Holden 9-port Red Engine - 2 questions for our mates down under......

[enigma57]

2 questions for our mates down under......

I am building a 292 Chevy inline 6 truck engine to replace the 235 6 in my otherwise stock '57 Chevy sedan. Regarding design architecture, these engines are in fact much like the Holden 9-port red engines.

Due to the long stroke, smallish bore, limited valve size and siamesed head ports, I am not attempting to build a high revving max effort race engine, but to enhance this engine's low and mid range power, whilst bringing it near to a 1 HP per 1 cu. inch displacement state of tune. This is a driver and will be used occasionally to pull a light trailer and boat.

So we have a stump puller...... A warmed over 292 inline 6 truck engine (3.875" bore X 4.10" stroke) for a 3,500 lb. road car. 9.5:1 static comp. ratio, cammed for max. average HP and torque from off idle to 5,250 RPMs with TQ peak at 3,600 RPMs. Very flat power band from off idle through self-imposed redline (these long stroke engines are notorious for harmonics issues resulting in broken cranks and slinging flywheels when spun over 5,500 RPMs for extended periods).

Here in the States, it is common practice when building a Chevy inline 6 to this level of tune to machine the cast-in head bolt boss away altogether and install a bolt-in 'lump port' in the floor of each of the 3 sets of siamesed intake ports whilst using a cap screw to replace the head bolt and threading the upper hole for a pipe plug to seal it at the port roof.

However, looking at port cross section needed for my purposes, I believe this particular head would flow sufficiently if the cast-in head bolt boss were either left in place and thinned/contoured to provide a symmetrical airfoil shape...... Or removed altogether and replaced with a thin metal sleeve whilst retaining the long head bolt (or stud).

I understand this has been the practice with the Holden red engine and was curious as to how well each approach worked, how it was done and if anyone there might have any photos of these head mods.

Also...... Like the Holden, larger valves, bowl work and port work are needed when improving head flow with the 9-port Chevy inline 6 head. Standard bore size is same as 283 V-8 (3.875"), as is valve size and spacing (1.74" intake, 1.50" exhaust). Though larger valves can physically be fitted, 1.94" intake and 1.60" exhaust seem to be the most popular sizes.

My next question has to do mainly with valve size versus valve shrouding. With a standard bore size of 3.875"...... I plan on keeping cylinder walls as thick as possible, so will keep overbore to a minimum (say 0.040" overbore, resulting in a 3.915" finished bore).

With 3.915" bore...... How large of an intake valve can I run before valve shrouding limits flow? How close to cylinder wall before this becomes an issue? Would I actually achieve equal or better flow using a smaller intake size than 1.94"? Possibly 1.84" 305 V-8 valves or cut down a 1.94" valve to 1.90"?

Any help much appreciated,

Harry

[KnightEngines]

It's late here, just reading before bed, so no long reply tonight I'm afraid.
But I can help you quite a lot I reckon, I'll see how I go for time tomorrow & I'll get back in here.

[enigma57]

Many thanks! Look forward to hearing your views on this. The Holden red engine shares quite a bit of architecture with the Chevy inline 6 and I believe similar mods and principles would apply to both.

Here are some photos of bolt-in lump port kit in common usage here......









Thanks,

Harry

[enigma57]

And here are some photos of a reworked Holden 202 head with a contoured center divider (flow vane) added (extends slightly into intake manifold).

Holden photos are oriented with head laying with chambers facing upward. Holden intake port appears to have floor angled as-cast similarly to that of Chevy with lump port added ......







http://www.performanceforums.com/forums ... -race-head

Best regards,

Harry

[KnightEngines]

Yeah, I did that one!
Made 340hp with a 4 barrel holley, he's yet to fit webers.
Back in a bit, morning stuff to do.

[hysteric]

Will this work?

http://store.yellaterra.com.au/holden-i ... bled-56cc/

HOLDEN INLINE 6 BLUE/BLACK 12 PORT ALLOY CYLINDER HEAD (ASSEMBLED 56CC)

[KnightEngines]

Ran out of day, but couple of quick tips:

Using a vane instead of lump port will give far better intake velocity profile on the active side of the port - better inertia ram.
Leaving the boss in place makes porting near impossible, gotta cut it out & then fit a vane or whatever after porting.
A round tube in the port flows real bad & causes turbulence, a shaped vane is much better.

Smaller valve sizing reduces shrouding, you can use steeper seat profiles to trick the motor into seeing a larger valve, I use 50 deg seats on the intake provided I have enough lift to play with.

If you're real keen you can relocate the intake valve guides towards the middle of the cylinder by offsetting in a mill with and end mill cutter & finishing with the normal thinwall guide reamer, this allows a larger valve with reduced shrouding.

