Bad cylinder heads- suggestions?
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Category: General Correct Craft Discussion
Forum Name: General Discussion
Forum Discription: Anything Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=36007
Printed Date: May-08-2024 at 8:30pm
Topic: Bad cylinder heads- suggestions?
Posted By: Orlando76
Subject: Bad cylinder heads- suggestions?
Date Posted: May-10-2015 at 10:27pm
| So I bought my '93 (485 hours and clearly sat a few years in a garage) and been chasing a roughness issue. I really associated the roughness with the drivetrain bc of an awful squeal coming from the stuffing box and the existing prop had a knick. About 1500 rpms the vibration/roughness went away. Long story short everything seemed to check out ok in the driveline so I went to Woody's and had him check it out. Come to find out what I associated to be a drivetrain vibration was actually two dead cylinders. Both heads need replaced. I don't plan on having the current gt40 heads re done, rather probably go to Clearwater Cylinder Head and buy a new set. Should I buy GT40p's or stick with the Gt40 or go a different route? |
Replies:
Posted By: lewy2001
Date Posted: May-11-2015 at 10:27am
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Get the P's ------------- If you're going through hell, keep going http://www.correctcraftfan.com/diaries/details.asp?ID=2999" rel="nofollow - 89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
Posted By: Orlando76
Date Posted: May-11-2015 at 10:31am
| Does anything have to change as far as springs or push rods? Is it just plug and play? |
Posted By: TRBenj
Date Posted: May-11-2015 at 10:34am
| As with any head change, you'll need to check lifter preload and shim rockers as appropriate. If wildly different there's a chance you may need new pushrods- but there's a good chance you can reuse those. Non issue on the other parts swapping over. Make sure the heads are drilled out for 1/2" head bolts. |
Posted By: halfnelly
Date Posted: May-11-2015 at 10:36am
| Might as well get the P's, you'll get a bump in compression and the straight spark plug angle is actually helpful in a boat with upswept manifolds. The bolt holes will need to be drilled out to 1/2" to fit on a 351, though. Since Ford made a bazillion Explorers with them they're pretty easy to find. |
Posted By: Orlando76
Date Posted: May-11-2015 at 10:50am
| I just got off the phone with Clearwater Cylinder. Yall used them in the past correct? Tim with Clearwater said the springs don't need changed is unaware of issues on the springs but when I search the Internet the Mustang guys say otherwise. Idk, engine builds are beyond my scope. The p's are 250 each out the door shipping included as well as drilling out for 351. Gt40's are 330 each. Seems to be a no brainer. If there's any other cast iron head out there worth my consideration I'm unaware. I asked about changing the intake, Wood said don't bother. I'm more upset that my picture perfect factory paint isn't going to be perfect anymore. Does anybody know where to get touch up paint or color codes? |
Posted By: TRBenj
Date Posted: May-11-2015 at 10:59am
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SkiDIM sold PCM silver in a spray can at one point. In addition to the 1/2 bolt holes, have them install brass core plugs too. Stock P springs won't support higher lift cams. Anything above .500 lift will warrant a spring upgrade. No need if you're keeping the stock .450 lift cam. Intake is a consideration, a performer (non-rpm) would be worth a handful of ponies without any ill effects but your call on whether the cost is worth it. A new timing set is a consideration too. Roller cam would be a real nice upgrade for both performance and longevity... But that might start to test your budget. |
Posted By: halfnelly
Date Posted: May-11-2015 at 10:59am
| I'd change the springs if they were going on a performance engine, but our motors have a pretty tame flat tappet cam which is probably even less aggressive than the factory Explorer hydraulic roller so I bet the stock springs would be OK. The only other cast iron heads I can think of are the World Products Windosor JR or SR, which would be a bunch more $$$ with no performance advantage, especially with the low-rise cast iron intake and stock cam. |
Posted By: JoeinNY
Date Posted: May-11-2015 at 11:03am
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If you were going with a bigger cam the springs might be an issue otherwise no reason to change them. I would be interested to see what makes the cylinders dead. Have you removed the heads already and checked for further damage? I would be curious as to the state of the lifters and cam, any damage there and you want to replace them. You might not see more performance with an intake changeout but if you have the budget it is nice to remove the heavy factory manifold. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: mark c
Date Posted: May-11-2015 at 12:03pm
| I too would wonder what would make two cylinders on opposite banks of an engine be "dead". What exacty is the issue, and which cylinders are dead. because if its two cylinders opposite one another its way more likly to be a cam issue than a two heads failing at the same time. Just a though before you tear into the engine. |
Posted By: Orlando76
Date Posted: May-11-2015 at 12:06pm
