Which 350 ?

Should I forgo my notion of hopping up my 305 and follow the most popular suggestion of going to a 350,
the huge question becomes:

What 350 to start with??

I want NO computers, hence NO fuel injection.
I want a 1 piece rear main so I don't have to purchase a new flywheel.

Should I be looking for a Vortec engine?

Then you’ll want to play it safe for the RMS and go with an ‘87+ short block. You want carburetion so I would recommend a block no later than 1995. IIRC, that’s the year they discontinued the opening and flange for the pump rod and pump. I would urge you not to go electrical with the pump. Not a Vortec (1996-2002) per se, but Vortec heads would be an option worthy of consideration. There are also a plethora of aftermarket cast iron and aluminum options out there. You have to be careful with used Vortecs because they have been known to crack. Also, the stock valve springs are supposedly only capacitated to handle a valve lift of .450 before you need to upgrade them. Remember that Vortec heads will require a Vortec carb intake, and that’ll run you higher on the price, but again IIRC, the price isn’t too rough for carb intakes. The newer block will give you the option of a roller cam if you’re interested in that. Plus, you’re not running a computer so you’re not backed into a corner with cam selection. As far as Summit vs. Comp grinds, a former, well respected member on here said that the Summit grinds were solid, but they feature a wide lobe separation angle vs. the Comps which use a narrow lobe separation angle. Pros and cons to both, and I suggest Googling some literature and articles on that. I would recommend going with an electric choke Quadrajet and therefore a spread bore intake.

As far as the 305 goes, you have the 416 heads, which is a good start for a 305, but I wouldn’t run a 305 in a truck of any kind. My car has the L69 305 as you do, and it’s okay in my application, but I’m not doing truck stuff. I know that when the time came for a rebuild, I’d have to do head work, a new cam, lifters, timing set, headers, etc. to get the best results out of it as (hopefully) a 300 hp motor. That or go to a 350. The current configuration gets annoying, which I’m sure you can attest to. If it were me, I’d go to the 350 and sell the 305. Now, was this a Camaro engine that someone swapped in or just a head swap? Trucks came with 601 heads. If you have an aluminum intake from a car of any sort, that might be worth holding onto. My 305 has a factory aluminum intake.

Interesting note about 416 heads on my engine.
The serial # on my block (K0190560) does not match that of the truck, nor does it appear to be any form of s/n for a vehicle installed motor. May have been a crate motor; not sure.
I wish I could see the casting # on the rear flange, but a wiring harness and limited accessibility have not permitted me to see nor photograph that #.
I have read that the '83 and later 305's had flat top pistons.
If my engine has them, I should have a compression ratio of 9.5:1
That would help.......

As for all the truck references..........I have a truck. No two ways about it.
1984 C-10 Scottsdale Stepside
However, when it comes to "doing truck stuff," that is not my primary focus.
I have removed the TH350 and installed a Muncie M20 4 speed.
Maybe someday upgrade to 5 or 6 speed if I get lucky.
Definitely NOT your typical truck setup.
My focus is shifting gears and having fun rather than having a utility vehicle.
That being said, let us not dwell on keeping this setup a "truck stuff" first project.

I have not ruled out the 305 hop up angle.
I will price out the headwork on Monday when the "Cruisin' the Coast" event is over.
If I can achieve 300hp with head work,cam and intake in addition to the other stuff I already have, that may suit me for now.

1987 GMC Jimmy said:

I would urge you not to go electrical with the pump.
.

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How come??

I understand. The utilitarian component of a truck is the first thing that comes to mind, but not everyone does that with them. That’s fine. I have a 305 here that was apart forever ago, but I can’t remember for sure what pistons it came with. Yours might be a crate 305. My car came with an LG4 305, and when the PO put a Jasper engine in there, it was a Camaro L69. I’d be careful doing the math on the 305 hop up. My math came out to 300 doing the works on mine, but I may have been too optimistic. There maybe a different approach that can squeeze more power out of it reasonably.

With the pump, it’s simplest to do the mechanical. If you have the proper steel lines, it’s foolproof. Electric, in-tank setups are fine, but then you’ll need a regulator for the carb. I don’t trust the little external pumps at all. Unless you’ve wiped the fuel pump eccentric, there’s no reason for an electric pump. I have gotten a lot of reliable miles on my 305 with the mechanical pump.

