Calgary280ZT Posted July 21, 2009 Share Posted July 21, 2009 Bought a Rebello built head a couple of years ago. It has an Iskey cam, oversize SS intake valves, and I had Dave do the full race port and polish on the head. It sat for 18 months before we got it installed and the motor running again...problems with the Wolf V500 EMS. Got it running about 3 weeks ago and spent a week very carefully tuning. Finally was running about 7 psi and AFRs were all in the safe range, looked like a nice conservative base tune. Z240 and I took it for a tuning run and aroudn 4,000 rpms it died. Got it started again, but big clatter from valve train, so shut it off immediately. Jim pulled the head and the #6 intake valve was stuck open. Only a little nick on the piston, should be ok there. Took the head to a local machine shop with a very good reputation, they do L28 heads regularly. Talked to the machine shop today. The reason the valve stuck open is because Rebello installed cast iron valve guides, there wasn't enough clearance, the SS valve rubbed on the guide, wore off enough material to create a little ball that eventually caused the valve to jam in the guide. The machinistsaid that if he had done the head he would have used brass guides at a minimum and honed them to make sure the clearance was correct. Is it common when building a race head to use cast iron guides? Anybody run into this problem before? I'm looking at a $500+ bill to fix the problem and before I talk to Rebello about warranty (300 miles on a new head) I want to get some feedback from the Z community. If I'm going to argue for warranty I don't want to be talking out my keester. Feedback and comments gratefully accepted. I have pics, but have never figured out how to post them on this forum. You can see them zcar.com if you want. On the plus side, the head shop said Rebello did a beautiful job polishing and porting...:0) Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted July 21, 2009 Share Posted July 21, 2009 (edited) Bronze guides are more forgiving and softer, have self lubricating properties, but don't wear as long as cast iron. Nothing wrong with cast iron guides in race heads provided they have the proper clearance. In fact some endurance engine builders prefer them for longetivity. In your description you talk about one guide, not all guides as a whole. Were they all too tight or just one? Being that it sat for so long the type of lube used to build the head can become an issue. I use white grease, some use oil, some use redline synthetic assembly lube and some use whatever else you can imagine. I have seen some builders use ATF! You say it was a nice port job, didn't you notice then that they were cast iron guides??? If you had a beef about that then you should of spoken up alot sooner than now IMO. Everyone makes mistakes now and then, even Rebello. Before you get the cart before the horse, well you already did, but I'd call them. Taking it to another shop painted yourself and Rebello into opposite corners. Rebello would be possible warranty for free and you've already got into that other shop for $$$ even if you don't let them fix it. Rebello would probably have wanted to see the head untouched, but now they can't. You get more with sugar than you do with vinegar. So keep that in mind and call Rebello IMO. Edited July 21, 2009 by dr_hunt Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted July 21, 2009 Author Share Posted July 21, 2009 Well, couple of comments. I'm not a mechanic or a machinist, so I wouldn't know a cast iron valve guide if it bit me on the arse...hence my post here asking for help. Not sure if all the guides were too tight...only one valve stuck and local machinist didn't mention the others, I'll ask him. As for Rebello seeing the head, did you notice my handle? I'm 2500+ kilometres away, no chance of shipping an 80 lb head to San Francisco from Calgary and back cheaply, plus the hassles shipping across the border, which have only gotten worse of late. I fully intend to talk to Dave, but wanted to get the experts' advice on what I was looking at. The point of asking for advice wasn't to load up on vinegar, it was to educate me so that I can talk semi-knowledgeably to Dave when the time comes. Your comment about the bronze vs cast iron guides is very useful. The Calgary machinist poohpoohed cast iron, but from your remark it sounds like proper clearance was the issue. Should the cast iron guides have been honed? Calgary guy says he would have honed the bronze ones. He also said the cast iron guides weren't honed at all. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 21, 2009 Share Posted July 21, 2009 I agree with Dr. Hunt, Cast Iron Guides last hundreds of thousands of miles. Silicon Bronze, Brass, and thin walled inserts...er...notsomuch! I replied at 'the other site' in a more vociferous manner on the painting of the opposite corners. Sounds like the guy is looking to drum up business and prey upon you more than being straight. Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted July 21, 2009 Author Share Posted July 21, 2009 Thanks Tony, I also replied on the other site as well. Your comments there were exactly what this noob needed to hear. Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted July 21, 2009 Share Posted July 21, 2009 You say you want to talk to the experts but honestly Dave at rebello is the expert. Honestly imo dave should of covered shipping. Your going to have a hard time getting Dave to pay for work at another shop. Its cash out of his pocket now instead of a few hours of work to fix the problem. Good luck on getting this worked out but i have to say that it was a mistake taking it to the other machine shop. