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| Head and exhaust questions. https://slantsix.org/forum/viewtopic.php?t=33794 |
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| Author: | lowbudget [ Sun Feb 15, 2009 9:01 pm ] |
| Post subject: | Head and exhaust questions. |
I have been reading all the old post's about Super sixes, head work and Dutra duals. I started on page 248 and now I am on page 120. I've leaned a lot and have had some good laughs. Now for my questions. 1. Did any of the late 70 early 80 heads have hardened seats installed from factory? If so when did they start? 2. If putting in oversize valves do cylinder walls/piston need reliefs cut in them? Assuming stock bore. 3. Roughly how much shaving can be done on head still using stock pushrods? 4. If running Dutra Duals are the exhaust flanges just standard ones with a 2" opening? Thanks in advance Mike |
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| Author: | Joshie225 [ Sun Feb 15, 2009 9:08 pm ] |
| Post subject: | |
Hardened exhaust valve seats actually started in the early 1970s, but often the hardening is gone after a valve job or two. If you want hard seats they are not that expensive when done along with a normal valve job. If you use 1.70/1.44" valves they fit the stock bore fine. Larger will fit, but usually aren't of much benefit unless the combustion chamber is relieved. I had a head milled .080" and it's working OK with stock pushrods. It was a pretty large chamber head to begin with. YMMV |
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| Author: | lowbudget [ Sun Feb 15, 2009 9:29 pm ] |
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Cool I'm just trying to get my ducks in a row. I bought a 76 slant and auto tranny f/100.00 of the net yesterday. It has 80,000 so I'm going to start doing a rebuild when I get home in March and want to get it planned out while I'm at work. I'm thinking of using The Erson 270 cam, will larger valves be worth the money spent or should I just port and polish the head and use the stock valves? 
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| Author: | Joshie225 [ Sun Feb 15, 2009 10:23 pm ] |
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Oversize valves and head work are absolutely worth doing. When I wanted to go a bit faster I put bigger valves in the head (1.70/1.44"), milled the head enough to get a true 8.5:1, put on an Offy intake with a Holley 390 and 2 1/4" exhaust off the stock manifold. I ported the head myself. This reduced my 1/4 mile ET by over 2 seconds with no loss of fuel economy. Stock 1967 cam even. Doug Dutra's DaCuda ran nearly the same ETs as my Valiant with a 1bbl Carter carb. He had a reverse dual pattern cam and less weight. Not sure of the extent of his head work. Personally I would run a stock cam or a very mild reverse dual pattern unless you have a higher stall torque converter and something better than 2.76 gears. The engine I'm building now is getting more cam duration and more compression than the '67 along with headers. This car has numerically higher gears and the torque converter is a PTC 9.5". It's all about the total combination. I suggest you either set a budget or a performance goal and plan accordingly. |
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| Author: | lowbudget [ Mon Feb 16, 2009 3:35 am ] |
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My plan is to build up the 76 motor with the 270 cam, super six set up, Dutra duals, distibutor recurve. If compression is ok I might just leave bottom end alone for now. I will be shooting for a 9 - 9.5 to 1 comp ratio. At the alttitude I live at (5500+-) I should be ok. I will do the tear down, do the math and decide where to go from there. Note this is only a temp. motor while I build the original, just think of it as a practice motor. LOL I just thought a little head work, cam, Dutra Duals and the super six set up would give my Valiant a little more pep while I build a bigger HP hot street motor. My weak link right now is the 7 1/4" rear. This way I can have one ready to change out when I pull the other one. Spares are a good thing! Besides having 2 motors might give me an excuse to pick up another A body 
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| Author: | rock [ Mon Feb 16, 2009 8:57 am ] |
| Post subject: | When I put in big valves I had the chamber cut to unshroud t |
Hello, Maybe not required, but I was in the head and only wanted to do it once. Using the 1.70 and 1.44 valves I had the chamber cut to unshroud the valves. Ported up the chamber surface, too. I can send you a pic if you PM me your regular email address. Head milled .100, ported and polished too. Like a sprinter, hard to run if you can't breathe. Course, you need an ignition system too. All part of a plan though. rock '64d100 |
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