1987 GMC Jimmy said:

With the pump, it’s simplest to do the mechanical. If you have the proper steel lines, it’s foolproof. Electric, in-tank setups are fine, but then you’ll need a regulator for the carb. I don’t trust the little external pumps at all. Unless you’ve wiped the fuel pump eccentric, there’s no reason for an electric pump. I have gotten a lot of reliable miles on my 305 with the mechanical pump.

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As I have dual tanks, the pump would need to be external. What ever happened to the fenderwell mounted electric pumps?? No good ??

dual in tank pumps are an option, but you’d want a nice reliable regulator to get the pressure down to 5psi or whatever it is your carb wants. Then you’re getting into electronic stuff with the pumps and relays which is what you didn’t want in the first place, right?

Some people use them and maybe even like them, but I’m not one of them. My dad tried that on a ‘86 K10 project, and I thought it was the most cobbled together, piece of crap setup. It would have to be relayed and oil pressure safetied to avoid flooding the engine or turning the truck into an incendiary bomb. I also have read literature on pulling pumps working harder than pushing pumps, and they don’t last as long. It makes sense. A pump in the tank is always submerged in cool fuel and the pickup is submerged because the fuel is right there. The external isn’t as fortunate. I know that GM tried the external pumps on the P30 motorhome chassis to help the mechanical pump and prevent vapor lock, and it didn’t work out for them. They had to go to an in-tank pump after a few years. Bottom line, is I don’t think it’s worth doing when all you have to do is just bolt on the mech. pump and run it.

By the way, I have a house in Diamondhead so I guess I’m pretty close to you. This is a busy year for me, but I’m hoping I can do Cruisin’ next year.

Frankenchevy said:

dual in tank pumps are an option, but you’d want a nice reliable regulator to get the pressure down to 5psi or whatever it is your carb wants. Then you’re getting into electronic stuff with the pumps and relays which is what you didn’t want in the first place, right?

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Very useful information!
ages ago the electric fuel pump just got mounted on the fire wall or fenderwell and was self regulated. It would pump up to whatever pressure then shut off.
But I understand the need for all the safety jazz.................
I'll definitely be seeking a motor set up fopr mechanical fuel pump.
Thanks to you and Jesse !!

Any money spent increasing power would be better spend on a 350 unless its parts that can be re used on the 350 that said, a crate vortec supposedly has the boss for mech pump check into this before purchasing. Hell I believe the motown block that uses ls heads has the fuel pump boss also... how crazy you want to get?

4WDKC said:

Any money spent increasing power would be better spend on a 350 unless its parts that can be re used on the 350 that said, a crate vortec supposedly has the boss for mech pump check into this before purchasing. Hell I believe the motown block that uses ls heads has the fuel pump boss also... how crazy you want to get?

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That is the plan. Make sure purchased parts will be usable on a 350. Should work for all except head work on 305 heads.

Get a vortec 350. 1 piece rear and just really needs the intake and a fuelpump to make work with a carb. (Bout to swap mine in just need to address the fuel pump issue as im not positive mine has the cam lobe for a mechanical pump). In my opinion best economical way to start.

Just look at the dyno figures compared to any other 350. Torque all over the place and is cheap. I bought a full engine for 420$ so no need to piece it together. Vortec heads are absolutely some of the best for a 350 (especially at the price point). They are 255 hp and 330 torque stock (plus the torque is better than an old 350 across the entire range.)

Basically you get the awesome heads plus hydraulic roller cam etc all in one package.

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1987 GMC Jimmy said:

You want carburetion so I would recommend a block no later than 1995. IIRC, that’s the year they discontinued the opening and flange for the pump rod and pump.

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Lots of good info in the post, but SOME of the later blocks were machined for mechanical fuel pump. In fact, my 97 350 4-bolt main block is like that.

It's a similar situation for 86-up one-piece main seal blocks being machined for lifter retainers and cam retainer plate. Some are and some aren't. You just never know until you get inside one.

On another note, I'd guess that 50% or more of junkyard Vortec heads have hairline cracks in the combustion chambers, so be careful. Overheating the engine will do it every time to those lightweight castings. The heads on the 97 engine I mentioned above were that way. It took cleaning and magnafluxing to find them. I ended up buying a new pair, but wish I hadn't. Just too many gotchas, like limited lift with stock valve springs, pricey intake and valve cover gaskets (at least for the good ones), raised exhaust ports and revised plug location that can cause header fit issues, special intake manifold, etc, etc.

