Flow Numbers 690 Heads

[jim_ss409]

We recently got some parts to build a tunnel ram.
We wanted to get away from the sheet metal look and try something a little different, so I ordered up two different plenum tops from a Holley Hi Ram manifold. (these are for an LS engine)
The plan is to use the dual quad top like the on the right of this picture. These are pictures I got on line by the way.




We also got a throttle body plenum top like the one bolted to the manifold in this picture...


The throttle body top and dual quad top have the same bolt pattern so we can bolt them together back to back, so now, the throttle body top becomes the base of the plenum.
A picture would be worth a thousand words but I don't have a camera here.
Of course I'll have to cut the snorkel end off the base and weld in a cover. That will be at the back near the distributor, so it won't be seen anyway.
The tapered shape of the throttle body top actually works out just about right because the engine is mounted in the car on an angle, so the carb pads end up being level.
The plenum works out to be just about the right length, so I think it will work just fine.
The plan is to build this intake for the Z11 heads we got. The heads are out getting the valves done so we can't get started on this yet, but when we do,,, I'll start a thread.

 

[61 Bubble]

Jim how much for your "old n used up sheetmetal" intake you want to take off?

 

[jim_ss409]

Jim how much for your "old n used up sheetmetal" intake you want to take off?

The new tunnel ram will be made to fit the Z11 heads, so we'll still need the old tunnel ram.
Right now the plan is to use the Z11 heads on a new shortblock we've got at the machine shop. "New" as in newly rebuilt. It's a 65 passenger car block we got from Quik9r a couple of years ago.
It's a 481 ci stroker with four bolt mains and we filled it with Hardblock to the bottom of the water pump openings.
I think we'll use the Z11 heads and a new tunnel ram on this engine.
The engine should have lots of compression so it should make decent power but we're going to stay somewhat conservative with the cam.
We'll build this as a complete engine and dyno it but we may not use it right away. It would be a great backup engine for either car.
If we aim for the horsepower to peak at about 6,500 rpm I think it should make around 700 hp.
I think we can make quite a bit more power with a bigger cam and more rpm, but right now, we're trying to use some restraint.
(we did decide to spring for titanium valves just in case we decide to rev it up a bit higher)

 

[1961BelAir427]

Jim, About your new short block: Didn't everyone here determine a few years back that the valve relief notches needed to be positioned slightly different for the Z11 heads? (vs. 583/690's) It seems like I remember someone confirming that the valve centers were different between them. ?????

I'd been meaning to ask about this one of the Z11 threads that is currently being discussed where people are talking about the "Z11 style" top end package that came out in '62 and racers swapped onto their 409's. I wouldn't think all of those guys would have replaced pistons or flycut them.

Edit: Found it. See this one:

http://www.348-409.com/forum/threads/z-11-heads-409-style-pistons.20302/

 

[jim_ss409]

Yes, the exhaust valves are in the same place but the intakes are clocked over a bit.
I put a regular head back to back with a Z11 head and used a center punch to show how different they are.
You can see a picture of that about 1/2 way down this page...
http://www.348-409.com/forum/threads/a-z-11-followed-me-home.28896/

I'm guessing the guys that bought Z11 heads over the counter probably had to modify the regular pistons. Some probably bought Z11 pistons to get the extra compression though.
There's a picture of a factory Z11 piston beside a regular high performance piston a little farther down that same page.

In our case, I'm guessing we'll have to flycut the pistons. They have been lightened so there's a limit to how much we can widen out the valve relief, but I think we'll be OK.

 

[1961BelAir427]

Apparently I can remember Brian's thread from 3 years ago but had forgotten you and I talking about this very thing in your Z11 followed me home thread just a few months back. Sad isn't it?