84 K10 305 to 350 swap

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CSFJ

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One other point I haven't seen mentioned. And it's only relevant if you've still got the factory 305 exhaust manifolds instead of headers. The #7 cylinder has a wider bolt spacing than the 350 head will have. By default, the #2 cylinder should also, but I don't recall that being a problem the last time I went to a 350 from a 305. Only the passenger rear most cylinder because I didn't have the budget to have the exhaust modified to work with the proper 350 manifold, I had to cobble up a clamp of sorts to hold the very back of the manifold flange to the head on the passenger side.
 

Ewhitaker0020

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One other point I haven't seen mentioned. And it's only relevant if you've still got the factory 305 exhaust manifolds instead of headers. The #7 cylinder has a wider bolt spacing than the 350 head will have. By default, the #2 cylinder should also, but I don't recall that being a problem the last time I went to a 350 from a 305. Only the passenger rear most cylinder because I didn't have the budget to have the exhaust modified to work with the proper 350 manifold, I had to cobble up a clamp of sorts to hold the very back of the manifold flange to the head on the passenger side.

Currently I have the 305 factory exhaust manifolds, but I don't plan on keeping them when I go to a 350. I have some headers, and I think they work for either a 305 or 350 but I can't remember. I think the bolt holes are elongated.
 

1987 GMC Jimmy

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Will this 89 TBI block be set up for a roller cam? I found it on Facebook for $100.

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Unless it came out of an F Body or 9C1 Caprice, it won’t have one installed, but it will accept the roller cam. You’ll just need the installation kit. Make sure it’s got the fuel pump block off plate, and if the block’s drilled already behind the plate, I think that makes it totally worthwhile and makes your job a bit easier. My ‘87 block has the mount for the pump, but the block isn’t tapped for the pushrod, and that is the case for the 87-95 blocks sometimes. Also, if this engine isn’t tired, that’s a screaming deal. If it’s rebuildable, it’s still good because it’s on the stand you gotta strip it down to the short block anyway, but if you could do a wet/dry compression test on it, check for constant blowby (startup smoke is usually valve seals, which doesn’t matter in this case), and make sure it doesn’t have bottom end knock, that would bring it all home. See roller installation kit below:

https://www.summitracing.com/parts/...mqo1zTpiVJxZx9N4k2aJ7D8FjwrA9y8hoCwjcQAvD_BwE

Oh, and it’s a serpentine setup. I’d get it for sure. I like v belts better in principle, but serpentine opens the door to more options for a Sanden compressor conversion down the road. I don’t hate the R4, I’ve actually had exceptional luck with them, but I’d be stupid to sit here and pretend like it’s not just about the worst auto A/C compressor design out there.
 
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Ewhitaker0020

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Unless it came out of an F Body or 9C1 Caprice, it won’t have one installed, but it will accept the roller cam. You’ll just need the installation kit. Make sure it’s got the fuel pump block off plate, and if the block’s drilled already behind the plate, I think that makes it totally worthwhile and makes your job a bit easier. My ‘87 block has the mount for the pump, but the block isn’t tapped for the pushrod, and that is the case for the 87-95 blocks sometimes. Also, if this engine isn’t tired, that’s a screaming deal. If it’s rebuildable, it’s still good because it’s on the stand you gotta strip it down to the short block anyway, but if you could do a wet/dry compression test on it, check for constant blowby (startup smoke is usually valve seals, which doesn’t matter in this case), and make sure it doesn’t have bottom end knock, that would bring it all home. See roller installation kit below:

https://www.summitracing.com/parts/...mqo1zTpiVJxZx9N4k2aJ7D8FjwrA9y8hoCwjcQAvD_BwE

Oh, and it’s a serpentine setup. I’d get it for sure. I like v belts better in principle, but serpentine opens the door to more options for a Sanden compressor conversion down the road. I don’t hate the R4, I’ve actually had exceptional luck with them, but I’d be stupid to sit here and pretend like it’s not just about the worst auto A/C compressor design out there.

If the block has the block off plate but isn't tapped, can the machine shop drill it out? I'd be lying if I said I wasn't excited about changing back to the single serpentine belt setup instead of the 3 v belts.
 

1987 GMC Jimmy

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If the block has the block off plate but isn't tapped, can the machine shop drill it out? I'd be lying if I said I wasn't excited about changing back to the single serpentine belt setup instead of the 3 v belts.

Yes, they can, but I’d still ask them individually to make sure they don’t shaft you. I’m sure there are some people who could do that with their eyes closed while in their backyard having Miller time, but I’m not one of them so I’d commission a reputable machinist to do it for me. Are you planning on having the short block rebuilt?

Pros and cons on the accessory drive. Individual belts are usually cheaper, but adjustment can be a bitch if you don’t have three arms and hands. If a belt slips, it’s a little harder to narrow down, but I had an issue where a serp belt slipped off a little/or I didn’t seat it in the grooves properly and a rib got chewed off.
 

