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By Y block guy - 10 Years Ago
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I'm trying to figure out why I keep having cam issues. Both cams(2) have gone flat on #6 cyl. Ex. Don't know why, ANY suggestions would be greatly appreciated. Engine a 312 w/ported ECZ-g heads,Mummert spec'ed cam
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By steinauge - 10 Years Ago
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I hate to ask this but you ARE using a new set of lifters with each new cam right?! If so I would proceed as follows; since it is the #6 cylinder I would pay very careful attention to valve spring installed height and seat pressure on that cylinder.Be sure that your springs have a minimum of .060" travel remaining before coil bind at full lift.Also be very sure of valve travel-I E how far the valve can move before the upper retainer hits the guide\seal.This also should be around .060"min. at full lift.Lack of clearance in either place will take the cam out right fast! I assume you are using plenty of cam and lifter assembly lube and paying careful attention to valve clearance.It sure sounds to me like you are bottoming a valve or spring.It is critical to check each valve for spring and valve travel during head assembly.
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By RB - 10 Years Ago
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Also check that guide to see if it is too tight. You should be able to wiggle the valve in it..It might be tighter than the others and seeing it is an ex valve it bears checking out.. Did the cam lobe go, the lifter, or both? Also check that lifter bore. The lifter should spin easily with your fingers and not have any tight spots or binding with up and down movement.. Losing cams really sucks. Finally, Comp and others offer a nitriding process which puts additional hardness on the surface of the cam.. Trend tool steel lifters seem to be very durable.. At this point you do not want to do it a 3rd time
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By mctim64 - 10 Years Ago
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What does the lifter look like? Is it spinning in the bore? What lifters are you using?
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By Y block guy - 10 Years Ago
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Thanks for the reply, I'll be pulling the engine out next month to investigate. Don't know if it's cam or lifters. Yes both new,
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By suede57ford - 10 Years Ago
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I suspect a guide that gets too tight when the motor gets warm. I had to replace a few valves after loosing a motor and bending a few valves once, and the new valves were just slightly thicker stems. They seemed to go in fine, feel good, but the same lobes were going bad. Had those guides corrected, and the problem seemed to be solved. Also, always make sure the lifters spin freely when installing them. You can watch to see if the pushrods turn when you start the motor.
I am a big fan of having everything perfect, including a known working carb, before start up. The engine needs to go to 2000 rpm instantly on start up and stay there for 20-30 minutes. The cam is only oiled by the oil slinging off the rods, and you must have enough rpm to get the oil pressure high enough.
I like to keep the timing advanced a bunch to keep the headers from getting so hot.
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By Ted - 10 Years Ago
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Y block guy (2/11/2015)
Thanks for the reply, I'll be pulling the engine out next month to investigate. Don't know if it's cam or lifters. Yes both new,
Here’s the link to a list of items that can contribute to cam/lifter failure. Any one of these or a combination of them can cause problems. There’s a known problem with offshore lifters so try to rule that one out also. If you purchased the lifters from John Mummert then you should be good on those assuming the lifters were also replaced with the second camshaft.
http://www.eatonbalancing.com/blog/2012/11/06/camshaft-and-lifter-failure-causes-2/
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By 2721955meteor - 10 Years Ago
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I have talked to 2 cam grinders in bc, they both say,most of the flat tapet cam failures are the source of the blank(china).1 of thes companies that do a lot of cummins cams(dodge) gets his blank cast in the us, to his spec. the 2nd co is verry sure the regrind is on a older cam of knowen quality. this is hearsay and i only have this info from the shops.Tho i have never had a failure with a regound cam,this includes maney years working for cat dealer with 3306 and 3208 engines with flat tappet cams. also as hobey of rebuilding gas engins,mostly ford ys fes,as well as289/302a.
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By Y block guy - 10 Years Ago
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Both cams and lifters were new from Mummert. With the v/covers off engine warm and running, lash set to .019 on in &ex, will the pushrods spin with the lifters? Will this confirm that the lifter is spinning? I will mark the pushrods #'s 5,6,7,8 to verify.
