What was wrong with this cylinder? (pics) March 31, 2013, 03:49:58 AM So I've pulled my old GT40P heads off today and found that one has a pretty nasty looking exhaust valve. I only know of this type of issue as possibly a cracked head? Input?Gathering numbers from the engine today, the block was originally zero-decked and had a pretty large quench height (0.47-0.48) since the installed gaskets were PT9333. The new heads going on are TW measured at 56cc but I stopped since I wanted to pick up new dowels. I should have a quench height of 0.39-0.40 and ptv clearance appears to be a bit over 0.300. I'm guessing the motor is going to run much better using 87 octane at 9.7:1 compression on aluminum heads, than the 9.2 or 9.3:1 it was trying to do on the iron gt40p heads, and without what was going on in that one cylinder. Everything looked good otherwise. Going back to my Comp Cams lifters and using stud mount rockers, I'm hoping the valvetrain will be a bit quieter. Quote Selected
What was wrong with this cylinder? (pics) Reply #1 – March 31, 2013, 05:25:05 AM You may have some seepage around that head gasket ring? Quote Selected
What was wrong with this cylinder? (pics) Reply #2 – March 31, 2013, 08:55:58 AM I'd get your injectors on that bank flow benched. You may have on under-performing. I would have to interpret #2 exhaust valve as indicating a lean mixture relative to the others. I don't look at exhaust valves everyday, but that's how it seems to me. Quote Selected
What was wrong with this cylinder? (pics) Reply #3 – March 31, 2013, 09:28:04 AM Due to the amount of carbon on the plugs it's probably worn valve guides allowing oil to enter the cylinder, #1 isn't exactly a beauty either... Pistons look good so I'll guess rings are OK, a compression or leak-down test would have been a good idea, but of course a little late for that now... I'd probably do one just after bolting on the new heads and setting the valves... Quote Selected
What was wrong with this cylinder? (pics) Reply #4 – March 31, 2013, 12:59:06 PM The heads just came off filthy after being thrown onto the ground after removal (too heavy). Much of what is all over the head is simply from laying in filth, coolant, and oil. Here is a better picture. The pitting is what caught my eye. Quote Selected
What was wrong with this cylinder? (pics) Reply #5 – March 31, 2013, 01:04:47 PM I don't really care if the heads themselves were at fault, but a bad injector would be bad. The injectors have maybe 5k miles on them since being rebuilt and flow tested. The head itself, well I'm just curious what could have caused the orange, pitted valve. I have the following ready to go on after I get some new dowels. TONS of PTV clearance - it barely touched the ball of clay I placed on the top valve reliefs. Quote Selected
What was wrong with this cylinder? (pics) Reply #6 – March 31, 2013, 01:10:53 PM Quote from: TurboCoupe50;412209 a compression or leak-down test would have been a good idea, but of course a little late for that now... Yeah, this was nearly impossible with the (gt40p-specific) headers bolted on with the GTP heads. I did a compression test years ago without any bad numbers. A year or so later, I had a shop do a leakdown test and blowby test, with great sealing everywhere. I love that I'm going back to a normal spark plug angle so such tests are easy again. Too bad it will take me another hour to install the header studs (2-3 to remove them after many years...). Quote Selected
What was wrong with this cylinder? (pics) Reply #7 – March 31, 2013, 05:37:26 PM The TW heads are light years ahead of those old iron 40s, you'll think you have a new engine with a extra cylinder...You're gonna need longer push rods with the TW heads, I wound up using stock length flat tappet push rods that are approx 1/2" longer than the roller push rod... That engine went together in '99 with no valve train problems at all, it finally expired due to a blown head gasket(2nd time, has deck issues) and the thrust clearance was way over spec... Quote Selected
