Joined: Tue Aug 31 2010, 09:20PM
Location: Cuyahoga Falls, Ohio
Posts: 5
Looking for any thoughts on torque converters and cams. We're running a 1969 Polara 383 with a 727. 650cfm dual feed, stock heads and exhaust manifolds.
Not looking to change the rear end or trans, was thinking a higher rpm converter would get a better launch for the street application. However, I'm wondering how agreesive I can get with the cam if I upgrade to an 1800 to 2200 rpm converter.
What rear axle ratio are you using? That will determine which converter you already have and what one you need (if any). The tightest converter the factory used on big blocks was an 1800 rpm stall unit -you'll find those on cars with 2.76/2.94 gears. Most 3.23/3.55 axle ratio cars used a 2000-2200 rpm one. Road Runners, Super Bees, etc. used a 1" smaller 2400 rpm unit.
The biggest cam you can use in a heavy C body with a 383 without having to upgrade the converter/gears is the Comp Extreme Energy XE268H: it works quite well with an 1800 stall/2.76 rear, and freakin' awesome with a 2200/3.23 setup (its useable power band is 1600-5800 rpm and it's designed with a longer exhaust duration to make it work well with factory iron exhaust manifolds).
Don't waste your time with the old style cam grinds (like the Mopar Purple Shafts) -the Extreme Energy profile cams are light years ahead. The XE268H has the same duration numbers at .050" lift as an old style grind 284/292 cam, but idles better for more vacuum to run the brakes. You get the low speed drivability of the old factory HP cam (268/284) with the mid range and top end of the 284/292, the best of both worlds!
<span class='smallblacktext'>[ Edited Sat Sep 04 2010, 11:09PM ]</span>
Joined: Tue Aug 31 2010, 09:20PM
Location: Cuyahoga Falls, Ohio
Posts: 5
Thanks for the input, and honestly I'm not sure of the rear end. It was never changed, and came with a 2bbl - not a 440 or even a Polara 500, just the standard issue 383.
From a quick ID reference guide, it appears to be an 8 3/4", but the chassis manual says there's supposed to be a tag with the ratio stamped on it, but I don't see it. I hear it's on the ring gear as well, but I've never cracked the case to see.
Thanks again for the cam info though ! I willl look into it today.
Joined: Sat Jun 07 2008, 12:59AM
Location: Fort Lewis, Washington
Posts: 394
LOL Kraut, I am going to call Comp and see if they will throw you some sponsorship swag or something. You are a heck of a promoter for that XE268H!!! Maybe they will send you a free hat or a sticker LOL
As for ID'ing your rear, it is in fact an 8 3/4. I doubt the axle ratio tag is still on the case after 40 years, but maybe. A cheater way check your axle ratio (and this is only an approximate figure!!) is to jack up the rear end of the car and set the axles on jackstands. Put the car in neutral and crawl under the rear end. With a piece of chalk or some marking device make a mark a few inches long lengthwise on the very bottom of the driveshaft. Make another mark on the bottom of one of your tires on the inside sidewall. Have a buddy then rotate that tire one full revolution while you count how many times the driveshaft spins around. If it spins about 2 3/4 times you have a 2.76, if it spins 3 1/4 times you have a 3.23....it's not the most accurate method in the world, but it will get you in the ballpark. I would also be willing to bet that if you do this method, the tire you are not spinning will rotate the opposite direction...woohoo for the one-tire wonder!
4DoorFan wrote ... LOL Kraut, I am going to call Comp and see if they will throw you some sponsorship swag or something. You are a heck of a promoter for that XE268H!!! Maybe they will send you a free hat or a sticker LOL
And I was hoping for an executive position with the company, not just some bling!
Seriously though, when you build a car you have to plan the whole thing out with matching parts so you only have to buy everything once. Too many guys throw in a big cam and nothing else, then wonder why their car runs like crap. Comps EX grinds are perfect for Mopars, and the XE268H just happens to be the biggest stick you can use in a 383 without changing everything else (440's can take up to a 284 grind and still run good with 2.76 gears). Our big heavy boats need a big fat torque curve in the low-mid range to make them fun to drive, and running too big a cam just won't get you what you need.
