PCV causing major vacuum loss.

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Oct 26, 2014 | 03:44 PM

#16

Franklin2

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From: Virginia

Quote:

Originally Posted by ebbsrig

FIXED, Well, sort of. It is definitely a PCV sizing issue and the mass of fuel in the oil sump exacerbated the problem. Adding to my pain was the inconstancy of over the counter PCV valves. Two identical part number valves had wildly different operating characteristics. Different flow, different closing vac, all around mess. There is a fully adjustable PCV valve made by M/E Wagner Performance. $130 bills is NOT an option at this time. When I get the dual carb intake and the other engine together maybe, but for now, not happening. For the interim I opted for a fixed orifice PCV elbow. It basically provides a constant flow and is thus not as efficient as the standard dual flow PCV valve. My vac is steady at 16"hg at idle and repeats after hard acceleration. 16" works, I lose 3" over a closed engine but still have plenty to work advance, brakes, and eventually the EVAP system. I'm down to jetting the carb and this little gem will be on the road. Weber carbs are awesomely adjustable, BUT you got to fiddle with them to get them right. For the winter I will have basically stock 300 with weber 38 on the factory log. Set of points in the dizzy, and set of points in the glove box. Thanks to everyone for their input.

Brew
1985 F150 4.9 (The Toy)
2007 F350 SuperDuty 6.0 (The Horse Hauler)
52 Dodge M37 232 Flathead (The Tank)
1932 Tudor body and frame (The Dream)

Once you get that weber carb dialed in, can you report back on what you found works best with the 300 and the original intake manifold? If you do any fiddling with the distributor, can you report back with that also? Weber carbs are nice, but like you said they need to be dialed in. There are a lot of guys on here that are stuck with the stock type 1 barrel, and would like a little more from their six. The single weber would probably be a nice small upgrade from stock, and if you do all the hard work, all they would have to do is follow in your footsteps regarding jetting and adjustments, adapting to the intake, adapting the throttle linkage, etc.

Oct 26, 2014 | 06:01 PM

#17

ebbsrig

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Joined: Nov 2011

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From: Central Montana

I will absolutely post the results. Bear in mind that I am at 4000' so I will be working to that altitude. I will tell you this much. I have no intention of buying a ton of jets and guessing at this operation. I already know I am lean so I will be drilling out jets till I get the size and then order what I need. Been almost 30 years since I dialed in a custom carb install to this level, but it's not difficult, just time consuming. I'm kinda new to the forum posting, but I think it would be better to make a new post which I will do. I will post the full conversion from computer TFI to Weber, points dizzy, on a stock Motor. Look for it as early at next weekend. If not then it'll be a couple weeks as I am off elk hunting the second week of Nov. *edit* For those that are wondering I held off ordering the jet kit till I got to the bottom of the PCV issues. Lot's of running, and adjusting gave the sparkplugs plenty of time to tell me I am lean. So I dug out the numbered drill set (you need #30-#80 and a pin vise to do most carbs) and decided to go all out old school. As I said I will do a full write up. *end of edit*

Brew
1985 F150 4.9 (The Toy)
2007 F350 SuperDuty 6.0 (The Horse Hauler)
52 Dodge M37 232 Flathead (The Tank)
1932 Tudor body and frame (The Dream)

Last edited by ebbsrig; Oct 26, 2014 at 06:31 PM. Reason: Added clarification