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65rag · 01-17-2005, 01:34 PM

Im experincing blow by in my newly installed 69 yz 400.Im using 1970 #13 heads and a stock ram air III cam.Oil is blowing out the dipstick when in the 4800rmp range,and out the valve cover breather cap.Any suggestions?

65rag · 01-17-2005, 01:34 PM

Im experincing blow by in my newly installed 69 yz 400.Im using 1970 #13 heads and a stock ram air III cam.Oil is blowing out the dipstick when in the 4800rmp range,and out the valve cover breather cap.Any suggestions?

Goathead · 01-17-2005, 01:44 PM

Evac system to the exhaust pipes should do the job....

runningbwdog · 01-17-2005, 02:20 PM

Hi,
Sounds like your piston rings are not sealling yet. You may have broken rings or the end gap was correctly set. Do a compression check. Check the hose from the PCV valve to the intake manifold. If has oil in it, then you have too much pressure inside the engine. Seal the grommet on the valve cover, seal the dipstick tube. Put a pressure gage (vacuum/fuel pressure gage) into the grommet for the PCV valve in the valley cover. Nominal pressure should be around 5-7 psi. If more, then rings are the problem. You can try this: put 2 containers of STP into the oil. Run the engine at about 1000 rpm until it warms up. Shut it off and let it cool down completely. Repeat the process. The STP will seal the rings better than low viscousity oil.
It may be that the gaps of the compression rings are aligned and allowing the pressure to easily escape into the interior of the engine.
Hope this works, let us know.
Mike

uneasyrider · 01-17-2005, 03:37 PM

Here's a story I think you will like...

The following is from another post called "To much crankcase pressure".

I'm sure this isn't the problem but for others that may have the same thing I'll post it.

My buddy has a BUILT 1970 Roadrunner with an evac. sys. on it and we kept having the dang breathers and the dip stick blow out of it. As it truned out (even though he had owned the car for 4 years!) the engine hadn't been broken in yet! We swapped out the auto for a 4-spd and drove it hard for a few days enjoying the new toy. At first we had to strap the breathers and dip stick down or they would blow out under load. It was summer and hot and the car was running on the high end of the normal range the whole time we were out. I was driving it the next day after scarring the crap'ola out of a few people along for the ride and I noticed it was pushing the very top of the normal range. It was 100deg out so I wasn't superised. BUT a few minutes later I was driving along and looked down at the temp gauge and it had dropped to 180! I thought "Oh know it's dumped all the coolent and the gauge isn't working right because of it or something." Didn't see any steam or smell any coolent but for the life of me couldn't think of anything else that would cause it to drop out of the blue. So I pull over thinking I've smoked my buddies car and can't see a thing wrong under the hood. I let it cool down and cut the tie on the dip stick and checked the oil and water. Everything is perfect! Ok, that was good but why isn't the temp gauge working right? It should be reading at least 200 I would think. I deside to drive it home and I get on it a bit trying to hear anything and see if it heats up and it doesn't. It also doesn't blow the dip stick. After driving it around for a couple days with out the tie on the dip stick we deside to pull the ties off the breathers too. Everything works great. The engine is also running "smoother" and is feeling stronger. After much descussion I found out that he had hardly drivin the car in the last 4 years since the engine was rebuilt. We had checked the evac. sys. right at first of course to make sure it was functioning and it was. The only thing we could figure is that since the car had so few miles on the rebuild and it had the auto (3500 stall) and he had only got on it a couple times before we put the 4-spd in it, it never had broken in and it was still getting a lot of blow-by building pressure. After the hard runs it sealed the rings and was fine. Of course this isn't proof but it was the only thing we could think of.

Oh, and BTW the temp gauge was checked and it funtions fine.

Uneasyrider

BVR421 · 01-17-2005, 06:13 PM

I second the notion of running the snot out of it for a few days. Drive it like you borrowed it from your ex's new boyfriend.

buwalda · 01-23-2005, 04:35 AM

Hope you are not using synthetic oil. It is not recommended for running-in new engines because the rings do not seat properly.

uneasyrider · 01-23-2005, 09:47 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Geoff:
Hope you are not using synthetic oil. It is not recommended for running-in new engines because the rings do not seat properly. <HR></BLOCKQUOTE>

VERY GOOD POINT Geoff! If you have synthetic in there get it out and put a straight 30W standard grade oil in until it's broke in.

Uneasyrider

WCWhitey · 01-23-2005, 05:31 PM

Similar story, my 400 dropped 20 degrees and smoothed out considerably once it was broken in. Took about 750+ miles. 220 at idle was common, but after breakin does not see +200. Sometimes I think we baby our engines too much. I have also noted that after the breakin is completed the temp will drop slightly with a switch to the synthetic oil, I am assuming less friction is the cause, this may also be the explanation behing the extra heat during break-in. It only makes sense.

uneasyrider · 01-23-2005, 06:52 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by WCWhitey:
...I have also noted that after the breakin is completed the temp will drop slightly with a switch to the synthetic oil, I am assuming less friction is the cause, this may also be the explanation behing the extra heat during break-in. It only makes sense. <HR></BLOCKQUOTE>

Yep, synthetic lubricates so well it wont let the parts "lap" together properly. They actually do a bit of their own machine work durning the break in process. The rings are the most critical. The hone put on the cylinder walls and the oil used during break in are very critical. Hone it wrong and the rings wont seat or use the wrong oil. If it's to slick the parts wont machine themselves together to form a good seal. Of course the MOST critical part IMO is the cam break in. Get that wrong and you are SOL.

Uneasyrider

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