Irish69427

Well Guys, it has been months since I posted on the status of my project. That is largely because I became so frustrated with the never ending problems that I simply parked it for months.

When it got put in the garage I thought had solved the oil consumption problem coming through the bottom of the intake ports of the tripower and was elated only to have it continue to use a quart every 400 miles. I checked EVERYTHING and could not find where it was coming from. I had reluctantly concluded it was the Fn rings AGAIN after the 4th build and was just disgusted.

The second problem was the engine was not making power like it should. Made over 500 on the chassis dyno and then power started dropping off over time and would barely make 430 and just labored to rpm to 6000 rpms. It had and itermittent miss that 4 mechanics could not figure out and ran very inconsistently mostly at light throttle. Acted like a lean surge or ignition miss. Seemed like ignition but everything checked out ok. MSD box, msd distributor, you name it. I checked EVERYTHING. Compression, valve lash, plug wire resistance, etc. Went through the carburetion several times, checked every possible source of a vacuum leak including using a smoke machine. But the car ran like crap.

Finally got the nerve to get back to it this week and FINALLY solved the problems. THANK GOD. I was about ready to sell the damn thing.

First the oil consumption. When I originally set up the distributor curve it had 38 degress total mechanical advance and another 12 degrees vacuum advance for a total of 50 degrees at part throttle cruise. This worked great. Great mileage, no pinging and super throttle response. As a part of my trouble shooting I had checked the timing several times and it was fine but only the mechanical advance. Then I noticed that it wasn't returning back down to the 17 degrees initial I had set it up with originally. Thought it was week advance springs but it turned out that the advance mechanism in the distributor itself was binding. Keep in mind this was a BRAND NEW MSD Pro billet distributor. I dissasembled it and found some rust on the interface shaft for the curve. Lubed it up with WD 40 and it loosend up and began working normally again. Reassembled and set the mechanical timing. By chance I decided to check the total with the vaccum advance connected. Holy caca it was 56 or 57 degrees!!!!!! Car didn't ping or spark knock at all with this which is unbelievable. But obviously way to much advance. Turned out the cannister went bad or had a bushing limiting it that had come off. Not sure which. Put a new canister on it with the 12 degrees and reassembled. Car ran much better but still had the same lean type miss at part throttle cruise. BUT much to my ABSOLUTE jubilation the OIL CONSUMPTION DISSAPPEARED. So my theory is it was getting some ring flutter or something but the extra advance was the culprit. Put 500 miles on it and it didn't use a DROP of oil. Hallelujah!!!!!!!!! One down one to go.

Still had the miss problem/performance problem. Stumbled on its solution by accident too. Was setting the fuel pressure regulator which is on the same side of the engine bay as the MSD box (passenger side). The box was mounted on the passenger front fender. Noticed in setting the regulator that the heat blowing on it was really FRICKIN hot. So hot I could barely do it with the engine running and the fan blowing on it. I don't know why but it hit me that maybe the fan was blowing all that hot air on the MSD box too. Gave it a touch and Holy **** it was SO hot nearly burned my fingers. All the hot fan air coming out was being directly blown on the box too. I knew this could not be helping matters. So I shielded it with a temporary insulation setup. Five minutes later after it had cooled the car purred like a kitten. NO miss, NO rough running, NO surge, NOTHING. Ran like a swiss watch. COULD NOT BELIEVE IT. So apparently what was happening was the box was getting so hot it was malfunctioning internally. Not enough to not run but enough to overload some of the internal circuitry. FIVE MECHANICS looked at this and NONE OF THEM NOTICED IT. Jesus.

SO FINALLY, I have a car that runs right, doesn't use oil, and I may actually get it to the strip to see what it can do. Next step is to replace the box as I am sure it has to have some fried something in there, insulate it permanently, and then take it back to the chassis dyno and see what kind of power it makes.

