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Discussion Starter · #1 ·
Im building a std. bore 4 bolt main 350 for a fairly big long bed 4x4 lifted chevy k20 truck on 40's.

i have parts for sbc's brand new everywhere(collected over years)
this engine was rebuilt stock so its really clean and nice.
I need some advice on doing a budget build for as much power as possible.I cant really afford aluminum heads.Im thinking intake, flat top pistons,HEI,etc
Im a bit of a novice.This isnt going to be a drag racer though..more for 4x4'ing.


Here is the specifications to the cam that i have- (if you need more info let me know)

lift: intake @cam .291 / exhaust @ cam .291 / intake @ valve .436 / exhaust @ valve .436

Cam timing S.A.E @.006 valve lift- intake opens @ 43.5* BTDC Closes 76.5* ABDC
Exhaust opens 79.5* BBDC closes 40.5* ATDC
 

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You have a single pattern cam,a duel pattern cam makes a good lumpy idle.I'm thinking a RV duel pattern cam with 1.6 rockers would make some torque.Also long intake runners on the intake man.will make torque,also long tube headers with about 12" of 3" pipe bolted to the collectors will help to.This is what I've done to my Camaro,350 also.
 

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Im building a std. bore 4 bolt main 350 for a fairly big long bed 4x4 lifted chevy k20 truck on 40's.

i have parts for sbc's brand new everywhere(collected over years)
this engine was rebuilt stock so its really clean and nice.
I need some advice on doing a budget build for as much power as possible.I cant really afford aluminum heads.Im thinking intake, flat top pistons,HEI,etc
Im a bit of a novice.This isnt going to be a drag racer though..more for 4x4'ing.


Here is the specifications to the cam that i have- (if you need more info let me know)

lift: intake @cam .291 / exhaust @ cam .291 / intake @ valve .436 / exhaust @ valve .436

Cam timing S.A.E @.006 valve lift- intake opens @ 43.5* BTDC Closes 76.5* ABDC
Exhaust opens 79.5* BBDC closes 40.5* ATDC
In all likelihood that cam is going to idle nice and smooth. Do you have the duration figures at 0.050" lift?

In your case you could swap heads for a set of production Vortec heads and pick up in the neighborhood of 40-50 hp over stock smog heads. What's the casting number of the heads you have now?

You will definitely want to use a dual plane intake. You could use a stock Q-jet aluminum intake and a Q-jet carb. This combo will make very good low end power- and that's what you need w/tall tires and a lot of weight. For an aftermarket intake, the Edelbrock RPM (w/o Air Gap) would be a good choice if you were going to use a squarebore carb like the Holley 1850 or an Edelbrock. But whichever intake you go with, don't use a single plane.

Tuning the ignition timing curve is VERY important. Stock GM HEI distributors always need help in this regard. More on the HEI can be seen here.

Headers can help a lot, but they'll require a floor shifter and some custom exhaust pipe work to allow them to fit that chassis. If at all possible, use long tube headers instead of the easier-to-fit shorty headers.

What gears are you running? You'll want lower than "normal" gears to work well w/the tall tires and weight. How low will depend on how important offroad performance is over street. Just how will you use this truck? If you plan on really getting after it offroad you may need beefier suspension as well as a tough transfer care/transmission package, strong drive shafts/U-joints, etc.
 

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agree with cobalt,get the vortec heads,small tube headers if they fit, the cam needs 206-212 at 50 and 430 ish lift. a 106 to 108 icl would be very torquey. this all means a mild street cam with the intake centre line advanced.,,430 lift works well with vortec heads.If you port the exhaust side of the heads that helps a lot. The performer intake works well and if you run across a street master intake it will work well and are usually cheap.if you buy new,get the performer.
If you can afford an after market efi that is what you want for low end torque and less bothered by offroad bumps than a carb.If you have to have a carb then a 550 cfm carter or equivalent.
 

