problem with aftermarket cylinder heads.
10-16-2015, 05:37 PM
#91
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How would a tight guide be more of an issue after 50-80 hours?
10-16-2015, 05:39 PM
#92
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10-16-2015, 05:46 PM
#94
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Thread Starter
10-16-2015, 05:57 PM
#95
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there are a lot more heads out there than afr...what about the budget stuff? some info to keep the inexperienced new guys out of trouble that might be looking at procomps, edelbrocks etc....
10-16-2015, 06:14 PM
#96
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Thread Starter
exactly the type of information i am looking for.i have heard all kind of war stories about pro comp heads but no one has posted anything on this thread.i had an edelbrock head stick a exhaust valve within one minute of initial startup,that was on a 95 inch kit for a twin cam harley.i sent it back and they never gave an explination on the failure,they just sent me a different head,app 5000 hard miles later it still runs great.
10-16-2015, 06:58 PM
#98
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There's more to valve guide clearance, than whether or not it sticks a valve, or it doesnt. So, if it hasn't stuck a valve at 80 hours, its good right?
What if it was a car? My GPS Chartplotter on my boat, logs miles, avg speed, etc. My average speed, is somewhere in the 30's. This obviously includes idle time, etc. So, lets just say, 80 hours, times say 35 miles per hour. Thats 2,800 miles in the car world. Would you guys call your heads a "Success", if you bolted them on your car, and at 2,800 miles, the valves didn't seize? What if the guides were worn to chit, at 3500 miles? Would you consider that good or bad?
I can probably link up 20-30 threads in about a 5 minute search, of guys complaining about prematurely worn guides, in car forums, with aftermarket heads. I'd be willing to bet, 75% or more of them, bolted them on out of the jegs catalog, or had poor valvetrain geometry. .
Valve guides transfer heat from the valve, control oil seepage to the combustion chamber, control valve to seat contact pattern, control air leaks from manifold vacuum, and must simply be setup, to go the distance. Different guide materials, different stem/guide sizes, coolant temperatures, combustion temperatures, and other things can dictate, what the ideal clearance may be. A head that's meant to go on a 500HP car engine with a 195* thermostat, may require a different stem clearance, than a engine that runs 90* coolant temps, and making in excess of 1000HP. If NONE of that mattered, I would think AFR, would simply erase
Our typical valve guide clearances are .0013”-.0016”. In some severe applications (nitrous, marine endurance racing, or blower usage) looser guides might be required. Check with your engine builder.
Or from Dart
Valve to valve guide clearance is finished at .0012” - .002” with our valves(OD .3415”). If you have a particular clearance for your valves or application the guides should be measured and sized to your specifications.
What if it was a car? My GPS Chartplotter on my boat, logs miles, avg speed, etc. My average speed, is somewhere in the 30's. This obviously includes idle time, etc. So, lets just say, 80 hours, times say 35 miles per hour. Thats 2,800 miles in the car world. Would you guys call your heads a "Success", if you bolted them on your car, and at 2,800 miles, the valves didn't seize? What if the guides were worn to chit, at 3500 miles? Would you consider that good or bad?
I can probably link up 20-30 threads in about a 5 minute search, of guys complaining about prematurely worn guides, in car forums, with aftermarket heads. I'd be willing to bet, 75% or more of them, bolted them on out of the jegs catalog, or had poor valvetrain geometry. .
Valve guides transfer heat from the valve, control oil seepage to the combustion chamber, control valve to seat contact pattern, control air leaks from manifold vacuum, and must simply be setup, to go the distance. Different guide materials, different stem/guide sizes, coolant temperatures, combustion temperatures, and other things can dictate, what the ideal clearance may be. A head that's meant to go on a 500HP car engine with a 195* thermostat, may require a different stem clearance, than a engine that runs 90* coolant temps, and making in excess of 1000HP. If NONE of that mattered, I would think AFR, would simply erase
Our typical valve guide clearances are .0013”-.0016”. In some severe applications (nitrous, marine endurance racing, or blower usage) looser guides might be required. Check with your engine builder.
Or from Dart
Valve to valve guide clearance is finished at .0012” - .002” with our valves(OD .3415”). If you have a particular clearance for your valves or application the guides should be measured and sized to your specifications.
10-16-2015, 07:05 PM
#99
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Platinum Member
Just a thought, Is the head at fault or ones diligence on preparing the head for intended service? Today most head porters will choose a brand solely on the casting giving them the material so they can get their port shape and design without welding. So I guess my point would be after you have done your homework and selected a head that is going to give you the best performance for your engine, maybe you should take the time to blueprint the head, check clearances spring heights, pressures, valves. Just like we all do for rod and main bearings. All the engine builders I am familiar with want to do their own valve jobs, spring set up and final guide honing anyway. If your buying a run out of the box head, then that should be part of your homework making sure it is done with all your specs. Just don't assume they will give you what you need.
10-16-2015, 07:24 PM
#100
Registered
Just a thought, Is the head at fault or ones diligence on preparing the head for intended service? Today most head porters will choose a brand solely on the casting giving them the material so they can get their port shape and design without welding. So I guess my point would be after you have done your homework and selected a head that is going to give you the best performance for your engine, maybe you should take the time to blueprint the head, check clearances spring heights, pressures, valves. Just like we all do for rod and main bearings. All the engine builders I am familiar with want to do their own valve jobs, spring set up and final guide honing anyway. If your buying a run out of the box head, then that should be part of your homework making sure it is done with all your specs. Just don't assume they will give you what you need.
If you were buying a short block, and the piston to wall clearance was spec'd for an automotive application, and in your opinion, too tight for marine, would you just run it anyway?
We are talking engines here that are at the risk of thousands, to tens of thousands of dollars in collateral damage, if something goes wrong with a valve seizing, or something else in the cylinder head, and it is literally, peanuts in cost, to have a machine shop dissassemble the heads, check them out, and put back together. I really don't see what the argument is, for ignoring all that, and just bolting them on, and hoping for the best.
Full force Tim was accidently sent solid roller springs on his heads, that had something like 750 lbs of spring pressure. How many do it yourselfer's , get heads shipped to their door, and are actually checking the spring pressure, to even verify the proper springs were installed? Let alone valve guide clearance.
Recieving heads with incorrect valve springs installed, right there, is reason enough for me not to bolt on an out of the box head. Period.
