Sick of this! Need some creative ideas.....

Chris Mureen · Post by **Chris Mureen** » Sat Mar 12, 2005 8:29 am

I am about to drive the POS over a cliff. I can not figure out why my KAMRFs are soo different between the two banks and the difference appears to be getting worse. The wierd thing is I only have the issue at lower air flows. In addition, the car runs great at WOT and makes good power. But cold startup and cold idle is intollerable. Bank 1 is the one running leaner at low flows.

Take a look at the differences between my banks as MAV increases:

MAFV --- KAMRF Diff between banks
0.899 -0.177
0.96 -0.169
0.99 -0.132
1.05 -0.108
1.1 -0.07
1.2 -0.05
1.3 -0.045
1.4 -0.037
1.5 -0.026
1.6 -0.008
1.7 0.01
1.8 0.018
1.9 0.016
2 0.012

But look at how close they get as the voltage increases and then the trend reverses! This is blowing my mind and I have been strugglinng with this problem for many months.

I need some good ideas. It isn't the EGR or exhaust (cats or mufflers or pipes). The problem appeared after my rebuild but the fuel system was the same too.

Let me also add that my idle vacuum is steady as a rock and all plugs look good.

Chris

JuiceSC · Post by **JuiceSC** » Sat Mar 12, 2005 8:47 am

I have a very similiar condition. I belive its due to airflow distribution/manifold design. There is really only one way to test my theory, swap out the intake for a different one. I'm not about to do that. Differences in injector tolerance will also affect the banks. You could swap injectors from side to side and see if KAMs will follow. Thats about all I can think of thats relatively easy to try.

Now here is how I am approaching it. I try to split the difference so the average of the left and right KAMFR=1. My car runs too good to even worry about it.

Chris Mureen · Post by **Chris Mureen** » Sat Mar 12, 2005 8:52 am

In my case the injectors and the manifold are the same as before the rebuild. :(

Do you banks have as huge of a difference as mine do?

JuiceSC · Post by **JuiceSC** » Sat Mar 12, 2005 9:14 am

Idle is the worst, maybe close to a 10% difference. But as soon as I start driving, the difference becomes much smaller. Maybe 4% max and I'm ok with that.

Chris Mureen · Post by **Chris Mureen** » Sat Mar 12, 2005 9:23 am

I think something is changing with mine. It used to be about 10% difference but as you can see it is now 17%! These huge differences seem to be the root of my startup and cold idle issues. If those problems would go away I wouldn't worry about it.

As you stated, I have also split the difference between the two banks but now it is almost become a no win situation.

Chris

final5-0 · Post by **final5-0** » Sat Mar 12, 2005 9:40 am

Say Chris

Have you ever thought about doing an O2 swap from side to side to see if one of them is more sensitive than the other?

Later
Grady

JuiceSC · Post by **JuiceSC** » Sat Mar 12, 2005 9:42 am

I had another thought. Your not going to like this but can easily be checked. A possible compression issue on the richer bank. Since a since a compression issue manifests as higher HC reading due to incomplete combustion, the O2's will read the extra oxigen as "lean" and will richen the mixture. So maybe a compression test is in order.

Sorry man, I know you didn't want to hear something like this.

boss96 · Post by **boss96** » Sat Mar 12, 2005 9:44 am

Chris, when you had the rebuild did you have a valve job done to the heads? If so, do a leakdown test to determine if any of the valves are leaking, a LOT of times when our alum. heads have a perf. valve job done the seats shift a little bit after some heat cycles. This happened to me as well as a friend who works at a HP shop speciallizing in L trucks.
You have to hand lap the valves in to fix it.
Same exact symptom on my car at the time.
You won't necessarily see it with a comp. test nor will you see smoke.
Bob

Chris Mureen · Post by **Chris Mureen** » Sat Mar 12, 2005 10:23 am

Well the O2s were switched and then changed and they didn't help....

