FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: flcomet on January 27, 2014, 04:40:57 PM
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New to the forum and new to fe motors. Been into hot rodding most of my life, so I have a pretty good knowledge base. Sorry, this may be a long first thread. I bought a 64 Comet Caliente a while back that had been setup for, and included a 390 fe motor. The car is pretty nice, but the motor was apart, as the owner said he blew a head gasket. Bought the car from calif, and I live in florida. When I received the car, he failed to tell me that the motor had been apart for a long, long time. The block was toast, it was bored out .060 and most of cylinders rusted. The car came with newly machined and ported cobra jet heads, with 2.090 intakes, and 1.750 ex. valves. I also got a factory low rise two four intake with carbs and cobra air cleaner and valve covers. The motor had TRW 12.5:1 pistons in it. So, I found another 390 block locally, and started taking apart the old block. Someone had put a lot of time and effort into it, as the oil pump plate bolts were safety wired, it had cobra jet rods, and the pistons looked almost new, the skirts showed almost no wear. The cam is a Crane solid lifter F-266/3528-8 that looks nice. The old block had exhaust valve notches cut in the cylinders. I had the replacement block machined for the pistons, and new cam bearings installed, and had the decks skimmed to clean them up. I forgot to have the machine shop notch the cylinder bores on the block. I wanted to check things out myself, so I removed one of the exhaust valve springs, and bolted up the head on the new block with an old head gasket to look at the exhaust valve from inside the cylinder. I put my dial indicator on the valve tip and measured .365 until the valve hit the block. I then looked up how to check for total valve lift out of the head measuring the cam. I measured 1.700 lobe height from base circle bottom to lobe peak. Base circle measured 1.360. Subtracting those leaves .340, and multiplying that times 1.76 for rocker arm ratio gives me .598 total valve lift. Subtract the original .365 that the valve moved before hitting the head, and that leaves .233 valve travel into the cylinder bore. I looked at the old block, and it looks like the upper piston ring mark is about 9/32, or .281 from the top of that deck. The valve lash is .026, so that theoretically could be subtracted from the gross lift I suppose. Doing that, and subtracting the .207 from the 9/32 (.281) leaves me .074 from the valve face to the upper piston ring top. Is this enough clearance? And how much clearance would be safe around the radius of the valve to the block notch?
Thanks guys
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See some old posts...and Bill's post at the very end for clearances.
http://fepower.net/simplemachinesforum/index.php?topic=40.0
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I did a search of old posts and saw that particular one. So I guess from what Bills says, with the minimum being .060 to .065, I should be ok at .074 from the top ring land............with a radius clearance of the same .060 around the valve?
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Sounds to me like that would be OK. I'm surprised that whoever did the heads put 1.75" exhausts in it, while leaving the stock intake valve size; you didn't get flow numbers with the heads, did you?
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Unfortunately, no I did not. They were shipped loose in the car. They look pretty good, some nice port work on them.
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Sounds to me like that would be OK. I'm surprised that whoever did the heads put 1.75" exhausts in it, while leaving the stock intake valve size; you didn't get flow numbers with the heads, did you?
would that be a case where the clearance to the side of the cylinder was chosen over flow, with it then being crutched with a split pattern cam to get sideways into the "70 percent" rule
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Sounds to me like that would be OK. I'm surprised that whoever did the heads put 1.75" exhausts in it, while leaving the stock intake valve size; you didn't get flow numbers with the heads, did you?
would that be a case where the clearance to the side of the cylinder was chosen over flow, with it then being crutched with a split pattern cam to get sideways into the "70 percent" rule
But why would someone choose to install way oversize exhaust valves requiring notching the block for them? Kind of doesn't make sense.
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Well, lots of things don't make sense ::). Hey, remember that "bigger is better" is the American Way! LOL.
I can remember the muscle car era when everybody wanted ever-bigger cams, gears, wider tires, etc. Heck, nobody but real racers even cared about flow rates, matched components, etc. Only more, bigger and more expensive (ouch!) parts would do. Today methinks we know better.....well, at least some of us :)
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Does anyone have any suggestions on a good way to cut the notches in the block? I am planning on trying to set up and adapt a small drill press on the decks and position it where the notches need to be and use a 2" round grindstone on the press to cut the notches. Things are going to be pretty tight between the head gasket edge and the accurate depth of the notches....... :-\
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I watched scallops being put into an FE block at Roush's shop in Livonia. They marked the area by using lay-out dye and then used a cone-shaped tool with a sand-paper face. Did it by hand, a little at a time.
KS
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That is also the way I've done it. Paint the area with blue layout die, scratch a line in the die where you want to cut the notch, and use a die grinder and an abrasive sand roll cartridge. Just do it slowly and carefully. I have also taped off the bore with duct tape to eliminate nicking the bores with the sand roll in case it slips.
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Thanks for the reply. Wow, a cone shaped tool with sandpaper face? So the sandpaper will cut the cast iron deck ok?? I would think that it would have to be some sort of grinding wheel? I will have to cut down into the cylinder about .220. I would think you would need something like this....
http://www.ebay.com/itm/400330260262?_trksid=p2055120.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
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You just need some of these to go with a die grinder:
http://www.goodson.com/1-inch-long-Straight-Cartridge-Rolls/
They have a variety of shapes, sizes, and grits. They work just fine on cast iron.
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thanks for all the info guys. looking forward to attacking the block and getting on with the build.