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Old 12-14-2010, 01:13 PM   #1
Guitarmaker
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350 Vortec; convert to carbureted and HEI ignition possible?

I've just been offered a 1996 350 Vortec; owner's a friend, and he's scrapping the entire truck. The engine runs, but it leaks antifreeze(intake gaskets, most likely). Since it's free(can't beat the price!), I'm tempted to grab it for a later rebuild. I'm keeping an eye open for a beater '66 to make into a simple street ride/daily driver/summer parts truck/trailer hauler. I know the electronics and fuel system can be made to work in the older truck(though I'm not getting the wiring harness or ECM or transmission; just the engine), I'm old school and for a long time was the go-to carb guy in these parts. I still have a box full of Holley's and Q-jets and tons of jets and power valves and all. In other words, carbs don't worry me none and I can set them up to run on the verge of perfect. Besides, I think old Holleys look mighty fine sitting on top of an aluminum intake, especially in a period-correct truck! I have everything from a 390 CFM to a 850 with milled choke horn and polished venturies available. Also 350 CFM and 500 CFM two barrel Holleys(from the dirt track days when we had to run 2 barrel carbs only). I also have a good Accel HEI distributor and coil and all, and again, with it's one wire connection, life is so simple.

Questions:

I see that aluminum intakes are available for small block chevys and vortec heads; I take it that a complete vortec block and engine can use these, also?

Will the older distributor drop-in and work? I assume the oil pump drive is still the same?

Any other surprises that would make this a challenge?

If this is do-able, I'd rebuild the engine(been there on older engines, not afraid of this one), and even keep the stock cam if it's in good shape. I'm not looking for more power than the stock vortec made anyhow, and if anything, I'd cam it for more low end grunt if possible.

I think the good flowing heads and roller cam and modern oil-leak fixes of the vortec would make this a no-brainer, but I want to check-in with y'all to see if it's at least doable. All Google searching leads me to is folks running vortec heads on regular small blocks, in high perf. uses. I just want a simple, reliable build.
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Last edited by Guitarmaker; 12-14-2010 at 01:57 PM.
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Old 12-14-2010, 02:42 PM   #2
bradh
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

You can use a carb intake for vortec heads, just get an intake made for vortec heads. A regular chevy distributor will drop right in. Chances are you'll need to run an electric fuel pump since your block is likely not drilled for a fuel pump pushrod. I ditched the plastic timing cover and replaced it with a standard steel one. I also got rid of the pickup wheel behind the balancer. To do that I ran a regular double row timing chain for a roller cam 305/350 and a regular 8" internal balance harmonic balancer.
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Old 12-14-2010, 10:26 PM   #3
Captainfab
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Yes it is totally doable....it's done all the time. As already mentioned, you'll need a intake specifically for the Vortec heads. As for the distributor, any Chevy V8 distributor will work. However, you'll need to make sure that the distributor gear is compatable with the roller cam. It's of a different composition than a standard gear. I believe you can take the gear off of the original distributor and install it on another OEM distributor such as a HEI. A lot of aftermarket distributors have slightly larger shafts. The timing cover can be swapped for an early steel one, of course you'll need the correct timing pointer. As for removing the reluctor ring between the balancer and timing gear, that is fine. But the original balancer has a shorter hub to account for it's thickness. So a switch to an earlier balancer may be necessary. What bradh did should work also. And yes you will need to run a electric fuel pump.
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Old 12-14-2010, 10:48 PM   #4
bradh
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

When I switched to a standard steel timing cover and got rid of the reluctor wheel I used and older style 8" balancer for a 350 with the longer stub where it goes into the seal and went to a standard width timing set, any roller cam timing set for a 305/350 from the late 80s to early 90s will work. Just spec a '90 camaro with a L98 and you'll get there. Add a couple 1/4" dowel pins to the block to locate the timing cover. The holes are in the block already. GM # 10456413 distributor gear should fit a factory HEI and work with a GM roller cam.

You'll get a sweet set of PM rods and a windage tray in there too! If you need an auto trans flexplate I have the number for that around here somewhere too.

Last edited by bradh; 12-14-2010 at 10:53 PM.
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Old 12-15-2010, 10:41 AM   #5
Guitarmaker
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Cool! Sounds like I have a plan....

I see no need to replace the stock cover and all that stuff. GM went through a lot of trouble to eliminate 40 years' worth of of leaks with these new parts, the old stamped covers being a major source of leaks. besides, I've never been a fan of roller chains on otherwise stock or slightly cammed street engines.

Thanks folks!
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Old 12-15-2010, 10:45 AM   #6
Guitarmaker
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Oh, on the subject of the flexplate...

I believe it's coming with the engine, as the owner's is keeping the tranny as a spare for his son's truck, but I doubt they took the flexplate with it. But.. Is this engine balanced differently than an older 350? Would a older SB(other than a 400) flexplate work? And I would like to use a manual with this setup if I can find a decently priced 5 spd. and hyd. clutch setup. Would an older flywheel work?