I can easily do a compression check but the fact thatthe trims equalize and actually flip make me doubt that is an issue......

I did have a valve job but my understanding is any significant valve issue would appear also with vacuum. It is rock steady and at 15hg, which is actually a little high for these cams I am told.....

I have a compression checker so could easily do that but I have serious doubts that si a problem given the way the banks equalize. It seems like either valves or rings would be more linear with their impact.

Please keep the ideas coming.

Chris

boss96 · Post by **boss96** » Sat Mar 12, 2005 10:33 am

Nope, vacuum stayed the same in my case and the fuel trims did indeed equalize as rpms increased. My buddies 4v motor had the same problem.
I really think this is your problem Chris.
Comp. test may tell you something, but leakdown is even more accurate.
Bob

Chris Mureen · Post by **Chris Mureen** » Sat Mar 12, 2005 3:25 pm

Well I'm going to find out once and for all. Hoping to do a leak down tomorrow and find out if that is the problem.

Stay tuned...................................

Chris Mureen · Post by **Chris Mureen** » Tue Mar 15, 2005 6:37 am

#2 is 26% down. Leaking through the intake valve. I may have more issues but once I saw that I knew the engine needed to come out so I stopped testing.

:( :(

So Bob, this can be fixed without replacing the head?

Chris

JuiceSC · Post by **JuiceSC** » Tue Mar 15, 2005 7:08 am

Chris Mureen wrote:#2 is 26% down. Leaking through the intake valve. I may have more issues but once I saw that I knew the engine needed to come out so I stopped testing.

:( :(

So Bob, this can be fixed with replacing the head?

Chris

Ouch. That sux.

boss96 · Post by **boss96** » Tue Mar 15, 2005 8:01 am

Well, fwiw, it does not have to cost that much is you do the work yourself. If you have shortie headers you should be able to remove the head in the car. The head does not need to be replaced, just get the valve spring removal tool ( I have them for both the 4 and 2 valve) and lap the valves in by hand. You can use a drill with an adaptor to spin the valves to speed it up. Just make sure you have a good seal after lapping and you're done. Now that the seats have shifted you shoud not have this problem anymore. If you pull the entire engine then I would do both heads while your at it. Should be the cost of head gaskets pretty much.
For another $200 or so why not get some ARP head studs too.
If you read the Sean Hyland mod motor book he mentions this problem in one of the chapters.
Bob

Chris Mureen · Post by **Chris Mureen** » Tue Mar 15, 2005 9:52 am

Thanks, Bob. It looks like that might be my path. I already have the head studs so my main cost will be the R&R. I've already pinged the guy who did my heads to see if he will treat me right. We'll see if he responds.

Chris

Chris Mureen · Post by **Chris Mureen** » Mon Mar 21, 2005 8:57 am

Well gang, it keeps getting better..... :(

Compression test shows 130lbs of pressure in 2 cylinders and the other 6 show less than 40lbs!!

Looks like my heads are majorly screwed up. The car actually ran but was a bear to tune. No surprise that I never heard detonation! Believe it or not, once you got in the upper revs, it actually ran strong and felt pretty good. I suspect the valves were sealing much better as the revs increased.

The engine comes out today and we'll know soon after what the heads really look like.

Chris

boss96 · Post by **boss96** » Mon Mar 21, 2005 9:49 am

Wow, that's really bad! For curiosity's sake, did you do leakdowns on all of them to make sure it was leakage past the intake valves?
Like you said, you'll know soon.
What did the eng. builder say about this?
Bob

Chris Mureen · Post by **Chris Mureen** » Mon Mar 21, 2005 10:00 am

We will do a leak down on the entire engine once it is out. The exhaust side is tough to do with the headers on so we'll do a final check later today before it comes apart.

My feeling is that the heated engine that we did the compression check on caused enough expansion that compression showed low. But the leak down was on a cooler engine which was a little tighter in the heads. In addition, the lash adjusters pump up a little when it is cranked but not with a leak down. I suspect preload on the valves as the issue. The bottom end seems pretty tight and no oil burning.

