Mildly modified 318 PCV valve selection

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prorac1

prorac1

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Location
Martin, Mi
1983 318
Hydraulic cam
214/224, 444/466 105 ICL cam
Holley street dominator intake
Holley 390 cfm vac secondary 4 bbl

Breather in driver side valve cover

Oil cap/pcv valve in passenger side valve cover.

Oil cap and pcv currently in the car are left over ford parts from a previous build.

Seems to work well. But……

When I pull out the pcv valve and plug it with my finger the idle drops 300-500 rpm I’d guess.

I know a pcv valve is a controlled vacuum leak, but how much is desired or wanted?

What is a good starting point for choosing a pcv valve?

Idle vacuum in gear is 10 hg

Idle vacuum in park is 15 hg

Thanks. Eric L
 
My guess is the butterflies are sitting too far up the transfer slots. Fix that first.

How much rpm do you loose going into gear?
What is the Neutral/Park idle speed ?
Idle timing is?
If that cam is really in at 105, then is it a 110 LSA (Lobe Separation Angle)?

Idle timing must be set with the Vcan defeated. And the Vcan should be plumbed to the spark-port. Power timing should not exceed 36*, 34* is safer with iron heads; until you are ready to tune that end.
The point is; IMO, your neutral vacuum is too high compared to your in-gear vacuum, and the in-gear vacuum is too low for that cam. Both are signs of a faulty T-slot sync, usually due to wrong idle timing, But , I agree that the PCV may be a little large also, for that cam. Possibly. But I think it's probably all in the Sync.
Set your transfer slot exposure under the butterflies to about square, or a tiny bit shorter than wide.
That cam, if a 110LSA or more, should idle nicely at 550 in gear, 600/650 in neutral, once the sync is set and the idle-timing adjusted to achieve the above idle speed. At that time, if decent idle quality cannot be achieved with the idle mixture screws near the center of their adjustment range; THAT is the time to consider the PCV.
Hang on, I know nothing about the 390 Holley,except that it has extremely small venturies,lol.
Ok so that is where I'd start.
 
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Here’s a picture of the cam card.

6C1CE707-A72A-40C1-8F9A-E5B5EB3BDC7E.jpeg


Cam is a 112 lobe separation.

108 intake centerline. I degreed it in 3 degrees advanced.

I regretfully haven’t hooked a tach up yet, but my ear is pretty ok. Lol.

The reason the car drops so much rpm (I’m guessing 3-400) (I know, I’ll hook up a tach Sunday lol) is the converter.

It’s the stock converter, and it’s just to tight.

I didn’t think about the slots. I’ll check them Sunday as well.

Thanks again. Eric
 
AJ/FormS said:
My guess is the butterflies are sitting too far up the transfer slots. Fix that first.

How much rpm do you loose going into gear?
What is the Neutral/Park idle speed ?
Idle timing is?
If that cam is really in at 105, then is it a 110 LSA (Lobe Separation Angle)?

Idle timing must be set with the Vcan defeated. And the Vcan should be plumbed to the spark-port. Power timing should not exceed 36*, 34* is safer with iron heads; until you are ready to tune that end.
The point is; IMO, your neutral vacuum is too high compared to your in-gear vacuum, and the in-gear vacuum is too low for that cam. Both are signs of a faulty T-slot sync, usually due to wrong idle timing, But , I agree that the PCV may be a little large also, for that cam. Possibly. But I think it's probably all in the Sync.
Set your transfer slot exposure under the butterflies to about square, or a tiny bit shorter than wide.
That cam, if a 110LSA or more, should idle nicely at 550 in gear, 600/650 in neutral, once the sync is set and the idle-timing adjusted to achieve the above idle speed. At that time, if decent idle quality cannot be achieved with the idle mixture screws near the center of their adjustment range; THAT is the time to consider the PCV.
Hang on, I know nothing about the 390 Holley,except that it has extremely small venturies,lol.
Ok so that is where I'd start.
Click to expand...

