"Hotrodding" my truck

clutchdust

Millionaire Playboy
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OK, that may be overstating the issue a bit. Anyway, it's a 1-ton with a 454. It had a bad piston in it when I bought it a couple months back so I overhauled the engine and installed a Comp 256 cam. I chose the 256 because the truck never sees more than 4000rpm and I wanted more torque for towing. It runs well now and has decent power but now I'm thinking of what I can do to maximize what I have for minimal investment. My thinking is the best way to take advantage of the engine in general and cam specifically is to open up the exhaust. Right now it has a 2-1 design with 2.5" pipes off the factory manifolds that merge (rather poorly) into a single 3" pipe, then hits the muffler and cat back by the back axle. So my thinking is to leave the factory "log" style manifolds on but have the crappy pipes replaced with mandrel bent pipes into a true "merge" collector, then run into a good muffler (I'm thinking Dynomax) and ditching the big, heavy pellet-type cat for a newer free flowing cat. I'm hoping all this will give me another 25hp or better. If I can get 25hp out of it, plus a little nicer sound and maybe even slightly better economy it will be well worth it.
So do you think my expectations are unreasonable?
 
I am certainly no expert but it sure sounds like your expectations are within reality. I'd say go for it, who knows, the old cat may be clogged up a bit anyway.
 
OK, that may be overstating the issue a bit. Anyway, it's a 1-ton with a 454. It had a bad piston in it when I bought it a couple months back so I overhauled the engine and installed a Comp 256 cam. I chose the 256 because the truck never sees more than 4000rpm and I wanted more torque for towing. It runs well now and has decent power but now I'm thinking of what I can do to maximize what I have for minimal investment. My thinking is the best way to take advantage of the engine in general and cam specifically is to open up the exhaust. Right now it has a 2-1 design with 2.5" pipes off the factory manifolds that merge (rather poorly) into a single 3" pipe, then hits the muffler and cat back by the back axle. So my thinking is to leave the factory "log" style manifolds on but have the crappy pipes replaced with mandrel bent pipes into a true "merge" collector, then run into a good muffler (I'm thinking Dynomax) and ditching the big, heavy pellet-type cat for a newer free flowing cat. I'm hoping all this will give me another 25hp or better. If I can get 25hp out of it, plus a little nicer sound and maybe even slightly better economy it will be well worth it.
So do you think my expectations are unreasonable?

I think a new Magnaflow Cat will give you better milage. As for the rest, don't expect too much Gary.
 
dual exhaust never hurts :D

but I assume you wouldn't pass smog testing in NV ???

how much room do you have there? There are BB stainless headers on Ebay for $200 ....

Don't expect too much from just an exhaust upgrade, I was very disappointed with my Mustang exhaust: found that the cat came aprt and a piece of ceramic crap plugged the muffler.... I went all out and built a 2.5" exhaust with no cat and Magnaflow muffler... very little performance increase (if any)... and that is from a clogged up 1 7/8" pipe to free flowing 2.5"

sound is pretty good though :) :D
 
Actually, I'm planning on sticking with the 2-1 design if for no other reason than simplicity. I also don't really plan on "gaining" 25hp from the exhaust, just letting 25hp out that's all clogged up. Since I'm sticking with the 2-1, I will also put a cat on it too. Just a generic 3" kind should work fine. Smog isn't an issue where I live but who says I don't do my part?
 
I dont know what year your truck is, but i had a '90 454ss and it responded well to headers with a 2 into 1 3" borla setup. Getting rid of the pellet cat made a big seat of the pants difference. I remember reading something to the effect of a 20 hp increase since they are so choked up. There mark iv tbi trucks also used a crappy 2bbl adapter on a quadrajet manifold which i read always caused 1,2,7,8 to run lean.
 
Well I could believe the lean part. When I first got the truck I had to overhaul the engine because #7 piston blew a ring land into the oil pan. But this isn't a Qjet manifold with an adaptor, it's a cast 2bbl TBI intake. As shitty as the mileage is on this I don't know if I could stand to run it much richer.
But I know the cat is a big plug and that's where I'm expecting most of the gain. I'm guessing roughly 25hp, maybe a bit more, by doing the entire exhaust but I'm betting 75% of whatever I get will just be for the different cat.
 
What year is it? The mark v blocks that came in the 91 - up trucks had the 2bbl manifold and a one piece rms.. and i think siamesed cylinders though i cant remember for sure.

I know changing the cat will help. The other big change is heads.. those peanut port truck heads are çomplete pieces of shit.
 
It's a 93. Actually, for what I'm doing, I think the peanut heads are pretty much ideal. Truck never sees 4000rpm and is about 8000# going down the road. I need torque. I say I'm hoping for 25hp but in reality I suppose it would be more accurate to say I'm hoping for 25lbs/ft (or more).
 
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