92SS3908

I just joined not long ago you probably saw a pic from my oven post. The cowl hood is new since then.

I didn't realize you had your car at the show. I remember you said you had a 98 Z but never made the connection. Nice car I like the wheels.

im talking vacuum gauge readings. hook one up to any car and watch it under WOT and decel from that.

 

Theres one mounted in the dash of my mustang just for this reason. at WOT its 0 " of vacuum. close the throttle, and it slams 21-22" then settles back down to its 10-8" it normally runs. even at part throttle, i had 16" or so, just cruising around. its great for trying to squeeze out max fuel economy. but i just love the sound of 14.5 to 1 barking thru 3 1/2 race bullets on the street, so staying out of it was my issue.

 

 

Got it. I agree with you there, I read pressure you read vacuum, but same idea.

 

but when you close the throttle on yours, the pcv valve is going to close off. and remember what opens the pcv valve is crankcase pressure.breather being clogged will just make it worse, if not make it work harder. and look at a lot of the late model stuff, all they have is a tube going to the air intake, for suction on the crank case. but thats before the throttle blades. now i can only assume your pcv valve is in the front of the valve covers. but alos think that there other cylinders moving downward at the same time some are pushing up, with pressure coming down thru the ring seal.

i mean it could be possible, but highly unlikely, in suck a rapid

rate that you are saying!

 

I'm not quite following what you are saying here but here's how I understand the PCV valve. It is a simple check valve with a lightweight that allows air to flow from the crankcase to the throttle body below the throttle blades. The valve gets seated if flow is the other way around (in case of a backfire so the flame does not go into the crankcase and ignite the potentially flammable gasses in the crankcase.) So when the throttle is closed pressure difference between the crankcase and the manifold is at its greatest making flow greatest. There is no reason for that valve to close off. I think the hose you are referring to on the late model stuff is the breather hose which allows filtered air to enter the crankcase as the PCV draws it out. The blow by you are talking about is what the PCV is designed to evacuate and hopefully sometime today when I do a pressure check on the crankcase under load we'll know how much of a vacuum it can pull with a restricted breather.

 

 

in which im almost starting to wonder about ring seal. when its running at idle, does the pcv click really fast? or suck open? is the pcv new? and is the hose show any sign of oil being drawn in?

 

No the PCV does not click or buzz at idle as far as I know. It was replaced within the last year or two. And I don't know about signs of oil I didn't specifically look.

manifold pressure gets low under WOT.like 0. and gets high with the throttle closed on decel. like full idle vacuum or higher.and i guess it would help to know or be looking at your crankcase vent system, which i have no flipping idea of or how you have it setup. and i have never seen vacuum pull a crank forward.at most it will suck oil out of the crankcase harder.

and if your thinking the breather is clogged, why not go check it?

 

 

with the wear being all at the rear, something is pushing it forward. suction is not going to be enough to cause this as fast as your saying.

 

I have a PCV system. It’s a simple hose going from one valve cover to the manifold. I think you have it backwards on manifold air pressure. Under WOT the pressure in the manifold approaches atmospheric (I’ve recorded right around 96kPa atmospheric=100kPa). During decel the throttle plates are closed yet the engine is still trying to pull air so pressure goes low (I’ve recorded as low as 18kPa under high rpm heavy decel). So with that into consideration the crankcase is exposed to that low pressure and I did check the breather it is not clogged but restricted so it may not be able to keep up with what the PCV is drawing, so although crankcase pressure will not be as low as manifold pressure it will still be low. As for the force this will create we aren't talking about suction there's no such thing. Its pressure differential from outside to inside. Pressure outside is higher than inside so in pushes in, not the inside pulling. Although I do not have the exact numbers, which is what I will be measuring when I get back to the car, here's a scenario to explain my theory. Let’s say the front diameter of the crank is 1.5 inches that’s an area of 1.767 square inches. Let’s say the back diameter is 4.5 inches that’s an area of 15.904 square inches. The front area will cancel the back so the area that can act on the crank is the front area minus the back area which is 14.137square inches. Now calculate pressure. If the crankcase pulled down to 30kPa that is equal to 4.41 psi. Atmospheric pressure at sea level is 14.7 psi approximately 14.3 psi here in Ohio. That’s a pressure difference of 9.89psi. Multiply the pressure by the area and you get a forward force of 141.6lbs. That’s a significant amount of force pushing the crank forward and a possible cause of failure.

 

 

does not mean that they are striaght or if infact in there wrong holes.

 

 

If you're talking about pistons in the wrong bore that isn't possible we marked all of them as they came out and double checked that when we tore the engine apart after the first failure. Even if they were slightly off (which I don't think they are) I’m told by my engine builder it shouldn't be a problem. On Pro Stock engines the crank journals were offset from the bores on purpose and it did not cause a problem.

 

 

and if i remember right, 8 thousands is high! to start with.

 

Factory spec is 5-8 thousands and some race engines are even higher than that.

