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Old 12-02-2014, 11:48 PM   #1
clampjockey
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Vortec swap questions

I recently bought a 71 gmc with no drive train. I have a th350 tranny, going with either 3.08 or 3.73 gears (most likely 3.08), and a rebuilt 350 from a 72 impala, not bored. I picked up a second hand set of 062 vortecs and RPM intake. I have a 375hp 327 cam/lifter set. I am planning on doing this head swap shortly and want to know everything I need and should know before I start.
I plan on buying a new water temp sensor and getting it cut/threaded to fit the head.
I have a set of tbi valve covers and plan to buy gaskets for vortec??
Buying intake gaskets and bolts for vortec.
Rocker arms came with the heads.

My questions are:
Which head gaskets do i use? Do I order a head gasket for a carbed engine or a vortec? Are they the same?
Is there a certain thermostat/housing I should use regarding coolant bypass topic?
Can I use my headbolts from the old engine or do I need vortec head bolts?
Spark plugs for vortec engine??
If there is anything I'm forgetting or should know, I'd appreciate it being brought up. Thanks
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Old 12-03-2014, 12:21 AM   #2
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Re: Vortec swap questions

Edit*
Performer intake, not RPM
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Old 12-03-2014, 12:42 AM   #3
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Re: Vortec swap questions

The head gaskets are the same for all small blocks with a 4" bore. The thermostat housing has nothing to do with the thermostat bypass. I have reused head bolts on several occasions, but new head bolts are a good idea. New GM head bolts can often be found for less than $100.00. You will want spark plugs for the Vortec engine. That will be a starting point and you can adjust from there depending on how they look after running a bit.
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Old 12-03-2014, 01:01 AM   #4
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Re: Vortec swap questions

For spark plugs, I use ac delco R44LTS.
Gaskets, don't go cheap, use the fel-pro reusable rubber/metal ones. Especially on the intake. (Can't remember part number off top of my head)
My water pump has a bypass hose that goes to the intake. If yours does not just drill a few small holes in the thermostat. All 350 blocks will have the holes in the block( where the water pump mounts) but the vortec heads do not.
And like captainfab said, new bolts are a good idea.
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Old 12-03-2014, 08:29 AM   #5
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Re: Vortec swap questions

"All 350 blocks will have holes in the block (where the water pump mounts), but the vortec heads do not"
What do you mean by this? Lack of accessory holes? Coolant passages?
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Old 12-03-2014, 09:38 AM   #6
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Re: Vortec swap questions

I was talkin about the coolant passages in the block. On the passenger side, there is a hole where the water pump mount that goes thru the block to the deck of the block then thru the head. But the vortec heads do not have a passage there so there is no way for the coolant to circulate. That is why you need some sort of by pass.
Not the best at describing things but I hope this helps.
Do a search. There is a lot of info out there.
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Old 12-03-2014, 09:44 AM   #7
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Re: Vortec swap questions

So I should look for a waterpump that has a hole for a bypass? I will need a new one anyway...if i order one for a vortec engine, will it have this bypass port?
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Old 12-03-2014, 07:51 PM   #8
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Re: Vortec swap questions

We'll that is what I did. I just got a water pump for a '96 vortec 350. It has a fitting for the bypass and a longer one for the heater return. But I am running a serpentine belt system. I am also running a GMPP tbi manifold. So I'm not sure how it would work for you depending on your pully and intake system.
I took a couple of bad pics so you can get an idea what I'm talking about. The bypass hose is the small L shaped hose on the pass side of pump going to the front of the intake.
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Old 12-03-2014, 07:53 PM   #9
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Re: Vortec swap questions

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Old 12-03-2014, 07:54 PM   #10
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Old 12-04-2014, 12:44 AM   #11
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Re: Vortec swap questions

Could I use the whole serpentine set up from a 98 donor?
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Old 12-04-2014, 12:45 AM   #12
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Re: Vortec swap questions

Here are a few pics I have of the hole in the block and the Vortec heads compared to the '95 and earlier heads.

The Vortec water pump will be along pump and reverse rotation for use with a serpentine drive. It really wouldn't be difficult to just drill a hole in the passenger side head. Just use a head gasket for a template.
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Old 12-04-2014, 12:55 AM   #13
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Re: Vortec swap questions

Wouldn't I trap filings in the passages if i drilled into the head? If I did drill it, i assume I wouldn't have to run the bypass hose?

