1990 C60 350 engine question

[choptop]

Our church has a 90 C60 schoolbus with a 350/ Allison combo in it. Well, it has about 130000 miles on it, a 2 barrel carb, and is somewhat lethargic. Several of us at the church are gearheads and it just isnt cool enough for to represent God in our opinion ( or you could just say its too slow for us)
We are considering rebuilding the engine, going to a 4 barrel carb, and see if we can make it breathe a little better. ( We still have to take a vote on the single chamber flowmaster tho )
  My question is, is there a difference between this 350 in the heavy duty application, and the standard 350? The reason I ask, is I replaced the starter a few months back, and it bolts to the transmission with 3 bolts. I dont remember seeing the flange where the normal starter bolts to, but didnt really look for it either. I cant get to the casting number on the block because of all the extra garbage on it, tho I may try again later this week with my mirror and flashlight. Anyone know if there is a difference so I can order a rebuild kit for it?

[Captkaos]

Should be the same. I think the starter mounts like that because of the trans.

[eventhorizon66]

Talk oldyeller into donating her 454.  That'll give the bus some pep and it'll make room under her hood for one of these.

[exilous]

haha i wish i could have a 572...although it would cost me a small fortune to keep fuel in the beast.

[choptop]

If it was financially feasible, Id just put the 572 in the bus I am the primary driver anyway and at least then I could enjoy it more. Overall, the bus runs pretty good. It does foul the plugs on the right side every so often, and uses a little oil. We are considering running a leakdown test and if the bottom end turns out ok, may just refurb the heads and put a 4 barrel on it. If the bottom does give way, at least the topend would be ready. If it is just a standard block, I have a Goodwrench 350 in my 79 that has about 20,000 miles on it, so We could judt swap it one weekend. Im sure the bus would have a 4 bolt main in it as well, so I could rebuild it for my purposes.

[Russ130]

That 350 is way better than a stock 350. If it is the original motor it should be a high alloy low core shift 4 bolt #3970010 block.

[Blue 82]

Since it's a 90 it will have a 1pc rear main seal block
4 bolt main with the fuel pump rod provision drilled
This will accept a OEM roller cam

The heads should be the 6217 or equivilant with 3/8" sodium filled exhaust valves like the marine engines
(there is another casting number, I can't think of it off the top of my head, but I do have a set in the garage)

GM made a cast aluminum 4 barrel Q-Jet intake to fit the 86 up style heads
I have one of these in the garage somewhere, i can dig it up and get the casting number
Or you can find a 79-81 camaro/vette intake and hog out the center bolt holes.
Once in a while you can find em on Ebay for $25-$40

I would use a roller cam
GM made some L98 roller cams with the fuel pump lobe
In the garage I have one, I can get the cam ID number if you like
Again Ebay for about $50
New LS7 roller lifters are $129
Ebay the spider and dog bones for $20
L98 valve springs are cheap as are pushrods
A bronze tip fuel pump rod is a must
Don't forget the dist gear also
A ZZ4 dampner is a good idea too ($80 or less)

If the engine is supported by a single mount the attatches to the front of the block
you can run Rams horn exhaust manifolds or shorty headers to clear the tranny

Pocket port the heads
and give em a decent HD valve job (think marine seat specs, due to the heavy loads)

A set of H345NP slugs are $12 each
a good Hyper flat-top if she needs to be bored

A rebuilt Q-jet from you local carb shop should do the job
as long as it has a functional electric choke

This should get you in the 275 hp range with lots of low end torque
If ya need a little more TQ, stroke it with a dished slug
but the flywheel/flexplate for the allison may have some balancing issues

[choptop]

Thanks Blue82, I appreciate the info, and will look into the majority of it. We found an Edelbrock with the manual choke (bus is setup for manual choke) and one of the guys thinks he has a square bore intake. I need to check the engine to see if it has the Vortec manifold. We may just order the proper intake when the time comes. We'll see. Thanks again

[Blue 82]

The 87 up intakes have the four center bolts at a 72* angle vs the pre 87 which has the 45*
if should have center bolt valve covers and 6 intake bolts per side.

Got any boat yards near you? The factory 87+ non vortec for marine applications would work well in your bus with a Q-jet.
they just about give those marine manifolds away, spend your money on a decent carb
In all reality a $150 intake manifold ain't gonna do squart for a school bus
they look like this
http://marine-performance-parts.com/cai8701987sbchighrisecastironintakemanifold.aspx

[choptop]

I forgot about the center bolt valve covers. If thats the case, then they arent Vortec. As far as being the original, It seems to be with all the smog garbage etc that was on it but after about 19 years, who knows what has changed. Regaurdless, I think the two barrel needs to go.