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SpeedPro shows a CS-112R cam with the .436 lift and 300* advertised duration. It shows 224* at .050 with a 108* LSA. If this is the cam you have, with 224* @ .050 and a 108* LSA it should have a lopey idle, but it's pretty long on duration for a 350 with a stock rebuild in a big 4x4 with tall tires. I would look for something with shorter duration, but a narrow 106 or 108 LSA like vinnie suggested. Comp Cams #12-310-4 260 AH-8 grind .444/.444, 260*/268*, 212*/218*, 108* is very close to the GMPP 350 HO and the Summit K1103 cams, which both have a mild lopey idle. The Comp Cam with it's tighter LSA would lope a little more, and make more torque. With the .444 lift it would work very well with vortec heads. The Crane 274 HO6/Elgin E1785P/Summit K00172 cam with .450/.450, 274*/274*, 218*/218*, 106 LSA would work but it's still a little long on duration.
 

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Discussion Starter · #7 ·
hmm, well im trying to do this on a budget, so these options are well,

but, i ALSO have a good running 1971-1972 402 big block contender for a build.
the truck is a freakin monster lol, so im in need of good power and torque.

would i be best with the 402 big block? or should i just junkyard search for a 454?

the 455 or cadillac 472/500 is too hard to find!
 

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6.2L diesels are a dime a dozen. Drop in, make some tweaks, make 600 lb-ft, get 20 mpg.

The cam you have will make torque, but it wont make it until 4000 rpms. Not good for getting a heavy truck moving. You need a mild cam with big cubes. Lumpy idle always means high RPM power/torque production. You can't have it both ways. You either need low end torque OR a lumpy idle. The lumpy idle comes from the cam being open too long to be optimal for low-rpm operation. It doesn't trap as much intake mixture in the cylinder which is why it doesn't make power until higher RPMs where the longer duration is better suited.

Finding a caddy 500 would be worth it, but its not as much of a drop-in swap as you would hope for. A big block chevy is a good choice. More cubes means you can have more torque down low.

Think of it this way: Lets say you want 400 lb-ft at 2500 RPMs. Doing that with a 350 means it will probably be a 250-hp wheezer at higher RPMs. Doing that with a 454 means it can be a 400-hp monster.
 

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for a larger K20 truck and those 40" tires that mild 350 will be a bit strained. it doesn't mean you can't do it but i dont think it is what most of us would start with. the 402 BBC wouldn't be bad but if you have the time then yes i would would into trying to find a 454 or even 502, a lot of the older Bluebird school busses used the 502's, they came factory with a forged crank, decent rods, so in a rebuild all that would likely be needed is a cheap set of pistons, the block cleaned up and the assy balanced. with the larger displacment BBC's it wont be hard to make 400-425hp and 600tq on a light budget.
 

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a lot of the older Bluebird school busses used the 502's, they came factory with a forged crank, decent rods, so in a rebuild all that would likely be needed is a cheap set of pistons,
Ummm... No. The 502 was never a factory-installed engine in anything. 502 is an aftermarket creation.

The only BBC gas engines installed in medium and heavy duty chassis were the 366 and 427T. It doesn't matter who made the bus body, the frame/chassis was designed independently, and GM never put a 502 in anything from the factory.
 

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chevrolet offered an 8.1 litre gas engine for some industrial applications,possibly other sizes too?

re 6.2 making 600 pounds torque? with what tweeks? and what would it cost to install?
 

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Here is a recipe for a 502 cid tall deck BBC using several different cams. The same thing can be done using a standard deck height block by using different rods.

Using a simulation program, they are at or over 600 ft/lbs. Real world? Can't say. Should be reasonably close though.
 

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Ummm... No. The 502 was never a factory-installed engine in anything. 502 is an aftermarket creation.

The only BBC gas engines installed in medium and heavy duty chassis were the 366 and 427T. It doesn't matter who made the bus body, the frame/chassis was designed independently, and GM never put a 502 in anything from the factory.

you're wrong

begining in 1974 through 1995, fleet vehicles could be had with a GM 366, 427, 454, and a 502.

