CommodoresPlus

Did a quick fitment check today before the manifold goes off to the machinist, port alignment looks reasonably good.  Those NZV8’s can’t have had much machined off the heads.

To do it correctly requires marking out the ports and then transferring marks over to the manifold and comparing.  In this case I just put it in place noted the position on the intake gaskets and fitment in the valley and then removed the manifold and checked it against the gaskets.  Good enough as I’m not port matching but if you were then marking it out is the only real way.  Some pics from HPE (on the AV8 forum) showing his port matching work.

LOL, yep it’s not even bolted on yet.  We will check bank to bank fuelling but that is a long way off yet.  Car needs to be on the road by the start of October if my job application goes well.

Car will be primarily road tuned (as I have all the gear hear for that) but it may spend a little time on the rollers as well so we may possibly run it with/without spacer to see if there is any difference as I will have a spacer.  I also have a NOS big shot kit which uses a 1/2 open spacer which may get fitted at some stage too 

edit: I know of another engine that had a large AFR discrepancy between banks, it had a full twin exhaust system, once they fitted a balance pipe into the system the banks balanced out (was a cammed up 304, with head work but still running banana’s).

• This reply was modified 8 years, 4 months ago by  Immortality.
• This reply was modified 8 years, 4 months ago by  Immortality.

cava454 wrote:

I didn’t know what milling it actual achieved, so good to know now. Just new it helped in some cases. Esp in some SBC

In a normal Dual plane manifold each intake port only see half of the total volume of the TB so if you have a 1000cfm TB than each port only “sees” 500cfm  of flow with a small plenum volume which promotes good airspeed at low throttle openings but limits flow at full throttle.

If you mill down the divider each runner can now draw on the full 1000cfm of flow as well as increasing the plenum volume.  There is also stuff with intake pulses pulling on opposite runners, gets quiet technical and I don’t understand it all either.

Comes down to application I guess, some people say the single plane is king but when someone like TK on the AV8 forum uses a dual plane on a 365 cu race engine that shows me it can’t be all bad.  Some other guy from the US says something similar and he’s kinda like the engine guru of engine guru’s…..

David Vizard,  Engine genius.

I’ve read some of his books, really wanted to go to his seminar when he was here in NZ but things just didn’t work out right.

Hoopstar wrote:

but it’s only air. Won’t the engine only use what it can take. Efi is dry induction compared to carby

Hoopstar wrote:

..And there lay another problem – the size of most throttle bodies are 1000cfm and more which is way too big for a 304 or 355. Even with 100% VE, a 355 turning at 7500 rpm only requires a TB that flows 770cfm. This reduces air speed and makes less torque in the mid-range. 1000cfm with 100% is nearing 10,000rpm CRD Engineering make a 750cfm TB which is a great match for a well tuned 355.

Well then a dual plane that only sees half the flow (per bank) should be ideal then

I had toyed with the idea of a single plane and then fitting a plenum divider which I think is fairly much what the Duggan manifold is (Smitty uses on his VK racer).

At the end of the day I know that this manifold, with standard 304 heads, 10:1 comp and a small solid FT cam will make 400hp (basic NZV8 tourer specs).

• This reply was modified 8 years, 4 months ago by  Immortality.