The engine builder is really helping me out with this but we are in agreement that the guy who did the heads likely screwed them up. I know for a fact I have 26% leakage in #2 and it is coming out of the TB so there is definitely head issues. The question now is just how screwed up are they?

The facts will tell the story soon.......

Chris

Dale McPeters · Post by **Dale McPeters** » Mon Mar 21, 2005 10:17 am

Chris sorry to hear that......

That is a major issue to contend with.....

boss96 · Post by **boss96** » Tue Mar 22, 2005 8:28 am

Chris, you mentioned lash and I forgot you have cams. Are they regrinds? If so you probably had to shim the lifters with washers to prevent lifter tapping and therefore maybe there is too little lash, if it was'nt measured correctly, and the valves are being lifted off the seats when pumped up. Motor should probably still come out though as that particular problem could be fixed in the car but it is a lot of work.
Bob

Chris Mureen · Post by **Chris Mureen** » Tue Mar 22, 2005 8:57 am

Yep.... I am also thinking the same thing. Theoretically with the shims that come with the cams, by setting the valves to stock height there shouldn't be any issue. The shims are supposed to make up the exact difference lost in the grind. However, this also assumes the regrinds are not off any. I actually suspect the stem height is wrong. Perhaps the seats were ground too much.

The engine should be out by noon today. Then a full leakdown... then the heads come off. I'll have them to a 3rd party head guy 24 hours later. Based on what his inspection tells us, I with then be having a little talk with the guy who did my heads.

Chris

Chris Mureen · Post by **Chris Mureen** » Wed Apr 27, 2005 2:25 pm

I figured I would post an update to my saga. Boy did I have issues with my heads......

1. The exhaust valves were sent wrong from the manufacturer. They were FR500 instead of stock replacements. The difference is 1/4 inch higher placement of the keepers. The exhaust springs weren't loaded enough and I had major leakage

2. The intake valve seats were a mess. Multiple ones had chatter marks on them that wouldn't lap out.

3. Valve guides were in very bad shape, but were new.

4. Cams were way off on preload.

The engine is back together now and hopefully the car will be running this weekend. I have new valves (correct ones), new valve guides (better quality ones), well done seats, correctly shimmed lash adjusters, and a great exhaust porting job. The bottom end was perfect but went ahead and replaced all rings and bearings.

My remaining issue is getting the HUGE Novi 2000 to fit where my old Vortech once sat. Got lots of plumbing to fix to get it to mate to my IC also.

Looking forward to firing this baby up and seeing what she will do with 20lbs of Novi boost!

Chris

Dale McPeters · Post by **Dale McPeters** » Wed Apr 27, 2005 2:36 pm

Chris Mureen wrote: Looking forward to firing this baby up and seeing what she will do with 20lbs of Novi boost!

Chris

...20lbs? Race gas?

Did the machine shop stand behind their work on this?

Chris Mureen · Post by **Chris Mureen** » Wed Apr 27, 2005 2:58 pm

No plans for race gas at the moment. I am running at 8.5:1 compression and have coated pistons.

Most likely I won't need it but if I do it will be fed the best. :)

It remains to be seen if the head guy will stand behind his work. So far he has not sent me a check and even if he does, he already has refused to pay for all of it. Thank heavens the guy who did the engine stood behind all of his work. The out of pocket will be minimal if I can collect for the repair of the heads.

Chris

Dale McPeters · Post by **Dale McPeters** » Wed Apr 27, 2005 3:06 pm

I would be interested to see what it will do with 20lbs and if you can actually run it on pump gas. I think the most that I figured that I could run would be about 12-15lbs with 93 octane at 8.5-1 in the GT.

