Power drops off rapidly after above 4,000 RPM...

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pvan
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Power drops off rapidly after above 4,000 RPM...

Post by pvan » Mon Sep 03, 2018 5:29 pm

Hi all,

After getting everything sorted I was still having an issue with top end power falling off early. Since I am satisfied with the how it is running otherwise, I have decided to go ahead and take things apart so I can add my upgrades. I have now removed the top end of the engine and the exhaust from the down pip forward and think I may have found the culprit: worn cam and rockers.

I've never seen a cam wear like this unless it wasn't broken in properly. If you look closely (zoom in) you can see the ridges on the cam and the valley on the rocker. Not sure exactly how much material was removed, but certainly enough to have an affect on performance.

Has anyone else seen this kind of wear on their cam/valvetrain?

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Mike McCreight
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Re: Power drops off rapidly after above 4,000 RPM...

Post by Mike McCreight » Wed Sep 05, 2018 8:40 pm

I've seen MUCH worse.
I had one brought here belching black smoke upon acceleration, and the oil I drained had so much soot in it, it was like a liquid abrasive.
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Ed Lijewski
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Re: Power drops off rapidly after above 4,000 RPM...

Post by Ed Lijewski » Wed Sep 05, 2018 9:40 pm

The missing zinc...

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zxr250cc
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Re: Power drops off rapidly after above 4,000 RPM...

Post by zxr250cc » Thu Sep 06, 2018 8:13 am

There are many discussions about oil additive packages in BITOG and the other site that has info is run by rat 540 with independent oil tests made by him. (This is a controversial web site, to say the least, however it does have good information about flat tappet cam oil additive packages.) Many of the diesel oils have zinc in them still, such as Ford or Lucas or others. Zinc is bad for a catalytic converter but if the car is not burning oil it should have little effect. I began running the rebuilt motor with 10-30 synthetic and had an intermittent tappet noise. I changed the oil at 700 miles to 15/40 truck oil and the tappets quieted down. I added Lube Gard oil additive after that and they are very quiet. It is high in moly, another anti wear additive. I use that in the Taurus as well and the chains in the 24 valve are much quieter with that in the engine, even though it has 215,000 miles on it. There are ZDDP oils for start up use made by multiple companies like Lucas, Permatex, etc.. Other additives seem to be able to substitute for zinc it seems, at least rat 540 tests seem to show that.

What cam set will you choose now for your motor?
1986 XR4Ti Mineral Blue Metallic
1999 Taurus SE 24v DOHC Spruce Green
2004 SVT ZX5 Focus EAP Screaming Yellow

pvan
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Re: Power drops off rapidly after above 4,000 RPM...

Post by pvan » Thu Sep 06, 2018 10:30 am

Here is a link to an interesting article on different high-zinc oils. They test 40 different oils for zinc and phosphorus and provide a ZDDP rating as well as a "load carrying capacity/film strength" which the tester describes as a "wear protection capability" for the oil in PSI at 230°F.

http://www.sccoa.com/forums/showthread. ... *Good-read***

This was published in 2015, so some of these manufacturers may have adjusted their chemistry since, but it is a helpful reference.

I was just reading an article that said many cam manufacturers won't honor a warranty on a cam if the break-in oil doesn't have at least 1,200 PPM of both. For the record, I'm sure this cam is as was purchased when I bought the car. I've been a flat tappet V8 guy for decades and have never wiped a cam on break in. Since they started dropping ZDDP levels in oil I have used Valvoline VR1 (#3 on the above list). It's expensive, but it gets the job done.

As far as my next cam set, I'm adding a Ranger roller cam with roller rockers. It's a used unit (with no dish to the lobes), but I am still using plenty of pre-lube and VR1 for the first time firing it up.

zxr250cc
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Re: Power drops off rapidly after above 4,000 RPM...

Post by zxr250cc » Thu Sep 06, 2018 2:09 pm

I note you have also been reading 540 rat data files. That is updated regularly and is easy to find by searching for the user name and oil data as a search. (I reversed the title earlier, sorry.) He is a big block Chevy fan I guess. What I noted from his efforts is that other compounds can substitute for ZDDP and still give good results in flat tappet motors. BITOG is also a good site for oil info. Bib is the oil guy: BITOG.
1986 XR4Ti Mineral Blue Metallic
1999 Taurus SE 24v DOHC Spruce Green
2004 SVT ZX5 Focus EAP Screaming Yellow

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