[tom s]

A 400 block and a set of pistons would pretty much solve the issue.Tom

[b-man]

Originally Posted by tom s

A 400 block and a set of pistons would pretty much solve the issue.Tom

Along the same line as Tom has suggested here searching for a used good-running 400 in your local area would likely be the same cost roughly as the hopping up the 350.

You mentioned your mechanic suggested the mufflers so I’m guessing he’s doing the major work so the engine swap might be out of your purview as far as room or equipment is concerned. But again still worthy of consideration, cubic inches are your friend when it comes to street performance.

[steve25]

Let me ruffle some feathers in terms of running aftermarket heads and their impact on drivability as compared with your current heads.

A base line 1970 400 4bbl motor will make peak torque at 3000 rpm, your 354 motor with the same heads and cam will make peak torque at 3200 rpm.

With these facts in mind you need to think about what your average street rpm in terms of drive time will be.

Now if you slap on a set of aftermarket heads with port volumes a little smaller then the norm aftermarket head you’re still going to increase your peak torque rpm up to 3600 rpm .

With a combo like that if you had let’s say 2.93 rear gears you would need a minimum of a rear gear ratio of 3.34 to keep the same throttle response feel at 2850 rpm that you had with stock motor.

Take a very close look at the dyno test of that motor in post 17 and notice that the dyno pull did not start off until 3000 rpm.

Just like the rule of thumb for cams is that it’s better for a street motor to be somewhat under Cam’ed , the exact same rule holds true for cylinder heads!

[tom s]

Pretty much all the parts except the block and pistons from his 350 will go into and on a 400 block.If necessary a set of custom pistons will get him too the CR he would want to run.JMHO,Tom

[Imperial]

Originally Posted by fairwayhit

I think I would just put a supercharger on it.

When my 557 block gives out I’m going with a blown 350


Sent from my iPhone using Tapatalk

I would have to get the engine rebuilt in order for it to comfortably handle the supercharger

[steve25]

Listen the Pontiac 350 has a longer stroke then any other 350 cid motor that was in GMs divisions back then, so it has superior torque available for great street driving.

Build for keeping that advantage up to 4000 rpm or so with changes you make for the motor and in rear gearing and you will be nice and happy.

[carbking]

As usual, late to a thread.

Your original request IS possible, however: I could NEVER have afforded the process without being able to trade out a bunch, and deduct more as advertising. You do not want to know what it cost.

It also produces an engine that is an absolute handful on the street, and more so every year I age!

I did it for a reason, and not sorry that I did, but it truly is NOT a practical street cruiser.

I have now read the entire thread (twice). The pretty much stock 400 is an excellent idea (opinion).

There are other "add-ons" not yet mentioned in this thread worth considering:

(1) Gearing - a number of folks have mentioned higher ratio rear gears (helps acceleration, kills gas mileage). Possible alternative: different transmission gear ratios. Memory is fuzzy, but I think low gear in the transmission I settled on is a 2.62:1. Better acceleration than standard ratios, but still have 1:1 4th gear and I still use a 3.08 rear drive. Gas mileage is very good; engine RPM's are quite manageable at any legal speed limit.

(2) Weight reduction - most folks talk about power adders, but few talk about weight reduction. Other than alloy wheels, and aluminum-cased 4-speed (mine came that way), I cannot tell you what weight reduction is possible on your Firebird, as my weight reduction campaign was on a 1974 GTO. Without going totally crazy; it was possible to change wheels, transmission case, water pump, rear drums, intake manifold, etc. Going totally crazy resulted in aluminum flywheel, elimination of the "5 mile/hour" bumper system, and some other mods I won't talk about.

How does it run? Low gear is virtually useless if driven in anger unless one likes buying rear tires!

Consider the 400, you will be glad you did.

Jon

[steve25]

Milage differences really only come into play at steady highway speeds as this chart shows, it also shows the other side of the coin.

That other side is the fact that around town driving dealing with stop lights and such that a 3.40 something rear gear will give the fuel mileage of a 2.41 rear gear, but with far better acceleration, as in fun.

[JLMounce]

Originally Posted by steve25

Milage differences really only come into play at steady highway speeds as this chart shows, it also shows the other side of the coin.

That other side is the fact that around town driving dealing with stop lights and such that a 3.40 something rear gear will give the fuel mileage of a 2.41 rear gear, but with far better acceleration, as in fun.

The difference between what we believed was a 2.73 to the 3.42 that we put in my wife's chevelle was night and day.

Not that we recorded mileage on the car, but it seemed somewhat the same and highway cruising wasn't terrible with the 27" tire combination. Around town where the car was really used though, it was so much more fun.

[PunchT37]

Originally Posted by steve25

Listen the other Pontiac 350 has a longer stroke then any other 350 cid motor that was in GMs divisions back then, so it has superior torque available for great street driving.

Build for keeping that advantage up to 4000 rpm or so with changes you make for the motor and in rear gearing and you will be nice and happy.