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted July 21, 2009 Share Posted July 21, 2009 Well, I know your half the world away, but when you have a problem I don't think it is prudent to run to another source first, but rather deal directly back with rebello. I too have had issues with many machine shops over the years and thankfully I don't have many problems now, but on occassion they do happen. There is virtually no way the guides were not honed at all. Guides come undersized for a reason. Actually the guides are reamed or honed to fit a particular stem diameter. If you using a used valve then that diameter can be .0005 smaller and some may be that half bigger, etc, in your set. It is possible and you can get guides that you don't have to hone so it is remotely possible, but highly doubtfull that even Rebello would use one. Could be also that his supplier of guides had one in the set for some unknown reason. Could be his head guy was mad at his old lady that day, could be alot of things actually. It is possible that they never finished one guide, that happens, but you should give Rebello the opportunity to fix it first don't you think? If not, then you will probably be on your own with a sour taste for Rebello in your mouth when you speak of them. Bronze guides were all the rage when they came out and you find them alot in aluminum heads, but you'll find better wear out of the cast iron and less problems if you go iron, just make sure they have the proper clearance. Bronze runs tighter clearance but doesn't last as long. Cast iron was one of the reasons for lead in gas, but race gas has lead in it, although you can get unleaded race gas too. So, to sum it up if it's going to be a street motor, I'd go cast iron. If it's going to be a drag only car I might use bronze, but, and I mean but, these days I pretty much use cast iron for everything, just that I pop off the springs and retainers one at a time and check them myself. Doc Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted July 21, 2009 Author Share Posted July 21, 2009 The consensus seems to be that I goofed taking it to the other shop. Mea culpa. Z240 and I put our heads together and it seemed like a good idea at the time. I guess I'll have to live with and pay for the mistake. Thanks for the feedback guys, now at least I understand the issues involved much better than before. Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted July 21, 2009 Share Posted July 21, 2009 Something does not sound as if it was assembled correctly if an INTAKE valve stuck. The usual scenario for a stuck valve is that EXHAUST valve will stick because it runs so much hotter and sees more gunk. Intake valves and their guides run so much cooler and cleaner that I just don't see how that a few hours of running would cause a failure in an intake valve guide. Also the intake valves see more "lubrication" since the stem does get squirts of incoming fuel. Getting that kind of serious wear on an intake stem in such a short time sure sounds like the problem was there when it was assembled. I think the shop was half right. He was wrong about the need for bronze on the intake guides and right about the assembled clearances being incorrect. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted July 21, 2009 Share Posted July 21, 2009 Wrong installed clearence. Cast has lubricity properties as well, and holds oil well. I always use cam break in lube on valve guides as well. Remember .0001" too tight will always fail, but .003+ will always work. Same goes with bearings. Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted July 21, 2009 Author Share Posted July 21, 2009 Looks like we may have a happy fix...talked to Dave. He says there could be a lot of reasons why it failed but the good news is it's an easy fix. And he didn't have a problem warrantying the head even though another shop took it apart. Even better news...an advertiser of my newspaper is a speed shop and he's going to take over from the other Calgary machinist (who actually has a good reputation, in spite of Tony's comments!! LOL). It'll probably be another couple of weeks before the head is ready, but total bill shouldn't be more than a couple of hundred bucks, maybe less if Dave decides to pony up for the new valve and a few guides. Thanks for the ideas and comments guys, you helped me understand some of the issues involved so that at least I was a better educated customer. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 24, 2009 Share Posted July 24, 2009 I'd agree with Bryan on the clearances as well. Slightly bigger is better than too tight. FYI, I bought a full set of Nissan Guides, and they ALL need to be reamed to size, and they are cast iron (or some magnetic material)... Good to hear you are getting it fixed. I fired up the Red Car and was doing blasts up and down the street today. And I found out my kid has dumped all my MS Tables and Megatune from my old laptop (to free up space..a whole 15MB!)... Now, I have no idea what Version MS-N-Se I got, options, or whatever. Looks like I got to download my USB driver from somewhere becasue he deleted that as well and the computer doesn't recognise it any longer. Download new firmware and reset everything to the numbers written on the cardboard box top I found under the seat. Let us know when you get it on the dyno! Quote Link to comment Share on other sites More sharing options...
