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| Porting, engine and valve unshrouding pics now at https://slantsix.org/forum/viewtopic.php?t=34063 |
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| Author: | emsvitil [ Tue Mar 03, 2009 4:40 am ] |
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Since gasket sizes vary, and are often larger than you need, what you need to do is 'port match' Which may equal the gasket size, but usually is smaller. You want to smooth the port, and keep it in alignment. Don't trumpet the openings it get to the gasket size and NEVER step down in size when mating the 2 opposing openings. You may be able to have a perfect match between head and manifold, but it's ok to have a slight step up in size in the flow direction. So the head ports should be equal to or slightly larger than the intake port (with no step downs anywhere); and then on the exhaust side the head ports should be equal to or slightly smaller than the exhaust manifold (again with no step downs anywhere) |
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| Author: | Rug_Trucker [ Tue Mar 03, 2009 5:54 am ] |
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I forget what my '69 model head looked like in the chamberswhen I was grinding on it. I am doing a 77 or 78 head right now for a van. I smoothed a trough going towards the exhaust from the plug hole. I am unshrouding the valves and making things more circular. Even with the stock valves I think there is restrictions. Just wondering why you didn't polish the chambers? |
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| Author: | rock [ Tue Mar 03, 2009 6:48 am ] |
| Post subject: | Thanks guys, and some answers, especially to manifold port |
Thanks guys, I, as anyone, likes to hear folks who knows what they are looking at say "nice job"! My ole truck is a long way from when I wore it out on the farm, had it in 4 colors including thinned school bus paint and a turquoise hood, and completely caved in rear fenders. The ole slant was still going so strong is why I decided to start playing with it. Imagine, start out to rebuild an engine and end up with a new truck and a whole forum full of online acquaintances! Now, as to your questions, and first, as to the manifold porting. I totally agree with Joshie and Emsvitil: the hole in the header or manifold MUST be larger than the one in the head so gases don't get restricted and bounced back. I don't believe any good comes from having both intake and exhaust holes on the head equally as large as one another, either. The two pictures of the head ports you see are dated 10/07. I forgot they were in Menko's album and they are from when I was teaching myself how to port. I wrote a thread about this activity then and what I was up to was an experiment to see how far I could take porting. I got the Aussie gasket which has huge holes and decided to trumpet the ports to match, to see what was involved and to develop technique. I got pretty good at it as you see, uniform flare, nicely polished. That is the head that I wrote about as the one that when I took one more polish pass I hit water in number 6 exhaust. About a 30 to 40 hour lesson that went to the scrapyard last month! But I got good at porting for the NEXT head, which is the one with the valves in it and the unshrouding. Ric, I don't have a good pic of the area under the valves, sadly. I never could get one to show what I wanted because it is so highly polished that I kept getting a pic that looked like a fireworks display, even in sunlight only. SO you can take it I don't believe in gasket matching, but proved I can do it. Now about unshrouding. No, Cars, not done with a die grinder! The head had 3 main tasks done sequentially. Port and polish, then mill off .100 and smooth the manifold plane, then cut valve seats and do the unshrouding. I had the large hole Aussie head gasket and decided to cut the combustion chamber as far as that gasket allowed, and even then got a couple thousandths under the gasket and had to "relieve" the gasket. Those are engnbldr valves with a set of 340 springs and I wanted a 5 angle seat, so there is regrinding done to the seats. The unshrouding is done with a fly cutter on a vertical mill that was CNC controlled for accuracy. I wanted equal head volumes so far as I could get. That work was done at an old time racer's machine shop here in town. They have lots of experience doing this work. Sandy, I kinda think the head (drool tube head) may have had some milling done before I got to it, because my notes show the final CC was 44. We used Wheelspin.net with standard bore and stroke and a .039 compressed head gasket thickness. I measured the piston deck clearance at .160, and got CR of 8.96. I was surprised to have only 44 cc left after milling is why I think it may have lost some before I got there. Or is that volume typical for you all? The pinging on 87 octane is why I set out to learn recurving and got the p ing out, but now run 93 octane. Last, pinkiedog, yep, there is HEI in there. Note you see NO alternator on passenger side and see a row of relays on driver fender. I moved the alternator to low down on driver side and used a GM 12 SI alternator (or 12 SI?). Relays are for high and lo beam, horn, and some spares for add ons like fans or AC if ever done. I wanted to split wiring so the starting side was on driver side and the running side was on the passenger side. (My terms) The wires come out of a grommeted hole in the firewall just to driver side of the old, unconnected regulator. All wires were put in corrugated cable tubes for neatness. You can see one yellow ground for the tach slinking out to the battery cable ground on the firewall. There are three ignition wire hookups tucked away: MSD in nook up front to side of radiator frame, HEI on inner fender, and conventional. Three complete wiring setups so all you have to do to switch is plug in another dizzy. All new wiring everywhere. The pic doesn't show the new Offy chrome valve cover with Dan't PCV adapter and braided hoses for fuel and PCV that are there now. Last, venable, glad you like the oil pan, glad to let you have the truck on same terms, but shipping might be high. Oh, as a safety item, DON"T drive with lights on and headlight shields on!! Those are only for bling because I can't go as far as curb ticklers. rock '64D100 |
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