I am considering upgrading to a zz6 for my 1971. It currently has a stock 350 270 hp motor. Can anyone give me any advice on what to looks out for.

Below are the issues I have come across.

1. Do I need to replace the long water pump. Can I use the Serpentine system
2. Is their issue with clearance. I will be putting a holley sniper on it. (This is currently installed on my engine now with the holley tank)
3. I have stock exhaust manifolds. Will they fit?
4. I currently have a 700R trans. I do not think that should be an issue.

Thanks

 

1. Yes you need to replace the long water pump with a short one if you are planning to use the accessory drive system for your car. If you are planning to use the serpentine drive that comes with the engine, you may be able to make it work but it will likely mean using electric cooling fans. It is probably easier to use the accessory drive system that is on the car now.

2. The ZZ engine should fit the same as the small block you have in there now. If the Sniper system fits under the hood, it should fit with the new engine, assuming you are using the same intake manifold.

3. Sorry, can't tell you about the exhaust manifolds. There have been some changes in the exhaust port configuration over the years.

4. The 700R4 should work but you will likely need a new flex plate. The early engines with 2-piece rear main seals use a different flex plate from the later engines with the one-piece rear main seal.

 

FWIW
zz6 fastburn heads: exhaust ports raised 0.200" for use w/ felpro 1470 ex gaskets.

perhaps you'll need to compare how well 1470 matches your manifolds.

 

not sure how many have done the zz6, but I did a zz4 a while back.

With the zz4 you changed from the long pump to a short pump because of the stock cooling fan and shroud. If you go electric you can probably use the long pump. As for SERP setups the big issue with the vette is the front crossmember.

you will need modified temp sensor because the factory 1/2” one will not fit in the head. Now you can possibly relocate it to the intake.

there should be no issues with the flywheel or the exhaust bolting up.

I think you will have an issue with the intake unless you have a taller hood. The zz4 intake was not as y’all, but cleared with a drop base air cleaner.

 

ZZ4 heads (discontinued) predate fast burn ZZ6
both have D-port exhausts and a fp 1470 gasket may need trimming
ZZ4 ex ports raised 0.100"
ZZ6 ex ports raised 0.200"

*source 2006 GMPP catalog, 2020 Chev Perf Parts catalog

 

GM serpentine system specs & install instructions
https://www.chevrolet.com/content/da...6-19417907.pdf

* LONG water pump only

 

Also, Corvette C4 85-91 run a Serpentine system w/ a SHORT water pump (reverse-rotation; Not reverse-flow)

 



Quote:

Originally Posted by Jguzzo;[url=tel:1602039296

1602039296[/url]]I am considering upgrading to a zz6 for my 1971. It currently has a stock 350 270 hp motor. Can anyone give me any advice on what to looks out for.

2 years ago I bought a new carbed ZZ6 “turnkey” from Scoggin-Dickey for my completely original 75 L48 4-speed. It was part of a complete makeover that included a 5-speed, headers, dual exh, coilovers, etc., etc.

I spent a lot of time fussing with all the final details. It would not have taken an experienced C3 guy as long as it took me. In the end though it was all worth it. What a magnificent motor.

Many will say that the same performance can be had for a lot less dough. I can’t argue with that. In my case I wanted something I could bolt in and it would work well from the start. Comparing my new 405hp ZZ6 to the original 43 year-old 165hp L48 isn’t fair but good gawd what a difference. From the first turn of the key it has run perfectly.

Speaking to your questions:

1- I can’t imagine not using the serpentine belt system. I did run into a clearance issue on the passenger side A-arm. I had to re-orient/modify the bracket for the fixed idler pulley. After that it worked perfectly. Whatever water pump they say you’re supposed to run is of course the one you should use.

Another consideration is spreader bar clearance if you choose to use one. Most will not clear the front of the engine with the serpentine belt system in place. I had to modify the brackets on my Speed Direct bar in order for it to clear. After I did that no issues.

2- The short answer is yes. There are hood clearance issues. I used an L88 style hood from It’s Fiberglass on eBay. Even then I had to use an air filter cleaner element that is 1/2 inch shorter than the element that came with my kit.

I had considered changing the intake manifold to a shorter one. In the end I wanted the engine to run like the designers intended so I changed the hood. The car looks a little boy racer but I’m glad I went this route.

3- I don’t know if you can use the stock exhaust manifolds. I can say with a set of headers and a decent exhaust this thing barks! When you want it to it will make an absolutely ferocious noise. At idle and putt-putting around the neighborhood your neighbors won’t entirely hate you.