To say I am relieved is the understatment of the year. Will post my results from the dyno etc.

elle88

good to hear that you fixed all those issues !

my MSD box is under the passenger side dash. move the box there

Jeff_Keryk

I don't intend to hijack your thread, but I am beginning to question the use of MSD Ignition boxes... Does my 68 L36 (basically stock) benefit from the 6A? It is mounted on the inner passenger fender.

Gordonm

This what I have gathered for ignition boxes over the years. It will provide no more HP over a GOOD running and setup stock ignition system on a basically stock motor. It will provide better starting and smoother idle and low rpm operation when you start cranking in more cam duration for more upper end power. The low speed mixture of a long duration motor is pretty rich under most conditions so the extra jolt if spark voltage does help some. It also provides a better spark at startup when you are most likely to get a very rich condition. At high rpm 6500 rpm or higher it does provide a little better spark but it would be tough to beat a good HEI unit setup correctly. The reason I use to use one was for the above reasons plus it had a rev limiter which got used very much and probably saved my motor on some occasions.

Irish69427

I can tell you this, lol. It sure as heck doesn't like alot of heat. But my opinion is it does help at least on a motor of my power level. Not sure on an L36 of around 400 hp. When we originally dyno tested my motor I was running a pertronix points conversion electronic ignition. It is supposed to be pretty good but the motor would start breaking up around 6500. When I switch to the msd pro billet and msd box the engine ran noticeably better at idle, seemed smoother overall and would pull flawlessly to 7k. I am guessing it was worth around 10-15 hp across the power band and at peak. In your case just a conversion to the pertronix or something similar and a good coil will probably be just as good.

carbster09

I rigged up an MSD box and kept my points distributer. The system "seemed" to work well for a time and then I started having "issues". I ended up getting the carb rebuilt again and it ran fine for a few months only. Maybe it was due to the box being located so far from the engine. I hid mine under the storage compartment behing the seat. Do you think this is possible? I know there would be a drop in the resistance of the wire on such a long run.

I will not rehook it up with the engine that GOFAST just build me. It dyno'ed at 500 hp with points. That is fine with me. I know how to adjust them; simple. I like simple. Although I will no doubt starting changing things in a year or two. I just can't leave things be

Zip Corvettes

Sometime or most of the time for me, it is better to walk away from it when I get frustrated or starting to. It amazes me how I can look at something for hours is seems and not see the problem when I am mad. Come back later nice and calm and it is like someone attached a neon sign to what the problem is.
As far as the MSD box, I like them on High horse applications, usually for me this is supercharged cars and they do work very well. I have always used a 6AL, I have not ventured into the 7's. I have used a unit similar to a MSD and it failed both times. Good luck with the build it sounds awesome.

babbah

What MSD Box are you running 6A or 6AL? Is it a relatively new unit?

I have been running a MSD 6A and MSD Pro Billet Distributor in my BB 67 Vette since 1985, it's mounted on the passenger inner fender area - never a problem.

NOTE: Since my 6A box was 25 years old I thought perhaps it was time to buy and install a new one - I did, installed the new one and I developed issues within 2 weeks - would hardly idle - the finally one day later the car would not start!

Long story short - I put the old 6A back in and the car and it fired right up! Idled perfectly just like it did before.

I still have the "old" one (25 years old) in the Vette and its runs great - IMO - I think there are issues with the newer produced boxes. I have bought some of the older boxes on Ebay just in case this one ever quits. I did not have much luck with the brand new replacement 6A box, so go figure?

The MSD ignition made a huge difference in my high performance BB, especially for starting and idling. I see tons of them in the engine compartments -

632C2

Mike, you have gone through more aggravation with that motor than I can even imagine. I really have to take my hat off to you for not giving up and selling it.

I'm glad it's running the way you want it to. If I'm not mistaken you ran it at the dragstrip once before so I am anxious to see what it does this time.

Steve

Irish69427

Where do I start on the voodoo vet. After my last post I finally got the car to the track twice. After blowing up the new transmission the first trip and blew a brand new clutch on the second outing. I am sure more chinese parts. Trapped in the mid teens, which is anemic. This was backed up by chassis dyno numbers. Something is not right.

