350 to inline 250 Swap

[2bits]

To start off with I wouldn't recommend any A/C bracket setup that utilizes idler pulleys, it's just a waste to me and it's only real purpose is to get the belt around the water pump. It is better to just get the third pulley that slips over the OEM WP pulley and use it. The kit I was supplied used one of the idlers to create the belt tension, not rotating the compressor. I am soo glad I didn't toss that original A/C bracket that happened to be with the engine when I bought it as it cleaned up nicely and worked perfectly with the tension adjuster right where it should be, on the bracket! Unlike the craziness with the power steering pumps on these engines, this setup is really simple as there is only one bracket you need aside from the two pulleys that go on top of your existing pulleys.

The bracket I have is like the factory one and has a vertical bar that goes down and bolts near the timing cover. This is fine except it is exactly in the way of the lower radiator hose, the factory hose is fine and routes around this, but unfortunately, I have a radiator for a 350 and the opening for the hose is bigger and the 6 cyl hose won't fit, so now I need to get a whole new 6 cyl radiator just so I can get the factory hose for A/C to fit (a flex hose didn't work very well). hmm... now I am scratching my head... the compressor bracket from Old Air is $85 and the new radiator is $250, I can swap the bracket a third time to the Old air version and get rid of that vertical bar altogether, and I can use my old straight radiator hose again! hmm.. thanks guys, responding to this post led me to my solution!

If I was going to do this from scratch again, I would get the complete A/C system from OldAirProducts.com end of story. They have great prices and all the right brackets and pulleys you need. The 6-Cyl compressor bracket is the best design I have seen yet. I attached a pic of their bracket, this is the one to get!

[LEEVON]

Originally Posted by Pyrotechnic

What would be really bad ass is a Vortec 4200 I6 out of a Trailblazer. V8 power, 4 valves per cyl. I'm sure you could get really great gas mileage while still having lots of fun.

I keep wishing that GM will make this the base motor in the Silverado instead of the 4.3 but it looks like the 4200 will forever be in the Trailblazer and won't ever be offered in another vehicle. They could really give the import trucks a run for their money if they did, considering that even though the 4.3 is cheap to make, it gets worse gas mileage than a V8.

That would be cool, except my wife's dang T-blazer 4200 2wd gets about 14-15 mpg

[70 GMC Trucker]

Could you tell me what the distance is between your bolt holes for your radiator shroud are ? I have a 70 GMC that had a 6 cyl and now has a 350 and am in need of a shroud and it seems that there is a two inch diiference ( 26 1/2 or 28 1/2 ) Any help ???

[BurnoutNova]

its off topic, but is your truck a blazer frame with a truck cab and cut down bed on it?

[70 GMC Trucker]

No , a straigth six has a rad shroud that has bolt holes that are 26 1/2 inches apart ,apposed to a 350 that has a shroud with bolt holes 281/2 inches apart. My problem is that I need a shroud for my 350 , radiator CU101 four core rad that is 26 1/4 x 17 x 2 1/2 whcih is two inches less than a stock 350 ???

[2bits]

Myself, I am not sure about the 6 Cyl because I have a 350 radiator and 350 shroud.

Burnout Nova, my truck was a long bed stepside that he cut down the "wrong" way. The middle was not cut out, the rear of the frame was cut off out almost all the way up to where the rear coil springs sat and a Leaf spring rear end was bolted onto the frame about 18" forward. I got it for a deal so I took a chance on it figuring the front clip alone was worth it, but it is working out great with a little tweaking.

[RJGeister]

2bits,
I have an old manual box that's shot and I want to put a power steering on my 250. Where did you get the power steering set up? Is it off of the Nova?

Rich

[2bits]

I got lucky when I went to the junkyard and found a integrated head 250 van with the complete setup. Everyone says the pump brackets wouldn't work, but they fit perfectly for me, so I dunno. When I bought a new pump at the store, I remembered that they don't come with pulleys so I had to go back to the yard and get a used pump just for the pulley. I figured I would just get the whole pump so I could use it as a core too, and it would probably slip through the cashier with the brackets on it, so I was lucky enough to find a second one on a 1980 292 truck and bought the whole thing. I laid all the brackets side by side and they are identical, and it worked on my non-integrated head 250, so I do believe I have a complete spare bracket set for you, but I have a feeling I was missing one thing, but I'll check it out to be sure and let you know. I will want to sell it, but not at an outrageous eBay price tho! Will you need a water pump pulley with two grooves too? I have one. The crank pulley should already have two grooves.

