06:17:56am, Friday, May 17, 2024
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valve problems
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Anonymous User
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Anybody had problems bending vales at the bottom of the guide? Have plenty of piston to valve clearence & not marking valve pockets, not just the exhaust but some on intakes. they look good until you chuck them in a machine then the crook shows up. need help on this. thanks Mike |
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Re: valve problems
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I run stainless steel valves and I have the same problem.
I think longer valve guides would help, but they take up space. MACK |
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Re: valve problems
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HP
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My drag racer engine builder claims that happens when they valve is open and cools down unevenly.
Supposed to turn engine over by hand (LONG ratchet) after shutting down and cover exhaust. Otherwise use Titanium valves @ $3000.00 + a set. We covered the headers and turned the engine over after shutting down. |
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Re: valve problems
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Anonymous User
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This is not a open exhaust system, turbocharged engine, small cube, small valve with 11/32 stem valves. Valves are stainless steel on both sides. Roller cam & lifters, rockers. Could cam grind cause this to happen? This happened in just one run @ 8000 rpm. thanks for your help! Mike |
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Re: valve problems
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wld4x4
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Mike
When the Pontiac Prostock heads first came out in 1986 and some guys wanted to put them on blower motors they had this same problem when they ran the 11/32" valve stems. I think it was because there was to much of the valve stem exposed in the port. They ended up going with a bigger valve stem to help the problem. Hope this helps Jeff |
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Re: valve problems
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Anonymous User
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Thanks for information, not sure just what needs to be done but have to make changes of some kind, was hoping to resolve this issue and move on. Also we have been running a Jesel belt drive and tearing the teeth out of center of belt, put a camscrew adjustable idler to adjust tension,still no help with old style belt, then went to a newer belt which Jesel said was 10 times stronger, only made 1 run with it, belt survived, valves did'nt. Mikw |
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Re: valve problems
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maybe
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sounds like too much valve spring on both of your problems |
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Re: valve problems
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Anonymous User
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Thought of that also, have been as low as 200 lbs to high of 300 lbs on seat. You think that's to much? |
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Re: valve problems
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Anonymous User
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I don't think spring pressure is the issue there. You can run 300 at the seat , with a roller cam running 8000 rpms and be ok ( tried it on a IMCA stock car engine a few years ago) Try checking your clearance of your outer valve spring at full lift, you need a minimum of .090-.120" clearance in the middle of the spring, otherwise you get coil bind and you will bend valves and shred belts. Been there , done that even with 120 lbs seat pressure on a 6000 rpm engine.
Thanks, Brian |
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Re: valve problems
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Anonymous User
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I'll look to insure my mine, but I believe there is plenty of clearance. thanks |
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Re: valve problems
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Anonymous User
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Another thought crossed my mind is valve STEM clearance to the guide . Too much there will cause the valve to kink in the guide. Even on a 5 horse Briggs kart engine, anything over .006" starts bending valves pretty quickly. Hope this helps too.
Brian |
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Re: valve problems
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Anonymous User
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What did the seats look like? Was this on a green head, (not jd but unseasoned)? ti and inconel will move on turbo motor if shut down hot and not allowed to cool down by running. 600 degree exhaust will cool off a 1300 degree valve much quicker in a running motor than natural convection. With a valve stuck in the open position, things move when they are that hot. |
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Re: valve problems
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Anonymous User
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This is a aluminum head on a 301 ih twin turbos, seats are fine, not loose and don't show excessive heat. Valve people are saying to widen the margin so heat can transfer from stem to head, then we discovered the intakes where also slightly crooked/bent in the same place just below guide, the margin thing made sense to that point for the heat issue, but the cool air charge on the intakes I thought should be much cooler and not show the same results, then again maybe everything was just to hot. We discussed using inconel on exhaust for the strength???? Would like to really fix this headache! Mike |
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Re: valve problems
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Anonymous User
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How much margin do you have on the face of the valve seats? A good margin will help transfer heat but it is after the engine stops where the warping happens imho. Assuming you are following ntpa rules and not injecting alcohol or water, intake heat is anywhere from 200 to 450 and stainless valves will struggle. fwiw, I have seen ti intakes and inconell show lots of run out when chucked up on the valve facer. I attribute it to not cooling down while running after the run. Just a wild guess here but continued cyclic warping might cause the head to pop off over time. I don't think you are any where close to too much spring pressure. Not enough spring pressure will beat the seats out and you didn't have that issue either. You said the seats are concentric so, imo, that leaves heat and/or material fatique. I'm no engine expert or builder so take it for what it is worth until the facts add up for your situation. I am assuming all clearances and machine work is correct. |
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Re: valve problems
