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Old 09-12-2017, 07:36 PM   #1
James903
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PVC valve questions

Ok, so I have a newer engine with a summit 1104 cam. Ive been trying to tune it in, and I feel like I'm close. But I kinda have one problem, I get it to run/idle better when I have the pvc hose disconnected from the base of the carb and the carb port plugged. Is it possible that I have a vacuum leak or something along the intake? Only reason I mention this is ive forgot to put the pvc line on before and it ran like crap (different engine). I was thinking about seeing how it would run if I ran the pvc line to the intake port behind the carb where the trans vacuum line connects. Is that a bad idea? I don't have power brakes. I have a few other ideas but just seeing if anyone had similar problems in the past. It kinda has me stumped and haven't had time to try a couple of my ides. (Ive ran this cam before in a different engine similar set up, with no issues with pvc plugged into base of carb) Thanks

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Old 09-12-2017, 09:22 PM   #2
truckster
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Re: PVC valve questions

Does your PCV valve work? Does it rattle if you shake it? If it doesn't it's stuck, and a stuck PCV can allow the PCV system to draw a constant vacuum.
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Old 09-12-2017, 11:36 PM   #3
James903
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Re: PVC valve questions

I just noticed that spell check pvc instead of pcv lol o well. Yeah I checked the pcv valve and the more I think about it I just have a lot of block pressure. My guess is since I have high block pressure going into the port on the bottom of the carb is why I had a hard time tuning it until I disconnected it, and plugged the carb. It was throwing off my air fuel mix?? Now I'm wondering if its because the engine is still fairly fresh? It was a Craigslist engine I bought last Friday. I scored it super cheap and all I really wanted was the block. It turned out it was recently rebuilt. I tore it down and checked all the clearances and it was good so I just threw that cam in it and sealed it up, and just decided to run it. I was thinking about just leaving the carb plugged and running the pcv down the side of the engine, so the blow by from the pcv wouldn't make a mess. I figure I will lose some oil but I'm thinking after I get some miles on the engine and more broken in I could try reconnecting it?? I need to change the advance springs in the distributor still. I think that is also a little bit of my tuning problem.
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Old 09-13-2017, 08:49 AM   #4
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Re: PVC valve questions

Give us some pics of your motor!
How long did you break the cam in for?

Just hanging the pcv over the side won't do anything. Your crankcase pressure will still blow out some gaskets.
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Old 09-13-2017, 09:55 AM   #5
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Re: PVC valve questions

Possible the motor isn't broke in yet. There is a recent thread involving a brand new engine with similar problems getting it to tune properly. Several of us suggested allowing more break in time and last report from the OP was it was behaving much better after more running.

I would check all the usual suspects for vacuum leaks including intake gaskets and if it checks out, connect everything the way it is supposed to be and go through the ring seating break in process.

Don't trust that the previous builder has the timing mark correctly lined up. Could be as simple as your timing is off.
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Old 09-13-2017, 10:58 AM   #6
BossHogg69
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Re: PVC valve questions

Keep in mind, not all pcv valves are the same. Different levels of engine vacuum have an affect on when the valve opens depending on the weight of the ball inside or tension of the spring. After you determine whether or not the engine is actually making excess pressure in the crankcase or if it has another vacuum leak, timing is off, etc, etc, you might try different valves that may work better with your particular cam. You'll have to know about how much vac it pulls at idle and you can go from there. You may look at using a valve calibrated for previous GM engines such as the '70 LT1 350, LS6 454, DZ302, or tripower 427's (1967??). PCV valves are just a couple bucks and you may be able to find one that works for your engine better than what's in there now. There is a lot of information on the web on different forums about this - some Google searching will uncover a lot of threads. Hope this helps.
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Old 09-13-2017, 06:27 PM   #7
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Re: PVC valve questions

I ended up figuring it out.
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Old 09-13-2017, 06:28 PM   #8
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Re: PVC valve questions

Thanks for the input
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Old 09-13-2017, 07:19 PM   #9
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Re: PVC valve questions

Quote:
Originally Posted by James903 View Post
I ended up figuring it out.
Inquiring minds want to know what you figured out?
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Old 09-13-2017, 09:20 PM   #10
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Re: PVC valve questions

Well basically I just kinda started from the beginning. I pulled #1 plug, made sure all was good there tdc. Pulled dist and I think that was part of my problem. I had it dropped in good but I checked the springs, and bushings. One of the springs was kinda binded up. So I popped them off and put the other ones in I wanted to try. Put it all back together and fired it up. Set the timing and runs great. I have the pcv hooked up and none of the issues I had before. I definitely learned a lot about tuning and tracking down the problem. I think a lot of the frustration was I blew up the original engine a couple weeks ago, then I threw in a different one I had on the stand that turned out to be really low compression almost none in 2 cylinders. Then the third (Craigslist find) made sure things were right as far as clearances other things. I just couldn't tune it at first, and had high oil pressure which I wasn't expecting. I basically kept jumping to conclusions but figured it all out. I will say that he $200 Craigslist engine I think is totally going to turn out to be a score! I wasn't expecting much from it based on price, but the thing seems practically rebuilt new. Thanks for the random input and advice on pvc valves (bosshogg I will always keep that stuff in mind next time) and everyone else.
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Old 09-13-2017, 10:46 PM   #11
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Re: PVC valve questions

glad you found your problem...... now what's it sitting in?
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Old 09-14-2017, 11:17 AM   #12
James903
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Re: PVC valve questions

47 international
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Old 09-14-2017, 12:15 PM   #13
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Re: PVC valve questions

Looks like a pretty fun vehicle.
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Old 09-14-2017, 07:10 PM   #14
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Re: PVC valve questions

Cool! I knew it was something different when I saw the front axle leaf spring mount.
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