Funny thing is the used pump I bought was full of water and I left it sitting for a week upside down and put it on just for kicks (a new pump was $75) and it has been working perfectly, so I took that new pump back!

[SCOTI]

2bits, I'm not sure if you found a solution for you radiator/hose/bracket dilemma but I have a suggestion.

I swapped to a V8 radiator when I was prepping my 68 for the road just after purchasing. The radiator was only a couple of months old when the vehicle was totaled so I figured it would be better than the original 6cyl's 2-row unit.

As you mentioned the lower hoses are different sizes. I used the water pump end of the original 6cyl hose & used the radiator end of the donor vehicles hose (in my case a 78 elcamino). I cut the hoses in an area where they could be 'optimally' spliced together & used an exhaust 'reducer' from the parts house to complete the splice.

All it took was a couple of extra worm clamps & I had a custom hose for cheap. I never had any problems w/the radiator or hoses & used that set-up until I tore the truck down for my current V8/auto swap (4+ yrs of use).

LIke I said..... just a suggestion.

[2bits]

Nope, I have been figuring I was going to have to get that $85 Old Air bracket, but oh man that is a great idea! Clamp that sucker on there, add a small section of larger hose to hit the radiator and there you have it! Those reducers are solid, and I have one left over from when I had the temporary flex pipe on the truck, maybe I'll get lucky with the sizes on that but they are cheap anyway.

That's one for the books, thanks alot, I am going to do that tonight, and I will get to drive my truck again!

[SCOTI]

Originally Posted by 2bits

Nope, I have been figuring I was going to have to get that $85 Old Air bracket, but oh man that is a great idea! Clamp that sucker on there, add a small section of larger hose to hit the radiator and there you have it! Those reducers are solid, and I have one left over from when I had the temporary flex pipe on the truck, maybe I'll get lucky with the sizes on that but they are cheap anyway.

That's one for the books, thanks alot, I am going to do that tonight, and I will get to drive my truck again!

They had several different sizes when I got mine so you should find what you need. I also used new hoses for each end & trimmed off what I didn't use (putting the splice in a 'straight' section) & used the compression spring for the hose that was on my 68.

[2bits]

Rich, Here are the PS brackets for ya, they are degreased pretty good,

I'll PM you for the particulars. See the second pic for the only problem I ran into... the belt lining up. See the 3rd pic for the solution... different pulleys. Some models came with a wider space between the grooves. I don't know where you would get one of these but you would need that and a crank pulley too. The auto parts store should have the crank pulley since it is the same thing as the harmonic balancer, but that's alot of extra $$$. I guess that's why they won;t usually work on a 250, but with the right pulleys they will!

[RJGeister]

Looks good. Thanks for the info and the PM. Will let you know ASAP.

[dhunt00c]

All this talk makes me want to ditch my plans on a 383 stroker and make my little 250 a hot number!!! Does anyone know if you have to move the motor mounts that bolt to the frame itselt up a slot (towards front) when you swap from a 6 to a V8 smallblock? There are 2 spots to bolt the mount to the frame, just wondering if its the same or you move it up?

You all rock!
DH

[2bits]

Hey DH, Check out this very same thread from the beginning tho, this chronicles my doing that exact thing. Yes the "perches" as they are lovingly called need to be moved, but back, not forward, the 6 cyl location is in the rear so you might be ok.

My 350 (Passenger side)


For the 6

[OhNoJoe]

Is that POR on the front frame? Where did you get your pully with the wider grove? I'm looking to put PS in my 63 but after 9 years as a DD I'm starting to get used to the manual steering.. but with my 72 burb it's just a little too heavy.

[2bits]

Yeah, after a swapped the 350 for the 6, I almost didn't need power steering, it was alot easier, but man, once I got it, I wouldn't give it up! I wish that was POR 15, I was on a time crunch to get the engine in (self imposed I guess), so that is just black spray paint.

I found the pulley's off a 292 I found in my local junkyard. I was real lucky to find it. You can get the lower pulley from the auto parts store new because it is a harmonic balancer, but the top pulley might be hard for you if you don't have any good junkyards around.

[RJGeister]

2btis,
You wouldn't have made a note of the numbers stamped in the pulleys? Might be able to use them to narrow down the vehicles that they were installed in.

Rich

[OhNoJoe]

I got my 292 pulled and striped over the weekend plus a few days. I ordered the parts for many up grades and wil be sending it off to the machine shop soon. Is there anything I need to be watchful of or ask about???
Should I insist on certain rings or piston. I have seen a big differance in prices. I don't want just an econo set-up but I don't need a motor that will done under 10 in the 1/4 mile either