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Old 09-03-2012, 07:40 PM
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pcv choice???

my 468 bbc has no place for pcv. 454-o victor intake 750 dominator. normally i wouldnt bother but i build so much crankcase pressure that my motor leaks from front and rear of the oil pan. how can i take some of that pressure out??

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Old 09-03-2012, 09:03 PM
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If u have big breathers on both valve covers and are still blowing the seals out of the ends of the intake manifold
You have excessive blow by and adding a PCV will not fix that.
The rings are not seated or are scuffed or end butted or you have cracked broken or distorted ring lands (heat, detonation, preignition). and or excessive piston to wall clearance or cylinders out of spec (taper, round etc)
do a simple compression test a leak down test and a simple cylinder balance test using a vacuum gauge to find the weak, leaky cylinder.

Tare it down and rehone it and rering it.
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Old 09-03-2012, 09:14 PM
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its not blowing the seals on the intake. i have a large breather on the driver side valve cover and a rubber elbow on the passenger valve cover with a hose going to the one inch space adapter. it doesnt leak with this set up but it creates a lot of vaccum on the carb. i feel like this set up adds initial timing. my idle can be erratic.
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Old 09-03-2012, 09:40 PM
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You have this set up with no PCV valve included?

This has no effect on the spark advance or initial timing at all. But will effect the idle speed and relative carb throttle angle @rpm at idle and idle Air fuel ratio if the flow is too high like with no PCV valve to control flow.

I meant to say blowing out the oil pan seals.

You need to clairify what you got there and what you are trying to achieve.
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Old 09-03-2012, 09:45 PM
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I see from your old posts you have had tuning trouble with getting the motor to idle clean.

"Rich" smelling idle.

Are you attempting to leanout the idle by adding PCV flow at idle?

What camshaft?
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Old 09-03-2012, 10:05 PM
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One thing you got to watch when using a PCV system with aftermarket valve covers is that the PCV is not drawing oil from the valve cover into the intake manifold.
Most aftermarket valve covers have crappy or no PCV/breather oil control baffling and or the
PCV/breather hole is located in the wrong spot on the cover.

Oil migration thru the PCV into the intake manifold must be avoided.
Sometimes you need to get creative with the oil control baffling or use a oil separater tank
with racing valve covers.

On a purely competition racing carburator that was never designed to use a PCV valve
(no 3/8" vacuum port on the carb base) by running a PCV valve you may upset the idle air fuel ratio.
(It will be leaner if you add a PCV) Could be a good thing or a bad thing.

most of the time a stinky "rich idle" is not a carb problem but is actually a inital timing at idle problem.

Big cammed motors need a ton of timing at idle or the fuel burns late in the exhaut pipes instead of fast in the combution chamber at idle. This is what you smell.
generous idle timing corrects this and allows correct pri and sec throttle angle at idle.
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Old 09-03-2012, 11:19 PM
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yes, i have no pcv valve.my idle is effected. i need to add a pcv to remove pressure from crank case otherwise i leak oil from oil pan. consequently by adding a pcv to a intake/carb that doesnt come equipped with a pcv port from factory my engine idle is effected. it idles nice and smooth when pcv is plugged. but when connected it goes high and takes a bit to come back down. i.e. a slight rev from the pedal may bring idle from 950 to 1200 rpm and take several seconds to come back to 950 or it goes lower to almost shut off.


so i would like to NOT run a pcv by way of intake/carb. any other method would be better.

i do need something to evacuate crank case pressure so im not leaking oil.

i doubt my rings are damage. i get no smoke and i still pull low 10s.
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Old 09-03-2012, 11:24 PM
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i do think maybe i need more timing???. im at 13 initial. before i had close to 20 but i had starter issues. car fires great now at 13. but my idle has always been werid no matter what timing.i cant member the cam size. i got so many cam cards i couldnt pick wich one i used in the motor. i feel like adding this method of pcv is effecting my idle and air/fuel mixture.
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Old 09-03-2012, 11:43 PM
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it makes a lot of sense what your saying. i think i have too much flow going through my pcv system. im going to add a pcv valve(any suggestion as to which kind to use) and a smaller diameter hose(currently using a 3/8 hose!!) ill let you know how it drives tomorrow.
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Old 09-03-2012, 11:49 PM
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Well you need a lot more than 13deg timing at idle.
it will never idle clean at 13deg .
if the engine has a rough idle and low manifold vacuum at idle.
( cam has more than 244deg @.050" duration.)

lock out the spark advance curve and set the locked out timing at 36-38deg BTDC
Starter issues. Ge the GM rear starter motor mounting bracket brace and install it.
If slow to crank when hot use a ignition interupt switch to releive starter cranking effort
on hot starts. It will fire up easily, when hot.
and idle clean, consistant and stable.

big cammed motors need 24+++ to 36deg timing at idle.
13 is not even close.

What you got there is a big vacuum leak, not near enough idle timing and a timing curve that is jumping around at idle.
And the carbs throttles are not in the correct sweet spot at idle.
It will never run right the way you got it set up.

i doubt my rings are damage. i get no smoke and i still pull low 10s.

I would not be so sure of that. A sure sign of damaged ring seal is blow by and oil seals being blown out.
It is not hard to damage a motor with incorrect timing etc.

Your starter motor issues are directly related to a lack of idle timing on a cammed up motor.
This lack of idle timing makes the exhaust headers way way too hot and cooks the GM starter motor.
the more the starter gets cooked the weaker it gets.

Last edited by F-BIRD'88; 09-04-2012 at 12:07 AM.
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Old 09-04-2012, 12:16 AM
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The newer small body gear reduction starters for GM motors are a lot better and less likely to cook. More air space between the starter and headers.
A Moroso starter heat shield and heat wrap and a hot start ignition interupt switch works wonders and allows very agressive idle timing for big cammed motors.
Again if your got the GM starter motor do not forget the OEM GM starter brace.
And use the correct starter motor bolts.
Or you will bust the starter nose.
correct clean idleing, no more crappy throttle response
quickler ET's and Starter motor and header gaskets last forever.
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Old 09-04-2012, 10:26 AM
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Yeah I def run more timing at the track. Starter is no issue there cuz its a few quick run then shut Off for cool down. When I go to shows or date night I don't want starter issue so I retard the timing. I put a valve today wih a smaller diameter hose but I still leak. Maybe a better pcv valve???
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Old 09-04-2012, 11:23 AM
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It's crank pressure common on 11:1 comp and tall dome piston
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Old 09-04-2012, 11:12 PM
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so it def runs better in the city with initial @ 20 with no starter issues. at the track its around 25 with 38 total. idles better with more air/fuel mixture. your right bout the blow by air diluting the air/fuel mixture going in the intake so adding a little more fuel helps. crazy thing is i dont see a lot of blow by at idle coming out the valve cover not do i feel pressure which would be compression passing the rings and coming out the opening of the valve cover. but it sure build up at high rpms. id rather have it come out some other method than reburning it and diluting my mixture in chamber.
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