choked the 307. The FE3X prototype with shorty headers, Y pipe in place of the crossover, Corvette cat and a functional hood scoop added 30 HP. Extrude honing Olds shitty exhaust manifolds and making a bigger crossover pipe might help and look stock. Not sure why GM didn't even use true duals on the TPI cars. They had dual cats and down pipes then went into a Y pipe, WTF? Ford went true duals on the 86 Ford 5L Mustang, lost 10 HP and gained torque due to the head design and maybe EFI vs the 4 barrel. They actually did keep single into dual on the 85 Mustang but enlarged all the pipes over the 84 Mustang. Along with a roller cam went from 175 to 210 HP.

 

[78Delta88]

I know we said not to..., but I'm all in for adding the rockets.

 

[78Delta88]

Realistically you have to look at two things, cost-benefit and risk-reward.

With a money no object plan and want to still call it a 307? Start with a Old's 350 DX block sleeve it down to 307 specs and build from there. Cranks, rods and pistons forged with small dome, choose cam lift and duration to DCR of about 7.5 or so to run pump gas.

Gapless rings on seconds, Molly on top. Heads needed don't really exist so would have to be custom made CNC. Induction would probably be an air gap style manifold and Sniper system or FI Tech on top, exhaust 1 3/4 headers heat wrapped and 2.5 duals.

And about this time your wife, family and close friends will be getting you into an intervention or maybe shock therapy. As they will be wondering why you have a $70,000 engine in a $9,000 car as a daily driver.

 

[CopperNick]

Not my build so I have no dog in this hunt........................That understood, if the need to stay numbers matching is a desired objective, then build the original block back to the stock specs. That has the additional virtue of making it easier to pass any scratch and sniff tests that may be required in your state/county/city/?

Then, put that engine on a stand, find another year correct 307 block and go as far to the dark side as your budget will allow and you think you can get away with. Bore, stroke, cam, intake, FI, blower ??? You already have a shopping list created that would give you the mill of your dreams, build a fund and have at it.


Nick