Technical SBC 427

I have a aluminum rodeck SBC 427 built by a local racer friend of mine,it only has 450 miles on it,I have some smoke out of the breathers @ idle engine builder says to run it,it has a pcv valve on one side and a breather on the other.The smoke @ idle is a little concern? Any recommendations? Add another breather on the rs so it has 2,or just keep driving.The smoke is getting less,but still there.

 

Was it built with Plasma Moly rings??
They are a harder material, take a bit longer to seat than just plain cast moly style rings.

Give your builder a chance on his advice, run it longer.

Also, run it hard, you need to bed those rings in and light loading isn't helping things. Stand on it from off idle, up to 3/4 or so of redline rpm in second gear locked for engine braking load, coast back down and repeat a dozen times.
May need to repeat this whole scenario 2-3 times also, with some 10 minute cruise breaks in between if you do it all on the same day.

Aluminum block is also likely to smoke a bit until it is fully up to operating temps.

If this is a street deal, why did you choose the aluminum block?

 

This is in my 29 model a and its what I wanted. I was told it would be ok.

 

You trusted the engine builder. I'm with Eric, run it kinda hard. Lean on it. Good thing is take it down the hi-way and get it up to temp and lean on it. Then take it by his shop and let him see what your issues are. I don't know how you drive it but I'd get on it. You've already got enough miles on it, it shouldn't hurt it. Lots of variables here but you say the smoke is getting less. Is it moisture or oil fumes? I'm not a keyboard diagnoser but Get it good and warm and run it awhile. Don't let it idle around. Lippy

 

Okay I will.When I drive it I try and run to up to 5 000 rpm and warm it up real good,I will take it on a long test drive this week,

 

To Portland?
No additional advice but I am subscribed, I'll be following this.

 

That’s a 4.125” bore and a 4” stroke and I’d bet some good compression. I’m betting some skinny rings. You need to run it and kit it in the butt. Your PCV system should be able hold apiece of paper when the rings are seated at idle on the vent. It’s plumbed correct. You need an 850 cfm carb too… 6500 is tops giving you a little safety factor. We run our 422”6800 - 7000 leaving a little for safety.

 

PCV and open breathers? if so thats not awesome you need filtered air going in the engine, PCV drops pressure inside and clean air comes in through filtered breathers. Photo maybe......

 

Sure!

 

ok filtered breathers , all good

 

I have a similar setup in my off topic car and it’s noisy and smoked a little when it was new and a little now when it’s cold. I run breathers on both valve covers with cloth filters. Now this is primarily a strip/street car and I built the motor for such activities. I am running a performance ring set and they did take a while to break in. The compression and
Leak down test are spot on after two years of street and strip duty so you may need to keep an eye on oil consumption and give it more time.

 

PCV valves have varied valving, but in general they close at least some during idle. So if the problem is at idle only I'd see which one I have.

 

How much vacuum does it have at idle? With a lumpy cam it may not be able to pull enough vacuum thru the pcv to create a drop in crankcase pressure to work as it should. They don't work at WOT and work best at a cruise or coast down in gear when vacuum is highest.

 

15 inches of vacuum at 800 rpm hot,street car 1929 model A t-10 trans 3.19 gear in the rear holley 3310 750 carb.

 

If you need more airflow thru the pcv at idle, you can add an adjustment screw to the top of the valve's plastic elbow. The screw basically serves as an adjustable stop to hold the pintle slightly off it's seat. This valve was cut apart just to see what was inside, but you get the idea...



Here you can see my modified valve located in the top of a separator can...



Here's another version of my breather system, you can see a modified pcv valve located between the breathers...



My current system uses a set of check valves inside the breathers, which allows the pcv valve to draw a vacuum inside the engine. I run low tension rings, drawing a vacuum inside the crankcase really helps with oil consumption on my street/strip car...



Grant

 

From engineering technical bulletins with your engine idling and breathers sealed the vacuum on an engine should be from 1 to 3 inches of vacuum. When I constructed mine on a dual quad Y-Block it read slightly over 1” on the dip stick tube which is a pretty easy place to check. Remember to put a leather or rubber seal on the dip stick flange.

