What camshaft Pontiac 400?

[67-400]

Well, I took the motor out, the cam is shot. The cam is a Crower 304-HDP

Adv Int Dur 304
Adv Exh Dur 312
Int dur @ .050 239
Ex dur @ .050 247
In lift 1.5 rockers 0.497
Ex lift 1.5 rockers 0.522
Lobe separation 108
RPM Range 3200-6500

What I need is input on what a matching combo is. It has a Holley 650DP, Turbo 400 trans w/2.41 rear gears. Yah, the 2.41 sux. But i'm wondering if I were to stick with a cam that generates higher rpms and get a higher stall converter (for example a 3400), would that counter-attack the 2.41's and launch better and still pull at the end? For the Pontiac fans, the heads I have are Pont 400 stamped with 62 and date code 1969

More on the motor....it appears to have been just rebuilt, I see the cross-hatch marks from hoaning. The pistons are http://www.jegs.com/i/Sealed+Power/844/L2262-STD/10002/-1, and I am unable to determine what the crank is. I see p/n 8782770 but I see no reference online to the p/n. The stroke is 3.75, 4.155 bore.

Alot of stuff here, sorry for the clutter....but any input is nice. Thanks :)

[Prince Valiant]

2.41 gears? I wouldn't have guessed such a high gear/low number was available on a regular housing...not that such high gears weren't unheard of. In the late 70's/early 80's there were some cars that run gears as high as 2.21's!!! BUT, oftentimes they required special housings to accommodate the large pinion needed to pull off such gears, as the ring had to be offset as a result.

How did you guys confirm it to be 2.41's? Count the teeth and do the math? Rotate the driveshaft and compare the number of turns the wheels made? Does such a high gear make sense given what it seemed like when you drove it? IE, first gear went forever, the car runs at hwy speeds around 1600rpm, etc?

That said, there really isn't an elegant way to correct your problem without getting new gears.

A general "rule-of-thumb" states that you wish to avoid getting a stall speed that's higher than the rpm's your car would turn while at cruising speeds...so if your car turn 2800rpm at 55-60mph, then you'd want a stall TC that runs around 2200. It's not that you can never break that rule...

With such a high gear and high stall TC, you'd likely be very unsatisfied with the driving performance of your car...it' feel soggy, rubber-bandish on acceleration, etc...your trans would develop a ton of heat and in short, you and your car won't be happy.

Best bet is go for a reasonable gear like 3.42's...good mix of hwy economy/quietness, but allows for a decent cam and great acceleration from a reasonably cammed poncho.

Combine the 3.42's with a 2200-2400rpm stall torque converter, and go for a basic 224-232 @ .050 duration cam on the intake side (typically seen in cams w/ 268-276 adv duration). More modern grinds like the compXE series will probably make you happiest.

If you want a nice cruising car and a healthy sound, with less sacrifice in driveability, there are series of cams made to sound bigger/badder than they are...called "thumper cams," they'll give you a good dose of the rumpity-ness that gets peoples attention when you pull into a lot.

But, there are virtually no scenarios that I'd recommend that would allow you to keep the 2.41's if that's indeed what the car has...

[Prince Valiant]

also I'd figure out why you're cam is shot...make sure you use oils that have high zinc content....usually you need an additive to bring the zinc content up.

Most modern oils keeps the zinc contents lower due to the need to lengthen the life of the catalytic converter...it's okay on modern engines since they all have roller cams. But large flat-tappet cams like yours won't last long due to the high spring pressures required to with such a big cam. Old cars with small flat-tappet cams are usually fine.

Best bet is to either run oil designed for diesel, such as rotella AND run STP, or many special off-road only racing oils, or just run a half a can of GM EOS (engine oil supplement) with every oil change.

[67-400]

2.41 gears? I wouldn't have guessed such a high gear/low number was available on a regular housing...not that such high gears weren't unheard of. In the late 70's/early 80's there were some cars that run gears as high as 2.21's!!! BUT, oftentimes they required special housings to accommodate the large pinion needed to pull off such gears, as the ring had to be offset as a result....