Oh. I forgot.

The idle timing is 20 degrees base.

Total is getting limited to 36.
 
Well then 20* is too much and will do the opposite; you'll be idling almost exclusively on the mixture screws, and the engine is craving air. Check your mixture screws; the factory setting is 3/4 turn out from lightly seated. Set them there . Then increase the curb idle speed until it runs. Then back the timing up to 12*. Then reset the idle speed to 550 in gear. That will be close, not as exact as taking the carb off and looking. but close. Now check the vacuums again.
 
AJ/FormS said:
Well then 20* is too much and will do the opposite; you'll be idling almost exclusively on the mixture screws, and the engine is craving air. Check your mixture screws; the factory setting is 3/4 turn out from lightly seated. Set them there . Then increase the curb idle speed until it runs. Then back the timing up to 12*. Then reset the idle speed to 550 in gear. That will be close, not as exact as taking the carb off and looking. but close. Now check the vacuums again.
Click to expand...


I initially had the timing at 12 degrees, and had the same vacuum readings.

Throttle response is much snappier at 20.

I attributed the extra timing to the bigger cam. Seems happier.

I re adjusted the idle screws and idle rpm after every timing change also.

Idle screws were always set for maximum idle speed, which also corilated with highest vacuum reading. (I always set idle mixture screws by ear than double check with the vacuum gauge and compare)

Thanks again. Eric.
 
AJ/FormS said:
Ok
Click to expand...

If my logic or findings is wrong, by all means feel free to correct me. I’m here to learn. I believe we all are.

The only thing I didn’t do when setting Timing and carb settings, was disable the PCV valve. If the vacuum leak is too much from an Improperly sized PCV valve that could throw everything off.
 
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I am also suspecting your throttle blades are too far open at idle exposing the transfer slots. The Holley 390 has some pretty small primaries. Even a "little" 318 will draw more at idle than a 390 will be set for out of the box. Remember that they are generally used on 2.5 to 4.0 liter engines. If there is ANY vacuum at all at the timed port (right side of the metering block, where the vacuum advance connects), this confirms. Easy to fix on a Holley, there's a secondary stop screw. Try about half a turn clockwise.

Also according to the cam card you show, your cam has 112 centerlines with 4 degrees of advance "ground in." Advancing another 3 degrees may have been too much of a good thing.

A great place to start for a PCV valve would be a common Mopar style valve of something common like maybe an 83 318. They were pretty much the same.

Was this originally a 2 Bbl or 4 Bbl engine? The mid 80's 318 4 Bbl engines had an insanely low compression ratio. Like 7.5, which is low even by 318 standards.
 
C130 Chief said:
I am also suspecting your throttle blades are too far open at idle exposing the transfer slots. The Holley 390 has some pretty small primaries. Even a "little" 318 will draw more at idle than a 390 will be set for out of the box. Remember that they are generally used on 2.5 to 4.0 liter engines. If there is ANY vacuum at all at the timed port (right side of the metering block, where the vacuum advance connects), this confirms. Easy to fix on a Holley, there's a secondary stop screw. Try about half a turn clockwise.

Also according to the cam card you show, your cam has 112 centerlines with 4 degrees of advance "ground in." Advancing another 3 degrees may have been too much of a good thing.

A great place to start for a PCV valve would be a common Mopar style valve of something common like maybe an 83 318. They were pretty much the same.

Was this originally a 2 Bbl or 4 Bbl engine? The mid 80's 318 4 Bbl engines had an insanely low compression ratio. Like 7.5, which is low even by 318 standards.
Click to expand...

Ok. I will give these a try tomorrow when I’m working on the car. I really appreciate it guys.

It was a 2bbl engine. It’s around 8-1 “actual” compression. Verified when engine was apart by measuring.

The car idles and drives great. Very very snappy.

