Help needed with crankcase ventilation (PCV), V8 with Edelbrock

[Defender425]

Just finished rebuilding my 3.5 V8 which has Edelbrock manifold and carb. Originally when I fitted that manifold and carb I had the rocker vent lines tee'd and going to the filtered side of the air cleaner. Ended up filling the aircleaner with oil so figured I needed to do it better after rebuilding engine. (Note- before rebuilding the engine was a mess with 3-4 very leaky cylinders and leaking valve seals so that contributed to some of the issues with oil in the air cleaner.)

I set it up using a PCV valve that "looked about right" attached to LH rocker cover with PCV valve going to port on front of carb and the RH rocker cover line going to air cleaner. After about 200 miles I am still getting oil in air cleaner.
So after reading as much as I could I learned that originally there is no PCV but there is a metered port on the rear of the valley in the block. So I removed the PCV valve and capped the RH rocker cover and connected the LH one directly to the port on the manifold. Works great, actually too great at idle!! Also causes another issue is that I can't get the idle slow enough because of the amount of additional air at idle entering the manifold. Pinching the line helps a lot getting a good idle speed. Also means that any leak in the covers or lines becomes a vacuum leak in the intake system.

So with that long winded explanation of my dilemma I think the best would be to set it up using a PCV valve to shut off or at least severely restrict the flow at idle so I can get a good idle and use the metered port as designed to allow air to enter block.

So what is the right PCV valve to use???? Need one sized correctly and also that is a configuration I can adapt to the engine. Anyone have a good part number or make and model to use?

Welcome any other suggested setup ideas that work. I feel like I am overthinking this!!

Thanks, Jeremy

 

[Parrie]

What truck, year? AB lists a PCV tune-up kit that is specific to D1, Defenders and RR however there is no reference to which motor it applies to. Part #9205

 

[Defender425]

What truck, year? AB lists a PCV tune-up kit that is specific to D1, Defenders and RR however there is no reference to which motor it applies to. Part #9205

1985 110 CSW. Not stock so I don't think that kit would help. Thanks for the info.

 

[Roverman2010]

As you said there is no PCV valve, just a inlet on the block. the size of the inlet hole if I remember is a 1/8" id, and there should be a common plastic fuel filter connected to this.

I thinks you got air leak(s) some where else?

 

[Uncle Douglas]

Could you picture how you have plumbed the two valve covers to the manifold ? Doing this should not have created a situation where you have a high idle.

 

[Defender425]

So did some testing /troubleshooting today.
Tried several PCV valves off similar displacement engines. None of them flowed enough at part throttle to prevent positive pressure in the block. Ended up with a line from one rocker cover using the orginal flame trap with a 1/8" diameter restrictor installed inline. Has slight negative pressure at idle and part throttle but nothing excessive like when it was unrestricted.

While the excess flow before contributed to the high idle the real contributor is the new distributor is not connected to the ported/timed vacuum port but the manifold port. Guess the advanced timing is too much for the carb to get a real slow tick over idle. I'll swap to ported and see how it idles and drives.

I'll drive it how it's set up now and see if oil says where it should.

Attached are some pics showing the orginal set up with PCV, the factory vent port and the final set up I'm trying now.

Before I rebuilt the engine I had both covers plumbed to a fitting inside the air cleaner which filled with oil!!

 

[Uncle Douglas]

On the ones I have done I plumb the the vacuum for the brake booster to the front port you are using for crankcase suction.
I use the original valve cover breather hoses and union those @ a T fitting which I then connect to the port on the back of the carb. No pcv, no blocked off breather port. No idea if there is any difference between the two. Since you have a high idle is there any chance your brake booster diaphragm is compromised ?
With your setup, if you pull the dipstick and put your finger on the tube is there significant suction ?
There's a thread on here somewhere entitled Edlebrock where I posted a couple pictures.
Your throttle cable looks awesome, I've just reused the Rover original with some re routing.

 

[Defender425]

On the ones I have done I plumb the the vacuum for the brake booster to the front port you are using for crankcase suction.
I use the original valve cover breather hoses and union those @ a T fitting which I then connect to the port on the back of the carb. No pcv, no blocked off breather port. No idea if there is any difference between the two. Since you have a high idle is there any chance your brake booster diaphragm is compromised ?
With your setup, if you pull the dipstick and put your finger on the tube is there significant suction ?
There's a thread on here somewhere entitled Edlebrock where I posted a couple pictures.
Your throttle cable looks awesome, I've just reused the Rover original with some re routing.

