PCV Question

[f_inscreenname]

I am replacing my old Carter carb with a new Edelbrock 750. The difference is my old one uses a PCV valve and the new one doesn't. I just block the hole in valve cover right? Second guessing myself over this long and cold winter.

 

[Bondo]

Re: PCV Question

Hey, Is this that 360 Mopar ??? If it is, Do the math... the 360 will Not support a 750CFM, till you get up around 7000rpms... Grab a 650CFM... it'll be More tuneable,+ Just plain Run Better....<br />for the PVC, just run a hose from the hole, up to a spur mounted on the edge of your flamearester.... ya gotta vent it....

 

[f_inscreenname]

Re: PCV Question

360ci that is built up a little. It is already vented by the oil filler cap. Tried a 600,650,750 and 850cfm carbs last summer. The 6 and 650 seemed a little sluggish. The 850 was great at any speed but wanted to load up at a idle (that and you could watch the gas gage drop). And you guessed it, the 750 was just right.

 

[charleswmoore]

Re: PCV Question

Hey f-in,<br /> Believe Bondo on this one. I had a stroked 350 / <br />383 and went to a elderbrock marine carb 750 for one season to replace my old Quadrajet and it only took that one season to get over it. My fuel consumption went up almost 15 gallons a day. (at a $1.70 a gallon it gets costly. Maybe I never got it jetted correct but I would consider a carter 530 to 600. Jegs pedddle these for around 350.00 and when you look at it the float bowl overflows dump back into the carb instead of outside into you bilge. I don't like to down play a product but this carb was a piece of S--T. The <br />throttle pump arm rusted into to mount and seized up plus jets had to be purchase indivitually not a kit. I guess I'm just trying to save you the 600.00 plus extra fuel. Ps the poor quaulity anodizing they used looked even worse than the performance. I guess you got the hint I wasn't happy with it! Just a thought or two. <br />Charlie

 

[f_inscreenname]

Re: PCV Question

Paid $137.50 for the carb (Edelbrock #1410 750 marine). Ran for less then 3 hours then taken off. He needed to go bigger (you should have saw his set up). Also came with a complete rebuild (I mean everything that was removable from the carb there was a new one) kit and different jets sets. He couldn't use it so he gave me everything. Best e-bay buy I ever made. <br />As for the gas......My boat is not really set up to be a gas saver. Not really worried about it. Just performance and like I said I tried a tired 750 Holly last summer and got the best performance out of all I tried. So with the new electronic ignition upgrade and a couple of other things I think it will be just what I want.

 

[Gold Bear]

Re: PCV Question

f_inscreenname<br /><br />The PCV system pulls a slight vacume on the crankcase. This suction takes care of the pressure that orginates from piston ring blow-by. The faster the engine runs, the greater the crankcase pressure that develops from blow-by.<br /><br />Without the PCV system working you take a chance of blowing a "crankcase" gasket - such as the one that seals the front or rear end of the intake manifold to block (in way of the valley). Those are usually to ones to go. If you plug the valve cover where the hose was you will be bowing smoke out the other intake filter.<br /><br />You need to find a way to connect the PCV hose back in place. Perhaps you could install a carb spacer with a fitting tapped to re-connect the PCV hose.<br /><br />Good Luck,<br /><br />Gold Bear

 

[f_inscreenname]

Re: PCV Question

If that is the case. I should drill out the place where the PCV would normally go in the carb (almost done now, just a thin wall to break through) and press in a sleeve to hook the hose to. Doesn't seem to hard. Just want it done right the first time (no quick fixes). Anyone see a problem with that? Thanks Mark

 

[Bondo]

Re: PCV Question

OK, I Did the Math for you......<br />360cid, running at 5000rpm, With a volumetric efficiency of 100%(Which you'll Never see)... Can move 521CFMs.... At 6000rpms it can only move 625CFMs !!!!... <br />You'll need to turn that mopar 7250rpms to use that 750CFMs.....<br /><br />You're going to have a hell of a time finding a good combo of needles,jets,+ springs to work right.... Because the vacuum signal will be too weak in the big carb...<br /><br />I just bought a 650CFM Merc. Weber carb. at the bay... Less than $125. to my door... i use Carter AFB parts for it... easier to find,+ Much Cheaper....<br />I've got the same carb. on my 4.3 now.. this one is for a 383cid stroker....<br /><br />Just because you tried 4 junk carb.s last summer, doesn't mean the best of Them is your answer....

 

[Bondo]

Re: PCV Question

All ya gotta do is Vent it...<br />the PVC that is.... throw the little rattly thing away, then just run a hose to the breather...

