Can you help with engine build?

[72kool]

Ok so quick rundown, my daily driver is needing more work and done putting money in it. So it will be sold and all funds go into the truck and it will be my daily going forward.

It's a 1972 GMC C20 with the stock 350. It has HEI already installed.

The plan is strip engine down to bottom assembly. I have stock vortec heads that I am going to install. I am not changing springs or doing anything to them other than valve job and resurfacing them. I am doing this on a tight budget because I need the truck soon

For a cam I have a torquer cam specs are 278/288 204/214 @ .050 .423/.443 lift
Also use an edlebrock performer rpm vortec intake.


My big questions are this, opinions on the cam? Anything to consider or worry about with the stock vortec heads?

Also what has everyone used for a carb with this head swap? I can't use the stock divorced choke because the intake doesn't have the setup for it. Anybody convert a divorced choke Rochester to manual or electric choke?

Main goal is I need to do this right, but tight budget. Any help would be huge. Thanks

[truckster]

Here's the one I purchased to put on the Vortec I put in my Blazer. I haven't fired it up yet, but I've heard very good things about National, and at least my visual inspection leads me to believe they did a first-rate job.

https://www.amazon.com/National-Carb.../dp/B00IA5L362

[weim55]

Everything for your engine recipe sounds fine. Your cam is under the .450" limit for the stock Vortech springs. As for the specs themselves that cam is a just above stock mild unit that should work well for a low compression 350. The head swap is a win-win, additional compression for better gas mileage and power, fantastic low lift numbers and velocity for great low-end torque and upper RPM horsepower. i've swapped these heads many times two older 350s and it really wakes them up. Make sure you have the rocker arms to go with the Vortech heads as the later heads do not have guide plates. The valve covers are different, and there could be issues if you are running stock exhaust manifolds. The spark plug placement is slightly different so there could be interference with those manifolds. I'm not sure if the exhaust port placement is slightly higher possibly creating interference with the head pipes (?) maybe somebody can chime in here that have run stock exhaust manifolds. All of the swaps I've done had headers.

Only one time have I converted the early Quadra jet to an electric choke. Took the electric choke assembly from mid 80s unit from the junkyard and wired it up. I only remember it was a direct bolt on but I don't know if they are all the same.

Steve weim55 Colorado

[slocityk20]

I think its just about how in depth you want to go. I just built a 383 stroker and went with a full roller set up. Here in California it is hard to find oil that has the zinc and other key components that you need with a tappet style lifter to not get cam degredation. I think that performer intake is plenty for your application due to the RPM range for the engine.

IMO engine builds are as crazy as you want to get! i hear you on the budget thing as well! Just make sure you degree the cam to the proper specs and that you have a good set of rings on the pistons!!

Good luck my friend! Sounds legit to me!

[AussieinNC]

Make absolutely certain those Vortec heads are crack tested before they are worked on....too many times I have had Vortec heads turn up cracked and irrepairable.

Have you considered grabbing a used Vortec from a salvage yard and building it first, then swapping it over when done?

That would allow you to continue to drive your truck as a daily until you have the engine ready to swap over....

Just my opinion....but roller Vortecs are really a better bet overall than the older flat cam engines....

[72kool]

I appreciate everyone's input. My biggest question now is what to do with my carb? I know I can't use the divorced choke, but don't want to add another$400 to the build for a new carb if I can help it. The quadrajet I have now runs good. Had it rebuilt a couple years ago and still running strong.

As for the head condition, I work for a parts store that has a machine shop. We already checked the heads for any warp or cracks. All they need is the valves cleaned and resurface for a clean mating surface. I would do more work to them if I had time but I don't, so it's a do what is needed, not what is wanted time. Overall I feel if I have the right parts to make this work, the numbers and power upgrade should be a good wake-up for the engine.

Also something to note, the truck has 72,000 original miles. I am going to check it all that I can while apart, but the engine does not smoke, has good compression all around. I'm betting the build on the bottom end being good and ready to go

[68Gold/white]

Just my opinion....but roller Vortecs are really a better bet overall than the older flat cam engines....

