# XE262 or 068 cam in 9:1 400??



## geeteeohguy (Feb 2, 2008)

I just rebuilt a TH400 for my '67 convertible, and am installing it soon. My rear main has been leaking like a pig for years now, so I'm going all the way and yanking the engine to reseal it. (I rebuilt it in '88). It's the numbers 400, bored 030, with stock manifolds and an 068 cam. The heads are 87cc #15's, converted to BBC studs with all new springs, seats, etc. The short block has 70k on it and does not use oil. The heads are fresh with about 3000 miles on them. When I did the swap, the cylinders looked good with some honing still visible and no scoring or ridge. Two Questions:
1. Would replacing the 068 cam with a comp cams xe262 or 268 offer any real performance gain? This is a 9:1 engine now, no longer high compression like the 068 was designed for.
2. Would running a TH350 converter instead of a TH400 converter offer any performance gain? I rebuilt the trans to OE specs with the exception of flat plates instead of waved. No shift kit. All clearances are in spec. 
The car as it sits now has a 2.56 posi in it, and runs well with good power and great economy. Just wondering that since I.m going to have the engine out anyway, it sure would be easy to do a cam swap and a converter upgrade. Any thoughts? Do it, or leave it alone? Thanks!!!!
Jeff


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## Instg8ter (Sep 28, 2010)

do it, you only live once...., i don't know on he specifics, but Lunati is making some nice modern cam grinds based on the original pontiac cams, thats what i went with mainly because i got a great deal on the kit but have heard nothing but good things about them from all the builders i talk to. would think a little higher stall would put you right in the power band, think the stocks stall at 2200-2400. How do you like that 2:56 and what MPG are you getting? Thats what i have now only its an open and i have a feeling i won't be upgrading until next winter when i can drop the whole rear end and do it right with adj. upper control arms and new posi 12 or 10 bolt chevy, i am thinking 3:08 or 3:24


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## Mr. P-Body (Jan 20, 2011)

We use XE262H as a "replacement" for 068 and 744 in lower compression engines. GREAT cam. With the auto trans, stick with 262. 268 needs a bot of "stall", but the power gains aren't worth the "hassle" of a higher stall. If a stall converter is to be used, XE274H is the choice.

In one case, a 406 CID, 6X-headed (8.5:1), with Edelbrock Performer, Q-Jet, Hooker "Comps", made 268 RWHP and nearly 400 lb. ft., all under 5,400 RPM. The '68 Firebird ragtop went 13.60s at VMP, in "total" street trim. He didn't even let any air out of the rear tires... He claims 17 MPG, too!

Lunati "VooDoo" cams are essentially the same technology as the XE grinds, Bullit and UltraDyne. Harold Brookshire was the designer. He has since "moved on" to General Kinetics, making high-end race cams. 

Any of the modern "assymetric" lobe designs will outperform the older factory designs in lower compression engines.

FWIW

Jim


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## geeteeohguy (Feb 2, 2008)

Thanks, guys. Jim, I guess what I'm asking is "out perform by how much?" If it's a small gain, I won't do it. If it's a bigger gain (enough of a difference to be "felt") I would do it. Do you think it would make a difference that I could feel?? What about an xe262 cam and a TH350 TC, which would put my stall at around 2200 rpm as near as I can figure? My highway cruise rpm is between 2000 and 2500, so I would need a stock converter or one with very little additional stall. Inst, I really like the 2.56 gears in this car. It's a convertible, and it's an automatic, so it's always been a "cruiser" . It came with a 3.36 open rear end originally, and I drove the car all over the country like that, getting 15-17mpg. The 2.56 posi was free from a buddy, so I freshened it up and dropped it in. I'm getting OVER 20mpg with it on hwy trips at 70-75mph. The car is not as snappy out of the hole as with the 3.36 gear, though. It is super impressive at highway speeds, though. I think my favorite rear gear for an automatic A body without overdrive would be a 2.93 or 3.08. My favorite gear for a 4 speed car is 3.23. Thanks, guys!


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## BearGFR (Aug 25, 2008)

geeteeohguy said:


> ...I'm getting OVER 20mpg with it on hwy trips at 70-75mph. The car is not as snappy out of the hole as with the 3.36 gear, though...


Sounds to me like you already are very happy with what you've got, so why make a big change? The more modern lobe profile on the 262 will probably have some positive impact that you'll be able to feel, but the real truth is that you probably won't see a dramatic difference in it unless you "do other things" that are also going to have an affect on your mileage and cruise-ability.

Whether the 262 will make "enough" difference to be "worth it" to you... well, that's up to you and your bank account 

Bear


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## jetstang (Nov 5, 2008)

A 2.56 geared car will only slow down with a bigger cam, as it will lose bottom end torque. If you are happy with that gear, then you aren't really worried about performance anyway. 20 MPG, I wouldn't change a thing until gas prices come back down, it would be nice to have an old car that you could afford to cruise.


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## Too Many Projects (Nov 15, 2008)

Jeff, glad to see you're gonna get that leaky seal outta there. I take it you aren't bringing it up here for that


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## geeteeohguy (Feb 2, 2008)

Mitch, great to hear from you. No, I'll be doing the seal "down here". I'm coming up there for my trunk support brackets!!!!! In a nutshell, my trans started making strange noises and shifting poorly a couple of weeks ago on a 160 mile trip. Rather than wait for it to explode, I rebuilt the TH400 that was pulled from the car and bagged in 1993. Planning on a weekend blitz of pulling/resealing the engine and installing the new trans. Was a sunny 68 degree day today.....no top down cruising for me! Had to "slum it" in the Tripower '65. I thought by now, rowing thru the gears would get old....it doesn't....just gets better. Put my cell phone in my console, and the lock froze up, so had to remove the console, take it apart, and remove the lock to get my phone. Time for another lock.....I spent 3 houts trying to "rebuild" it, but the cam is shot. Oh well, another $30 down the drain....


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