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Post Info TOPIC: 348 Truck Engine HP Increase


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348 Truck Engine HP Increase


Just purchased a 1961 348 truck engine #3798962. Is there a good menu out there that can be done to increase the horse power by an additional 100hp. Suggestions please.



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A Poncho Legend!

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100 HP  comes in a bottle

 

download.jpeg

 

 



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Thanks, I should have thought of that (lol)

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A Poncho Legend!

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Just kidding  biggrin  

348 responds to hop ups like any other Chevy      

Nice intake and modern 4 bbl will add 50hp  

Some small diameter headers will add 35-50 hp    

Nice 2.5 inch exhaust and you are there

 

do not add anything too big and unnecessary 



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I think the truck 348 was rated at 220hp.
Like Carl said it will certainly respond to bolt on parts,,, but the compression was really low on those truck engines,,, 7.75 to 1,,, so that tends to hold them back from responding as well as they should.
If you're going to be rebuilding the engine and getting the compression up a bit, you can easily get the power up into the 300 to 350 hp range and still have a good idle and good fuel economy.
The top passenger car 348 made 350 hp in 1961, you can match or exceed that with no problem if you bump up the compression and add a few parts, but if you want to just go with bolt on parts it'll be very hard to get there.
You should have #333 cylinder heads on that engine. You can make good power with those heads. There are a couple of guys on the 348/409 forum making more than 450 hp with those heads on 409 ci engines.
I used to have a 348 that was stroked out to 437 ci that made 650hp with the help of a lot of aftermarket parts so the 348 certainly has potential.
let us know whether you're planning a full rebuild or just going with bolt on parts.

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Barrie Ont.

409 powered 61 Poncho

best time 9.06@ 148 



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A guy on the 409 site recommends (tongue in cheek) the K&N air filter for a big gain in HP.

youtu.be/TCuvT2B5WN4

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63 Pariesienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC.

Mahone Bay, NS Still not old enough to need an automatic



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Just watched that Youtube video and that car was a 4dr. Back doors have been welded shut and filled in.
Brian

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You might want to upgrade camshaft....when doing intake and exhaust mods...

Showcars/Dr.409 would be a good consultant on camshafts......

They sell Isky cams....as I recall........and Ed Iskedarian......was grinding cams for W motors......when they were current in Nascar......

Also have a set of larger 1pc valves ...in stainless....for a reasonable price...



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im starting to recommend roller cams, I know they are more expensive, but the extra power is worth it, and if a dinasour like me can evolve from flat tappet.



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Magician40 wrote:

Just watched that Youtube video and that car was a 4dr. Back doors have been welded shut and filled in.
Brian


 Actually maybe fiberglass, I know he said he had some glass work done to it, it was just a car to put a motor in when he had it. He had it for sale (sold) for $10,000, the motor was easily worth that. Ronnie has built 20 or 30 or more great 409's and is an old drag racer.



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63 Pariesienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC.

Mahone Bay, NS Still not old enough to need an automatic



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DonSSDD wrote:
Magician40 wrote:

Just watched that Youtube video and that car was a 4dr. Back doors have been welded shut and filled in.
Brian


 Actually maybe fiberglass, I know he said he had some glass work done to it, it was just a car to put a motor in when he had it. He had it for sale (sold) for $10,000, the motor was easily worth that. Ronnie has built 20 or 30 or more great 409's and is an old drag racer.


Yeah, I had an engine that Ronnie built in my 55 Chevy.

It was a stroked 409 (476ci) that was built for bracket racing.

My best 1/4 mile ET with that engine was 10.26 



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Barrie Ont.

409 powered 61 Poncho

best time 9.06@ 148 



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Update: I just got the engine home and now have it on a stand. Here are the numbers.

BLOCK:
3798962
GM4
CFO
176

HEADS:
3815857
GM3
42462

INTAKE:
3770083
GM1
C1880

EXHAUST:
3732783

Is this engine worth rebuilding and if so, what changes need to be made?

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The truck engines are a good starting point, they're very similar to the passenger car engines.

It would be no problem to build a nice 350 hp engine but these days, with the weak Canadian dollar, parts get a little expensive.

Show Cars is as good a place as any to get parts. They show engine rebuild kits on this page...  http://www.dr409.com/03_Engine-Int_03.html 

They can also give you advise and put together a package where everything will work together.

 

The main difference is that the truck engines have low compression.

All 348 blocks have a notch at the top of the cylinder but some truck blocks have an extra notch added to further reduce the compression. Your #962 block should have a single notch but it was right around 1961 that they did away with the second notch so it's possible that it has two. Either way you can get enough compression but the single notch blocks are the preferred setup.

The heads are fine for 350 hp or so but they'll probably have small valves so if you're rebuilding them, it would be good to put in bigger valves. Many people install 2.06 int. 1.72 ext. valves in the truck heads. (that's the size on valves used on the 340 hp 409)

There are also valve rotators under the exhaust valve springs on truck heads. You'll want to get rid of those and install new springs.

I'm not familiar with the casting numbers of your exhaust manifolds but all 348's had similar looking manifolds. Most had 2" outlets but some had 2 1/2" outlets. (the 350 hp 348 had 2 1/2" outlets)

I think your intake manifold is the same as the one used on the 305 hp 348 in 1961. It would be OK but it's probably set up for the smaller WCFB sized carb, so it would be nice to get a new aluminum Edelbrock intake.



-- Edited by jim_ss409 on Wednesday 25th of January 2017 11:47:16 PM

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Barrie Ont.

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best time 9.06@ 148 



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What Jim said + avoid installing hardened seats for the valves, there is a risk of going into the water jacket (I had this happen on a small block) and very little, if any, benefit.

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63 Pariesienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC.

Mahone Bay, NS Still not old enough to need an automatic



Poncho Master!

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I think installing hardened valve seats.....is a highly over-rated ...and usually unnecessary procedure...

Most of these old cars see so little miles........it's not needed.......great for taxi-cabs......and cop cars though....

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.....formerly 64 Custom Sport.....now appearing as MoboMac

    Fender dice,furry skirts and flames...just say NO...

These guys really know how to do a ROCK video...

https://www.youtube.com/watch?v=Pn0w7vciQCE

 




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All good info everybody. I think I'm good to go now. Looks like I'll have no problem getting an extra 100 hp out of this engine.

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