Let us know how it does.....

boss96 · Post by **boss96** » Wed Apr 27, 2005 3:33 pm

That's good to hear, Chris, I was thinking of you the other day.
FWIW, about using shims under the lifters for the cams, they guy knows how to do that? I had a lot of experience with regrinds a long time ago and people seem to get the shims wrong sometimes.
Bob

Chris Mureen · Post by **Chris Mureen** » Wed Apr 27, 2005 3:43 pm

Bob,

I was actually heavily involved with the process and learned way more than I wanted to know. :)

I talked with John Mehovitz and got his method. Then talked to Al Papitto and got his method. And then confirmed my approach with a 3rd party who had done many heads with regrinds. The good news is that the approaches all yielded the same required shim size. I am pretty confident they are now done correctly. The amount of shimming we needed was consistent with what the 3rd party said he always saw with these regrind cams as well.

90% of the folks you install these cams probably just use the shims that come with them and they are wrong most of the time.

Dale - newer Cobras frequently get 19lbs of boost on 93 octane fuel. Mine should have a better IC and better pistons. Frankly, I suspect I will run out of fuel before I see 20lbs. These 52s are just too small for that kind of power.

Chris

Dale McPeters · Post by **Dale McPeters** » Wed Apr 27, 2005 4:04 pm

Chris Mureen wrote: Dale - newer Cobra frequently get 19lbs of boost on 93 octain fuel. Mine should have a better IC and better pistons. Frankly, I suspect I will run out of fuel before I see 20lbs. These 52s are just too small for that kind of power.

Chris

Chris, I did not realize that they were going that high on the boost with 93 octane, good info. I thought that you had upgraded to 60lb/hr injectors? Or maybe that was Bob talking about it a while back..... In any case have you looked at the 83lb/hr injectors? I was looking at those the other day but some of them are rather high in the prices that they want for them....

You should make more power than you did with the Vortech.....

Chris Mureen · Post by **Chris Mureen** » Thu Apr 28, 2005 7:08 am

Dale McPeters wrote:[
Chris, I did not realize that they were going that high on the boost with 93 octane, good info. I thought that you had upgraded to 60lb/hr injectors? Or maybe that was Bob talking about it a while back..... In any case have you looked at the 83lb/hr injectors? I was looking at those the other day but some of them are rather high in the prices that they want for them....

You should make more power than you did with the Vortech.....

When you get down to it, detonation can also be controlled with timing so I can always play with that too.

I have thought about 60s and know I could get a good price for these great 52lb RC injectors, but you get a bit tired of throwing money at these cars. According to my calcs, depending on BSFC, I might be able to do it with these current ones depending on how much power I try to make. 83s are pretty big. Are those high impedance?

Chris

boss96 · Post by **boss96** » Thu Apr 28, 2005 8:36 am

Chris, if you already have the 52's I would at least try them first to see if they will work. You can raise your base fp to 50lbs and if you have a 1-1 regulator (I'm sure you do) then it should add 1lb per lb of boost. If you don't already have them, then certainly get the 60's since they are pretty cheap compared to what they used to be. If you get the 60's though be prepared to drastically reduce your "batt inj comp volt" table as these seem to make a car really rich for some reason, perhaps the spray pattern? I had a set for a short time and either had to cut the maf curve by 30% or use the other table to get the car to idle. Forget using inj slopes :)
As far as setting up the regrinds, you beat me to it by using Al Pappitos "guide", that is how I would set mine up and it worked fine. There is a certain range of lash that the lifters will compensate for and as long as you shim in that range you will be fine. Most people would set it too loose and have lifter noise (and rockers popping off randomly) or too tight because they did not get the oil out of the lifters first and then have hanging valves.
Dale, I don't have the 60lb injectors, I will be installing a vortech on a friends car soon and recommended them to him so he won't be upgrading injectors anytime soon. If they were as cheap as they are today when I needed them I would have bought them too.
As far as I know any of the bigger injectors over 60lbs are low impedance and you need an inj driver like Acceleronics has.
Bob

Sick of this! Need some creative ideas.....

Oops

Who is online