 

Also please understand I’m not trying to shoot down everything you say I’m just trying to think through this logically. I have thought about a possible rod problem and bad crank grind and plan on doing more checking on that. I’m just trying to search every possibility so I don’t get everything back together and have to replace another bearing. Thank you for all suggestions thus far. Keep them coming.

one peice or two peice dont fucking matter.

 

the lt1 is the one with pressure differential that your thinking of. cause half the crank is internal balance, the other half is external.

and there is not way you are pulling that much vacuum in the crank case without a vacuum pump!

 

 

All i'm saying is the possibility is there because the facts are the rear surface of the crank is larger than the front surface. This is true on the one piece but not the two piece that the only reason I mentioned the seal. And yes I know its not likely that i'm pulling enough vacuum but it is possible if the crankcase is sealed (or almost sealed due to a clogged breather) becasue manifold pressure does get low enough during high rpm decel.

 

are they pressed pins

 

They the rods and pistons are stock the only thing that was done during the rebuild was stronger rod bolts and the big end resized so the pin position shoudn't be a problem, it was never taken out.

I know there are cars out there with neg crankcase pressure but with my block, using the one piece rear main seal the rear area of the crank is greater than the front so there is potential for a pressure differential. In the older/ aftermarket blocks that area difference from front to back is not very big so the pressures more or less equal out. I know it’s a long shot. I don't think it’s a rod problem because that should show up as an abnormal wear pattern on the cylinder walls which was not evident when we took the engine apart after the first failure.

Did the internals of the trans move forward because of something that broke? Also what kind of trans was it?

Any ideas on internal engine problems? Thus far we haven't come up with much the only long shot idea we have had is if the breather is restricted under decel there could be a large vacuum building in the crankcase. The rear sealing surface of the crank is bigger than the front so if the pressure in the crankcase gets low enough the crank could be forced forward but to have enough force to do any damage we're going to have to see some very low pressures. We're going to put a gauge on it soon and see what it reads under decel. As for the trans, in the incident you've seen what do you know what caused the input shaft to walk forward?

Trans is a 700R4 (4L60) brand new Coan 2500 stall converter was installed before the latest failure. Stock serpentine belt system: air pump delete, a/c compressor is there but not hooked up, alternator, and water pump.

With the trans bolted to the block, the torque converter bolts out and the converter pushed all the way back there is about a 3/16-1/4 inch of clearance between the flexplate and the converter bolt pads. From what I've read thats what it should be so that should cause any force.

So I got my new engine (350 small block) together about a month ago and ran it for a little on the street doing some tuning and such then dumped the oil to see what it was looking like and is was slightly metallic had chips in the filter. We took the engine back out and tore it apart and found the thrust surface on the rear bearing was completely worn (down to the steel shell in one spot). After asking around we were told the excess thrust could have been caused by torque converter ballooning, so we got a new Coan converter. The thrust surface on the crank also seemed rough so we got it polished. Got the engine back in Thursday and ran it up and down the street a couple times then dumped the oil and again it was metallic. Checked the endplay on the crank and it was at 24 thousands it should be, and started at 8, so we ate through another bearing. The only odd thing I noticed Thursday was a shutter in the higher rpms, somewhere above 5000, on the one full throttle test I did. Anyone run across this problem? Any suggestions would be appreciated.

Since the post said 4L60 I assumed he was not running the electric transmission (4L60E). But you are correct the ebl flash system will not run an electric transmission.

Before you go any further on prom burning I would suggest looking into dynamic efi:

http://http://www.dynamicefi.com/

Send your ecu in and they put in a new board that uses a flash based memory rather than a prom, increases the performance, and allows for a full range of tuning and data logging. Search EBL or EBL Flash on thirdgen.org for more information. I've been running this system on my Camaro for about a year now and I am very happy with it. You shouldn't have any problems with your setup. I would recommend a wide band O2 sensor if you don't have one already regardless of the tuning system, if you will be doing it yourself.

Thanks for joining I was checking out the dynamic efi , never heard of it! Nice car love the tbi. What Tbi are you running?

 

The dynamic efi system is great I would highly recommend it. After this winter's mods I will be running a big block throttle body with 90lb injectors.

 

did you take alot of RS emblems and cut them to say SS? i had a red 92' when i was in high school that i did that too.

 

I was wondering if anyone would notice that. A friend works at a vinyl shop and they scanned the S from RS then printed the letters on brushed aluminum vinyl. Right now they are just the stickers which looked good so I left it at that but I also have the vinyl letters with adhesive on both sides and a set of emblems I polished the letters off so I can replicate factory badges.

Thanks for the comments and rep everyone

 

i went to big nuts too...-rep

 

unless you still have all the 5 speed part left so i can swap one from a auto..

 

No I don't have the 5 speed parts I sold all of it together just after I took it out.

best guess Big Walnut

Can I take my rep back ?

 

Where did you go?

You should come to the track day in april. It will be a good way to meet alot of the members

 

I would definitely be interested in a track day. I'm at the track every weekend anyway.

that was at high school nationals a year ago, we raced as a team and each time you won a round you got a point for your school. I went to Olentangy High School