 

[f_inscreenname]

Re: PCV Question

It wouldn't be the first time I learned a lesson that cost over a hundred bucks (I have owned a couple internet stocks and did mention Big K-mart, those dogs.Then there's the ex-wife......). If it doesn't work out I will move on to something else. Better then running a 30 year old rebuilt carter carb (that and according to the manual there's a piece or two missing) on a new (less then 30 hours) 320hp motor.<br /> So what is it? One says to just vent the PCV hole in the valve cover. <br /> The oil filler cap is vented now. Made that mistake when I built the motor. Didn't open the metal tab inside the cap. At five grand RPM's I blew oil everywhere. Popped open the tab in embarrassment and cleaned up the oil. All fixed. <br /> Then there is running a hose either to the flame arrester or to the base of the carb. What is the way it should be???????<br /> I'll be honest. I am not a big fan running it to the flame arrester.If that is the way it should be? I think I would rather tap out to vacuum hole that's in the base plate of the carb. A cleaner looking install. I am kinda big on that.<br /> Thanks again

 

[snapperbait]

Re: PCV Question

The PCV valve hooked to the carb or spacer plate will allow the vaccum the engine produces to pull negative pressure inside the crankcase... <br /><br />That will help the front and rear main oil seals and valve cover gaskets to last a long time, as there will be less pressure trying to push the seals outwards...<br /><br />Thats how I do it..

 

[f_inscreenname]

Re: PCV Question

Sounds good to me. Its a five min repair now. Glad I asked the question. I don't want to have to reinstall the intake. A good way to ruin a weekend.

 

[charleswmoore]

Re: PCV Question

Pulling the vacuum off the base of the carb instead of off the air cleaner? I'm not sure i would do this! All boats that I can remember just has a hose off the two valve covers going to the <br />the backfire flame arrester. if you try to pull vacuum off the input side of carb and then the crankcase will have to be totally sealed or you will end up with a vacuum leak that causes a hole new set of problems? I wouldn't try this because a few items on the block are not sealed Ie dipstick, oil filler cap (maybe, maybe not)All I can think about is how leen this motor will be running and how poor the performance would be.<br />Again go with bondo on this one he's is steering you in the right direction.(Don't try to pull negative vacuum on an unsealed block)<br />Ps, At 5 grand on a stock motor, Maybe you should consider repropping. Most I/O's are rated at 4400 to 4600 with my 5.7L at 4800. My V/P is considered a mild performance motor and I still <br />cringe above 4200.<br />Just another thought.<br />Charlie

 

[f_inscreenname]

Re: PCV Question

The Carter (all most identical to Edelbrock) that came with the original motor was set up with a PCV hose running to the base plate fitting on the carb (like most cars). I didn't have any problems all of last year running like this. So I am putting it back like it came from the factory (Edelbrock recommends this also). That and I really don't like the idea of running engine air (oily air,blow by,smoke what ever you want to call it) through my flame arrester then through the body of the carb just to get to the intake when you can go straight there with no difference (the PCV valve regulates the air flow right). Just have to make sure there is no leaks. The factory already had the hole drilled out 98%. I then just pressed in the hose fitting and done. Any motor that I have saw that was set up running the hose to the flame arrestor had a (what I would call) very dirty carb. My 30 year old carter still looked like it came from the factory except for the outside. I believe that a clean fuel system is a happy system and on the water being clean (even though I like to go fast and loud) is the only to be. After 30 years of working this way they must have done something right. Also it was a quick and easy fix.<br /> As for the prop. WOT is 4800rpm's now. After I add my box of tricks I have been buying over the winter I will see if I need to cup it up a notch or two. If not (for me ) it is prefect like it is.

 

[charleswmoore]

Re: PCV Question

Then yes why not. I agree if your gonna pull vacuum off base of carb then definetly use valve. Like I indicated my boats never had a PCV valve only a straight openning to the outside world. Previously mentioned in the string I would not gut the valve. If you do, you may see the issues that I stated above with Air fuel mixture problems. Other than That I do concur that the thru flame arrester does cause it to gum up relatively quick pending on amount of blow by you have. You also pose a good question of why even as new as my recent purchase (2001) why the marine industry doesn't do this anyway and still runs crankcase ventilation through the flame arrester??? Makes you go duh huh sometimes doesn't it? So did the old oil cap have a pcv valve built into it? Because I don't think a pcv valve will open unles it has vacuum applied which will never develop off the flame arrester? If only life was this simple! PS I don't know how aggresive you buit this motor but I have seen some motors so radically built they needed a trap<br />in the ventillation system to allow oil to run back into motor after a good 5500 to 6500 turn up.<br />take care, Charlie

 

[f_inscreenname]

Re: PCV Question

I had two mandates when I did the research on what motor I wanted. They were - power 50%, reliability 50%. I run allot of rivers and stuff. Never out of site of land. Originally being a small block 318 Chrysler set up so I went for the 360ci (longer stroke) easier on the motor and good oil pressure at any rpm. A must! A dyno test said 329.8hp/401.9flb's at 5 grand. I could have built the 380hp but I wanted the motor to last for more then a year. My last boat had a 302 hoped up crazy and it was every spring I was doing a rebuild. Finally I built a 351w for it and never had a problem again. Says something about that longer stroke. I have to say I still watch that gage like a hawk. When it starts heading for the red line you know you have big money problems. <br /> as for the PCV to the flame arrestor set up. I have always thought it was a jury rig that's cheep for the manufacture. That and technically it is a vacuum port below the fuel bowls on a marine carb. I wonder if that has anything to do with it? Like I said though mine came from the factory like that. Maybe they changed the law on carbs over the years.