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By Ted - 10 Years Ago
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Y block guy (2/14/2015)
Both cams and lifters were new from Mummert. With the v/covers off engine warm and running, lash set to .019 on in &ex, will the pushrods spin with the lifters? Will this confirm that the lifter is spinning? I will mark the pushrods #'s 5,6,7,8 to verify.
In most instances the pushrod will be turning if the lifter is turning but that’s not true 100% of the time. If there is some friction going on at the cup end of the pushrod, then the lifter can still be potentially turning while the pushrod is not.
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By RB - 10 Years Ago
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I would take a very hard look at the guide clearance on the exhaust valve where the failures occurred.. I remember a conversation with Mummert where he emphasized the need for additional clearance in Y Block guides above what most shops would normally provide... Ted may have an opinion also
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By Ted - 10 Years Ago
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Adding to what Royce brings up, if the cylinder heads have had bronze wall guides installed, then even more additional valve stem to guide clearance is required. Stock iron head clearance values being used for bronze guides are simply too tight. If the guide clearances were not checked when heads went together, then the potential is there for inadequate clearance as there seems to be more variability in ‘new’ valve stem diameters now than in the past. Exhausts tend to give more problems in this area simply due to the higher heat loads placed on the exhaust stems.
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By pegleg - 10 Years Ago
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And those clearances (new) should be?
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By Ted - 10 Years Ago
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pegleg (2/14/2015)
And those clearances (new) should be?
Mininum clearances for Y-Block stem/guide clearance with bronze guides in a racing application would be 0.002” for the intakes and 0.003” for the exhausts. For a street application this can be downsized to 0.0018” for the intakes and 0.0028” for the exhausts. Erring to the large side is always recommended where clearances are deemed critical.
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By Y block guy - 10 Years Ago
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I'll have to give Mr. Mummert a call next week as he was the one who did my heads.
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By Ted - 10 Years Ago
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Pushrod alignment within the holes in the heads is critical on the Y engines. If the pushrod is contacting the head, then camshaft/lifter failure becomes highly probable. The Isky 3/8” diameter pushrods brings this to the forefront but likewise if the rocker arms are not positioned correctly on the shafts. Look for wear marks on the pushrods. If you find some of these, then this is something that will need to be addressed. Pay particular attention to the #6 exhaust pushrod in your case.
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By pegleg - 10 Years Ago
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I'm not sure most shops will be able to get to the tenths. Probably would stick with the .002 and .003 dimensions.
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By John Mummert - 10 Years Ago
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Ted brings up a good point on the bronze valve guides. Bronze tends to need extra clearance as it seems to shrink for a few heat cycles. It eventually stabilizes. Check your ignition timing also, as Pat pointed out, too little advance will raise exhaust temperature and make the guide sizing more critical.
We generally used K-Line style guide liners in Cast iron heads and set up guide clearance in the .002" intake and .0025" exhaust range. I would definitely have the guide clearances checked.
As Pat pointed out the only oil on the cam/lifters is what is thrown off the rods. Check the side clearance between #2 and #6 rods. I would not run with less than .012". .015-.018" is better.
All of the cam cores we see are CWC # 3358 B-S regardless of cam grinder. I have no indication that these are made off shore.
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By Y block guy - 10 Years Ago
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Thank you John, When I remove the engine , i'll start checking for all these issues and get back to everyone here
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By 2721955meteor - 10 Years Ago
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no indication of wher the basic casting came frome would not saticfy me,colt cams of langley bc went to the trouble of insureing ther cam blanks are cast in the us to his spec. i am not saying that is the case in all cams ,onley when 1 has consistent failures ther has to be a isue we are all missing. tho basice failure analisis tells a student you need all the facts, and the builder must have 1st axcess,frome oil analisis to tear down to establish probel cause. other wise one will most likeley miss the cause,frome base metal to profile to lifter finish ,to lifter material,to siting to long and pre lube.
just when we think we have the answer new evidence comes from the builder or asembler. it is not a exacting syence,just a learning curve. have to admit i have learned a bunch frome this syte. cliff
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