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Old 12-20-2004, 11:46 PM
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Pontiac Horsepower help.

Well, first off i'd like to say hi! Now, I got a 1970 LeMans with the original 2bbl 350 that was equiped with dual exhaust outfitted with flowmaster mufflers. Other than that I think the engine is stock. The guy i bought it off of said he overhauled the engine like 2-3 years ago. Stated he made the 350 into a 396. I asked around other boards to see if this was possible. People said yes, but was hard to accomplish this without some strange bore and stroke set up. SO i dont know whether it's a true 350 or a 396 So having said that, I would really appreciate some help on bumping up the hp since Im not familiar with Pontiac engines and I'm still learning. I want to keep the 350 engine seeing as i heard from my car club that the value of the car will drop if i replace the original engine. What carb, headers, intake, cam (If you can help since i still dont know if its a 350 or 396). What kind of rwhp will i be looking at when I these upgrades?Also keep in mind that will be a daily driver, but with balls! One last thing, is there a way to find the size of the engine without having to pull out the engine and opening her up? Thanks much!!!

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Old 12-21-2004, 07:13 AM
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Regarding the value, if you have Speed channel watch the Barrett-Jackson auction coming up in Jan. (I think). Hot rods draw more $ than originals (provided they are done right). So swapping the engine most probably will not hurt the value of a 70 LeMans. A 70 GTO might be questionable. If the 350 is bored and stroked to a 396, you don't have an original car anyway.

Anyway, let's say you build up a nice 455. You oil up the cylinders on the 350, seal all the openings, bag it with desecant, and store it in a climate controlled area. The 455 is a bolt in (there may be certain blocks which have odd motor mount positions, double check before you sink the cash). Enjoy the performance. If, at the time you would want to sell, the value would be greater if the car was original, pull the 350 out of the moth balls, clean it up, slip it back in, and now you have an original car and an engine for your next hot rod.

Since the 350 is basically the same externally as the 400 and 455, all of the performance parts for a Poncho will work on the 350 and you will get performance improvements. But if you really want horsepower, there is no sub for cubic inches.

Oops, forgot your last question. If memory serves, there is (or was) a displacement tool that threaded into the spark plug hole and determined the size of the cylinder by rotating the crank from BDC to TDC. I remember seeing one when I helped a guy with a roundie rounder many (many, many) years ago. See if anyone in you club is or knows a dirt tracker and find out if the local track has one. On race night, if things are slow, they would probably check a cylinder for you. The most accurate way is to take off a head and measure the bore and stroke.
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Old 12-21-2004, 11:49 AM
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Pontiac 350 v8
9.5:1 comp
650 CFM carb (typical 4bbl)
dual-plane intake manifold
"small tube headers and mufflers"
and a cam with .454 lift on both sides, and duration of 290 for both sides also.

My Desktop Dyno 2000 says...
torque: 360 @ 4000
power: 326 @ 5000

torque at 2000 rpm (just fyi):325, @2500 it's 342, so it'd be a grunter set up as I had it.
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Old 12-21-2004, 12:11 PM
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turning a 350 into a 396 is not a weird combo over the last 10 years it has become popular with chevy engines i have a 94 trans am with a 350 lt1. a year ago i stroked it to a 396 using a eagle forged rotating assembly i consists of a 30 over bore a 3.875 stroke crank, 6" rods and a srp forged pistons with very high pin height. mine makes around 550 hp flywheel and has 13.6:1 compression.
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Old 12-21-2004, 05:47 PM
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What crank?

Must be a 428 or 455 crank in there?

I think the 326 and 350 engines had the
same stroke as the 389 & 400's? 3.75

I would check into whether or not the
bore is big enuf to use bigger valved heads without hitting the cyl walls, or
at least seriously shrouding the cyl wall side of the valve.

I think that suggestion of mothballing
the original motor and bolting in a
bigger one is sound advice - even a
relatively stock bigger cube motor would
have more torque than a warmed up smaller cube motor and likely wouldn't be more expensive even with some basic freshening up than a higher level of mods on a smaller motor.

