Pulling truck engine "again" BBC

[randy331]

Steve, the average csa is correct, I used CC and length to figure it.
The throat remains the MCSA.
As far as welding, it isn't going to happen this go around. Maybe later.
The ex ports are too big. Someone has matched them up to some big header tubes sometime in the past.
They could use a little welding.
Got the intake back from the machine shop, it sits about right now but still needs matched up to the ports.

About got the heads roughed in and ready for a valve job.

Randy

[MadBill]

...The ex ports are too big. Someone has matched them up to some big header tubes sometime in the past.
They could use a little welding...

How about knife-edged primaries extending into the ports?

[randy331]

...The ex ports are too big. Someone has matched them up to some big header tubes sometime in the past.
They could use a little welding...

How about knife-edged primaries extending into the ports?

Actually Bill, that has crossed my mind.
May look into that.
I'd like them removable so it'd be easily tested on the dyno.

Randy

[MadBill]

These inserts added almost 15 lb-ft. ~ 4500 RPM, but then they turned inside out...

On the bench they were good for 20 CFM @ 0.700". They were just supposed to be for proof of concept, but I'd counted on them surviving at least one 600 RPM/sec. pull.

[RevTheory]

Oh damn

[randy331]

Bill, interesting devises. not surprised they didn't stay in there.

I'd like to try something similar, but I'm thinking a short pipe that just does fit in the ex port and extends into the header tube a bit. Something I can take out easily.

On a side note,.... the throat discharge seems much better now that the throat size is correct.
Amazing what a little csa mistake does to the rest of the math. LOL

Randy

[Walter R. Malik]

Depending upon the amount of improvement someone is willing to pay-for,
you could have all the exhaust port floors braze/filled just like most cast iron NHRA Super Stock stuff.

[randy331]

These inserts added almost 15 lb-ft. ~ 4500 RPM, but then they turned inside out...

On the bench they were good for 20 CFM @ 0.700". They were just supposed to be for proof of concept, but I'd counted on them surviving at least one 600 RPM/sec. pull.

So they survived flow bench testing,.....but not even one dyno pull on a running engine .

Does that tell us something about how well a flow bench simulates an ex port of a running engine ?
Or,...at least should it tell us something ??

Randy

[MadBill]

I think it tells us that 304 Stainless gets pretty flabby at 1300° F with say a 100 psi pulsating pressure delta.

[af2]

I think it tells us that 304 Stainless gets pretty flabby at 1300° F with say a 100 psi pulsating pressure delta.

HAHA when they turn brown you can bend stainless easier than soft copper.... Harden one with a dull bit then heat it till it turns brown and it cuts like butter.

[Momus]

I think it tells us that 304 Stainless gets pretty flabby at 1300° F with say a 100 psi pulsating pressure delta.

Bill, some Mazda rotaries came with a port forming and heat insulating insert in the exhaust side of the chamber. Conditions there are very arduous with almost continuous hot flow - they ended up using an investment cast inconel part pinned either side and designed to float. I'd remove these inserts and replace them with a little cast aluminium Floor insert that would work well for reshaping experiments and last when screwed to the housing to sink heat.

[MadBill]

Yes, the heat sink/thermal conductivity path is the key; there was virtually none in my construct.

[randy331]

I think it tells us that 304 Stainless gets pretty flabby at 1300° F with say a 100 psi pulsating pressure delta.

Since a flow bench isn't 1300* or have a 100+ psi pulsating pressure delta, but a running ex system does,... could a flow bench lead you off course on ex ports/systems ?

Randy

[Walter R. Malik]

I think it tells us that 304 Stainless gets pretty flabby at 1300° F with say a 100 psi pulsating pressure delta.

Since a flow bench isn't 1300* or have a 100+ psi pulsating pressure delta, but a running ex system does,... could a flow bench lead you off course on ex ports/systems ?

Randy

certainly ... though, it can give you some kind of idea about which direction to go.

[MadBill]

I think it tells us that 304 Stainless gets pretty flabby at 1300° F with say a 100 psi pulsating pressure delta.

Since a flow bench isn't 1300* or have a 100+ psi pulsating pressure delta, but a running ex system does,... could a flow bench lead you off course on ex ports/systems ?

Randy

It certainly could, but the single good data point from the dyno (+15 lb-ft.@ 4,600 RPM) supported the flow bench results: a quieter port and increased flow starting ~ 0.350" lift and peaking (with a 2" stub) at 271 CFM @ 0.750", up from 248 with the base 2.0" round port of the circa-1970 porting job. (Just sticking my thumb into the bottom of the port gained ~ 15 CFM.)