I assumed the low idle in gear as opposed to the park idle was from the tight converter. But a cam this small shouldn’t have that problem

Thanks again. Eric
 
What cam is that? Looks like a good one for a Teen.
 
Doesn't look like a ton of duration at .050 but it gets with the program with the advertised total.
 
Where is the pcv valve plumbed for the vacuum source. The 390 4V carburetor does not have a proper port. I dumped mine after over a year of trying and tuning and installed an eddy Avs 2 now the car runs.
 
DesertRat said:
Where is the pcv valve plumbed for the vacuum source. The 390 4V carburetor does not have a proper port. I dumped mine after over a year of trying and tuning and installed an eddy Avs 2 now the car runs.
Click to expand...

You can see it in the pic below on the passenger side of the carb.

I played with it today and seem to have it running much better
 
AJ/FormS said:
Well then 20* is too much and will do the opposite; you'll be idling almost exclusively on the mixture screws, and the engine is craving air. Check your mixture screws; the factory setting is 3/4 turn out from lightly seated. Set them there . Then increase the curb idle speed until it runs. Then back the timing up to 12*. Then reset the idle speed to 550 in gear. That will be close, not as exact as taking the carb off and looking. but close. Now check the vacuums again.
Click to expand...

Having some trans issues, but we will tackle that tomorrow. Lol

We did some experimenting with carb and timing today.

Removed carb

Squared up transfer slots

Reset idle mixture screws

Set timing to 12 degrees

Disabled vac advance

Wired tach

Lowest we could get it to idle was

950 in park

750 in gear

Vacuum readings were

15 in park

10-11 in gear.

Engine seemed slightly lethargic with 12 degrees.

Increased timing back to 20 degrees woke it back up.

After readjusting everything to compensate for increased timing the vac readings remained the same. 15 and 10.

Eric
 
Looks like a good cam. I see Elgin has a good selection of mid mild cams for small blocks. There's a couple split lift/duration cams that would fit the bill.
elgin cams.JPG
 
Ok
Minimum 950rpm is telling you something; don't blame the lethargy on the 12*. That cam is way too small to need or want 20 degrees, and the huge rpm drop and vacuum readings are screaming it .
Look,my 292/292/108 cam idled at 700 in a 360@14* idle timing. And I could retard it to 5*, drag it down to 550 with the clutch, and drive it in a parade for an hour. That 292 IIRC was 249@.050. And somehow your 214 wants 950 with 12*?
OK. have fun
 
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AJ/FormS said:
Ok
Minimum 950rpm is telling you something; don't blame the lethargy on the 12*. That cam is way too small to need or want 20 degrees, and the huge rpm drop and vacuum readings are screaming it .
Look,my 292/292/108 cam idled at 700 in a 360@14* idle timing. And I could retard it to 5*, drag it down to 550 with the clutch, and drive it in a parade for an hour. That 292 IIRC was 249@.050. And somehow your 214 wants 950 with 12*?
OK. have fun
Click to expand...

Then tell me what I’m missing?

I set the timing at 12°

I removed the carburetor and squared out the idle transfer slots.

I set the idle screws to 3/4 of a turn out with minor adjustments to attain Max vacuum reading. But 3/4 of a turn was almost dead On like you said.

I’m getting no vacuum at the time the spark por at idle, just the way it supposed to be. Telling us the idol transfer slot is correct now.

I agree with you 110% that the idle speed seems high. My next step is to try a different tachometer and see if it’s an error in the gauge. Because it sure sounds a lot lower than 750 rpm’s in gear.

I totally get what you’re saying, and would never think of arguing with you about it. I had a big block Chevy with a solid roller cam and 30° more duration then you have, and it idled under 1200 RPMs. Closer to 1000 RPM. So I totally agree with you. This engine combo, Albeit running very very nicely right now, doesn’t make sense. LOL.

I hope you didn’t take any of my replies as being snarky. It wasn’t meant that way. I’m just telling you my results of what i did. I greatly appreciate the help you’re giving me. Thank you. Eric
 
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