I celebrated a little early on the other problems too. Car spent the better part of 9 months of the last year in the shop with one problem or another. Will not even go there. Could not get a good dyno pass on the chassis dyno as fuel kept coming out the vents. Finally ran a custom return line and solved that problem. Then the real bad news. I don't know where all the power went. Can't get more than 430 to 450 rwhp out of this thing which is way to low from 650 at the motor. I never got to dyno the engine again after the 4th rebuild out in oregon but it was the exact same motor so shouldn't be any different. Even checked my dyno sheets to see if the correction factor was to rosy on build number 3. The raw uncorrected data was 610 hp so I am sure the corrected data and 646 HP were there at one point.

The oil consumption problem came back and turns out the intake gasket began leaking oil again. Just corrected that for the second time with a thicker gasket so I think oil consumption is o.k (for now). Still has some drivability issues but considering all the other fun I have been through I will live with those for now. Found problem after problem in the vaccum system for the headlights and wiper door that created vacuum leaks in the intake system but largely fixed now.

So the real issue now before I get rid of this thing is to see if I can find the 100 HP I lost somewhere. If not, I think she goes bye bye. Just not worth it anymore. I am now on year 3 of trying to get the bugs out of this engine, etc. and have really had my fill.

I am going to leak down the engine this week end but honestly, the short block seems sound. No evidence of blow by, no oil leaks, just anemic power. She makes 400HP at 3900 rpms but then the power curve just goes flat and eeeks out another 40 or so by 6k. AF mixture is right on in the low 12's. Timing is perfect at 38 degrees mechanical in by 2800 rpms, which was peak power on the engine dyno. I just don't get it. I am thinking maybe the cam timing was changed when they reassembled it for the 4th time (hurts just saying that. LOL). Any ideas would be appreciated.

Based on the relationship between the engine and chassis dyno numbers on my wrecked 69 vette I should be seeing 520+ rwhp. Where did the power go!!!!!!!!!

632C2

Mike,

I hate hearing these kinds of stories. It seems it happens all too often.

I realize that this isn't much help but it would be nice if you were in my area of the country. Together we could get that thing running like it should. I'm not sure anyone will be able to solve this without having the car in front of them.

Steve

DRIVESHAFT

Maybe you will get "lucky" and the power loss was from your toasty MSD box.
It sure sounds like you have had plenty of bad luck so far. You deserve something easy.

jcloving

Irish,

It sounds like you have made some progress and had some setbacks. Keep chuggin and you will get there.

Sometimes it helps to have a second or third set of eyes look over things. I know you had multiple mechanics but some other Vette owners might see something else. Are you in a Vette club in Fla? Just a thought.

Good luck,

post a video when you get it running right!

Irish69427

Some good news. Just finished leak down test. Wow, what a pita. No room in these 3rd gen big block cars. Getting the plugs out with headers is a near miracle, let alone getting the test hose in. Hot engine made for some nice burns. Lol. Anyway, can eliminate this as a source of the power loss. Worst cylinder was 5% and most 3-4%. Tested all of them more than once. So finally, I got a short block that is actually tight and right. That is some consolation. So far the thicker intake gasket seems to be working on the eliminating the oil consumption also. Not ready to celebrate yet but no use in 250 miles.

With this out of the way it is on to cam timing and ignition components. I can't think of anything else. All ears on suggestions. I am really down on MSD components. Lots of problems with the made in china issues. Anyone runnng the crane box and or mallory distibutor? If I replace parts I don't want to buy anymore MSD. Just not reliable anymore.

Lastly, the leakdown noise was only audible through the valve cover breathers. Nothing through the carbs or dipstick or exhaust. Is this ring leakage or intake valve? In any event it isn't much and the internals finally appear sound and right after 4 builds.

scottyp99

Just think about it, man. If pressure were leaking past the intake valve, where else would you be able to hear it except through the carb?


Scott