Ewhitaker0020

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Yes, they can, but I’d still ask them individually to make sure they don’t shaft you. I’m sure there are some people who could do that with their eyes closed while in their backyard having Miller time, but I’m not one of them so I’d commission a reputable machinist to do it for me. Are you planning on having the short block rebuilt?

Pros and cons on the accessory drive. Individual belts are usually cheaper, but adjustment can be a bitch if you don’t have three arms and hands. If a belt slips, it’s a little harder to narrow down, but I had an issue where a serp belt slipped off a little/or I didn’t seat it in the grooves properly and a rib got chewed off.

Yes I am. At a minimum I'm doing a cammed 350 with updated roller lifters and vortec heads, headers, Edelbrock intake and carb. There's a chance I'll go bigger and do a stroker 383 and change the whole rotating assembly. But even though that's a good idea I doubt I'll go that far just because of money.
 

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Gotcha. I like the Quadrajet, and that’s what I’d do with the Edelbrock intake. I depend on one with my daily driver, and bear in mind it’s the vilified E4ME feedback model, but it’s let me down zero times, and the original owner had the same results. That’s almost 300K miles of trouble free service for going on 35 years with one rebuild done as preventative maintenance; even though it looked disgusting and slimy before, it still ran like a top. A Holley might survive that long, but the amount of people that come on here with Eddy carb calibration/programming, choke issues, it’s not doing this or that, my truck runs like **** with them makes me think that’s not the case for them. Some people like them, and I’m sure there are perfectly good reasons why, but I’m not one of those people. I like the high, variable CFM of the Q-Jet, the integrated fuel filter, small primaries, small fuel bowl, the steel fuel line going from pump to carb... It’s well ahead of anything Holley or Carter ever made in terms of design and quality, and the latter two have been making carbs for thirty years sans new Quadrajets in the picture, but who’s still the best? You can also rebuild/reprogram the Quadrajet for cheaper than buying a new carb.

The Vortec intake options are slimmer than regular head intakes. I see that Jegs has one for somewhat cheaper, and I don’t know what options Summit or Holley/Weiand has, but I’d keep an open mind at the benefit of saving money.

For a cam, I’d see what Comp has going on, but there are a few other good brands. I like for my HVAC, cruise, brakes, and whatever other vacuum accessories to work so I wouldn’t go crazy with it. I’m more privy to the hydraulic flat tappet options so I can’t offer you a solid recommendation. I think Gen II style small block cams are desirable, like an LT4 hot cam, and the performance oriented LT 350s were hot little motors once upon a time in the 90s. That’s probably something I’d go with if it didn’t screw up my manifold vacuum stability.
 

Ewhitaker0020

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Gotcha. I like the Quadrajet, and that’s what I’d do with the Edelbrock intake. I depend on one with my daily driver, and bear in mind it’s the vilified E4ME feedback model, but it’s let me down zero times, and the original owner had the same results. That’s almost 300K miles of trouble free service for going on 35 years with one rebuild done as preventative maintenance; even though it looked disgusting and slimy before, it still ran like a top. A Holley might survive that long, but the amount of people that come on here with Eddy carb calibration/programming, choke issues, it’s not doing this or that, my truck runs like **** with them makes me think that’s not the case for them. Some people like them, and I’m sure there are perfectly good reasons why, but I’m not one of those people. I like the high, variable CFM of the Q-Jet, the integrated fuel filter, small primaries, small fuel bowl, the steel fuel line going from pump to carb... It’s well ahead of anything Holley or Carter ever made in terms of design and quality, and the latter two have been making carbs for thirty years sans new Quadrajets in the picture, but who’s still the best? You can also rebuild/reprogram the Quadrajet for cheaper than buying a new carb.

The Vortec intake options are slimmer than regular head intakes. I see that Jegs has one for somewhat cheaper, and I don’t know what options Summit or Holley/Weiand has, but I’d keep an open mind at the benefit of saving money.

For a cam, I’d see what Comp has going on, but there are a few other good brands. I like for my HVAC, cruise, brakes, and whatever other vacuum accessories to work so I wouldn’t go crazy with it. I’m more privy to the hydraulic flat tappet options so I can’t offer you a solid recommendation. I think Gen II style small block cams are desirable, like an LT4 hot cam, and the performance oriented LT 350s were hot little motors once upon a time in the 90s. That’s probably something I’d go with if it didn’t screw up my manifold vacuum stability.

I already have my freshly rebuilt Edelbrock 600 CFM carb so I'll probably just stick with that. I'll also probably just grab an Edelbrock intake and be done with it.

I also rebuilt my original qjet carb, but I could never get it to run right. I'm sure it was more my fault than anything though.
 

Devin W

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It is a direct swap nothing special needed except you may want to make sure the torque converter stall is correct. My 305 had a 1300rpm stall and the 350 I bought required a 1800rpm stall converter, the difference would be noticeable off the line at a stop light. Too low of a stall could make it a dog off the line, the higher stall isn't noticed in normal driving IMO.
 

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