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| Advice on rebuild. https://www.slantsix.org/forum/viewtopic.php?t=9569 |
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| Author: | rrither [ Mon Jun 14, 2004 10:05 am ] |
| Post subject: | Advice on rebuild. |
I have a 64' Dart, 170, 225cid, auto, 2:73 rear, super six, 2 1/4" exhaust, with petronix conversion. It's my daily driver, with 210,000 on the clock. It has been using about one quart of oil each 6 to 800 miles for the past year, and 18,000 miles or so. No leaks to speak of, no smoke until last week, now a bit a idle, and off line. I replaced valve seals last year, with little or no change in oil use. Just the excuse I needed. Anyway I plan on rebuilding it in the near future, and would like to run this by you all, as confirmation of what I have read here. A quality rebuild,and balance by a reputable shop in town (Dugans in Riverside Ca), is planned. Head work, 3 angle valve job, shave the deck a bit, porting as outlined various times here. Questions on head, 1.Should I try porting myself? or pay for it? I feel I have the ability, but time is a factor. 2. Should I find a 73 or later head to start with? It looks to me like the #252 Comp Cams, cam would be a good choice. Other recomendations? As I said this is a daily driver, not a racer. I would like to keep the 18 to 22 MPG that I have been used to, and the longevity I expect out of this engine. But at the same time better performance is on my mind. |
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| Author: | Dart270 [ Mon Jun 14, 2004 10:42 am ] |
| Post subject: | |
For your purposes, I'd say that 252 cam will work well. I would also recommend 0.040-0.050" mill off your head (or block deck) to boost overall performance, mileage, and compatibility with a mild cam upgrade. There is no drastic difference between the head types, but 74-up eliminate the plug seals but make it difficult to get the lifters out if you want to change cams w/o removing the head (not a big deal for you, I think). '68-up heads have a supposedly better combustion chamber shape, but I and many of the racers have not seen big differences in performance there either. Personally, I'd do the porting myself for that buildup, but of course it will take some time (including back and forth to machine shop). You'll want to get new guides pressed in and milling done, then do porting, then take it back for the valve job. Lou |
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| Author: | Guest [ Mon Jun 14, 2004 3:55 pm ] |
| Post subject: | Thanks |
Thanks. I am diving in. |
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| Author: | oibrownskin [ Tue Jun 15, 2004 5:14 pm ] |
| Post subject: | how to port? |
When you port heads, what exactly are you looking to remove, preserve, and avoid? what is the preferred tool, a dremel or some other rotary tool of that nature? on a difficulty rating for a mechanically inclined person from 1-10 1=chaning your oil and 10=building a car with an avacado, a snorkel and a corkscrew that will run 10's ; how difficult is porting? Caesar |
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| Author: | Thropar [ Tue Jun 15, 2004 6:03 pm ] |
| Post subject: | Porting away |
when you port and polish a cylinder head, you are trying to increase the flow of air and fuel through the head so it makes more power. Bigger is not always better.... taking off corners, smoothing areas that impede flow of air, and visualizing how the 'flow' goes through the head is what I do... use a high speed die grinder (makita) with a 1/4" shank, and a medium sized carbide bur (bit) with an oval head on it.... it's not difficult, if you can imagine shaping an avacado with a really sharp knife without cutting your finger off, and keeping the pit intact (don't grind into the water jacket).... i'd say have someone show you how to do one of your intake & exhaust ports, then do the rest yourself.... or have someone point out what to do on another cylinder head... you will want to do the porting after your new guides are put in (if needed) and before you get your valve seats ground... if you are going to put in larger valves, have them roughly cut the seats to size, do your porting, then have them cut the seats to perfection and lap them in... 3 angles on the intake, 1 on the exhaust is my preference... open up the bowl area considerably to flow into the size of the valve you have chosen... round off the guide protrusion... I take off quite a bit of material on the ports, in the right spots, usually spending 30-60 min./port to rough in. I will do all the intake ports first, then all the exhaust so i stay "even" with the metal removed. I never use a flow bench, so it's backyard porting at it's best... get it flow tested if you are really racing... use the carbide to shape, then use sandpaper rolls to smooth it all down, don't go too smooth on the intake, shine up the exhaust, and take all sharp corners off the combustion chamber (any sharp edge) with the sandpaper, don't grind anything in the chamber with the carbide.... scribe the gaskets on the ports, then shape the ports to fit the gasket shape perfectly.. port the manifolds to the gaskets too... don't mess with anything but 1/4" shank bits, the 1/8" dremel's are too rinky dink... use good goggles with earplugs and a dustmask, brush off consistently (metal dust in hair, eyebrows, eyelashes, it will get everywhere!) ... i've had rusted metal dust drilled out of my eye twice because of messy porting... happy porting |
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