454 XE268 2.41 gears Will It Work? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-30-2007, 06:55 PM
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454 XE268 2.41 gears Will It Work?

I have a 1946 Ford coupe with a 8.5" 10 bolt. I just swapped from 3.73 to 2.41 gears. The 3.73 gears were terrible for anything more than 45 mph. My tires are 25.5 inches tall. That calculates to about 2100rpm at 60mph with 2.41s. I have th350 tranny with a mild stall converter. My 454 has an LS5 spec cam and peanut port heads. It is limited to about 4500rpms. Right now the car runs great. Off the line acceleration is good and highway cruising is great. Now the question. If I build this motor with 290 heads (good oval ports) and a Comp Cams XE268 cam, will it be able to pull this gear? I have considered a 2004r swap and going back to the 3.73s but, I was wondering if this would work as a low buck way to a fun combination. I know all the hardcore guess will say no it won't work, run 4.10s and rev the piss out of it or get the overdrive its only money. I want some real answers.

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Old 05-30-2007, 08:17 PM
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Had it been me, I would have kept the 3.73`s and just added a 700R4.
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Old 05-30-2007, 09:07 PM
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A little history of the car. Bought it built with a 350 pontiac and 350 tranny. Swapped in the 454 and a built 350 trans. It had, I'm guessing, 2.73 gears. The rearend had a bad wheel bearing. So, I swapped a 3.73 rearend. Big mistake, it exposed another problem. Drive line angles are not within the operating range of the u-joints. Anything over 45mph the mirrors were buzzing. Lack of time to rebuild the car lead me to my current fix. Thats where the 2.41 gears come from. Now, no vibration. Now the car really does drive good, but I know it is not right. I plan to start a rebuild of the car this winter. I am looking over all options, hence the original question.
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Old 05-31-2007, 06:26 AM
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25.5" tires and 3.73 gears comes out to more like 3,000 RPM at 60 MPH.



Quote:
Originally Posted by F-BIRD'88
If you want a low rpm combination, you want a short duration low rpm cam.
If you increase the cam duration (xe 268) the motor wants to run at a higher rpm.
Use the cam you have. Build some torqi Tri-Y headers to work with your present cam and gear. Find some 454 Vortec heads.
You really have to resist "camming it up" when you really want a low rpm motor. Make the cam, intake and exhaust work in the rpm range you will be using during real driving. With 2.41:1 gears the Rpm will be low. I'd go back to a stock converter as well (12")
I'll second that, with 2.41 gears and those go-kart tires you'll be turning about 1700 at 60 MPH, very doable with a Peanut head Rat and a mild TQ cam. BUT, my first thoughts were............ Sell the Rat, put the Pontiac back in and tweak it a little, put a 200-4R behind it then swap the 3.73's back in. People just don't give the "little" Poncho enough credit, you would have something "interesting" under the hood capable of decent performance and mileage and a swap to a 400, 428 or 455 later on would go unnoticed until you squeezed the go pedal plus Pontiacs look really cool all dressed out, especially in a rod because you so rarely see them in one. I know none of those is probably an option at this point but I had to throw that out there for the benefit of the next guy.
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Old 05-31-2007, 09:14 AM
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I would say no. That cam is too big to pull that gear with any torque feel. I would install a 252H or a 260H. It also depends on the curb weight. My truck weighs 4500 pounds, has a 3.08/thm400, and feels strong with a 454 with a 252/260 cam. I'm guessing you could run more cam if the car is under 3500 pounds, but feel you would have a better driver with the smaller cam.

Compcams also makes two DEH cams for the BBC with more exhaust duration if you are using a weak flowing exhausts system (quiet or with manifolds). I think the cam that would work for you is numbered "255DEH" which is the smaller of the two DEH offered.

I don't think the 290 heads will have any effect on low rpm torque. Just more high end power. FYI, a 252H will pull to 5000 rpm and a 260H to 5500 rpm. And they work well with stock springs.