I think the only difference is the size but I'll check with a gauge this weekend. I was surprised there was quite a difference between the two ports for the distributor.
I did check the brake booster and hose because I thought the same and they where good. If I unplug the advance I can get a nice slow tick over so I'll try the times port and see how it performs.

I basically have the same setup as you did but less vacuum. Without the restrictor I was afraid the super high vacuum would damage something! Right now it will hold the oil cap down pretty well at all throttle settings and never pops up. Wish I had a dipstick but it just broke at the cap a few weeks ago.


Thanks for the comment on the throttle cable. I struggled making the stock work. Spendy but works great.

Thanks for the help

 

[Uncle Douglas]

what distributor are you running ?

 

[Defender425]

what distributor are you running ?

Pertronix D174510 Ignitor II with their coil
Get about 40 degrees total advance. Happy with it so far despite mixed reviews. Time will tell!!

 

[Uncle Douglas]

Only has vacuum advance and if you pull vacuum line off it idles down ?
Which port are you pulling your advance vacuum from ? Should be one with suction only when the throttle plate is off idle.

 

[Defender425]

Only has vacuum advance and if you pull vacuum line off it idles down ?
Which port are you pulling your advance vacuum from ? Should be one with suction only when the throttle plate is off idle.

It has both vacuum and mechanical advance.
I originally had it connected to the non timed port (vacuum at idle) despite the instructions say to use the timed port. This does give a high idle due to the advanced timing increases the efficiency.
Some good information in the second post #2 of this link. Figured I try it. Other that the high idle it works just fine.

Ported vs manifold vacuum advance - The BangShift.com Forums

QandA for everything mechanical

bangshift.com

I have swapped it back to the timed port and have yet to drive it with this set up. This did get my idle back. I was interested in the point they talked about reducing the engine temps with the advances timing.

There is a lot of conflicting info about timed and untimed vacuum. Kind of like asking what's the best oil! What works best for you is the right choice

 

[NMEXPAT]

I've done the edelbrock manifold and carb conversion as well. When I first tried to set it up, I had the distributor connected to the timed vacuum port. It wouldn't even start. I switched it over and it started immediately. I searched high and low on the internet and seen it done both ways. The edelbrock instruction manual has a vague blurb about non environmental restrictions engines not to use the timed port.

My valve covers are basically vented to atmosphere. I don't know if this matters. Very little oil residue comes out.

I've driven my defender like this in Texas, in summer and winter and for about 1000 miles. It doesn't have a high idle or misfire idling or high rpms. I did replace the needle set, with the offroad needles commonly recommended, this requires adjusting the floats a little, maybe this is why my idle wasn't too high.

Sorry for the late response. I've always mean to do a write up on my experience with this conversion.

 

[Defender425]

I've done the edelbrock manifold and carb conversion as well. When I first tried to set it up, I had the distributor connected to the timed vacuum port. It wouldn't even start. I switched it over and it started immediately. I searched high and low on the internet and seen it done both ways. The edelbrock instruction manual has a vague blurb about non environmental restrictions engines not to use the timed port.

My valve covers are basically vented to atmosphere. I don't know if this matters. Very little oil residue comes out.

I've driven my defender like this in Texas, in summer and winter and for about 1000 miles. It doesn't have a high idle or misfire idling or high rpms. I did replace the needle set, with the offroad needles commonly recommended, this requires adjusting the floats a little, maybe this is why my idle wasn't too high.

Sorry for the late response. I've always mean to do a write up on my experience with this conversion.

Kind of went the same route for now. Dumped the PVC valve and connection to the vac port. Vented the shielded valve cover port to the air cleaner. Little residue but tolerable.

 

[NMEXPAT]

I noticed one difference between mine and yours. The vent at the rear of the block, black with a brass hole. On mine it is connected to a circular plastic box. I have no idea what it is. It has three connection points, marked C,P,T.
I have a hose running from the P connection point to that other one on the rear of the block. It has a fuel (?) Filter connected inline as well.
When I did my conversion I photos everything and labeled everything. A little OCD. it was connected with the original dual carbs.