 

They make adjustable pcv valves. Pricey but they work.

http://mewagner.com/?p=444

 

I put breathers on, each side and took it on a test drive got it hot,seem better.Ran it some what hard,then got worse at times.Took it home and found on the breathers on the rs valve cover which is located near the rear full of oil.There is a baffle built in the valve cover ,but no room for a plug in baffle.I need to space the breather up or put higher valve covers I think. Any Ideas?Maybe turn the valve cover around so both breathers are forward.

 

Valve cover spacers.

 

That was also a thought.

 

Do a 'leakdown' test on the engine, see if all cylinders are the same. It might be 7 cylinders are sealed up fine and 1 cylinder the builder messed up the rings or something simple that needs fixing right now or it'll get expensive.
Thats an old engine, probably been run hard and you might have a time to get it sealed up.

 

480 miles on it as of yesterday,Block I have owned 30 plus years,but wasn't put together until recently.8 new sleeves put in it ,guy that put it together has done a many. New crank ,rod, pistons ,cam and lifter rollers, everything new expect block

 

Did you have to grind rod clearance on the old 400 block with 4" stroke? And you have a stroker pan on it?
There is alot of windage with that big crank wheeling around in tight places especially at higher rpms.

I run a header crankcase evacuation system Moroso #25900 and I like it, at idle you can feel vacuum with your finger over the hose, also a Moroso lifter valley tray along with extra baffles under the evac breathers to slow & catch the oil before it gets sucked into the header.

The 1st time winding mine up past 6500 the windage pulled the dipstick to the crank and the noise made me back off, thought I had hurt it , then felt lucky when finding a mangled dipstick that was still in one piece.
Now got a special short dip stick and keep a full length one in the race box to check the oil

Norb

 

I think the issue you should be looking at is the root cause of the problem rather than trying to find a way to bandaid it. You have a lot of money in it, and if there is an issue, the guy should correct it. I'd do a leak down test............

One other thing, is oil being trapped in the valve cover rather than flowing back to the oil pan?

 

Scat rod and crank,didn't have to machine anything, stroker pan.

 

So at wide open throttle you have close to zero vacuum in the crank case and as much as the cam will allow at idle. Putting the adjustment screw in is a good idea but probably helps more with setting up carburation at low throttle opening. I would put a flow {volume} adjusting valve between the PCV valve and the intake manifold vacuum for higher rpm control. Crank seals must go in back wards or will leak a lot, about 12" is about the most that should be attained so wrist pins won't run dry/over heat. {for those unfamiliar}

 

Roller rockers grinding on the inside of a valve cover????....
It happened to me after installing a set of svo 1.6 rockers on a Ford 302.....

 

Do the leakdown, that'll tell you.

 

I've been running this pcv/sealed crankcase setup since 2012 with a couple different engines, crank seals are reversed. Rear seal is a fluoroelastomer 2912 Felpro, which seems to last pretty good reversed against this much vacuum. Front seal is viton SCE 21102, it had to be replaced last winter. I think next front seal will be one designed for a reverse rotation boat engine, my thinking is that the small directional ribs going in the wrong direction will help lube the seal lip. No signs of wrist pin oiling issues @ 15-16"Hg.

Here's a RacePak graph from 3 years ago showing crankcase vacuum during a 6.25sec long WOT 3rd gear pull...
...Red line- engine rpm
...Blue line- WOT switch
...Yellow line- crankcase vacuum



The pull started out with 12.6"Hg @ 2600rpm. When the pull ended at 6250rpm, the crankcase still had 3.9"Hg of vacuum left. I should add that the engine is well sealed, no dipstick (oil level sight tube).

It's a low compression (pumps around 100psi) flat top pump gas 355 with a couple nitrous kits in a crossbar plate. Total Seal gapless top rings, solid roller 114 LSA nitrous cam, aluminum rods, rolled 11R heads w/ titanium valves, shaft rockers. Car weighs 2325lbs, 28" drag radials, 3.73 gears, Top Loader 4spd (no overdrive).

Took it on a long drive across the pass a few weeks ago, included a 8610rpm blast inside a tunnel and still got 20.98 mpg. Low tension rings are the biggest reason it gets great fuel mileage while spinning that fast without overdrive. A pcv valve, combined with a sealed crankcase, is the key to making those low tension rings work on the highway without excessive oil consumption.

Grant