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Author Topic: Upgrading TBI 305 to Vortec 350  (Read 154 times)

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Offline Lifeguard

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Upgrading TBI 305 to Vortec 350
« on: August 04, 2018, 03:01:38 AM »
I don't know if there are a lot of third gen owners here, but I've been having some thoughts on my next project car when the '78 is restored and upgraded.  I want to expand my winter vacations to Florida and was considering having a second Camaro down there to keep in storage so we can travel in the winter by car or plane and I'll still have my own car to use down there.  When I was in high school on vacation in Florida, I saw 1988 Camaro RS on the lot down there as they were expanded in their exclusive markets from CA to TX and FL.  I loved the clean look of them and thought they were the best looking 3rd gens I had ever seen.  In '90, I almost bought a new RS 305/auto, but instead went for the practicality of the front wheel drive of a Beretta for Illinois winters.  I kick myself to this day for not going with the Camaro, I'm sure I'd still have that car today if I had bought it.  But I'm thinking that maybe I should make an RS my next project for my snowbirding car. 

So I'm thinking about what are some upgrades to do to a good driver that I can pick up cheap.  Most of the '89 and '90 RS were 305/auto, so that's pretty much the best place to start.  I found this site awhile back which has a lot of thoughtful budget friendly upgrade recommendations:

http://tbichips.com/?page_id=22

A lot can be done to the exhaust, air cleaner, TBI, transmission, rear gearing, and ignition to upgrade a 305 that will then become the basis of a crate Vortec engine swap.  I considered rebuilding a wrecking yard Vortec to get the cam and compression optimal.  But the ease of a crate Vortec seems like a pretty good stage 2 to the project, with those upgrades saved for a later stage.  I'm making a list of things that will be done when switching 305 TBI to 350 Vortec with TBI, here's what I've learned so far:

Send 42mm TBI to be bored to 46mm for a 350
install 350 injectors
18psi regulator spring and chip from Harris Performance
I can remove AIR, EGR, and cat.....no one checks where I am
use Edelbrock Performer EPS 2716
use Holley 17-41 TBI adapter and 375-1255 gaskets (not sure on the studs needed)
Felpro MS9800T intake gasket kit
manifold bolts from local hardware 5/16" 18x1.5" and flat washers
3/5" spark plugs R44LTS
Purolator PV774 PCV
I think the 305 flywheel just swaps over as far as I know?
plug the timing sensor on the Vortec plastic cover
block off fuel pump opening and use the AC Delco Vortec fuel pump EP381
carry over log exhaust manifolds? (the author on that page seems to think they are good up to 300hp and that is what a Vortec with exhaust and intake will produce)
an oil cooler adapter with a Wix 51036 seems like a good safety upgrade too

Aside from bolting over the upgrades done to the 305, that's the list I've made for myself so far.  Is there any parts I missed (there always is something you didn't think of needing), anything that has a cheaper option, or anything that will work better?

Not sure what people do with their 3rd gen vintage AC systems these days.  Is there a kit or tricks to making it work with modern refrigerants?  I don't have AC to deal with on the '78, but it's pretty much guaranteed to be on any '89 or '90 RS. 


Offline Burd

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Re: Upgrading TBI 305 to Vortec 350
« Reply #1 on: August 04, 2018, 09:50:23 AM »
I keep my 78R-12, it works way better, and the price leveled off, if not being lower, I sell the cans for $30-40 , Iím out of R-12 at the moment.  Except for the big tank, which isnít for sale. 
Wasnít there a pc to even out the airflow for those, I did one on my chev pu and it had smoother throttle response.  It was cheap too. It was a 2 pc kit. 
1978 YEE

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Offline Lifeguard

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Re: Upgrading TBI 305 to Vortec 350
« Reply #2 on: August 04, 2018, 01:21:48 PM »
I keep my 78R-12, it works way better, and the price leveled off, if not being lower, I sell the cans for $30-40 , Iím out of R-12 at the moment.  Except for the big tank, which isnít for sale. 
Wasnít there a pc to even out the airflow for those, I did one on my chev pu and it had smoother throttle response.  It was cheap too. It was a 2 pc kit.

I've never touched AC systems before.  My first '76 Camaro didn't have one, my second '76 had a non-working one (in retrospect the refrigerant was probably just low), the '78 of course doesn't have one, everything else I owned never had an AC issue and was fairly new.  I had no idea the R-12 was still readily available, but I guess there are stockpiles of it still around.  It's one of those mystery systems I don't touch and then when I finally have one and need to work on it, I soon become pretty knowledgable.  It always seems more intimidating and complicated until you finally try your hand it. 

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Re: Upgrading TBI 305 to Vortec 350
« Reply #3 on: August 04, 2018, 04:12:34 PM »
It was getting expensive, cans at the swaps here are $45.  I get a top off every 10 years or so.  Itís not bad. 
1978 YEE

Just Say No to Facebook, your Foums Life Depends On It.

Offline Lifeguard

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Re: Upgrading TBI 305 to Vortec 350
« Reply #4 on: August 04, 2018, 04:30:54 PM »
It was getting expensive, cans at the swaps here are $45.  I get a top off every 10 years or so.  Itís not bad.

Yeah, that's still probably a lot cheaper than retrofitting an older system.  Since I want this to be my Florida car, AC is kind of a necessity.  Three seasons in Illinois you can pretty much live without it in a second gen.  They were really designed for driving with the windows open.

Offline xtopfuel

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Re: Upgrading TBI 305 to Vortec 350
« Reply #5 on: August 04, 2018, 06:20:05 PM »
If you don't want to spend a ton of cash that mid to late 80's 5.0 tbi performed pretty damn good and many mods available
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Re: Upgrading TBI 305 to Vortec 350
« Reply #6 on: August 05, 2018, 07:25:55 PM »
If you don't want to spend a ton of cash that mid to late 80's 5.0 tbi performed pretty damn good and many mods available

Indeed, there is a lot of hate on the 305cid.  The guy on Harris Performance website does a pretty good summary on the L03's week spots which are the restrictive exhaust pipes, the TBI, the air cleaner, chip, and the peanut camshaft.  Swapping in a higher stall torque converter from a truck and the LT1 camshaft are pretty cheap improvements and probably worth 230 net hp.  But if the short block needs rebuilding, and the heads are really weak and would need a set of HO/TPI heads to replace them; which at that cost of rebuilding the whole 305 it is just as easy to swap in a 350 Vortec and if you get the crate motor there is even a warranty.   

So stage 1, upgrade the bolt ons with the 305 and add an LT1 camshaft, torque converter, and rear posi with gears
stage 2, swap in a vortec long block with 350 TBI mods and a Performer EPS with adapter
stage 3, after warranty is up, swap cam, springs, and headers onto it

Seems like a good ongoing project plan to do over a few years.

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Re: Upgrading TBI 305 to Vortec 350
« Reply #7 on: August 05, 2018, 07:36:44 PM »
Forgot to ask what 3rd gen Fbody owners think the power limitation of the T-top cars are?  How much net horsepower and gearing can they take before the twist in the body starts to warp the panels and their frame?  Looking at the production numbers it seems like maybe half of the hard tops were T-top equipped.  So it might be hard to find a solid top car for rigidity.