engine running on 7 1/2 cylinders, CR issues, what to do ???

[Austrian455]

Hey,

The troubles with my 455 seem to be the endless story.
Today I rebuilt my Q-jet again. I did it like described in the book
"How to rebuild and modify Q-jet".
I put it back on the car. The car runs not bad as long as the transmission
is in park position, or as long as there is no load on the engine.
I don´t have a H or X pipe in my exhaust system. So I can hear which
side of the engine makes the troubles.
On the passenger side you can hear that one cylinder cuts out sometimes.
So it runs on 7 1/2

Then I drove around a bit.
The engine has no power and stumbles sometimes.

So I thought about things that can cause that.
It´s no ignition problem. All ign. parts are new and correctly tuned.

1) Is it possible that a woren timng chain causes those symptoms?
2) Can CR be an issue?
I checked the CR on all 8 cylinders.
It was very interesting. It´s a 72 engine.
I had CR readings of 9.7 - 10:1 !!!!
Except the front cylinder on the passenger side. This one has 7.8:1

Any ideas??
What would you do? What should I check before doing anything?
Can I check the timing chain. I thought I could check this when I take the
fuel pump off.

[gashog]

Sounds to me like a vacuum modulator problem.
Recheck your vacuum line connections.

[Smartin]

It sounds like you have a vacuum leak. Check all your vacuum lines and fittings to make sure none are disconnected or loose.

[centurion 455 ragtop]

Quick check; with the engine running and air cleaner off cup your hand and loosely cover the carb. If the idle speeds up its a vacuum leak for sure.

[Robroy]

It’s a long shot but if you still have the EGR valve you may wanna check that it’s not stuck in open position. It’s easy to do by pushing the diaphragm on the underside of it with your fingertips making sure it moves as it should

Any chance you some how have got a little dirt inside the carb messing with it?
I once had problem like yours with a Chevy 305 and I tried a lot of things including letting a local GM shop look at it. Even they couldn’t figure it out although they charged me big time for trying :Blasting::Blasting:

I ended up disassembling the carb totally and then put it in a can of diesel overnight, then I cleaned it out real through with compressed air. Put it back together with a new set of gaskets and voila! Problem was gone and stayed gone for the rest of the years I had the car:beers:

[Austrian455]

It sounds like you have a vacuum leak. Check all your vacuum lines and fittings to make sure none are disconnected or loose.


Quick check; with the engine running and air cleaner off cup your hand and loosely cover the carb. If the idle speeds up its a vacuum leak for sure.

All vacuum lines are new. I disconnected everything and pluged the vacuum ports. That doesn´t change anything.
Took off the intake again. Cleaned everything really fussy.
Then I had the intake at the machine shop to get the gasket surfaces checked for straightness. They are OK.
I put everything together with a new fel pro gasket and enough rtv sealer.
I´m sure there is no leak. I had the engine running and sprayed some brake cleaner on the gap between heads and intake. That also doesn´t effect idle speed.
I checked compression on n0. 5 cylinder again. Same thing as the last time. Then I put some oil in it, checked again and it has nearly normal compressoin readings. :Dou:
What´s your opinion? Looks like I have to build a motor.

[Smartin]

Maybe a cracked piston or broken ring...

[Austrian455]

Holy crap!! A cracked piston?????
Would the engine run "nearly normal" with that?
I also thought about a broken ring.
Do you think that I have to bore it out to .030 ?
Sure, the only way to be sure is to take off the heads
and check the walls.
A broken ring would scratch the cylinder wall badly, or not?

[Robroy]

What I learned in car mechanic school one thousand years ago is that if the difference in compression between the cylinders is less than 10%, then there’s no really need to worry. Not on an old engine with some miles on it.

If something is broken mechanically you should have symptoms like noise, higher oil consumption or blue smoke.

You could try cutting up the oil filter to see if there is any track of metal in there ...