It is said to have a 70-80 rear axle housing, (Butler Classics pointed it out). I pulled the axles out & they are definitely after market, heavier duty axles alongside factory 10-bolt axles.


How did you guys confirm it to be 2.41's? Count the teeth and do the math? ...

Removed the cover, counted the teeth.


Does such a high gear make sense given what it seemed like when you drove it? IE, first gear went forever, the car runs at hwy speeds around 1600rpm, etc?...

When traveling at 65mph, the tach is actually revved at 3000 +/- a bit.
Maybe the tranny has gear-work done to it???? I just pulled off the stall converter, it appears to be the factory 12" stall conv.


A general "rule-of-thumb" states that you wish to avoid getting a stall speed that's higher than the rpm's your car would turn while at cruising speeds...so if your car turn 2800rpm at 55-60mph, then you'd want a stall TC that runs around 2200. It's not that you can never break that rule...

I see the logic with that, but on the flip side when the rpm band is higher and its full potential doesn't start until 3200....don't you want a stall as high? As the car sits with its current configuration, I would be driving 40 - 45mph & dump it into 1st, it would pin me and climb like no other upwards of 7000, but if I were to hammer on it going 15 -20 in first gear, its a pooch. My wifes S10 blazer would take me :rolf


With such a high gear and high stall TC, you'd likely be very unsatisfied with the driving performance of your car...it' feel soggy, rubber-bandish on acceleration, etc...your trans would develop a ton of heat and in short, you and your car won't be happy...

Thanks for that input, which is the reason why i'm trying to get as much feedback on my dilemma as possible.


Best bet is go for a reasonable gear like 3.42's...good mix of hwy economy/quietness, but allows for a decent cam and great acceleration from a reasonably cammed poncho....

Wish I could, I would need a different carrier + the gears. Then the install has been quoted to be a ton by some speed shops. Unless anyone here has a decent used set and can install them for me as a side job at a fair price??



If you want a nice cruising car and a healthy sound, with less sacrifice in driveability, there are series of cams made to sound bigger/badder than they are...called "thumper cams," they'll give you a good dose of the rumpity-ness that gets peoples attention when you pull into a lot.....

That thumper cam sound is the sound I am looking for (which is what it had) and I don't have a 12 second or better desire of performance. Though it would be nice to achieve roughly 300 r.w.h.p. (13.0 et)ish that launches nice & pulls hard.

[juicedimpss]

2.41 gear and 3000ish rpm @ 65 doesnt come close to computing,unless the trans never shifts into high gear.

[DR.FORD]

2.41 gear and 3000ish rpm @ 65 doesnt come close to computing,unless the trans never shifts into high gear.

exactly-
or it has VERY short rear tires- bro!:rolf

[67-400]

2.41 gear and 3000ish rpm @ 65 doesnt come close to computing,unless the trans never shifts into high gear.

It was measured in its highest gear, its not exactly a 6spd transmission. Tires are factory size.

[Prince Valiant]

Hey Mike!

Anyways, before going further I think we should double check that rear-end...certainly before making any purchase decisions.

Here's why you're getting some skepticism about the gearing from Ron and Jim:
w/ 2.41 gears, and even revving to only 6000rpm, you'd be doing 85mph in first gear! At 7000rpm, it'd be doing over 100 in first!

So something isn't adding up...so if you like, I can come check it out and we can see what we come up with....

to be at 3000rpm, you'd need to be traveling 70 mph...in second gear!

This is all assuming a 28" tire, which is a typical outside diameter.

BTW, ~3000rpm @ 65mph calculates to 3.91 gears...as third gear is always 1:1.

I wanted to respond to this point:

I see the logic with that, but on the flip side when the rpm band is higher and its full potential doesn't start until 3200....don't you want a stall as high? As the car sits with its current configuration, I would be driving 40 - 45mph & dump it into 1st, it would pin me and climb like no other upwards of 7000, but if I were to hammer on it going 15 -20 in first gear, its a pooch. My wifes S10 blazer would take me :rolfUnderstand that a torque converter's stall speed is a function of torque....and the stall speed given is usually as what this converter would stall behind in a 350chevy.

