Hello all, I've just finally got my roadster running and have been working on getting my freshly built 327 tuned and dialed in. To make a long story short, I took the roadster out for a spin before work today to check the adjustments I made to timing and carb adjustment. About a block from home, I noticed a ticking/ knocking / tapping sound coming from the enginethat matches the rpm. I had to go to work and I've been stressing all day that I have rod knock. When I got home this evening I checked the following: Interference between rocker and valve cover. - no problem Checked for broken valve springs or anything out of whack. - all seemed normal Fired up with valve covers off all seems normal. Checked oil level- fine Checked for metallic flecks in oil. - none I pulled one plug wire at a time to see if the nous stopped. - no change All spark plugs look nice an tan. #8 seemed a little oily around the threads, but the electrode and insulator are dry and tan. Oil pressure stays between 45-65 when hot. The engine has never gone over 180 and runs cool. I took a piece of tubing to try to hear where the sound is coming from, but it was difficult to hear well with the solid lifters and lakes headers although it did seem more pronounced around cylinder 8. From what I could tell the sound is coming from the middle if the engine. I'm not getting any back firing, smoke etc. to indicate a cam going flat. But then again I'm a novice. Specs of engine are: 327 bored 0.060 over Flat top pistons, cast rings, 9.8:1 compression 0.015 steel shim gaskets and 0.035 quench. Camel hump heads Solid lifter cam 230/236 @0.050 and 0.501 lift 0.016 valve lash hot Roller rockers Double valve springs to match cam All valve train is brand new Initial timing is 18 BTDC And full timing is 36 BTDC all in by 2700 rpm. New distributor with pertronix and vacuum advance on full manifold vacuum. Vacuum seemed steady, but I could never figure out why the vacuum gauge would read backwards when I blip the throttle. I started another thread on this topic. The carburetor is a rochester tri power on an Offy manifold. I seemed to have worked through most of the gremlins and it starts instantly and idles well. Seems pretty responsive without any bogs. The headers are some cheapy lakes headers with glass packs cut in half as baffles. There are minor exhaust leaks and I plan on getting a set of gear drive headers when I have the cash. The transmission is a muncie with a brand new flywheel and clutch fastened with new ARP bolts. I hope that covers all if it. Alm advice is greatly appreciated. Thanks in advance.
I have a 327 with forged pistons that makes a ticking, light knock untill it warms up. Forged pistons are noisy as hell.
I had a pontiac 400 that did it once, actually 2, engine one was piston pin, engine 2 was pvc valve. It created low vacuum and it would pick up and drop the piddle valve inside it. Although it would go away above 2000 rpm. Took me an hour to figure that one out.
Pull the valve covers and check your valve clearances again, be sure they are correct. That will be the 1st place a worn can lobe will become apparent. You do have a baffle in the valve cover below the pvc valve in the cover, right? I had a friend that screwed up 3 sbc because there wasn't a baffle under the pvc, the pvc would suck the oil out of #8 cylinder. Started as a sound like a lifter tick and would score the cylinder wall in short order. Also, a header flange exhaust leak sounds like a lifter tick. Gene
Yes I have the stock soup can baffle. I will try snugging up the exhaust, but the ticking sounds mechanical.
I will do that and I hope this is it. I just can't understand why it would start making that noise all of the sudden if it happens to be a valve adjustment issue. Thanks for the input Posted using the Full Custom H.A.M.B. App!
I had a dipstick on one of my flattys that was slightly bent. Installed one way no noise, installed upside down, rubbed the damn crank. I was ready to pull the intake and i just happened to check the oil as it was running and it magically disappeared!! Damn dipstick
You might have just opened up a bigger exhaust leak. They tend to grow suddenly, sometimes when chunks of slag blow out of things you thought were welded.
While checking your valves lay a straight edge across the top of the valve rocker studs to see if one has pulled out if you don't have screw in or pinned studs.
Sometimes using a pair of exhaust hoses will quiet the engine inspection, so you can diagnose this one better. Sure sounds like unexpected valve lash.
Every rod knock I've listened to would go away under power, then become really audible when you let off on the gas. Or do I have it backwards? It's been a long time since I hammered a bearing out.
You got some good advice so far, but try to remember that EVERYTHING happens "all of a sudden" with engine failures. One minute it's great, the next it's broke. Try to embrace the challenge and good luck.