Getting back to the serpentine thing...do you know of any links of swaps doing this? How would I get an alt to work? Would the PS lines from a 98 fit my steering box? Could I run the newer AC compressor too?
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Old 12-04-2014, 12:59 AM   #14
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Re: Vortec swap questions

Thanks captainfab! A picture is worth a thousand words. I saw that pic before and was looking everywhere to try and find it again to help explain what I was trying to say to clampjockey a little better.
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Old 12-04-2014, 01:02 AM   #15
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Re: Vortec swap questions

Yes, thank you!...I totally understand what you are saying now.
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Old 12-04-2014, 01:03 AM   #16
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Re: Vortec swap questions

For the belt system, do a search on this site. There are several good threads on this. Search for the power steering as well. If you use a newer ps pump all you have to do is change the fitting on the pump with your original one.
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Old 12-04-2014, 01:07 AM   #17
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Re: Vortec swap questions

When you're done drilling just blow the head out with compressed air. It is only into the water jacket and a tiny amount isn't going to hurt anything. If you're really worried about it you can put grease on the drill bit or place a magnet close to the location on the head.

The '72 and earlier trucks all came with short water pumps, so when changing to a long water pump, certain factory parts will no longer work. You will need to change your alternator wiring for the CS130/144 alternator. The power steering pump will have Metric with an O-ring fittings and the steering box in your '71 has SAE fittings. You should be able to run the newer AC compressor, but I am not familiar with just what may need to be changed. I would imagine there are several guys over in the '67-'72 message forum that have changed to the serpentine accessory drive that would have more definitive answers for you.
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Old 12-07-2014, 03:00 AM   #18
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Re: Vortec swap questions

Vortec heads on earlier engiens have been done for years without any issues. This is the first I`ve heard of having to drill any water passage. This is a very simple swap. Aside from requiring a intake with a vortec bolt pattern its a direct swap.
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Old 01-05-2022, 04:10 AM   #19
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Re: Vortec swap questions

I'm rebuilding an 880 L31 Vortec engine right now. The water pump passage was already drilled in the block from the factory, so I followed Captainfab's advice and drilled the corresponding hole in the head. I drilled a 3/32" pilot hole and then drilled it out to 1/4", which matches the hole size in the head gasket. The head is less than 1/4" thick in that spot, so it was easy to drill through.
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Old 01-05-2022, 05:24 PM   #20
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Re: Vortec swap questions

Whats the point of this? I've ran vortec heads on a non-roller block. I've run an entire vortec motor in a 79 without using this bypass. So whats its purpose?
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Old 01-05-2022, 05:42 PM   #21
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Re: Vortec swap questions

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Whats the point of this? I've ran vortec heads on a non-roller block. I've run an entire vortec motor in a 79 without using this bypass. So whats its purpose?
It allows a small amount of coolant to circulate when the engine is cold and the thermostat hasn't opened yet. From what I've read, having no coolant circulation during warm-up can cause temperature spikes in the heads. As an alternative, coolant can circulate through the heater core during warm-up, but this doesn't work if you've got A/C with a shutoff valve to the heater core. Most people end up adding a small hose from the front of the intake manifold to the top of the water pump. I thought it would be cleaner to just drill the missing hole instead of adding this extra hose on the front of the engine. Another solution is to drill some holes in the thermostat.
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Old 01-06-2022, 06:04 AM   #22
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Re: Vortec swap questions

I've got a Vortec head roller motor in mine. But my heater valve has a circulating design when it's off to the heater core (Old Air).
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Old 01-06-2022, 06:22 PM   #23
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Re: Vortec swap questions

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Originally Posted by pjmoreland View Post
It allows a small amount of coolant to circulate when the engine is cold and the thermostat hasn't opened yet. From what I've read, having no coolant circulation during warm-up can cause temperature spikes in the heads. As an alternative, coolant can circulate through the heater core during warm-up, but this doesn't work if you've got A/C with a shutoff valve to the heater core. Most people end up adding a small hose from the front of the intake manifold to the top of the water pump. I thought it would be cleaner to just drill the missing hole instead of adding this extra hose on the front of the engine. Another solution is to drill some holes in the thermostat.
Cool, thanks
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Old 01-16-2022, 11:27 AM   #24
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Re: Vortec swap questions

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Originally Posted by clampjockey View Post
I recently bought a 71 gmc with no drive train. 375hp 327 cam/lifter set
I have a th350 tranny, going with either 3.08 or 3.73 gears (most likely 3.08),
You will not like the cam with 3:08 gears. Are you really adding this solid lifter cam to your motor? This is the same cam used in 1969 z28's and is too radical for your combination IMHO. You will also need a stall converter to run this camshaft. Idle speed is 850RPM. I would use the 327-350hp cam. You will be much happier. I have actually ran this 375HP cam in a Camaro back when I didn't know any better. The car would do almost 60MPH in first gear and was a dog. Changed the gearing to a 3:73 and you couldn't tell it was the same motor. GM only used this cam with a manual transmission. You have been given notice of what you are stepping into. Now it's your turn to make a decision to get some on your foot or not.
Cheers.
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Old 01-18-2022, 12:38 AM   #25
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Re: Vortec swap questions

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You have been given notice of what you are stepping into. Now it's your turn to make a decision to get some on your foot or not.
Cheers.
Sorry. I brought this old thread back to life.
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