Now, if your building a little light weight A body with a four speed and 4.11's, that's a whole different story (and a whole different web site too!) in that case the old 383 will take a really big stick and run like a scalded cat. !banana !banana !banana !banana
Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
4DoorFan wrote ... LOL Kraut, I am going to call Comp and see if they will throw you some sponsorship swag or something. You are a heck of a promoter for that XE268H!!! Maybe they will send you a free hat or a sticker LOL
As for ID'ing your rear, it is in fact an 8 3/4. I doubt the axle ratio tag is still on the case after 40 years, but maybe. A cheater way check your axle ratio (and this is only an approximate figure!!) is to jack up the rear end of the car and set the axles on jackstands. Put the car in neutral and crawl under the rear end. With a piece of chalk or some marking device make a mark a few inches long lengthwise on the very bottom of the driveshaft. Make another mark on the bottom of one of your tires on the inside sidewall. Have a buddy then rotate that tire one full revolution while you count how many times the driveshaft spins around. If it spins about 2 3/4 times you have a 2.76, if it spins 3 1/4 times you have a 3.23....it's not the most accurate method in the world, but it will get you in the ballpark. I would also be willing to bet that if you do this method, the tire you are not spinning will rotate the opposite direction...woohoo for the one-tire wonder!
This only works if you have a sure grip (both wheels spin the same way when you rotate them. If they don't, you need to have another buddy hold the opposite wheel still or rotate the wheel 2 revolutions to get your ratio.
Joined: Sun Oct 09 2005, 05:02PM
Location: ALLEN PARK, MI.
Posts: 2007
Here, let's just "cut to the chase" on this thread and save you TIME & MONEY in our journey! A: 9 times out of 10, unless this car was a special order, you have a 2.76 gear. B: Forget the cams and torque converters! With a stock intake, heads, and log exhaust and a 650 cfm carb, your power is all done by 4,800 to 5,000 rpms being a 383 anyway. SOOOO...here is the BEST money spent on this car...3.54 rear gear with a sure grip if you can afford it! WHY you ask? Forget a 3.23 gear. Baby step from a 2.76! A 3.54 you will notice. Forget the 3.91 to 4.10 gearing. Your engine can't use it very much. A stall converter upgrade means wasted time tearing the trans out for a factory engine. A cam means head work! You were gonna stick a bumpity-bump with factory old/tired valve springs? NAH! On the street, the BEST money spent is always a nice set of DUAL EXHAUST and a better gear ratio! A 4 BBL always helps! SPEND WISELY! !thumb Tony P.
PIETIN440 wrote ... A cam means head work! You were gonna stick a bumpity-bump with factory old/tired valve springs? NAH! On the street, the BEST money spent is always a nice set of DUAL EXHAUST and a better gear ratio! A 4 BBL always helps! SPEND WISELY! !thumb Tony P.
Yep, I didn't mention that when swapping cams you need new lifters, timing set, valve springs, (you might as well get the heads rebuilt while you're at it-they're going to need it anyway) and then you need a better exhaust system.... the money starts adding up very quickly !nope
Joined: Sat Jun 07 2008, 12:59AM
Location: Fort Lewis, Washington
Posts: 394
Depending on how big you go with the cam you dont "need" new valve springs...it's a good idea but not absolutely required. Cam and lifter sets are available and much more economical than buying seperately. I would throw in a new double roller timing set no matter if I was changing cams or not...those nylon teeth are more brittle than the Declaration Of Independance and you sure dont want that thing to let go when you are out on the road. While you are there changing out the timing set...might as well pull that factory bumpstick out and throw in a more modern grind. It doesnt have to be huge, heck the HiPo 383 cam will give you a noticable little lope at idle and make more power. I agree with Kraut though...money will start adding up mighty quickly.
Thanks for correcting me on my cheater gear ratio method. It's been years since I have done that LOL