Z,in theory, you want all cylinders feeding the PCV system.
In actual practice, it doesn't matter as much as you might assume. I have 25 years,and over 180,000 miles, experience using the Cobra Hi Rise manifold. That manifold uses the #4 runner for the PCV inlet. Yes, that cylinder does run a bit leaner. But not enough to make tuning difficult, not enough to require a colder spark plug, not enough worry about. and the crankcase pressure is just as low as it is with traditional PCV systems
Z,I would definitely try using that port if I didn't have a carb spacer alternative. I'd be surprised if you had a problem with it.
PS if you have the room under the hood for that one inch spacer, there's no reason it won't work.
What's the part number on this spacer? Have you used on a 4100 with a Weiand intake? Thank you.it is typically not a problem using a runner port for the pcv but i avoid it if possible.So, in theory I can use that port (which I think is for the vacuum for power brakes) and not have problems, am I understanding it correctly? I ordered a phenolic spacer with a PCV port https://www.summitracing.com/parts/trd-2529. Thinking if this spacer won't work, I need to see if that manifold port will work or find another spacer.
you can also get an adjustable pcv if the one you use affects your idle too much.
that spacer will not insulate the carb from heat, plus you may loose a little bottom end with it but you would have to test it with and without. i often use these spacers.
Ok. As mentioned, I'm hoping that spacer will work for me. Am I better off just using the Boss 302 spacer and hope it won't break.I would definitely NOT use that port. The PCV system is "open-ended", meaning that there is constant flow through that port whenever the engine is running, a low volume of air at idle and closed throttle, and a higher volume of flow as the throttle opens, which means that at idle you won't be leaning out the cylinders fed by that runner all that much but under large throttle openings would be significantly leaning out those cylinders, asking for potential detonation. The difference, when it's used for a brake booster or to supply vacuum for advance or transmission modulation is that those are "closed-end" systems and there is no flow, just vacuum generation.
Think of the two types as sucking soda through a straw as the former and sucking it through a straw with the bottom plugged as the latter.
This is exactly what I was talking about. In theory it sounds like a terrible idea to use a single port for the PCV entry, But in actual practice it doesn't make enought difference to matter. There are thousands of Shelby's using the cobra hi rise manifold which has the single port entry, and none of them have the slightest problem in the affected cylinder. I ran my Shelby's pretty hard, and over a period of many many years. If there was a real issue here, I would've seen it.I would definitely NOT use that port. The PCV system is "open-ended", meaning that there is constant flow through that port whenever.........".
I am going to cut my own gaskets. I'm planning on getting this https://www.summitracing.com/parts/fel-3060 and cut it to fit.i also use fl-pro gaskets because they are thicker than most others . either way, i would not use the paper thin ones as they don't seal as well and require more torque to seal an irregular surface, and if you tighten the bejesus out of the carb nuts it can crack but its not common . the factory ones were nearly impossible to break but the repos like these are flimsier because they are most likely "heche de china" but rick from npd would know. you can occasionally find orig ones on ebay.
I understand the importance of over torquing. I invested on a good torque wrenches before I started building the motor. I'm going to look up that heat insulator from Edelbrock. Does it go on the intake then the gasket then spacer? Do I need to do a spread bore or four hole type for the gaskets? I do have a Napa store nearby. Thank you.Bob & Sue;9302986 said:The curved one says it's made from OE tooling C9 1969
The straight on is made from OE tooling D0 1970
I like the looks of the 1970.
In response to gaskets, leaks & over tightening I just bought the Edelbrock Heat insulator to solve a gas boiling problem that I'll put on soon.
When I remove any carb I always use a straight edge on both mating surfaces carb & manifold, if someone has over tightened the carb it will be warped from engine hot & cold expansion. Never tighten any bolts with mating surfaces without using a TORQUE WRENCH there are all kinds of charts to get the specs.
I use the thicker Holley gaskets with the correct gasket sealer, thin gaskets will work fine if mating surfaces are flat & not over tightened I just like the thicker ones. By over tightening bolts on a carb you can end up buying a new throttle shaft body from warpage. Same thing with thermostat housing, intake manifold etc on head bolts if they're over torqued you run the risk of stripping breaking a bolt, stretching the threads causing lack of holding power, galling the threads trying to remove them from burrs.
Never tighten a bolt rated to 20 ft lbs to 40 ft lbs thinking tighter is better. I've learned the hard way in hours and money spent.