[/QUOTE]

What makes the Vortec engine better? The roller cam?

Just asking, I have no experience with them...educate me!!!

Thanks!

[72kool]

Flat tappat cams need a higher zinc in the oil than most oil brands have so you should add zinc when changing oil. Not a big deal but important. Also they seem (I don't have facts, I apologise) to have a higher chance to flatten a lobe if not properly maintained such as using the proper amount of zinc.

Roller cams don't require that high a zinc content and can use any synthetic blend oil on the shelf. They also use what's called a roller lifter. They basically have a bearing on the end that meets the cam lobes. This reduces friction which creats less wear, lower heat production, and just all around better. That's a basic early morning run down. Others are way more informed and able to give a better explanation

Sorry, I reread your question. A roller cams is the biggest reason a vortec is better. There are other small reasons but that's the biggest one. One thing to consider though about switching to a vortec block, it does not use a mechanical fuel pump. You have to install an electric pump. Not a huge deal, but another thing that you have to do.

[geezer#99]

You can get an electric choke conversion for your carb.
https://quadrajetparts.com/electroni...971-p-399.html
You’ll need to fab a mount bracket to mount it. Easy to do.

[72kool]

I just thought of another question. This is a daily driver truck. So I want good usuable power, but also gas choice friendly. I would like to monitor my compression ratio with what I do. What are the stock pistons on the factory 72' 350? Also what is a good way to calculate my compression ratio? I can dictate it a little with head gasket I know, but don't know what I need yet

[jojo-munson]

Originally Posted by weim55

The spark plug placement is slightly different so there could be interference with those manifolds. I'm not sure if the exhaust port placement is slightly higher possibly creating interference with the head pipes (?) maybe somebody can chime in here that have run stock exhaust manifolds. All of the swaps I've done had headers.

Steve weim55 Colorado

I did a vortec head swap on a 72 C20 350 and kept the stock style exhaust manifolds (both originals were cracked, so they're the Dorman replacements) and have no issues with clearance regarding spark plugs.

I ended up getting a new carb with electric choke so can't help there.

[72kool]

Originally Posted by jojo-munson

I did a vortec head swap on a 72 C20 350 and kept the stock style exhaust manifolds (both originals were cracked, so they're the Dorman replacements) and have no issues with clearance regarding spark plugs.

I ended up getting a new carb with electric choke so can't help there.

Do you mind sharing your build plan? What parts did you use? Cam, did you do any work to heads, what was your compression? Stock botom end ? What gas you running? Sorry for the 20 questions haha just want as much info as possible before I start. This will be a get everything ready and piled in the garage, and start to finish in a weekend and back to work monday

[bigmac73]

I have to ask , since you are from Kearney Nebraska. Did you look at Blueprint Engines built in your hometown?
AS an option?

[72kool]

Yes I have looked into them. They are a nice option for most, but not a good choice with my budget. Now most times it is cheaper to go with a crate engine vs a rebuild. But as I mentioned before, I work at a parts store that also has a machine shop. So all machine work is done for free by the machinest teaching me how to do it. I get free lessons and my engine is the curriculum.
Also working at a parts store, I have access to many supplies at a discounted rate. As machine work is what can make or break a budget, that is not an issue in my case and therefore this is the most budget minded route for me. I would do more and make it higher performance engine with my resources except for two reasons. 1) I need this truck finished asap and sooner than that. 2) it's going to be my daily driver. If I need to go somewhere, this truly is getting me there. So I want reliable and adequate to perform the job at hand for that day.

[MARKDTN]

Originally Posted by 68Gold/white

Just my opinion....but roller Vortecs are really a better bet overall than the older flat cam engines....

What makes the Vortec engine better? The roller cam?

Just asking, I have no experience with them...educate me!!!

Thanks![/QUOTE]

Factory roller cam, 1-piece rear main seal that doesn't leak, and centerbolt valve covers also minimize leaks.

I too would build a used Vortec motor instead of putting heads on an old one. To use a carb you will need an intake either way. I would much rather put an engine in one of these than try to swap heads in the truck-and you will get one that won't leak as much.