And no problem with the electric fuel pump; I should have one or two kicking around, still.
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Old 12-15-2010, 10:19 PM   #7
Captainfab
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

You cannot use a flywheel/flexplate from a '55-'85 two piece rear main seal small block. It will have to be from a '86-'02 one piece rear main seal small block. The bolt pattern is different and the balance is different.
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Old 12-16-2010, 12:39 AM   #8
Guitarmaker
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Okay, perfect! That gives me a target to shoot at. I wasn't aware of the balance issue and bolt pattern change(kinda shows my age, but hey, I know to ask what I don't know!).

Anything else change while I was asleep? Like, bell housing bolt pattern, or the motor mount locations? What about the alternator and power steering mounts? Do the old ones still bolt up, or will I have to run the newer ones? No problem either way, but it's nice to know ahead of time.

Yeah, it's been a good while since I last did this sort of stuff, but ya know, the itch is getting strong again, and damn, I need to scratch it!

My last swap was a 3.8L Buick V6 into a S-10 Blazer('84? '85?), and before that it was a Kenne Bell built Stage 1 455 Buick into an '81 Olds Cutlass! My Grand National is mostly stock, with only headers, exhaust, and some turbo and waste gate mods.
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Old 12-16-2010, 07:44 AM   #9
bradh
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Quote:
Originally Posted by Guitarmaker View Post
Okay, perfect! That gives me a target to shoot at. I wasn't aware of the balance issue and bolt pattern change(kinda shows my age, but hey, I know to ask what I don't know!).

Anything else change while I was asleep? Like, bell housing bolt pattern, or the motor mount locations? What about the alternator and power steering mounts? Do the old ones still bolt up, or will I have to run the newer ones? No problem either way, but it's nice to know ahead of time.

Yeah, it's been a good while since I last did this sort of stuff, but ya know, the itch is getting strong again, and damn, I need to scratch it!

My last swap was a 3.8L Buick V6 into a S-10 Blazer('84? '85?), and before that it was a Kenne Bell built Stage 1 455 Buick into an '81 Olds Cutlass! My Grand National is mostly stock, with only headers, exhaust, and some turbo and waste gate mods.
All your regular sbc brackets/engine mounts will bolt up and the bellhousing bolt pattern is the same. You'll want to get a new plastic timing cover, don't use the old one over again. It will have a hole for a crank position sensor that will need to be plugged. You'll probably get a fel-pro one piece pan gasket. The instructions will say to put it on dry. Unless you like to drop oilpans after they are in the truck I would put a bead or permatex right stuff on the timing cover and rear main cap area where the gasket seals. Also put a bead on the pan in the same areas.

Check the deck height when you tear down the engine, it will probably be .025". These are just over 9 to 1 in stock trim and it is doubtful that it will need bored or new pistons. The gasket that comes out of it will probably be around .026-.028 thick. I would use a .015 fel-pro steel shim head gasket, the oem gasket from GM or zero deck the block and use a thicker .040" or so fel-pro. You'll have to measure to check it all out. I just built one so most of the numbers are still fresh in my head.
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Old 12-16-2010, 12:20 PM   #10
Guitarmaker
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Sweet! Good info. Do you have the Fel-Pro part numbers for the various thickness head gaskets? I live in an area that rarely sees very hot temps(80f is HOT around here; we never see the 90s), and I'm used to running premium(that's all the GN will run on), so a slightly high comp.ratio works well for me, especially if I don't need to spend a thing to get it(IE: choose the right gasket).

I'm hoping it's fine inside; the engine isn't the original to the truck, so we don't know the actual mileage, nor how well it was maintained. I'll see what I have next summer, as the truck is now buried in snow in a field and it's too cold to go turning wrenches out there anyhow. But as I read more on the vortec, it appears it didn't wear as much as the old small blocks did, and my own 4.3 vortec shows me the same, too; at 248 clicks, it still doesn't burn or leak a drop of oil between oil changes, and when it runs right, it's just about as strong a puller today as it was new. Bodes well for the 350!
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Old 12-16-2010, 01:19 PM   #11
bradh
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Re: 350 Vortec; convert to carbureted and HEI ignition possible?

Fel-Pro 1094 is the coated .015 head gasket. Make sure your block and heads are clean and flat if you use these. I also retorqued my heads after the engine had been warmed up a few times. You'll have to double check to see how far your pistons are sitting down in the hole but they should be around .025, that's what mine was when I tore it down. With the .015 gasket and .025 deck height you'll have .040 quench, perfect. It should put you in the mid nines for compression, no problem even on 87 octane. The pistons have a slight dish but not bad. If they are good I would use them. They take a metric ring size so don't just grab a set of regular chevy rings. I ended up boring my block and putting flat tops in since it sat outside at the salvage yard for a few weeks with the heads off. I ended up at 10.05:1 and it does not ping with 87, my new pistons were also .025 in the hole. I'm running 35 degrees total ignition advance and a roller cam with 218/228 at .050. I'm also running RHS heads and a LT1 intake. Even without the heart shaped vortec chamber I have not run into preignition problem with 10 to 1.

I really like these vortec truck engines and I'll be looking for another one next time I need a 350.
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