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| Head porting https://slantsix.org/forum/viewtopic.php?f=30&t=61020 |
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| Author: | MOUSETRAP [ Sun Apr 16, 2017 2:37 pm ] |
| Post subject: | Head porting |
I plan to gasket match ,debur intake and exhaust . Installing larger engine builder valves I'll be running 6-9 lbs of Boost with super charger So I am assuming I can polish the exhaust port smooth ?? Intake is normally left semi rough to help fuel mixture is this true on forced induction ?? And the chamber on the head polished smooth or rougher as cast finish ?? Thank you all |
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| Author: | MOUSETRAP [ Fri Apr 21, 2017 1:13 pm ] |
| Post subject: | |
Pulled the valves and Ran the head thru the washer few times all clean 👍👍 I magnafluxed it all is good ready to start with port and polish Let the fun begin !!!! |
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| Author: | Badvert65 [ Mon Apr 24, 2017 2:03 pm ] |
| Post subject: | |
Be careful removing material. Especially in the area where the two valve bowls are next to each other. Don't ask me how I know. -Matt |
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| Author: | MOUSETRAP [ Wed Oct 21, 2020 3:32 pm ] |
| Post subject: | Re: Head porting |
I plan to gasket match ,debur intake and exhaust . Installing larger engine builder valves I'll be running 6-9 lbs of Boost with super charger So I am assuming I can polish the exhaust port smooth ?? Intake is normally left semi rough to help fuel mixture is this true on forced induction ?? And the chamber on the head polished smooth or rougher as cast finish ?? Thank you all So after life getting in the way this project is back on does this type of porting seem right thanks |
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| Author: | Joshie225 [ Wed Oct 21, 2020 4:06 pm ] |
| Post subject: | Re: Head porting |
I have come to believe that port matching is useless. Who says the gasket has the correct port size? Have ypu noticed the intake ports are already larger at the head face? Productive work will be within 1" of the valve seat. |
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| Author: | emsvitil [ Wed Oct 21, 2020 4:23 pm ] |
| Post subject: | Re: Head porting |
Gasket matching isn't necessary. You just need to make sure the casting boogers are removed and things are smoothed. Since the exhaust manifold (and possibly the intake manifold) move with heat, just make sure the airflow never hits a step. This can be done by a slight step up in port size in the flow direction. (head port slightly bigger than intake manifold / exhaust manifold slightly bigger than head port). The small step up in size doesn't affect flow (at least at our power levels) but a step down in size would affect flow. |
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| Author: | Dart270 [ Thu Oct 22, 2020 4:08 am ] |
| Post subject: | Re: Head porting |
Your plan sounds good. Everyone's comments above are good ones. Most of the action is in the bowls, where you want to open to match the valve sizes. Yes, do not get happy with the section near the bowls and between each I and E port. Water lurks... Lou |
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| Author: | MadScientistMatt [ Thu Oct 22, 2020 6:55 am ] |
| Post subject: | Re: Head porting |
I ended up gasket matching both the head and the manifolds. I'm not sure if it will do very much, but it didn't add very much time to the overall port job, and revealed a pretty significant mismatch (around 2 mm) between the Clifford intake manifold and the head ports. |
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| Author: | DadTruck [ Thu Oct 22, 2020 5:49 pm ] |
| Post subject: | Re: Head porting |
the one thing i have to offer is that I agree with Josh, the most port flow gains happen due to improvements that occur with in inches of the valve seat. Gasket matching, port arm refinements are hocus pocus at best a waste and an energy killer at worst. Find a better way if you choose to or consider what DV says on the subject. https://www.musclecardiy.com/cylinder-h ... ds-part-8/ I am working with a valve seat guy that does porting on circle dirt track sprint car motors. Bigger motors than ours, but motors that need instant response. He thought the 30 degree seats were nuts, I am the customer so I got him to do it, time will tell. Bottom line is I don't think there are any 'slant six experts',, its more about experimenting and testing and finding the combinations that work for you. This is not to say the slant six is totally unique in engine architecture and requirements, but to say slant six engines have their own optimization, like any other engine. |
