28 replies to this topic

[lctriples]

Just wondering if anyone has had a go at port matching there own cylinder head? and if so, how difficult/easy was it? ie: is it a job best left for the professionals. I presume you need carbide tip burr tools, not sure if they work in a drill or only die grinders. I was hoping to have a go at 12 port 3.3 blue motor with triple webbers. Not a full on port and polish, but just to match extractors, intake manifold/s to head. any help or advice greatly appreciated. I tried to find a thread on this forum and found a Q&A type thread but didn't have any info as yet. Final Q, does it make much of a difference? Thanks Paul.

[lctriples]

Thanks Daz, appreciate that, as they always say, "How hard can it be!"

[LC-GTR-1969]

Not hard if you are just port matching. Use a gasket as a template to help you match the manifold to the head- use a scribe to outline your sizing. 

 

You will need a die grinder and some carbide burrs. I bought some cheapos off ebay for about $35 (think it came with 5 burrs for that). These have held up well with alluminium but cant say how good they would stay sharp with cast iron. Still, they are cheap enough.

 

Patience, take your time and you will be fine. Also with porting, less is more. Only port enough to create a smooth transition from the manifold to the port face. There will be some gains with smoothing out the short turn as well but others who have a flow bench will be able to give you more specific advice for that area.

Edited by LC-GTR-1969, 24 June 2016 - 06:39 AM.

[lctriples]

Bomber, does that mean don't touch inlet ports at all? Thanks paul

[lctriples]

Bomber, this is how much I may need to remove, but is obviously the no-go area you are talking about. The exhaust ports are almost spot on with extractors. All three inlet port/s need almost exactly the same metal removed (I have only shown the first port) and the engine builder mentioned when he re-coed the heads he gave them a bit of a "tickle up".. I notice the area that needs to be removed is mostly top of port, almost a "v" shaped rectangle, so maybe he had already ported the lower section, as this would be where the fuel flows into engine? The other thing is that manifold/s I have for the triples are 3 piece, (not fixed one piece) so I have a bit of flexibility to try and move each manifold to match ports as close as possible without machining them. If engine builder has already fiddled around with them I definitely won't touch them, as if I break through the walls, the head will be stuffed and have already spent a bit of dough on it. (re-seated, larger valves ect). At this stage it may be best to leave as is, because it isn't going to be drag motor, just a cruiser with a bit of grunt, Cheers Paul.

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[LC-GTR-1969]

Dont rely on just the gasket though, check through the end of the manifold to see what the match is like. The gasket shoudl be first checked against the manifold then checked against the head, then decide where to go from there.

[LC-GTR-1969]

Sorry for the thread hijack, What are your thoughts on matching carbs to the manifold Johnno? Like 2 inch SUs to a 1 3/4 manifold? 

[N/A-PWR]

what oldjohnno said ^,

 

 when dealing with just atmospheric pressure ( 1 bar - 14.7psi ), or a partial vacuum,

 

 the bigger diametre - area size of the manifold - tube, get's the best flow, as size is the go.

 

 

This is because we have no greater pressure to force air flow like a turbo or supercharger. 

learned this installing ventilation ducting with multiple inlets. 

[LC-GTR-1969]

Sure, make the hole in the manifold as big as the hole in the carb.

 

Sorry, my wording was not clear- What I am interested to hear your thoughts on is how far to extend the transition from the face of the manifold- how far along the length of the manifold to blend the hole? 

[LC-GTR-1969]

You were clear, I wasn't.

 

If you wanted the best possible flow - and this assumes that the head end of the runner has a bigger area than the carb end - then you'd try to expand the runner gradually so that flow separation didn't occur. Separation usually starts to happen when the walls diverge from the centreline at an angle greater than around 5 to 10 degrees. If the runner is short and/or the port-end area is large then it mightn't be physically possible to make the angle so gentle. So you'd just blend it for as long as you could. On the other hand if the runner was long you'd angle the walls out until the area equalled that of the port face and make the rest parallel.

 

But all this probably doesn't matter so much in the real world of street cars that don't flow much anyway. For a Holden six if you just blended it far enough in that the runner no longer reduced in diameter it'd be fine.

Cheers mate, pretty much what I was thinking but I thought I should check. Ill be having a dig at the manifold in the next week or so. I might throw some pics up here...

 

Thanks again, regards

[lctriples]

Thanks for everyone's input and feedback. I think I might er on the side of caution and leave well enough along at this stage, might even pick up an old 12 port to practice on. There is some good info on an internet post entitled "Holden Six Motor Build".  I tried to link or cut/paste onto this thread but unable to do so. LC-GTR-69, if you can post pics as you go that would be great, or if anyone else has any relevant pics like Muzzy's, that would also be great. Cheers paul

[lctriples]

Sorry, made a bit of a blue, the engine build info is actually called "building the hot holden six by [email protected]", my bad!

[N/A-PWR]

* that's our snarley oldjohnno Paul.

[lctriples]

Wow, small world hey, its a great read oldjohnno, you obviously know your holden 6's.