[FSJplumcrazy]

Small blocks like to rev high and big block don't like them so much, so where does a 389/400 fit in this equation?

Fill in the blank
Best power range for a stock 350 is

Best power range for a stock 389/400 is

Best power range for a stock 455 is


Long story short, I need help and figure if I post in here then the next person that comes along won't have to fight with the search engine that likes to separate words such as "power" and "range" and come up with a zillion posts.

The perfect calculator would be drop down boxes with different transmissions (so you don't have to figure out the different gear ratios for each gear), plug in your tire size (without having to get another calculator to figure out what is the diameter of the tire...no it's not 15" it's 25.6" or 27.3" or...), and then drop in your choice of rear gears to compute the RPM of your engine at 60 mph.

Toss in a side order of "Here is your target area" and I would pay money for it.

Does such a thing already exist and it is not advertised in "Muscle Car Craft Thunder" magazine?

Wayne S

[v8drinker]

you do realize that the 350 and 400 share the same stroke?

As far as powerband for a "stock 400", these engines were produced over a period of years with varying emissions requirements, cams and compression. Thus your powerband on a stock 77 400 vs. a stock RAIV 400 is not the same.

If you want to figure the ideal gear ratio for a *stock* engine, maybe the stock gears would be a good place to start?

PS there are no big and small block Pontiacs, only big journal and small journal engines.

[uneasyrider]

Originally Posted by v8drinker

...If you want to figure the ideal gear ratio for a *stock* engine, maybe the stock gears would be a good place to start?

PS there are no big and small block Pontiacs, only big journal and small journal engines.

Ditto. Stock engines have the gearing behind them that matched what the factory engineers thought the engine needed for that application. As said above a stock RA IV is designed for different usage than a 2bbl 400 in a Tempest wagon. There is no getting around "power band" and "rpm range" that IS what it's all about. There is NO "generic" engine, it's all about application.

To give an extreem example:

My 467 is about 450hp, I drop a 450hp diesel engine in it, do you think they will perform the same even if the weight difference is ignored given the same tranny and rear end gears? You're right, they wouldn't.

Now if you tell us you pulled a bone stock 455 4bbl out of a '70 Bonny w/auto and 3.55 gears then someone can tell you to keep the cruising rpm range at 2,500rpm and max at 5,000 and it's putting out 300hp and 450ftlbs or something like that. See what I'm getting at?

[johnta1]

Go to my Tech Articles:

Tech Articles

Click on Engine Theory for some info on the Pontiac engine parameters and stuff.

Then click on my Calcaulators page.

Try this gearing calc and this one for tire diameter calc or this Tire Height calc

Or one of many others.

[FSJplumcrazy]

Sorry about that.

I'm going to either finish this convertible or watch it get made into a coffee table.

It started out with a 326/4sp/???rear and the PO installed a 350/th350/ and spun a bearing in the rear...so by time I got to her there was an open 3.08 from a Cutless stuck in there.

I'm trying to put a 389 together and ordered some h2o divider plates to replace the nasty stuff I pulled out and they don't fit...shoulda known...it was one of those days...go to the DVM to get tags then have to go to the tax assessor's office to update my assessment of personal propertay, go over to the collector's office to get the paper signed to show I paid taxes last year then go back to the DMV and wait...I was looking for something easy and it seemed I could not pass go and collect $200 and when I tried to figure out what to put behind the 200 4R (gear/tire combo) I had to "run" around again.

Again I appologize.

Wayne S

[FSJplumcrazy]

Long story short I don't know how to figure out where max torque or hp
is so I am asking for help.

66 convertible

389 "YF" block (65 block/thick walls)
Bored .060 over so I could use standard 400 pistons (STL-411NP)
Stock 76 heads (70cc)
Summit cam kit 2801

Using your vehicle Bore of 4.122 inches and Stroke of 3.75 inches :
Your HP for street is 384.81.
Your HP for racing is 641.35.
Your displacement is 400.44 CID
The Compression Ratio is: 10.12

Intake and carb are undecided, I have the stock intake and an AFB on hand.

200 4R (2.74, 1.57, 1 and .67 final drive)

Trying to decide gears and tires...not sure where I want the tach to rest at highway speeds and still be able to stomp the crap out of the rice burner at a red light.

Wayne S

[uneasyrider]

johnta1 THANKS for the info source. Great site! Two thumbs up from uneasy.

[Region Warrior]

Johnta1 is the man.
Use his calc's alot just for fun.

BTY, anyone have a 12 bolt 4.03 R&P

[69birdboy]

411np pistons will NOT give you 10:1 with that setup. If you did not zero deck, figure about 9:1. If you did, maybe 9.5. They are deep down in the hole (about .040) and have 16cc valve reliefs. Figure about 330 hp tops, at about 5000 rpm with those stock heads. That setup will like a stock intake and carb.

With that OD transmission, I would go with gears anywhere between 3:55 and 4:10 with that setup. Gearing is much more forgiving on a street car with an OD tranny. If you go too low (i.e. 2:56 etc.) it won't like you, though.

[FSJplumcrazy]

Thanks for the replies...I used the calculators with 0 deck heighth, 72cc and gasket thickness of .041 to come up with those numbers. I was hoping it would be lower so I didn't have to pony up for the expensive stuff in my gas tank.

I found a 10 bolt with 3.23 gears that may or may not bolt up (just word of mouth right now) and am playing with those numbers.

Wayne S

[69birdboy]

I'd be wary of zero decking with those pistons - if you do that, other pistons will be as much as .020 out of the hole on the next rebuild!

You will probably still have to use 91 octane or so with that setup. I have a somewhat similar setup, 411np pistons, not zero decked, and 72cc heads for 9:1, and use premium gas. The quench distance isn't so great on those unless you zero deck, for one thing. Other forum members have reported good success with 3:23's and 200r4, but I have no first hand experience. Summit 2801 builds plenty of torque, should be fine I would think.