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| Author: | Killer6 [ Sat Jan 02, 2021 1:48 pm ] |
| Post subject: | Re: Head porting |
Port matching isn't really about "gasket matching", and with the way a Slanty intake can be mis-aligned with the actual ports in the head, it pays to use the gasket as a guide to open the head to accommodate this. The port in a "peanut-plug" head is embarrassingly small, only~1.25"sq. where the guide boss & floor are closest in proximity. That will port velocity limit a 225 to 4,600rpm, period, unless You're using a roller or fast-ramp/high rocker ratio combo. As stated, the bowl & valve job along with larger valves is critical to making the oats & step #1, especially with boost. But that choke-point in the port must be corrected, & it certainly can be. There is enough meat there to take You well into the 6's. Boost can cover-up flow inefficiencies, down low & mid-range for sure, but (esp. turbos) can expose them fast at higher rpm's where the curve can fall off a cliff.............. |
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| Author: | Rick Covalt [ Sat Jan 02, 2021 2:57 pm ] |
| Post subject: | Re: Head porting |
[quote]with the way a Slanty intake can be mis-aligned with the actual ports in the head, it pays to use the gasket as a guide to open the head to accommodate this.[/qu This is true! The intake and exhaust can be misaligned a great deal in my opinion. I always use the gasket to get the intake ports lined up with the head when I mount them. Also on aftermarket intakes the runners themselves can be misaligned- Up an down from each other quite a bit. |
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| Author: | MOUSETRAP [ Sat Jan 02, 2021 4:00 pm ] |
| Post subject: | Re: Head porting |
Santa gave me a Milwaukee 1/4 die grinder Elf’s gave be carbide burr set and a sanding roll porting set #1. I need to test fit windage tray and crank scraper #2 Test fit timing tab for Romac balencer #3. Pull pistons and mark bores on to head Then the porting and polishing will start |
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| Author: | DadTruck [ Sat Jan 02, 2021 7:43 pm ] |
| Post subject: | Re: Head porting |
Another place to work to add port flow is in the combustion chamber, by un shrouding the valves. A way to do that is, with the crankcase on the rollover, prior to installing the crank, bolt the cylinder head to the block and roll it over so the pan rail is up. Reach inside each cylinder and using a very fine tip marker, trace the circle that is the interface of the combustion chamber to the cylinder wall on each cylinder. Roll the case over and remove the head. Observe if there is material on the combustion chamber wall that can be remover to increase the gap between the intake - exhaust valve and the combustion chamber wall. If so remove material from the combustion chamber wall out to the diameter of the cylinders. This is where when doing an overbore on the cylinders going to +.060 or more can make a difference. If you feel racey, open the chamber close to the valves to the diameter of the head gasket. As with any combustion chamber work, keep the final volumes equal as possible. Coordinate the volume change with other deck work to achieve your targeted compression ratio. |
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| Author: | mpgmike [ Fri Jan 29, 2021 8:45 am ] |
| Post subject: | Re: Head porting |
There aren't many books on the subject, but this head porting book even has /6 examples: https://www.amazon.com/Head-Porting-Sec ... oks&sr=1-2 |
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| Author: | volaredon [ Wed Feb 03, 2021 7:04 pm ] |
| Post subject: | Re: Head porting |
I have a /6 head ported as far as I dare, I started to unshroud the valves a bit in anticipation of new oversize valves... I found my stack of head gaskets and set one on the head... wow I don't seem to have much room to do much work there... the head gaskets I have are the old Fel Pro gray/silver ones before the Print-o-seal, and without doing hardly anything to unshroud valves the stock chambers are right against the fire rings it seems..... I did a little (very little) on a couple of cylinders and it seems I am into the fire ring area already.... my HGs are the old 7918SB.... I see specs for thickness, etc on the new style Fel Pro 7918-PT1 which shows 3.5-something bore size in teh gasket, which witha 3.420 bore would seem to leave me some room.... I' gonna have to measure the ID of teh bore on tehse gaskets I have before I go any farther.... if the new style FP head gasket has a bigger bore it looks like I will have to get one of those instead. |
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