DavidL Posted March 21, 2022 Share Posted March 21, 2022 My 1700 SuperSpint CrossFlow has always coughed a bit of oily smoke at start-up, which I assumed was a bit of oil getting past the valve guides. But lately it seems like things have gotten worse. The spark plugs are very oily (that's new), and there is even some oil seeping out where the headers meet the head. So I'm trying to figure out what to do. A full head rebuild with new valve guides? Or just replace the valve stem oil seals? Does anyone who has gone down this path have ay advice, and can anyone recomend a trustworthy place to do a head rebuid? I'm in the San Francisco Bay area. I know that these engines can break rings, but a compression test showed 180 - 185 psi on all cylinders (cold), so I'm thinking the rings are OK. The car is a 1990 Caterham, and has 17,500 miles on it. I've owned it for the last 10,000 miles. I'm going to pull the engine do do a clutch soon anyway, so maybe a good time to get head work done if needed. Cheers, -David Link to comment Share on other sites More sharing options...
coffee break Posted March 21, 2022 Share Posted March 21, 2022 As a double check on the rings try a compression leak down test. If you are going to open the motor up it would be good to know how far you need to go. Link to comment Share on other sites More sharing options...
IamScotticus Posted March 21, 2022 Share Posted March 21, 2022 ask Ken who builds engines near you ken@davebean.com Link to comment Share on other sites More sharing options...
ashyers Posted March 22, 2022 Share Posted March 22, 2022 David, If the car's been sitting for a while, you may have an oil ring that's sticking or the valve seals have turned to something akin to porcelain. Are all the plugs oily or just one? Andy Link to comment Share on other sites More sharing options...
IamScotticus Posted March 22, 2022 Share Posted March 22, 2022 my vote is on valve seals Link to comment Share on other sites More sharing options...
Christopher smith Posted March 22, 2022 Share Posted March 22, 2022 One way to check valve guides is to get up some speed going up to the crest of a hill and then coast, throttle closed, in gear, down the other side of the hill. If you then accelerate strongly and a cloud of smoke erupts behind you it is probably guides or seals. The engine braking pulls a vacuum trying to suck oil in. If it smokes at other times as then possible rings are at fault. 1 Link to comment Share on other sites More sharing options...
DavidL Posted March 22, 2022 Author Share Posted March 22, 2022 Thanks for all the advice, I'll try coast-down-a-hill test. I'm also working on getting a leak-down test done. I'm leaning on having someone with experience do it, and I don't have compressed air anyway. Link to comment Share on other sites More sharing options...
ashyers Posted March 22, 2022 Share Posted March 22, 2022 David, If you want to head over to the East Bay I'd be happy to do a leak down test. I still owe you for that fit test and ride some years back! I'm not familiar with the style valve seals the Kent motors use, but most are relatively easy to replace and inexpensive. Andy Link to comment Share on other sites More sharing options...
TheDingo8MyBaby Posted March 24, 2022 Share Posted March 24, 2022 (edited) I don't know what caterham used, but there may not be any valve guide seals. My pre-crossflow has bronze guides and runs without them. After several thousand miles, it does have similar problems with fouling and smoke on #4. It's getting time to have the head refreshed. Head gaskets, Guides and seals are not very expensive. Machine shop labor shouldn't be so bad either. While you're in there, you should have the rocker geometry looked at to ensure that there is minimal wear to the guide. Edited March 24, 2022 by TheDingo8MyBaby 1 Link to comment Share on other sites More sharing options...
DavidL Posted March 27, 2022 Author Share Posted March 27, 2022 With Andy's help, we ran a leak-down test, and things seemed pretty healthy. Leak down was only 10-15%, and any air that was escaping was going by the rings into the crankcase, not past the valves. We could see a nice cross-hatch pattern on the cylinder walls using a boroscope. Also, although the plugs were a bit dark, they were not wet with oil after the 45 minute run on the highway. So maybe the wet plugs I had seen were more a result of the car being used for short runs and siting a lot lately. I was very relieved to see these results, thanks a ton Andy! It still definitely coughs out a cloud of blue smoke at start-up, so I'll look at valve seals (if there are any). Pegasus has some teflon seals that look like they might work with the Caterham Supersprint double valve springs, has anyone used these? https://www.pegasusautoracing.com/productdetails.asp?RecID=5175 Also thanks to Rich Kampena (longtime local Lotus garage and caterham dealer) for a helpful discussion about options and diagnostics. Onwards! thanks for all the help, -David 1 Link to comment Share on other sites More sharing options...
Christopher smith Posted March 27, 2022 Share Posted March 27, 2022 Any thoughts on reading plugs for normal or fast road use? For racing, we always used a full throttle run with a quick simultaneous shut of ignition and throttle and declutch, coasting to the pits. Does that still work with the much more modern engines? And is a light tan electrode color pretty good? We always used leaded race fuel so wonder if unleaded means a different color optimum. My experience is with the likes of 1500 non-crossflows and similar. Link to comment Share on other sites More sharing options...
IamScotticus Posted March 27, 2022 Share Posted March 27, 2022 I don't think these X Flows can run anyway but rich. I tried dialing in my idle to run leaner but all i got was popping. I think it helps to remember these are pre-emission engines on short pipes. They've gonna spit gas, smoke, etc. They're dirty. If not, they're probably running too lean. my 2¥ Link to comment Share on other sites More sharing options...
IamScotticus Posted March 27, 2022 Share Posted March 27, 2022 Pegasus gets more of my $$$ Link to comment Share on other sites More sharing options...
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