Unless you have a 350 Buick.

[steve25]

True .100” longer.

[Squidward]

350 guy here.

I've done a couple of iterations on 350 motors.

The first iteration was a very basic 69 350, #47 heads. This was the 1969 equivalent of your 1970 350. I put a Summit 2800 cam in it, with 4 barrel intake. I ran both Qjets and Holley carbs on it. The Qjet was a better all around carb, but Holleys were simpler, and did fine too when that is what I had. I ran an HEI ignition, with dual exhaust. This was a very basic, fun street cruising combo that did not require any exotic build elements or parts. The 2800 cam works great with stock valve train parts. It is similar to the previously suggested 067 cam. This was all in a 67 Firebird with 3 speed auto and 3.23 mid level performance street gears. In retrospect, it was a wonderful blend of cost effectiveness, simple tech, performance, and drivability. It broke just under 15's in the quarter when I decided to chase after more power and performance in iteration number two...

Iteration two is a 350 with forged parts (planned on doing a turbo build that never happened), and Ram Air big valve #12 heads. This was a compression bump, which gave more power, but kept it pump gas capable. I run a Lunati 702 Voodoo cam, HEI, headers, 3.73 gears, and a 2000 stall converter. This cam required careful selection and upgrade of valve train and head parts, because too much lift with big valves on a 350 WILL cause valves to contact the cylinder. I also run a FiTech system, because I wanted to play with some modern style fuel delivery. All of this cost significant money, and made the car less street friendly (3600-ish rpm on the highway).

Here in the Phoenix area there is only one drag strip in town, and every time I went I would have to take a day of vacation, lose sleep, and spend a good $100+ just to get one, maybe two runs down the track in a night. Most of that time was spent pretending I was part of a cool drag race culture while the track spent an hour cleaning up somebody's oily breakdown, pretending they cared.

Not my thing anymore.

I'm not going to undo what I built engine-wise, because it is no doubt a blast to drive. But what I will do is go back to a simpler time, with better street gears and street manners. I will go with a quieter exhaust, and stop making life goals of burning down the Dairy Queen parking lot while pretending "Street Outlaws" has ANYTHING to do with me.

Make your car reliable. Make it affordable. Make it fun but not crazy. Enjoy the time with your dad. Get a stereo in it with bluetooth, and tell dad to throw on his playlist that probably had a lot of spandex and hairspray involved. See how many different hamburger places you can visit in one summer, and how many burnout strips you can leave on that one almost deserted road that everybody has nearby.

To put it in very simple terms, I have now arrived at a point where I lean more toward "Roadkill" or "Vice Grip Garage". It saves money and sanity.

4 barrel intake and carb? Yes.
HEI ignition? Yes.
Headers and reasonable exhaust that doesn't make you an enemy of the state? Yes.
Good wiring that doesn't catch on fire? Yes.
Brakes that can stop you? Yes. Front disc/rear drum are fine.
Seat belts, preferably 3 point? Yes. After breaking my neck in a car with air bags and 3 point belts, I am a fan of some reasonable safety gear.
Cam swap to something like the 067 or 2800? I like it. Best time to do this is when the intake is off.
Changing rear gears or adding a limited slip differential? This is not a lightweight diy project. Best saved for later as money and/or skill develops.

Wow. I've turned into such a "square".

[Imperial]

Originally Posted by Squidward

350 guy here.

I've done a couple of iterations on 350 motors.

The first iteration was a very basic 69 350, #47 heads. This was the 1969 equivalent of your 1970 350. I put a Summit 2800 cam in it, with 4 barrel intake. I ran both Qjets and Holley carbs on it. The Qjet was a better all around carb, but Holleys were simpler, and did fine too when that is what I had. I ran an HEI ignition, with dual exhaust. This was a very basic, fun street cruising combo that did not require any exotic build elements or parts. The 2800 cam works great with stock valve train parts. It is similar to the previously suggested 067 cam. This was all in a 67 Firebird with 3 speed auto and 3.23 mid level performance street gears. In retrospect, it was a wonderful blend of cost effectiveness, simple tech, performance, and drivability. It broke just under 15's in the quarter when I decided to chase after more power and performance in iteration number two...

Iteration two is a 350 with forged parts (planned on doing a turbo build that never happened), and Ram Air big valve #12 heads. This was a compression bump, which gave more power, but kept it pump gas capable. I run a Lunati 702 Voodoo cam, HEI, headers, 3.73 gears, and a 2000 stall converter. This cam required careful selection and upgrade of valve train and head parts, because too much lift with big valves on a 350 WILL cause valves to contact the cylinder. I also run a FiTech system, because I wanted to play with some modern style fuel delivery. All of this cost significant money, and made the car less street friendly (3600-ish rpm on the highway).

Here in the Phoenix area there is only one drag strip in town, and every time I went I would have to take a day of vacation, lose sleep, and spend a good $100+ just to get one, maybe two runs down the track in a night. Most of that time was spent pretending I was part of a cool drag race culture while the track spent an hour cleaning up somebody's oily breakdown, pretending they cared.

