Hope they fix it but if not...

[Gerry A.]

A couple of days ago I had an interesting experience. was going on the freeway, shifted from first to second, was headed for third at somewhere around 85 maybe 90 or so. when I put in the clutch the throttle stuck wide open, the tack hit about 6000 and in the blink of an eye the engine locked up, rear end locked and my wife and I were in for a wild ride with a camper in front and a semi truck behind us.. Well that incident prompted the removal of the engine from the car and the discovery of perhaps the cause of the lock-up. My McCloud clutch looked like someone had pulled the pin on a grenade, tossed it into the scatter shield and then put the engine back on. Ok so much for the lock-up reason (most likely). This brings me to my real question.. ever since the car was brandy newbie it has been backfiring through the exhaust, both sides. It started out only at high RPM then later on doing it even starting out at stoplights. It made no difference cold or hot. I did have a speed demon 650 on it originally but due to this latest incident I've finally talked them into putting a holley 750 with mechanical secondaries on it.. anyway, we replaced the carb twice, ignition system. checked and re-checked the timing. but nothing we did seemed to matter, it still backfired like a machine gun. In addition to this it keeps blowing oil from nearly every gasket and orfice in the engine including the dipstick tube. All the bolts have been check and seals and gaskets replaced several times but it appears that the crankcase is being pressurized somehow.. I'm convinced that it's in the valve train somewhere but am having trouble convincing others of the same. My question is this... could I be right? I'm thinking maybe cam or valves that aren't seating or maybe even floating. If I'm not correct what could it be.. I'm getting very frustrated and would like to finally solve this mystery. I really love the car but I think it's been in the shop more than it's been in my garage. Please someone help me with this so i can take the answer to Brian and we can once and for all get her running like she should be...
thanks.

[PatBuckley]

What is your cranking compression?

Perhaps some piston rings are in upside down?

What kind of crank case breathers are you using?

Pat

[TomH]

If you were doing a 2/3 upshift at >85 and THEN had the throttle stick, my guess is that your engine wound a bit tighter than 6.5K. Since it's a Roush motor, I would get them involved in the investigation. Their engines have warranties.

Good luck.

[Gerry A.]

I did a compression check on all cylinders prior to this incident and they were all equal and right on the button 175 psi. I was told though that a std. compression check at slow cranking speed won't reveal blowby and I didn't spray any oil into the cylinders to basically put them under "load" and recheck the pressure. I should have but forgot that aspect of the test. I saw 6.5k and you are correct the engine could very easily have gone higher but in my opinion and others as well it should have held higher RPM longer than it did. When I said blink of an eye I wasn't exagerrating. Whatever RPM it did reach it locked in litterally a split second. I took it back to Brian immediately and he is looking into it. He said that no one is harder on the cars than he is in fact he refered to himself as the ultimate crash dummy LOL. He also agrees that it should have held RPM longer but when we saw the clutch that is most likely the souce of the lock-up and not the engine itself but the backfiring problem is in the engine.. we pulled it and sent it back to the builder but my worry is this no one is standing over his shoulder to make sure he checks and replaces the needed parts. I would like some insight so that I can put pressure in the right direction to get the problem resolved. I want to enjoy the car not take it to Granby every week to have it worked on, that's my point in posting this..and don't take this wrong I greatly appreciate every bit of information all of you provide.
BTW: the rear end ratio is 3.0 so unlike most of the other cobras out there with 4. something gears I don't turn quite as high but I like it coupled with the 3550 in 5th cause I don't have to stop for gas every hundred miles..LOL.

[Gerry A.]

Well, I spoke to the engine builder today and he swears up and down that the backfiring is the timing but we have checked that so many times it allmost embarrasses me. Unfortunately I have a sinking feeling that when I get it back it'll do the same thing and I'll have to declare it a lemon.. then everyone gets to start all over again.. and that's going to be the pits. I hope I"m wrong and it comes back purring like it should. You spend almost 40k on something you'd think they could get it right. Well we will see what happens.

[Excaliber]

Blowing oil out the various orifices is to easy.

You need to vent the engine better. While the pros and cons of a Positive Crankcase Ventilation (PCV) valve have been debated at length in various threads, I STILL don't know what the "fuss" is all about.

In my opinion it's just plain COMMON SENSE to run a PCV valve or SOME POSITIVE method to VENT the internals of the engine. A "breather" on the valve cover OFTEN just isn't enough!