1998 and up CV200 GMC B7 conventional chassis fleet vehicles have them as well.

here is a link to by a manifold for a 98-up GM fleet 502 engine:
http://www.unitedmuffler.com/images/pdfImages/SchoolBusCat/Chevy/3-Chevy-8.jpg

I personally have seen 2 of these complete engines in one of my good friends garage in virginia beach. this is the same guy who taught me how to work on engines.

do some research on it, you'll find out that you're wrong!
 

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here is a link to by a manifold for a 98-up GM fleet 502 engine:
http://www.unitedmuffler.com/images/pdfImages/SchoolBusCat/Chevy/3-Chevy-8.jpg
No, that is a link to some aftermarket parts that fit common BBC engine displacements.

Many 502s were made from tall deck truck blocks, but the 502 was never (and I mean never) installed in any vehicle as a factory option. In fact, the 502 didn't even show up in GMPP's performance catalog until about 15 years ago.

Its OK, you're young. You'll learn.
 

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chevrolet offered an 8.1 litre gas engine for some industrial applications,possibly other sizes too?

re 6.2 making 600 pounds torque? with what tweeks? and what would it cost to install?

Dropping a stock 6.2 in place is cheap. Buy one, hook up some wires, bolt it on and drive. Getting it to make 600# isn't too tough if you're crafty and in-the-know. If you just buy aftermarket parts and toss them on, you'll pay a lot.

Turbo from a 6.5, reworked stanadyne pump, modified prechamber cups, some other tweaks, and you're squarely in 600# territory.
 

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No, that is a link to some aftermarket parts that fit common BBC engine displacements.

Many 502s were made from tall deck truck blocks, but the 502 was never (and I mean never) installed in any vehicle as a factory option. In fact, the 502 didn't even show up in GMPP's performance catalog until about 15 years ago.

Its OK, you're young. You'll learn.



really guy, what are you old enough to be my dad or something, you're 9yrs older than me WOW!


like I said do some research and you will see that the 502 has been used is various fleet vehicles. I can spend 5 minutes online and find multiple different sites mentioning the GM502 fleet engine, and multiple sites selling replacement parts for it. The link I posted to you came off of here, take a look:

United Muffler - school bus GMC

The link I posted was not for aftermarket exhuast it was for BUS exhaust.

how are you going to explain the 98-up 454-502 CI gas Bluebird CV200 GMC B7 conventional Bus
 

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Ain't got no dog in this fight- but 87Z's right on the BBC 502. Moving on...

littleredridingwood, the 402 is a better choice than the SBC 350. But displacement is what you need. If you're on a budget, chances are that will mean no turbochargers or superchargers. The diesel option is all well and good- but that's going to require a lot of finnessing to get the kind of power that a 454-up BBC will get you NA and will be an easier to build option IMO.

Unfortunately, finding a good 454 core is getting harder every day and the cost is rising as well. I hear how there are good $200 454 cores- until you go to pin one down, then just like $5.00 Q-jet cores- suddenly they are nowhere to be found.

The best deal I have seen recently was on a Demon reman 454 engine in a CC article, Cheap Big-Block Chevy Engine Build. Who knows what the current pricing is like, but you could easily find out.

Searching the machine shops in your area might turn up something that was left behind, then there's craigs and eBay, etc. But you already know all that.
 

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^^^^^Cobalt327


That is what I started out saying in the first place. If you are willing to scower junkyards you should be able to find a factory 454, and possibley a fleet 502 if you get really lucky. I would bring a jump box and a compression tester, not make sure the cylinders are okay but to make sure there are no major issues. tons of 80's and 90's GM work trucks, utility trucks, tow trucks, you can find them in lots of medium duty chassised Chevrolet Kodiak/GMC Topkick, B6, B7 fleet vehicles. If you where to look through these you could use the 7.0L 427T block as well.

with one of these engines you could easily just buy a plain jane rebuilder kit (although I'm not a fan of these), splurge and buy a set of aftermarket iron heads (used or new) go with a mild cam, and it would be easy to make a minimum of 400-425hp and 550-600tq all day long.
 
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