My guess is the cam is eating a lifter, which is getting revenge by eating the cam right back. Sometimes this can be detected by a finger test, feeling which rocker arm is looser than the others. It seems almost like a 50/50 shot these days putting a new cam in. I won't do it without GM new engine lube (Around $20 for two small bottles. Cocaine is cheaper by weight.) and a high quality new engine oil like Gibb's or Penn (not Pennzoil). ZDDP, sulfur, whatever.........new oil doesn't have it and fresh engines need it. The last several engines I've built/put new cams in have lived with these combinations. Before that, I don't want to talk about. And it was always cams eating lifters.
Does it go away when warm?? I had a 327 short block with cast pistons---has a cracked skirt that went away when warm.
God, I hope not. I assembled the engine using the comp cam lube and broke the engine in using comp's break in oil. I drained about a pint of oil from the pan and didn't see any metallic particles. Maybe I will check the filter for metal specs also. Posted using the Full Custom H.A.M.B. App!
Since you said it was a roadster, I am going to assume you probably have open headers or straight pipes, since it seems most do these days. (If you don't have open pipes, you can probably ignore this). You also said that you just got finished trying to tune and time the carb and dizzy. I can not say for sure since I am not there, but it could be a good guess that you may be too far advanced or lean and are getting detonation ping that sometimes sounds like a knock with open headers. Further, if you do have open headers, it's pretty hard to pinpoint exactly where a noise is coming from since the sound from the headers bounces off about everything around it and can make sounds appear just about anywhere. Try dialing back on the timing and richen up the A/F mixture a bit and see what happens. Since it is happening when warm and at higher RPMs it may be a product of distributor advance settings. So you could check that also. One other thing to check...if you can, is the flywheel or flex-plate. If they have any cracks especially around mounting holes, it can sometimes make a sound that sounds like a knock. If your oil pressure is good and staying that way, it likely isn't crankshaft related. Lifter tap is a pretty unique sound and can usually be found pretty easy with the screwdriver to ear trick. If you aren't getting any results with that, it is probably unlikely as well. Whenever you get it sorted out, make sure to post your findings on here so that if others run into similar issues there is some resolve in the threads they are searching.
same way as your tubing to the ear trick. You touch the screwdriver to the place you want to hear and press your ear against back of screwdriver. Sound travels through the screwdriver. Basically a low-budget mechanic's stethoscope. Just helps pin-point sound sources better and muffles background noise if you plug your other ear. Use the longest thinnest screwdriver you can find and use common sense with your face that close to the engine. PS- you can buy a cheap mechanics stethoscope from harbor freight if you don't want to risk your face and want to make it easier. I use mine about 2 times a year. They are good to have around.
I've used wooden dowels, pieces of plastic PVC tubing to ferret out engine noises. Try to round up someone who possibly can help you with the diagnostic process. I personally like the valve lash re-check and a potentional header leak scenarios. Bob
I just noticed you said "solid lifter" cam. You will have some valve ticking with solid lifters. It's the nature of the beast with solid lifters. Some degree of ticking would be pretty normal and expected since there is lash between the rockers and valves and the lifters aren't hydraulic and applying constant hydraulic pressure to the push rod. Knocking on the other hand wouldn't be, in which case many of the suggestions above would still be valid and can be checked. Also, does the issue only happen when at operating temp? Does it happen at cold idle and start developing at warm/hot idle? If it doesn't do it when cold, it may just be solid lifter tick. When cold the oil is thicker and has more cushioning, when it gets warm it thins out and will have less cushioning.
One of the members of the dominant car club around here (old club, old guys with bought cars) had a knock in a SBC engine in an otherwise nice mid '30s Dodge Coupe. It was a con rod. He asked, I listened, and ascertained it was a con rod. No doubt! The oil pressure gauge was mechanical, and the pressure had dropped alarmingly...the knock was such that I advised him to shut it off. Two minutes later, he's got some late-comers listening to it...I sidled up to hear some of their 'diagnostics'...everything from "lifter!" to 'timing chain, heard that before' to 'cracked flywheel, they always sound like that.' His friend insisted that he bring the car to my shop, which he finally did...I was able to get the pan off after raising the engine. Spun bearing on #2 con rod. Crank was .020"/.020". "But...How did you know???", he asked. I replied, "Mileage..."
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