[weq92f]

.
One more note on the Roller vs. Flat Tappet cam... With the roller cam, lobe ramp rates are higher/faster, which means the valves open/close quicker which allows more air/fuel to enter the chamber on Intake and more exhaust to exit the chamber over the same timing period, thus producing more power and torque. Flat tappet ramp rates are slower due to the friction between the lifter and the cam lobe limiting them.

The other advantages:
1) lifters can be reused with new cam
2) no break-in required
3) no special oil or additives required


-klb

[weim55]

The power and performance upgrade with the Vortech engine is in the cylinder heads. And by this I mean only the 96 and up Vortech 350. GM used the Vortech name for V-8 engines before 96 so it's important to know if you are using the earlier Vortech heads (1995 or earlier) these are not a true Vortech head. The earlier head is junk and a complete waste of time to change out on a 70s small block. The number of intake bolts should be four per side for a true Vortech. If you have a six bolt intake flange it's the older style head.

Your compression increase should be pretty easy to figure out. You're going from a 76cc head chamber to a 64cc chamber. Look up your stock compression ratio (9.0 ??) and just Google a site to calculate the compression difference with the smaller chamber. It's not a huge difference, I think you're going to about 9.75 with the smaller chamber head. I've noticed I haven't had to change the grade of gasoline used because the newer chamber is so much more efficient. YMMV. Once you've completed the swap keep your ears sharp for any engine detonation. Jump up a grade of gasoline if you're having an issue with that. May you may also need to dial back your total advance in the distributor as the more efficient combustion chamber requires less Advance timing.

Steve weim55 Colorado

[72kool]

I appreciate it weim55. I have heads from 1997 Tahoe. They are the .096 casting. Which should be the better of the two. The .062 from my understanding are the lesser of the two castings. These are true vortecs

[jojo-munson]

Originally Posted by 72kool

Do you mind sharing your build plan? What parts did you use? Cam, did you do any work to heads, what was your compression? Stock botom end ? What gas you running? Sorry for the 20 questions haha just want as much info as possible before I start. This will be a get everything ready and piled in the garage, and start to finish in a weekend and back to work monday

Hey I get it! I spent a lot of time doing research before doing the conversion.

I used the Edelbrock performer intake manifold as well! But I swapped from the old quadrajet to an AVS2 carb.

Tried to get factory style vortec rocker arms so went with part# 12495490 off of summit.

The heads I got new from a local machine shop, they gave a me a decent deal and reused some of the hardware from the old stock heads. If I remember right they swapped the valves and springs.

Didn't mess with the cam at all, pretty sure the one in there is stock. Same with the bottom end. Also using standard gas. I live in an area with a lot of hills, and the swap definitely made going up them a lot easier!

No idea what my compression is unfortunately, but it's on the list of things to find out...

[Quikshft]

Here's what I did to solve the choke problem. My carb is a Rochester 2GC, I think the 'C' designates electric choke, which is what this carb had when I got it. Didn't want to mess with it so I stripped off all the electric choke pieces and rigged up a bracket to mount a traditional manual choke cable. This works great, and really my truck started and ran without choke at all. But, I've got it if I need it.

[Coley]

...just backing things up for a second.

You mentioned you can't run a divorced choke? (assuming for a Rochester)
Is this because of the Edelbrock performer manifold and its different (angled) shape?

Well...Edelbrock makes a choke adapter plate kit (approx. $20-25) to allow for mounting of a divorced choke for small block chevy's.
Google this 'Edelbrock performer choke adapter plate' and you will see it.

It bolts/mounts onto the performers angled shape and then you should be able to mount/rig your divorced choke to it....thus allowing you to keep your Quadrajet and also allowing you to forgo the electric choke stuff.

All good
Coley

[geezer#99]

He has a performer vortec intake Coley.
No mount pad of any kind on those.

[clay68c10]

I think I have a q-jet with an electric choke on it in my stash at work. If you are interested, I can get a look at it and post up whatever info you need. I bet it’s an easy switch over.