[centurion 455 ragtop]

What I learned in car mechanic school one thousand years ago ...

Man was that when new tires had to be carved from stone....LOL :laugh:


Just to add to your post (which is a good one) I would start with all the easy, cheap and basic trouble shooting methods first. Sometimes after you spend all this cash and time ripping things apart you find it was some simple easy fix after all.

Huge question first: Did you have this exact problem prior to doing the carb work? If you didn't then find a spare carb and swap it with yours to see if its the carb. I would say then its the carb then. I tried years back on rebuilding a carb for my 1977 K5 Blazer. Did I say tried ONCE. I damn near burned it to the ground after a backfire ignited spilled gas on the intake:Dou: Now my carb work is limited to looking at it and changing jets. ;) Some things are just best left for the professionals.

Basics (I saw that some of these you have covered already.)

Check timing
Check ignition wires including coil wire. Maybe swap a set before buying a new pair.
Check points or electronic stuff and inspect cap and rotor. Replace if old, can't hurt.
Check your firing order
Check all vacuum lines
Inspect plugs, regap or replace if old.
Get a full tank of fresh high octane gas and throw in an octane booster.

[Robroy]

Man was that when new tires had to be carved from stone....LOL :laugh:.
Almost, 1978 LOL…:laugh:
I never worked as a car mechanic though except for one summer at a gas station and another at a friends yard where my main task was pulling Saab transmissions :laugh:.
It’s always been my hobby and interest however ;)



Just to add to your post (which is a good one) I would start with all the easy, cheap and basic trouble shooting methods first. Sometimes after you spend all this cash and time ripping things apart you find it was some simple easy fix after all. Dead on Rick...that’s my experience too



Huge question first: Did you have this exact problem prior to doing the carb work? If you didn't then find a spare carb and swap it with yours to see if its the carb. I would say then its the carb then.
I was thinking the exact same thing….

[Austrian455]

Man was that when new tires had to be carved from stone....LOL :laugh:


Just to add to your post (which is a good one) I would start with all the easy, cheap and basic trouble shooting methods first. Sometimes after you spend all this cash and time ripping things apart you find it was some simple easy fix after all.

Huge question first: Did you have this exact problem prior to doing the carb work? If you didn't then find a spare carb and swap it with yours to see if its the carb. I would say then its the carb then. I tried years back on rebuilding a carb for my 1977 K5 Blazer.......

I had problems like that before I did anything. That´s why I started all this.
The car wasn´t running as good as I bought it. But with this Truck muffler in that strange welded single exhaust it had on, it wasn´t as easy as it´s now to find out that one cylinder is missing.
Then I put on the performer intake and rebuilt the carb. After tuning it ran fine. I had to park the car for a few months. When I got back there to pick the car up it ran OK but by far not as good as it did when I parked it.
So I thought the ignition is the problem.
I renewed points, condenser, cap, rotor, wires, plugs and coil.
I adjusted the breaker gap and the timing. timing is set to 10deg. now.
But after that it didn´t run much better. I put on a 750 Holley to find out if it´s the carb.
It ran much better with the Holley but not good.
So I took off the intake again. and put it all together with a new gasket.
After this it ran a little bit better. Now I did my carb again. Exactly like described in this Q-jet book. Put the carb back on and now it runs good at idle. Only one thing: You can hear that one cylinder doesn´t work every time.
It works for 1 or 2 firings then gets out and comes again for 1 - 2 firings.


Basics (I saw that some of these you have covered already.)

Check timing
Check ignition wires including coil wire. Maybe swap a set before buying a new pair.
Check points or electronic stuff and inspect cap and rotor. Replace if old, can't hurt.
Check your firing order
Check all vacuum lines
Inspect plugs, regap or replace if old.
Get a full tank of fresh high octane gas and throw in an octane booster.