4- Yes that transmission will bolt right up. For only $7500 my engine came with a flex plate already bolted to it. I had to buy my own darn flywheel LOL.


I say do it you won’t be disappointed.





it was meant to be

 

Kie:
With Your serpentine setup, You are running electric fan(s) in lieu of mechanical; right ?

 

yessir

i’m even pulling 12 V power directly from the alternator main lug like everyone told me not to LOL

 

FWIW a serpentine setup (like early C4) with its SHORT wp, pulls pump serp belt and all accessories rearward about 1-1/8" from a LONG wp setup.

https://www.corvetteforum.com/forums...-a-69-a-2.html

 

I pulled the trigger on the ZZ6 EFI Turnkey for my 71 coupe. Got the engine from a friend at GM (employee discount). Still expensive. There was and is a lot of details to work out but it is a hobby, right? …

• It came completely assembled with a short water pump. The serpentine setup is in a box with a reverse water pump (Reverse rotation; not reverse-flow) that you need to change out the installed pump with and install the rest of the serpentine system.
• The heads are D-port so you will need exhaust accordingly. I used the American Racing headers that I had ceramic coated to keep the heat in. Expensive but it’s done.
• The flexplate on the ZZ6 EFI turnkey is the three-bolt pattern that the 700R4 and torque convertor perfectly bolts up to.
• The EFI is an Edelbrock ProFlo 4 with GM branded single plain EFI intake manifold that has a bowtie cast into one of the manifold tunnels. They say that this setup it is an inch lower than the turnkey intake and carb that will clear the lower L48 hood. I am just about to set my body back on the frame (next couple of weeks) and that will confirm it (fingers crossed).

As Kie says “spent a lot of time fussing with all the final details” especially with the EFI with baffled tank, 58 PSI fuel pump, regulator as well as many many other non-EFI related details that I have documented throughout the process.
Like i mentioned above, the body goes back on for moc up in the next couple of weeks and I should iron out a few more details before the body goes back on the dolly and sent out of body and paint.

Not to hijack the thread but Kie, what upper hose and thermostat housing did you use? My thermostat housing is more on an angle and the stock hose interferes with the alternator as well as being a bit too short.

Thank you,
Richard

 

For a t-stat housing/upper hose version 1.0 I got one of those billet aluminum swivel housing gizmos from Summit with a slight (15 degree I believe) upward angle. Everyone told me it would leak. They were right!

At that time I just tried all the upper hoses from the car parts store until I found one that fit. For the brief time I had that set-up I hated how “floppy” that long hose was as well as how close it got to the serp belt. Then the housing started leaking and I started over.

For version 2.0 I went with a good old cast iron housing... I think from Mr. Gasket. A friend who has the dream job of being a caretaker/technician for a billionaire’s 50 car fleet made me an alloy section of pipe. That acts as the main upper hose section. He connected it with 2 rubber hose sections he had lying around. I’m very happy with the final result.

 

Nice job on 2.0! Is that a bracket from the rad holding one of the billet parts of the hose?

So the picture that you shared up in the thread was the “long floppy hose” that you changed out for the billet pieces?

thanks Richard

 

Yessir my first picture is of the long hose that was floppy and too close to the serp belt.

And yah for the new pipe there is a small aluminum bracket coming off the radiator to stabilize things.

 

Thank you Kie

 

No worries my friend. You will love this engine. Mine lit up the moment I breathed on the key the very first time. Runs like a banshee. Mine is carbed and makes all the cool blubbery noises and of course drinks the fuel like no ones business. I can only imagine that the efi version will run that much better and use lots less fuel to boot.

Since yours is a 71 I guess you’ll have to figure out how to drive the tach. My 75 has an electronic tach and it plugged into the ZZ6 dist with zero mods.

 

i converted the tach to electronic and its ready to go.

Regards to the 700R4, I used a G-Force cross member (my stock one had some damage). What did you use for cross member and how much shimming?

 

My car is a factory L-48 4-speed. 66k 1 owner miles and zero mods when I started. At the same time as when I swapped in the ZZ6 I installed a Tremec 5-speed kit from SST. I made no changes to the stock crossmember.

The first time I bolted everything together the ex pipes sat slightly low where they passed through the crossmember. I spaced the SST trans mount “up” with a couple extra thick grade 8 fender washers that have a huge outside diameter. That centered the ex pipes while leaving the driveline angle still close to 0.

 

Those Oring T stat housings are a crap shoot..pulled the oring out, filled it with silicone and used a gasket .Then it warped

Summit still sells the aluminum GM housing they put on all their crate engines, they are about 10 bux
once they are gone they are gone. Highly recommend one.