Those $630 heads (2015 price) probably cost me $1,000 total, which would have bought me some entry level aluminum heads that would handle .510" or more lift with no need for special parts.

***Edit: Good call on the fuel pump lobe! Most of the GM roller cams don't have it. One exception is the RamJet/HT383 cam, which works very well with Vortec heads and LS6 beehive valve springs. But that's another story.

My 97 vortec 350 was machined for a mechanical fuelpump aswell. Had to double check before buying!

The issue with the carb is rectified with just an intake but yes that does cost money. And the heads can be pretty easily worked with for more lift but yes thats time and or money. I get where youre going with the cost and "gotchas" of serious build, but wasnt the op considering working on a 305 with a budget?....( I never knew about the vortec heads being so bad about cracking... good to know...)

For that level of performance you could swap in the vortec cheap and get the intake like i have. I can grind the head later if i want a big cam and turns out headers atleast performance wise dont mind being persuaded the old fasioned way. Ever seen that motortrend video where they beat the crap out of the headers? [emoji23] cracks me up.

But yes if i had the money and wanted a full build id just get aftermarket heads. I guess its a performance and budget thing. For a 420$ engine plus the intake and fuel pump i go up from 175-255 hp and 275-330 lbft torque. Its the most economical and simply executed performance gain i could come up with. (But dang i hope my new vortec doesnt have cracked heads...)

EDIT: ive thought about doing that cam/spring combo! Gotta wait til budget allows

MikeB said:

Lots of good info in the post, but SOME of the later blocks were machined for mechanical fuel pump. In fact, my 97 350 4-bolt main block is like that.

It's a similar situation for 86-up one-piece main seal blocks being machined for lifter retainers and cam retainer plate. Some are and some aren't. You just never know until you get inside one.

On another note, I'd guess that 50% or more of junkyard Vortec heads have hairline cracks in the combustion chambers, so be careful. Overheating the engine will do it every time to those lightweight castings. The heads on the 97 engine I mentioned above were that way. It took cleaning and magnafluxing to find them. I ended up buying a new pair, but wish I hadn't. Just too many gotchas, like limited lift with stock valve springs, pricey intake and valve cover gaskets (at least for the good ones), raised exhaust ports and revised plug location that can cause header fit issues, special intake manifold, etc, etc.

Those $630 heads (2015 price) probably cost me $1,000 total, which would have bought me some entry level aluminum heads that would handle .510" or more lift with no need for special parts.

***Edit: Good call on the fuel pump lobe! Most of the GM roller cams don't have it. One exception is the RamJet/HT383 cam, which works very well with Vortec heads and LS6 beehive valve springs. But that's another story.

Click to expand...

Sent from my SM-G920V using Tapatalk

MikeB said:

Lots of good info in the post, but SOME of the later blocks were machined for mechanical fuel pump. In fact, my 97 350 4-bolt main block is like that.

It's a similar situation for 86-up one-piece main seal blocks being machined for lifter retainers and cam retainer plate. Some are and some aren't. You just never know until you get inside one.

On another note, I'd guess that 50% or more of junkyard Vortec heads have hairline cracks in the combustion chambers, so be careful. Overheating the engine will do it every time to those lightweight castings. The heads on the 97 engine I mentioned above were that way. It took cleaning and magnafluxing to find them. I ended up buying a new pair, but wish I hadn't. Just too many gotchas, like limited lift with stock valve springs, pricey intake and valve cover gaskets (at least for the good ones), raised exhaust ports and revised plug location that can cause header fit issues, special intake manifold, etc, etc.

Those $630 heads (2015 price) probably cost me $1,000 total, which would have bought me some entry level aluminum heads that would handle .510" or more lift with no need for special parts.

***Edit: Good call on the fuel pump lobe! Most of the GM roller cams don't have it. One exception is the RamJet/HT383 cam, which works very well with Vortec heads and LS6 beehive valve springs. But that's another story.

Click to expand...

Thanks for straightening me out. I always forget that the later blocks were, in fact, machined to accept a mechanical pump.