Not my thing anymore.

I'm not going to undo what I built engine-wise, because it is no doubt a blast to drive. But what I will do is go back to a simpler time, with better street gears and street manners. I will go with a quieter exhaust, and stop making life goals of burning down the Dairy Queen parking lot while pretending "Street Outlaws" has ANYTHING to do with me.

Make your car reliable. Make it affordable. Make it fun but not crazy. Enjoy the time with your dad. Get a stereo in it with bluetooth, and tell dad to throw on his playlist that probably had a lot of spandex and hairspray involved. See how many different hamburger places you can visit in one summer, and how many burnout strips you can leave on that one almost deserted road that everybody has nearby.

To put it in very simple terms, I have now arrived at a point where I lean more toward "Roadkill" or "Vice Grip Garage". It saves money and sanity.

4 barrel intake and carb? Yes.
HEI ignition? Yes.
Headers and reasonable exhaust that doesn't make you an enemy of the state? Yes.
Good wiring that doesn't catch on fire? Yes.
Brakes that can stop you? Yes. Front disc/rear drum are fine.
Seat belts, preferably 3 point? Yes. After breaking my neck in a car with air bags and 3 point belts, I am a fan of some reasonable safety gear.
Cam swap to something like the 067 or 2800? I like it. Best time to do this is when the intake is off.
Changing rear gears or adding a limited slip differential? This is not a lightweight diy project. Best saved for later as money and/or skill develops.

Wow. I've turned into such a "square".

Thanks for the input! My dad and I are getting this done by a shop cause we don't have the time or tools to work on it sadly but I'll bring up the cams. The shop said they recommend getting an aluminum intake cam, 4 barrel carb, and headers since we don't know the integrity of the block. Going down Woodward in the Le Mans with my dad and my buddies has to be my favorite times in this car. Also doing burnouts on Woodward with my dad with Atomic Punk blasting has to be the most kickass thing I've ever done lmao. At this point with the car, my dad and I wanna be able to beat at least a Prius.

[Formulas]

I took a bone stock 70/350 2bbl 4speed 3.31 gear and put in a 204/204 - 110 Erson cam and quadrajet and that made a big difference... you dont have to follow standard big cid. cam recomendations a small single pattern cam will fill cylinders just fine with modest bump in .050 duration and single pattern keeps low rpm torque up due to less overlap

[steve25]

A factory iron intake is perfectly fine for what you’re doing, they can produce far more HP than what your motor will be making.

If you can turn up a used Edelbrock performer then that’s a good choice also.
Do not get a performer rpm intake.

[Squidward]

Originally Posted by steve25

A factory iron intake is perfectly fine for what you’re doing, they can produce far more HP than what your motor will be making.

If you can turn up a used Edelbrock performer then that’s a good choice also.
Do not get a performer rpm intake.

Agreed. I think your suggestion for a Performer is a good one. I like the dual pattern intake for the flexibility to run square or spreadbore carbs. And it saves your back if you pull it off.

Remember the "Crosswind" intakes that you could get on ebay years back? It's a knockoff of the Performer RPM, but better IMO. They used to be $150. They are now $290 as a "Speedmaster" brand. But hey... the economy is in great shape! I use them on both my cars, and they fit better than either the Performer or the RPM. I like all the open space between the intake and the valley pan cover. Lots of room to "conceal" hoses and wires!

Imperial, sounds like you might be near the Motor City? I'm from Michigan originally. Cars are in our DNA!

I was gonna guess Motley Crue, RATT, or AC/DC were on dad's play list. But Van Halen fits perfectly too!

[kingbuzzo]

Those are my current playlist...what are you saying?

[Squidward]

Originally Posted by kingbuzzo

Those are my current playlist...what are you saying?

I'm saying "Well played, sir. Well played."

I spent this week burning up some Def Leppard (Pyromania), Scorpions (Blackout), and a "best of" collection of Tesla.

[Imperial]

Originally Posted by Squidward

Agreed. I think your suggestion for a Performer is a good one. I like the dual pattern intake for the flexibility to run square or spreadbore carbs. And it saves your back if you pull it off.

Remember the "Crosswind" intakes that you could get on ebay years back? It's a knockoff of the Performer RPM, but better IMO. They used to be $150. They are now $290 as a "Speedmaster" brand. But hey... the economy is in great shape! I use them on both my cars, and they fit better than either the Performer or the RPM. I like all the open space between the intake and the valley pan cover. Lots of room to "conceal" hoses and wires!

Imperial, sounds like you might be near the Motor City? I'm from Michigan originally. Cars are in our DNA!

I was gonna guess Motley Crue, RATT, or AC/DC were on dad's play list. But Van Halen fits perfectly too!

yep I live in the Metro Detroit area, my dad used to wake me up with Van Halen blaring as a kid lmao

[kingbuzzo]

classics.... 👍