| We were both short on time and didn't get to pull anything. Obviously I hope to hell the bottom end checks out good. As far as cam goes, it is what it is, if bad, maybe I can get something a lil better. One cylinder just does nothing. Good spark but you can put your finger on it and no air moving. Valve stuck open? I made four short test runs with the boat totaling less than 2 hours. I did notice Saturday evening for the first time it blew blue smoke on start up which kinda made my heart sink. I felt like out the hole boat was not up to par but mid range acceleration was pretty good, wot I was only getting 4300 at 43-44 mph which disappointed me. Now I know why. All this on factory 3 blade OJ. Knowing now it was running on 6.5 cylinders, 8 cylinders should be amazing, still pulled me decent in the course. We have spark at plugs. No water in oils, no oil on plugs just wet fuel. |
Posted By: Orlando76
Date Posted: May-11-2015 at 12:09pm
| I forget which cylinders. I'm wanting to say number 1, or maybe the cylinder behind number one. Sorry I don't know the locations by heart. Then the port side bank it was I think second cylinder from the bow. I really didn't pay attention which ones. When I get home tonight I can verify which cylinders but I don't plan on tearing it down, Woody would probably rather do that than get a partly started project. |
Posted By: TRBenj
Date Posted: May-11-2015 at 12:12pm
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Yikes. Time for a compression test followed by a leak down test before you do anything. Fingers crossed that it's a leaky valve or 2 and not bottom end issues. Way ahead of ourselves talking cam but I'd give serious consideration to roller if you replace. I would go roller on my 90 if I could go back in time. It has implications on heads (springs) and a few other things (dizzy gear) so just keep that in mind if that ends up being the path you start down. |
Posted By: Orlando76
Date Posted: May-11-2015 at 12:29pm
| Can one enlighten me on a leak down test? |
Posted By: baitkiller
Date Posted: May-11-2015 at 12:58pm
Its a test using compressed air to determine the percentages of compression loss in a given cylinder and to identify whether the loss is rings or valves related. It takes about the same amount of time as pulling the heads and looking which is gonna happen anyway. Once a simple 20 minute compression test has found a dead hole you know its coming apart. In your case it (leak down) may prove beneficial to determine whether you are buying just heads or a long block before tearing it down. If, in the case of a piston issue would you rebuild you existing bock or replace it? If the answer is rebuild what you have then the test is a waste of time. ------------- Jesus was a bare-footer............. |
Orlando76 wrote:Posted By: TRBenj
Date Posted: May-11-2015 at 1:16pm
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What his intentions are in the case of a piston sealing issue is irrelevant until he determines he actually has a piston sealing issue. It is equally irrelevant to decide which heads to buy until he determines he needs new heads! You lose the ability to perform a leak down test once the heads are off, which is why that should be done first. I disagree that the problem will be obvious once it's apart... You only have the ability to inspect at that point, you can't test unless it's assembled. A proper leak down test will give you a % loss, but more important is WHERE the compression is being lost. Through a valve is best case, through the rings is worse news. |
Posted By: Orlando76
Date Posted: May-11-2015 at 1:43pm
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One thing for certain due to it sitting and at $500 I'll buy new heads. Hopefully that's the problem. If it turns out it's rings, I'll still replace heads so I don't see me being out much more money, only time and anticipation. My next question was going to be does the engine need to be assembled etc for leak down test so Tim answered that. Other than the carb now being out of tune this engine is completely unmolested. Who does a leak down test, machine shop? Too bad I've never heard of a good one in Orlando. How much am I looking at for a test? Eddie Backfoot, you seem to be more experienced engine guy in central FL, can you recommend somebody? |
Posted By: baitkiller
Date Posted: May-11-2015 at 2:16pm
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Not really Tim. Give me a cup of kerosene and Ill let you know where and by how much including a comparison of all 8 holes and intake vs exhaust valves. I'm not denying its a cool tool to have, I own one and use it when warranted. I'm just a time vs value guy. If I see >15% variance I'm pulling the head. In most applications I find leak down testing a waste of time. The big exception in my mind is four stroke outboards and to impress clients who expect to see something techy to be satisfied. The OP said ; "two dead cylinders" Not "low compression" So don't blow smoke up my skirt Tim, You and I both know that you would be able to spot it (whatever it is) in seconds. ------------- Jesus was a bare-footer............. |
Posted By: Orlando76
Date Posted: May-11-2015 at 2:34pm
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Ok I read up on leak down tests, I just need to find someone to do it. Let me back up, the cylinder on port side is nothing, nada, zilch. The starboard cylinder read low, like 90? I'm gonna go home tonight and do another compression check and record results. |
Posted By: baitkiller
Date Posted: May-11-2015 at 2:50pm
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Zero compression....... Yeah, better do a leak down to find that sucker,, could be real tricky.. Don't know why I bother sometimes. Y'all have fun. ------------- Jesus was a bare-footer............. |
Posted By: JPASS
Date Posted: May-11-2015 at 2:59pm
