FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: My427stang on October 17, 2017, 09:47:32 AM
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I am building a mild 390, nothing too fancy, but would like to put a set of CJ valves in the C8AE-H heads. normally a big old nothing-burger, but I am running stock pistons in this mild one
Has anyone ever used a 2.09/1.66 combo with the factory 390 4V pistons? These are the cast 4 valve relief with no dish like the ones below and marked 390 4V in the pin area. Example below, but not mine, found on the net.
(https://www.ford-trucks.com/forums/attachment.php?attachmentid=39730&stc=1&d=1312400681)
Specifically concerned with radial valve clearance going from a 2.03 to a 2.09, not a lot of difference, the exhaust should have plenty of room but the intake side looks pretty tight and I need to make the decision before assembly.
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Have zero experience Ross with your combo but (and you for sure know this!) it would still pay to mock same up (one piston, yada-yada...) with clay to check same. Here's why: another poster may say it's fine, he's done it, etc. But, with so many manufacturing tolerances (stack-up) you may be fine....or not.
Brings back a real life story. My bro' helped his pal do a real stock-bore (maybe +010, forget now) 427 FE years ago. But the used race heads had IIRC something like 2.19 BBC sized valves!
Right at fire-up, the valves hit bore edges, he lost like 3-4 intakes immediately with subsequent head/bore damage. I still have the left-over (Donovan SS I think) intakes and exhausts from that fateful build in my basement!
Wish I had been asked to help!
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I have a 30 over 390 with C8AE-H heads and CJ valves running 2291 TRW flat tops and a 242/246 cam w/.595 lift. When I checked it with clay the intakes cleared fine but the exhausts were close enough I had them fly cut to be safe. Your cam may be the determining factor overall. Jim
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Pocket location on the exhaust is a bigger problem than pocket depth. They can hit along the back wall of the pocket.
I have (almost don't want to admit this) added some radial clearance on an assembled engine many moons ago using a die grinder alongside the relief edges. Grease around the OD, tape everything off, and proceeded to butcher away. Darn thing ran for years...
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Interesting, the relief is so big I wouldn't expect the exhaust side to be an issue, but makes sense if it's not on centerline with the valve.
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I decided to go 2.09 / 1.55 undercut stem with a little bowl work and a gasket match to a 1247. Easy to do and for this mild one, will do good enough.
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Here is a picture of the exhaust cut on my 2291's. The cam is 242-246@.050 and .595 lift. Its not any deeper. Just made the eyebrow a little larger.
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Oh, no! I see Fel-Pro's blue silicone trimmed intake gaskets we've all talked about here, on other Ford forums, even marine forums and more.
I guess, like Clint Eastwood's Dirty Harry said....feelin' lucky today?
And yes, I saw the other post about your 'lucky' experiences.......
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When I did a shade tree 410 some years ago, I rolled the pockets back with a hand disk grinder and a air dremal grinder. Ised a digital scale to keep the weight close my. I used a smaller cam, but I found both pockets too small on the Pistons I had. Don't remember the brand, Badgers I think.