So, if you had a 2500rpm stall TC, and put it behind a little 265 chevy, it might only stall at 1600rpm. Put that same converter behind a 572ci big block, and it'd stall around 5000rpm!

Now, take a generic 350 again...and let's say that it's converter allows it to stall at 2500rpm again. SO, we swap in a MUCH bigger cam but change nothing else...exact same torque converter.

So what happens in this scenario? Would the stall speed stay the same? Nope. It'd decrease!!! So instead of stalling at 2500rpm, it might stall at 2000rpm!

Why? Well, with the new camshaft, it's making less torque at lower rpm's than the same engine did with a different cam. The torque it now produces at low rpm's is only enough to get a 2000rpm slip from the converter vs the 2500rpm of the old cam that made more torque at lower rpms.

SO, what this means is to get the desired stall speed from your torque converter, you'd need about the loosest torque converter built. Again, this would make for funny driving dynamics, ESPECIALLY from such a tall-geared car.



-now, this isn't to say that one HAS to swap the gears...but then the recommendation would be two-fold:
1. Small cam, such as a compXE 256...something that would make good torque at low-mid range rpm's. (256/268 adv duration, 212/218 @ .050, .447/.455 lift, 110 LSA...smooth idle, power from idle-5200rpm)
2. Small vacuum secondary carb...like a 600-670cfm job with a heavy secondary spring

With a reasonably light car, healthy cubic inches, moderate compression and a stock torque converter, this would be a nice driving car w/ the 2.41's. BUT, it wouldn't reach your goals of 13.0-ish second ET's w/ the 2.41 gears....and short of turboing/supercharging it, there are no combos that reach low 13's w/ 2.41 gears. What would the combo above do? Maybe low 15's?

[67-400]

Yah chris, thatd be nice to have you over to check it out. Ill send u a msg after work tonite, 7ish.

[Sprayaway Fox]

a 26'' tire and a TH trans with 3.73's would put you around 3100-3200 with converter float. a 3.50 would put you around 2800 at 65. Just a FYI

Something not too crazy though, Pontiac stock bottoms dont like RPM's that well.

[67-400]

a 26'' tire and a TH trans with 3.73's would put you around 3100-3200 with converter float. a 3.50 would put you around 2800 at 65. Just a FYI

Something not too crazy though, Pontiac stock bottoms dont like RPM's that well.

Thanks for that input, there appears to be a mechanical mis-communication between me and my car....my tach could be off, my speedometer I KNOW is off, the transmission might be modified (no idea) but one thing I do know is that the teeth on the ring/pinion equal a 2.41 gear ratio. I am 99% confident that I was in Drive on the freeway, Prince & I are going to look at it. Thanks for the info

[SLOWC5]

Call 414-801-9230

His name is wayne, His shop is strictly BOP. Mainly Pontiac! He should be able to help you out. Tell him Jeff sent ya.

Jeff

[Ricky Bobby]

Call 414-801-9230

His name is wayne, His shop is strictly BOP. Mainly Pontiac! He should be able to help you out. Tell him Jeff sent ya.

Jeff

is that wayne out in waukesha if so +1 for him just built my buddies poncho 455 in his lemans wagon

[SLOWC5]

is that wayne out in waukesha if so +1 for him just built my buddies poncho 455 in his lemans wagon

yes sir:thumbsup

[Ricky Bobby]

yea he def knows his pontiacs 12.5ish at 117 in that wagon :thumbsup

[67-400]

I just picked up an 8.5" 3.42 posi rearend. Chris, ill text ya tomorrow, thats a start to figuring out what cam and stall.

[Prince Valiant]

wow mike! Good kill on a real rear-end! :thumbsup

[67-400]

Took motor apart, blown head gaskets btwn cylinders both sides. Motor end caps cracked. Valves too big for seat. Piston pin too tight on pistons. Weld spatter on crankshaft throws from chopshop balance job. I guess im taking my time on this project, do it once, do it rite.