I am unclear as to your "back fire" condition. Is that a "popping" sound you get on deceleration in the exhaust? If so, many there are several potential different causes. Usually an exhaust leak allowing fresh air in mixing with the exhaust. Not a "big" issue unless the "noise" bothers you, won't hurt anything.

Now BACK FIRE is through the carb (or intake in you would). Timing and ignition is the most common cause. A WEAK spark can cause it. Check the ADVANCE of the timing, not JUST the base timing. A "lean" condition will cause it (lean could be AIR leak at the carb or manifold).

Unlikely (and more serious) causes would include things like:
Cam profile/timing not right or valves hanging (not closing properly or on time).

Ernie

[Gerry A.]

Thanks for the info. and I'll look into the breather issue.. at present the only thing on the engine is the stock valve cover breather and the pcv valve. That may solve the oil problem.. as for the backfiring. no it's not on decelleration.. it's on accelleration, any gear from stop all the way up.. both sides. and it's in the exhaust. not the carb. In essence I guess you could almost say it sounds more like pre-ignition but that's timing for sure, at least in most cases, actually sounds like a machine gun...spitting and sputtering maybe backfiring was not the right term to use. We have checked, checked and rechecked the timing. The vaccuum advance has been disconnected and it's running strictly on the mech. advance. initial timing is set at 12 degrees with total being somewhere between 34 and 36. I told the engine builder today that both I and Brian felt that it could be in the cam and his answer was "no way in hell" could the cam cause backfiring in the exhaust.. it has to be timing.. my answer was uh-huh sure. and it's up to you but if I get it back and it backfires one time the you know what is going to hit the fan. I agree with you on the valves as potential problem areas.. in my opinion they are the most likely culprits. Either not seating properly or sticking or something. I'll pass this along next time I talk to the builder or to barry as Brian is on vacation for 3 wks.

[wilf leek]

Gerry - is the engine REALLY at TDC when the pointer and the marks on the crank damper say so?

Is it a rubber bonded type damper? Could the outer rim have spun on the rubber?

Probably worth checking the real TDC position using a bolt down the No 1 spark plug hole. Then you can at least eliminate incorrect timing.

Also, do you have an MSD ignition? They can sometimes give spurious results with some timing lights.

HTH

[bittentoo]

What kind of valve lash adjustment do you have? Could be that an exhaust valve is adjusted to tight and not closing all of the way. Just a thought....

[Excaliber]

Hmmm,,,,backfiring in the exhaust, what would a guy call that??? LOL

Backfire doesn't seem like the right word. Popping in the exhaust under accelleration? Wow, this IS a tough one!

Makes me wonder if your to RICH and the excess fuel is being burned in the exhaust area. I'm not sure how "timing" would play into such a scenario. Sounds more like a cam/valve issue, but this IS a tough one!

Ernie

[wilf leek]

Ernie - excessively retarded ignition could dump unburnt air/fuel mixture into the exhaust.

Poor exhaust valve sealing could do the same.

[Back in Black]

Can also cause "detonation" which sounds like what you might have there... could be leaky valve guides. (could also be cam timing) check the condition of your plugs in this way...

Get the motor hot and be somewhere that you can pull off the road into a lot or safe shoulder or your driveway.... then while running, shut down your motor using the key, and immediately pull over. This way you can better see if there's unburned oil in there... at least this is the theory I was taught. Check each cylinder before taking off. Just a long shot, and I would think there have to be other contributing factors .

[Excaliber]

Wilf,,,,good point! I should have made that connection as a "rich" condition is OFTEN about a weak (or retarded) spark!

Ernie

[John Poling]

I'm in on the valve idea, what would timing have to do with it? Check your rocker arm adjustment and make sure they are correct. Is it a hydraulic cam? If it is, you could have a lifter that is siezed/jammed solid. This will cause the popping in the exhaust, as your exhaust valve on the effected cylinder/s will never close. This does not however explain the fact that you are reading 175psi consistant on all cylinders unless you have lifters that are pumping up solid when oil pressure is applied which would not be present when just cranking an engine over. If it is a solid lifter cam, they are adjusted differently than a hydraulic cam.

Let us know your progress.

John

[Gerry A.]