Here's a website that I think you might
be real interested in - never have seen
or heard of Pontiacs putting out power
like this guy gets out of them.

http://www.pontiacpower.com/
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Old 12-21-2004, 10:20 PM
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Thanks to all that replyed!

@redsdad... I thought about getting a 400 some time back, and looked for one, but it's very hard to find one. The car club has helped but to no use. Not only that, but building one up would be almost close to impossible right now seeing as im going to college full time and all my money is going to that. I going to have around $1800 in Jan because of a refund the college is giving me back, but I dont think its enough to get a 400 up and running. There's some suspension and cosmtic things (interior) that i will use that money for also. Good advise! I'll will surely use a 400 or 455 on my next project . Also, good to know I can find the size of the engine without having to rip it apart. My local track opens on friday's for test and tune day so i'll head out there friday.
@chevelle are the numbers rwhp or flywheel? Those are pretty good numbers. What about for a 396 Pontiac (Just in case my engine is a 396) using the same modifications? I dont want a 400 hp beast....(just yet )


@amean94ta
IS it really possible with a pontiac 350 though not a sbc 350.

@macx I would take the advice about the 455, but im on a tight tight budget so i don't think it's possible at this time. Im going to check the bore in the up coming weeks before I do and head work, and i'll report back. If i get some extra cash I would go for it, but it's gunna take a while. Thanks much for the link!
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Old 12-22-2004, 01:02 AM
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Look on the driver's side of your block, toward the front, just behind the fuel pump. Around '69 or '70, Pontiac started casting the displacement into the block at that point.
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Old 12-22-2004, 01:19 AM
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It's a YU code 350
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Old 12-22-2004, 07:11 AM
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350 options

Yes, back to "the real world" hey?

I scrounged good used parts for 3
years to build a mild engine for my car.
That old budget thing, of course!
I cruised forum classifieds and ebay.

As an interim measure, I'm sure a decent 4bbl intake and carb would help, as likely would headers and a hydraulic cam.

With a little shopping, you could probbly locate stuff like that quite reasonable and add a good bit of punch to your stock shortblock. Maybe even a better set of oem heads if you get lucky. do a little carb and advance curve timing, and you'd be amazed at the improvements.
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Old 12-22-2004, 08:07 AM
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LeMans:

Rather than searching for an engine alone, I'd search for a beater with a decent rebuildable engine.

There were pleny of big-cube Pontiac motors produced over the years. If I recall correctly, the 400 was available in Bonneville/Catalina/Station Wagons up until the mid-to-late 70's - maybe early 80s. I don't remember when the 455 was discontinued. Early 70's I think. You might even wind up with a better trans and/or rear end, possibly better brake parts too, depending on what's "swappable", especially on the bigger cars.

Try to find a rusted four-door or beat-up wagon with a 400 or 455. The advantage, assuming you have the room, is the beater becomes both an engine stand and a source for all the odds and ends (hoses, bracketry, etc.). You could then rebuild the engine in the beater, while still driving the LeMans. When the beater engine is the way you want it, you can spend a couple of days swapping the two and trash the hulk. If you're lucky, you may even be able to recoup some of your original investment selling off some of the beater parts. Ebay's great for unloading all those little odds-and-ends (especially interior parts) that the junkyards don't want to bother with.

Its getting harder to find old Pontiacs, but if you keep your eyes open, you'll probably be able to scrounge one for a couple hundred. If you're going to freshen up the engine anyhow, then you're really just looking for one that is rebuildable without major damage to the engine. The body and interior are pretty unimportant to you.


If you're strapped for cash, my advice would be to first concentrate on getting the new engine back to good running order. Don't worry about a new cam/intake/carb or dress-up pieces unless you need to replace worn/broken parts. Concentrate on a solid base - bearings, gaskets, new rings. Spend your initial money on making sure the block is solid - there's plenty of good advice on the board. You can probably live with the existing pistons, crank, possibly even the lifters, rockers, pushrods and valve springs for now. Get a solid base established, clean up everything, paint what you want (paint is cheap) and get it running well. Then swap it into your LeMans and enjoy it while you save up for better parts.

If you're not attached to the old engine and whichever trans/rear is left over, you can then sell them and get some more money to invest in the new one.

Just my opinion...its worth what you paid for it.
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