katman Posted July 25, 2009 Share Posted July 25, 2009 Well this ranks right up there with a fellow racer who brought me his Rebello "rebuilt and recurved distributor" that he'd just had Fed Ex'd to the track. It wouldn't turn and he asked if that was normal. I told him it was normal for Rebello. Quote Link to comment Share on other sites More sharing options...
luckygerman Posted July 25, 2009 Share Posted July 25, 2009 My Buddy who is an Engine builder and is building this N/A 780 hp Drag motor uses Brodix heads with Brass Valve guides, I'm sure there is a reason why they use Brass. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 25, 2009 Administrators Share Posted July 25, 2009 You are correct, bronze guides have their place. As a professional engine builder/machinist myself, (1 fast z is as well), when I built this, Twin Turbo, water to air intercooled, MPFI, 540 CID Big Block Chevy for this world record holing endurance Jet boat, (produced 1168 HP on the dyno at sunset Engine development in the picture below), we used not only bronze guides, but beryllium copper seats! Good place those exotic materials, but because it works in this extreme application doesn’t necessarily mean it works in all. I also use mostly iron guides in my L-6 cylinder head builds. Quote Link to comment Share on other sites More sharing options...
luckygerman Posted July 26, 2009 Share Posted July 26, 2009 WOW, that is a nice engine, I thought I have seen it all. how much boost are you running on this big block? Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted July 26, 2009 Author Share Posted July 26, 2009 Thanks BRAAP, this has been a real education for me. Dave Rebello said the problem might have been caused by a little rust in the guide from sitting so long. Or other things. Or anything. My best bet is to work out the best deal I can with Dave...which means if he'll supply a valve and some guides and get them up to me quickly, not a big cost for him and my buddy's shop will put the head back together etc. at no no cost to me. One thing the Calgary head shop said in our last conversation was curious....he said the head needed to be planed, the surface was very rough and he was surprised that Rebello would let it out of his shop in that condition. Unlike BRAAP, he doesn't have a problem slagging another shop's work...LOL Quote Link to comment Share on other sites More sharing options...
1 fast z Posted July 26, 2009 Share Posted July 26, 2009 Actually it all depends on the head gasket used. You want a "course" surface finish (125 or larger) for a composite style gasket. What it does is help keep the head gasket from moving around on the block, but the coursness is not so much that it lets water leak past. And on the rust thing, if there was a heavy duty assembly lube used on the guides and valve stems, then there is no way it could of rusted, unless submerged in water. Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted July 26, 2009 Author Share Posted July 26, 2009 Brian, we used a metal HG. Will that work ok with the coarse surface on the head? Quote Link to comment Share on other sites More sharing options...
luckygerman Posted July 27, 2009 Share Posted July 27, 2009 I like to use a multi layered head gasket with some copper gasket sealer. I think you can get Copper gasket for your engine. It is nice assurance to use Copper spray, it will fill in any imperfection and assures a better seal. Quote Link to comment Share on other sites More sharing options...
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