[Circlotron]

A round tube in the port flows real bad & causes turbulence, a shaped vane is much better.

I wonder if it would increase flow and reduce downstream turbulence if that round tube had dimples in it like a golf ball, for the same reason a golf ball does.

[chevyfreak]

Sort of on topic.
Found this image when i had fb for a brief period . On a opala page on what the brazilians do. Dont know if their heads is cast so tube is oblong shape and extends to face of head and blended or maybe it had some welding done and then blended. Making it teardrop shape to guide air past.



On a side note to the siamesed ports used on inline engine.
Here in south africa we had a 2.3 4cyl based on the 2.5 (153). Unique to za and done by gmsa in late seventies and stopped using them in '82.
Had same size bore as 153 but shorter stroke. Longer conrod and they moved ch of piston.( Only they would know why as finding pistons is a major headache.) And the castings are softer and cracks way easier than the 153/230/250.
The head were a 8port design. Roof of port was raised to enlarge the port volume. Only came with 1 barrel intake with small monojet and intake had a small divider like a knife edge just before face.
Always wondered how that sort of 12port design head would respond on a 230/250 or even the 292.

Chevyfreak.

[Truckedup]

As the OP of this post has probably read....The several men who built the best Chevy engines in the USA says the open lump port makes more power thn a divided port..These were drag racing engines that domnated their classes...

[Geoff2]

Probably the same reason the front of an aeroplane wing is rounded, not sharp.

[enigma57]

I studied that issue when we were working up the first EFI intake for Dan Miller's early hemi EMC engine in 2010, Geoff. You are spot on. A sharply pointed (knife edged) leading edge will induce shear and turbulence. That is why we went with a symmetrical airfoil shape for all leading edges of divider walls in interiour flow path on that project.

See airfoil shape at bottom......



On the other hand...... We were using the symmetrical airfoil shape on the leading edge of port divider walls at the extreme upper end of very long IR runners.

Whereas the knife edged vertical center vane on the modified Brazilian Opala head that Chevyfreak posted......



Would seem to do a good job of splitting the inflow and directing it towards the 2 valves served by the siamesed Chevy intake port if turbulence at that point of the overall flow path might serve to atomize rather than separate fuel droplets? Not sure, just wondering.

Best regards,

Harry

[enigma57]

I wonder if it would increase flow and reduce downstream turbulence if that round tube had dimples in it like a golf ball, for the same reason a golf ball does.

Interesting thought! I have actually considered doing the golf ball indentations for the lower half of my intake runner cross section. Lots of work doing it all by hand with a small round carbide bit on a long shank chucked up in a 3/8" variable speed drill motor out in the shed, though!

Best regards,

Harry

[enigma57]

As the OP of this post has probably read....The several men who built the best Chevy engines in the USA says the open lump port makes more power than a divided port..These were drag racing engines that dominated their classes...

I agree, Tony. Point well taken.

There seem to be 2 issues at play when comparing lump ports as used on American and Brazilian Chevy inline 6 heads and vertical center vane dividers as used on Australian GM Holden red engine heads......

1. The American and Brazilian 9-port heads have siamesed intake ports cast with flat floors and in their unmodified form...... The flow path is brutal, requiring a sharp 90 degree turn to enter the bowl and reach the intake valve, whereas the siamesed Aussie GM Holden 9-port head has a radiused floor to begin with. So the single best thing you can do with the American and Brazilian head is to do a lump port installation and give it a radiused flow path to the valve.

2. The vertical center vanes added to the Aussie GM Holden 9-port head seems to work well, as they are cast with a radiused flow path and do not need the lump port mod as do American and Brazilian heads. So what I am curious to know is whether my 292 head will have sufficient CSA after installing lump ports to allow me to experiment with a vertical center vane divider, as well.

Best regards,

Harry

[enigma57]

Ran out of day, but couple of quick tips:

Using a vane instead of lump port will give far better intake velocity profile on the active side of the port - better inertia ram.
Leaving the boss in place makes porting near impossible, gotta cut it out & then fit a vane or whatever after porting.
A round tube in the port flows real bad & causes turbulence, a shaped vane is much better.

Smaller valve sizing reduces shrouding, you can use steeper seat profiles to trick the motor into seeing a larger valve, I use 50 deg seats on the intake provided I have enough lift to play with.

If you're real keen you can relocate the intake valve guides towards the middle of the cylinder by offsetting in a mill with and end mill cutter & finishing with the normal thinwall guide reamer, this allows a larger valve with reduced shrouding.

Much appreciated, KnightEngines! That helps a lot. Do you have another set of the vanes there? My ports are probably slightly taller than those on the Holden red engine, but I would very much like to try both the vanes and lump ports together on my 292 head.

Best regards,

Harry