What was wrong with this cylinder? (pics) Reply #8 – March 31, 2013, 06:10:52 PM I have some 6.700" pushrods, but won't know if I can use them until the heads are on. Since TFS includes 6.750 with their kits I figured I may be good pre-purchasing some used (value) 6.700 since my heads were milled .030 and the deck was taken down a bit to get the pistons lined up. I'll know for sure in a bit.On my previous heads, I've used three different sets of injectors so any cylinder-specific issue could have been any of many issues in the past. The valve seals were fairly new and there was limited play with the guides, but the P's weren't reworked before I installed them years ago. I don't remember there being any valves that looked orange and pitted though. I've been hoping that a slight stumble/rough spot at idle that felt like it was coming from one cylinder will be resolved after this work. Since the deck appears fairly even, as do the heads, it looks like each cylinder should be very close to one another in terms of combustion quality. It would be awesome to get back to a near perfectly smooth idle with the HO cam. Quote Selected
What was wrong with this cylinder? (pics) Reply #9 – March 31, 2013, 06:25:03 PM Make sure to use harden pushrods with the guide plates Quote Selected
What was wrong with this cylinder? (pics) Reply #10 – March 31, 2013, 08:26:55 PM While I don't think it will cause any issue, is there a reason why some gaskets seem to not be aligned well enough to a factory block? It's pushing it, but I think most of the "blue" ring around the upper left and upper right coolant holes will continue to seal.I shouldn't have any issue with these gaskets, correct? Everything else lines up, and the fire ring sits pretty much even around the cylinders. I just haven't had alignment issues like this in the past.Quote from: STANG8U;412254Make sure to use harden pushrods with the guide plates Of course. I have TFS 6.700" units to hopefully use. No expense was forgetting on this update. Fresh heads with new manganese bronze guides and new valves, aiming for 0.035-0.041 quench height, have a newer, freshly ported lower intake from Matt Moss, new PS bracket, March alternator bracket, etc. Hell, I even got ARP intake studs so I can get a more even clamping force, over the stainless bolts I've been using for years. I just want the long block to be good indefinitely. It already has near perfect external support items, like balancer, ignition system, distributor, etc. I just REALLY dislike the gt40p heads that I only got for their "efficiency". My previous GT40's did just as well, and burned cleaner, with over 100k miles on them, not rebuilt.Life should be pretty good with the new setup. 9.73x:1 static compression with an '89 HO cam should run fine on 87 octane with even a stock tune, but I'll adjust that a bit when the carpc is in, so I can't have to use a laptop all the time with Binary Editor. CarPC and custom fabricated audio system will be coming soon as the improving weather allows me to work with MDF and fiberglass outdoors. Quote Selected
What was wrong with this cylinder? (pics) Reply #11 – March 31, 2013, 09:24:14 PM Quote from: Seek;412264Life should be pretty good with the new setup. 9.73x:1 static compression with an '89 HO cam How's you figure that??? Reason I ask is when I ran the TW heads on '86 HO flattops without valve reliefs, would pop 170 psi per hole, defiantly was up there in compression...BTW that was with the Stage 1 TF cam that specks at 221*/225*@.050... Quote Selected
What was wrong with this cylinder? (pics) Reply #12 – March 31, 2013, 09:33:16 PM 4.03 bore, 3in stroke (this may be a little lower), 56cc chambers, .039 quench, 4.1 gasket, 7.40cc pistons. 9.7 is a good rough estimate. Quote Selected
What was wrong with this cylinder? (pics) Reply #13 – March 31, 2013, 09:35:17 PM Mechanical compression ratio is different from sweep compression. Compression pressures are directly related to cam selection not compression ratios!!Static Vs. Dynamic Compression Ratio is entirely two different things.I would check the Valve springs for fatigue and the seat contact area. It might be to THIN!! Quote Selected
What was wrong with this cylinder? (pics) Reply #14 – March 31, 2013, 09:48:31 PM I understand that. Using the same cam though, I think 9.7xx:1 static on a stock '89 HO cam/TW heads should run pretty well with 87 octane. That is all I'm saying. I previously ran 87 octane with my gt40p's, which were a little over 9:1 static. I'd have to cc them to be sure what I was running, but I don't really care about them now.Also, I didn't notice my buddy failed to put a towel in the exhaust hole on the side he pulled off yesterday and of course, I ended up dropping a nut down there today. It wouldn't be much an issue if I had a lift, but yeah, it connects all the way back to the lers as a single piece. I don't know of any good ways to fish that out from 3 feet of tube where I think the nut stopped, since there are multiple junk bends. I really need to take it to a good shop for a better quality exhaust. Quote Selected
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