Thankyou for all your reply's I will look into each issue and I am in total agreeance with each of you as far as the valvetrain/cam being the ultimate cause of the problem. As for the timing I didn't check for true top dead center as the engine only has a couple of hundred miles on it and it was freshly built. I naturally assumed that it was initally set correctly but you are right it could very well have slipped and the damper is stock as far as I know for a 351W. It is true however what "they" say assume makes an ass out of you and me.. so I will look into it. We also thought of a "rich" condition in the fuel system and therefore checked and replaced the carburator twice. also set and reset the adjustments on both. One thing we didn't change however is the jets inside the carbs. It could be possible I suppose that they are simply to large to start with.. If memory serves me the jets are pri: 74 and sec: 78. At least that's really really close pri may be a bit smaller but I don't have the paperwork in front of me to verify it.. anyway that will be moot as Brian is going to replace the speed demon with a holley 750 dp when it is returned to him.

The cam is hyd and that is also a possibility that one or more of the lifters is sticking when pumped up fully but not showing at cranking speed. All of your suggestions could be right on the money and I'll pass along the info to the builder, now the problem is getting him to listen to me and actually check/replace defective parts. In his present attitude I fear that he'll just clean up the engine re-torque everything and send it back. I hope he doesn't but I really have no way of policing his work and that bothers me. In the end however it will not be I that suffers if that happens because I'm not going to accept it in the condition it was in that's for sure. Only problem is I hate thinking of the several months it will take to build a completely new car and engine from scratch if they can't or "won't" get this one right. In that respect I will suffer for it.
thanks again and keep the suggestions comming..

[wilf leek]

Gerry - another thought, this time pertaining to the excessive crankcase pressurisation. Assuming that Pat's suggestion of rings maybe upside down is false, what oil have you used from day 1?

If you have used a synthetic, could well be that the rings have not bedded in, would advise a dinosaur oil like Valvoline racing 20W-50 (non synth) for 5000 miles at least to bed the rings.

Although I never had a crankcase pressurisation problem on my engine, it did take 5000 miles before it stopped using any oil (and hence completed ring bed- in). Even so, it never puked any oil like yours is doing, so I would supect a more major issue than just that.

Luck in your pursuit of a well-behaved engine.

[M & M]

When the builder is done doing his thing, why not go to where he is and have him dyno the thing with you there? I realize this is going to cost some time and money but if it is not right when you get it back it will cost you a lot more. Especially when you consider the time to install and pull the engine again, send it back, agrue, yada, yada, yada.... you get the picture.

Good Luck,
Mike

[Gerry A.]

Totally agree with you M&M, I will be on both the builder and B&B several times a wk. until this is resolved and will approach the dyno idea. I'd like to see it on a dyno for several reasons.. I should have pushed that aspect the first time but didn't think I'd have the problems I'm having. BTW I see you are in Portland.. my hometown is Corvallis.. so you are in my old stomping grounds. As for the type of oil I'm using, I've used 10W40 from day one. Valvoline.. now I know everyone has their preference but that's what it came with and that's what I've stuck with. I was also told under penalty of death to never never put synthetic in it so I intend not to.. the pressure does drop below 30 when she's hot so I may go to a heavier wt. say 20W50 or something like that. Although cruising the pressure is somewhere around 35 to 40 so actually with the high volume pmp that is a good cruising pressure, after all it's volume not pressure that lubes the bearings etc. I am keeping track of all the suggestions and Friday when I call the builder back I intend to bombard him with them. and Monday the same with B&B. With all this vast knowledge and experience I'm sure we can solve the situation it's a matter of getting the proper people to realize all of you know what you are talking about.
Thanks.

[Ray R]

I have to agree with Mike. I had a 351W built for my SPF, and had a tuner in town break it in on an engine dyno. We discoverd an issue with the metals mated between the cam and distributor gear. That was easy to fix. The peace of mind you get knowing all is well BEFORE you install an engine is priceless.

A good engine dyno has sensors for EVERYTHING! Knock, air/fuel mixture, water flow, oil flow, analysis for particulate in the oil, and on, and on.....

A great investment! If you want to bring your engine to Portland, there's a great shop here that has the dyno and expertise to do the work. It's Sunset Engine Development (Pat Usher). 503-805-5252.

[Woodz428]

I'm with the valve problem too, especially with it being hydraulic, it may have too much pre-load. I don't think the timing would effect it in the way you described, one or 2 cylinders occasionally and then consistantly, timing should have created the problem in all the cylinders, not just a few. It sounds like a few of (or maybe all) of the valves had too much preload and were starting to "burn by", as it got more miles the problem would get worse and ultimately burn some valves. I don't think a cranking compression check or leakdown would have pinpointed it since the lifters pump up some under oil pressure(one reason correct pre-load is so important) and at cranking speed wouldn't have built enough pressure to simulate the condition.