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Anonymous User
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We are running .090 on seat now, it is a alcohol engine. Stainless is not good on intakes? |
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Re: valve problems
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Anonymous User
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Seat margin sounds like more than enough to me, stainless should be ok in your application.I suspect there are plenty of LSS's using stainless without issues. Assuming boost on your 2 turbo setup isn't 90 lbs. I would guess with 90 lbs on a 2 turbo setup compressor effeciency is off the map and intake temps would be too unless you have something special. most of my suggestions can be eliminated if the tractor was driven off the track and had time to cool before shutdown. |
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Re: valve problems
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Anonymous User
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Just looking a data, 71-72 lbs of boost with #1 intake high temp @ 439 & #2 @ 526 |
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Re: valve problems
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Anonymous User
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Ouch. |
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Re: valve problems
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Anonymous User
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Ouch to mean what? This engine was destroying itself inside, spun every rod bearing, blued two rods, blacked the main throws + the bent the valves. That's why I'm looking for answers! Mike |
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Re: valve problems
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You better start puttin some water injection on that pig. |
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Re: valve problems
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Anonymous User
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So what's the idea temp? Colder the better. |
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Re: valve problems
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Mike,
Something to consider would be ignition, misfiring can cause every problem you just mentioned including excessive intake temps. In high boost applications very special steps have to be taken to prevent misfire or engine damage like you see, lower end trouble warped valves and broken belts will result. A crank trigger is absolutely necessary, and phasing the rotor is critical, plug wires are critical and even the routing of the wires from like an 8 box to the coil and trigger are critical. The motor will start and run fine even excellent but when the boost comes up, it puts and extreme load on the ignition to fire the plug under pressure and if everything isnt perfect, it easier for the fire to actually jump to the next post in the cap and boom problems galore! Distributor cap is important, we use a Ford V6 cap from napa, cap adapted onto a crank trigger MSD distributor, they have nice brass terminals and the carbon piece is pressed solid into the center of the cap, avoid the ones that are spring loaded. A little dielectric grease in the plug boot aint a bad idea either! Most problems on alky supers is the Ignition, #1 problem! Crutch is 100% right never shutdown a motor right after the run drive off track and let it idle itself cool, good on turbos also! BB Stormy |
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Re: valve problems
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Anonymous User
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Thanks, we are running the ford cap setup & MSD crank trigger & wires, plugs at .014, also running 8.6 compression ratio. Think our intake heat had help from exhaust heat under hood, ran without outside inlet tube, very tight under hood. |
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Re: valve problems
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Registered: 04/04/2008 Posts: 1,523 |
wouldnt the fuel going lean cause excess heat also |
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Re: valve problems
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Anonymous User
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You don't want intake charge at valve below 180. 250 is very acheiveable with the right nozzles if you do it right. You can probalby get away with anything below 300, 350 or more with really good parts.
RE: Bob's post below, good advice but you never mentioned any issues with the one run. If you did pop then you have to fix that first. Drop your plug gap down to .012 anyway. |
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Re: valve problems
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Anonymous User
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Thanks all for all your suggestions, we'll give a go for Henry. |
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Re: valve problems
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Anonymous User
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Sorry, just backed up and read this post.
That changes things. Sounds mechanical or you had some severe detonation. I know everyone wants to believe they can build and enigne or their engine builder is the best but you have to check and double check everything. There are so many things that can be happening and without all the fact it's hard to help. Was the crank straight and counter balanced right? what weight oil? What do the plugs look like? What was EGT's. What was oil pressure? Excessive heat might cause detonation which will pound the rod bearings out quick, mains should have faired a little better. I'm leaning toward oiling. I suspect the clearance is factory on rod to crank but you might look at the side play. Oil keeps a protective layer there but it also is used to cool. If it can't flow out it can't take the heat with it. |
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Re: valve problems
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Anonymous User
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20-50 cenpeco, side clearance was to tight .0012 as we have learned since this happened, new clearance will be .080 to .100. Also the main bearings had only half groove & thinking not enought volume to rods. 130 lbs oil pressure the entire 235' but if it had no place to go, pressure mean nothing. Ran 0.0035 clearance on mains & rods. Used a hemi rod bearing which was a 0.0100 narrow & harded surface. Crank was straight & a fully counter blanced. No extra weight added. |
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Re: valve problems
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Anonymous User
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Sounds like you found internal issues. .0035 sounds right to me but side to side caused the issue.
Sorry for your troubles. Still lean towards head on valves. Hopefully you are on the right track now. |
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Re: valve problems
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Anonymous User
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Thanks to all, we'll give it another go for Henry |
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