I would also avoid the extreme series cams. They are going for slightly more power by making very aggressive lobes. This also causes extra noise and wear. They tend to go flat very quick if there are any minor geometry issues and just plain don't last as long as the "old school" high energy series. Sure, they make more power, but not for long. Not worth it to me.

Also, use diesel engine oil with your new cam.
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Old 05-31-2007, 05:07 PM
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25.5 inch tires and a 2.41 gear will rev at 1907 rpm at 60 mph with no converter slip. Most likely will be a little over 2000 rpm at 60 with some slip since it is below the stall speed.

31.462 mph/1000 rpm is what you got with a 25.5 inch tire and 2.41 gear, so 80mph will rev at 2543 rpm, again assuming no converter slip.

Yes, you should fix the driveline angle. Just point the trans output shaft parallel with the rear end input shaft. They don't need to be inline, just parallel. Both level or the trans pointing down and diff pointing up, or trans pointing up and diff pointing down. Buy an angle level. Can get one for 10 bucks. This keeps the u-joints spinning at the same speed. The engine should also be installed square with the body. It can be offset to one side, just not "angled" towards one side.
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Old 05-31-2007, 10:33 PM
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I think the 290 heads have a much smaller chamber than the smogger peanut port heads? If so the compression increase would probably go well with the XE268 cam which is a fairly small cam for a 454 in a light car.
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Old 06-01-2007, 07:53 AM
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OK, I changed a rearend to make the car drivable. I would call it a "quick fix." Not exactly 20 things or stabbing in the dark. I know about drive-line angles and have an angle finder. The problem is that the car has a Camaro stub on it and the engine sets high. I made my own motor mounts to lower the engine and raised the trans as high as I could. I am limited by the frame and floor pan. The u-joints are operating at about 6 degrees each. Max normal operating angles are to be 3 degrees or less (from what I've read). To fix right would mean a body off rebuild, which is planed. This a rod not a factory built car. Things are not bolt in and go. Just so happens this rod was not built correctly. My original question was do you think this proposed engine combination would be able to pull 2.41 gears. With the mild stall it seems to me it might be a fun combo. Has anybody experienced this sort of set up? Thanks for the insight!
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Old 06-01-2007, 07:56 AM
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Yes, good point. The 290 do have smaller chambers. 105cc to be exact.

The 236 peanut head (75 to 87 truck) have 120cc and the 156 peanut head has 115cc.

So assuming 7.5 cr with a stock smogger 454 with 236 heads then install some 290's then the compression should go up to 8.26:1. That is a good jump but still not high enough to justify running a bigger cam. I run 8.75:1 on my 454 and 9:1 on my 396, both with an advertised intake duration of 252 and run 91 octane with full ignition timing in a 4500 pound truck with thm400 and 3.08's.

If compression was 8.0:1 with 236 heads then it would jump to 8.9 with 290 heads. Now this is getting into the range of running a bigger cam so lower octane fuel could be used.
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Old 06-01-2007, 08:26 AM
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Well, I think it will work just fine. I really like the 2500 rpms at 80 mph!

Both heads would work well. Just be careful to not over cam it.

I would use the 252H or maybe a 260H if the curb weight is under 3500.

With a 2.41 gear and 25.5 tires and a thm350.....62.4 mph at 5000 rpms in 1st gear. If you install a xe268 cam which should make power to 6000 rpms then that would come out to 75mph in 1st gear which I think is way too much cam for that gear in a street car.
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Old 06-02-2007, 02:54 PM
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I,m currently running a 427 BBC with this very same cam. It runs great in my engine but like "454CK" said you my not have enough static compression at 7.5 . This cam will idle @ 650 all day and have about 15 inches Hg. It pulls like hell right from idle to 5500 but thats with a 3.55 rear gear. If you lived closer to Oklahoma I,d give you mine it's like new. I'd like to go a bit bigger, something with a nasty idle. The big "O" port heads will still pull hard.
On cam choice "it's better to be too small and be disappointed than to be too big and be miserable"
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