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Sorry to hear you're having engine troubles Todd. Try giving Hanz Engine House in Longwood a call. I know Jerry used them a few years back for his engine rebuild and he seemed pretty happy with the work they did. ------------- '92 Correctcraft Ski Nautique |
Posted By: TRBenj
Date Posted: May-11-2015 at 3:13pm
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Agree that zero compression will likely be pretty obvious when disassembled... But I still fail to see the harm in running a simple test as a confidence builder before you lose the ability to do so. I wouldn't necessarily pay someone to do a leak down test for me but putting some compressed air to a cylinder and listening for the escape path is a quick and easy test. A reasonably priced compression tester kit will likely come with the connections necessary to connect a compressor right to the plug hole. Did you have any valve/lifter/rocker noise (stuck valve) or blow by pushing oil out your dipstick? |
Posted By: Gary S
Date Posted: May-11-2015 at 3:23pm
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Harbor Freight has leak down testers for 40 bucks if you have a compressor ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: Orlando76
Date Posted: May-11-2015 at 3:24pm
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No noise, no blow by, engine and bilge is clean as a whistle. I don't think I could pinpoint where air is escaping if I attempted a leak down test myself. reading up on 0 compression I feel I should mention Saturday night when skiing, as I climbed into boat I could smell straight fuel from the exhaust (stuck valve?) Thought it might've been my imagination. Edit-I guess if piston were burnt or ring collapsed air would come out dipstick? |
Posted By: Orlando76
Date Posted: May-11-2015 at 3:26pm
I saw that? Anybody have confidence in that? |
Posted By: Gary S
Date Posted: May-11-2015 at 3:42pm
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Not much to them,I have an article at home that tells you how to make one, I think it would be fine ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: SNobsessed
Date Posted: May-11-2015 at 9:28pm
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You can clearly hear where the air is escaping (valve vs. crankcase). So actually what they are suggesting is just get a spark plug hole air fitting - most auto parts stores have this, probably around $10. Just make sure the cylinder is at bottom of firing stroke when you give it air, especially if you leave the breaker bar on (hint: it moves very fast). ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: mark c
Date Posted: May-11-2015 at 11:26pm
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Measure at top dead center, otherwise one or both valves will be partially open. Leak down tests are usually done at 100 psi, but if your not careful the engine will rotate with that much pressure in the cylinder. If you can hear air whistling thru the intake then you have a leaking (or stuck open) intake valve, if you hear it in the exhaust you have a stuck open exhaust valve, if you pull the PCV line off and hear air escaping thru the valve cover hole you will have ring leaks, or other issues that will probably require a tear down of the engine. Obviously we are talking orders of magnitude here, intake and exhaust valves should have no leakage at all, the rings will have some leakage and therefore some amount of air leakage into the crankcase. but if you can't build much pressure in the cylinder and have a large amount of air coming out the breather hole then theres a major problem with your rings and/or cylinder walls and the heads are not your problem. If you hear air escaping thru the intake or exhaust the next step would be to pull the valve covers, roll the engine over an watch the rockers move. Ideally measuring them at the valve end of the rocker with a mic over a full engine rotation and comparing the non functioning cylinders to one of its functional neighbors to see if you have a stuck valve, collapsed lifter, or possibly a worn lobe on your cam. Stuck valve will be easy to diagnose, figuring out if the lifter or cam lobe is bad is trickier, but either way the intake will need to come off which will make it easier to figure out. |
Posted By: JoeinNY
Date Posted: May-12-2015 at 10:44am
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Whether you do a leak down test or tear it down, either is recommended before you start ordering parts. I have a leakdown tester I use on other peoples engines - if its mine I just start tearing it apart- but I have sbf heads, short blocks, cams, gaskets, etc lying all over shop and a place to leave it all torn apart without paying someone else to work on it and be in a position where they need to get it back together and out of their shop. You could have a bad cam and perfectly fine heads Or a whole in a piston and perfectly fine heads Resist buying the heads until you know you need them ... ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: Orlando76
Date Posted: May-12-2015 at 2:53pm
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Maybe this weekend I'll play around with doing a leak down test, weather and wind is too perfect this week, I'm skiing. I'll still order the heads to get the ball rolling. If not needed I'll save them for an upgrade to one of the other SN's since there's no core required. I have no filter nor dryer at the moment on my compressor. The moisture created from compressed air going into the cylinder won't create an issue will it? Since it might be a few weeks (fingers crossed) until the cylinders fire again. |