So there are only a few things I know:
1) carb is ok
2) vacuum lines are all new and ok
3) no vacuum leak because I sprayed everything with break cleaner (no effect)
4) very low compression on #5 cylinder
5) put some oil in #5 and checked again: nearly normal compression
6) all ign. components are new and correctly tuned
7) no power
8) only fresh premium fuel in my tank. I removed all fuel that was those few months old (from parking it) and filled it half full with fresh premium.

[Gum,beest]

Peter
Have you tried to switch out the (new)spark plug wire from cylinder 5 with another one (old)
I have been told that some times even new wires can be broken
Had a similar experience with my old wires parked the car for the winter period and in the spring it didn't want to start with the old wires

[centurion 455 ragtop]

So Peter am I correct on thinking that you rebuilt the carb because you had this stumble and loss of power.

[Austrian455]

So Peter am I correct on thinking that you rebuilt the carb because you had this stumble and loss of power.

jep, correct

[Austrian455]

So what do you think? Build one?

[73 Centurion]

From this and other threads I get the impression you'd really like to build a monster 455. It's your hobby, give yourself permission to go for it.

I recommend you copy Adams engine specs. He's spent considerable time and money sorting out what it takes to hussle one of these beasties down the 1/4 mile in a hurry.

Pick out your parts, ask for advice on your selections here and on the V8 Buick board. They'll make sure you get what you want from your engine.

I think this is going to be interesting.

John

[Austrian455]

John, after thinking about what you said I know that you exactly hit the nail right on the head.
I´d love to build a strong 455 for my car.
If I´m going to pull the engine I going to do it right.
That means to put all the good stuff in.
But that will cost me a lot of money.
I´m not done with building a motor. This will also require to buy a converter, to get some strong clutches and bands in the transmission and to fabricate a 3 inch dual exhaust. By the way, does anyone need a brand new Centurion dual exhaust with stainless mufflers :D

So my problem is that I don´t have much time at the moment. The engine of my 57 Cadillac Fleetwood needs a complete overhaul. It has to be bored to .030, new bearings, cam, lifters ...... a full rebuild. You know what this means.
And the body shop needs the rolling chassis for the 57 Bel Air within 2 weeks.
A lot of work to do. So the Buick has to wait now :(

[Austrian455]

Another question:
Adam, you have the most experience with "Centurion drag racing".
What does it take to run low 13´s or high 12´s with a Centurion?
Is this possible on 1) pump gas
2) without a stroker
3) without having a rough idle ??

[Austrian455]

OK, some news here.
Yesterday I thought again about the problem.
I knew it was no vacuum leak. And I knew there is only one cylinder which isn´t working 100%
I know that I´ve got low compression on one cylinder. But I don´t think its low enough that I can´t get this cylinder working.
So the only way could imagine was a ignition problem like Rick said.
I put in 8 new spark plugs, tested all 8 wires and put in the MSD 6AL I had sitting in the shelf since years.
I set the gap to 0.040 . When I fired it up and let it warm up it was running on all 8 cylinders. Throttle response is still not very good but driveable. Idle is also not good.
Sounds not bad, but the whole engine shakes a bit too much.
So I´ll tune the carb again to get it running as good a possible. I´m going to park the Buick for a few weeks, maybe months, at a friend. I need the space at home to start assembling of the 57 Chevy and to pull the motor of the 57 Fleetwood.

[73 Centurion]

Sometimes it's good to take a break when a car stops being fun to play with.

It's odd that the problem appears limited to 1 cylinder. If the distributor or carb was the problem I'd expect different cylinders to act up from time to time.

Each cylinder will work within a range of conditions. It seems the low compression cylinder is on the borderline of one of those conditions. The poor throttle response also indicates the engine is not working in the center of it's range. Barring anything mechanically wrong the problem is either air/fuel ratio or timing.

You've gone through the distributor and wires so we can assume you've checked the timing. Did you check it by the timing marks or by ear? It's rare but the timing marks can be off, either the pointer or the dampener.

That leaves the air fuel ratio. You said you changed the plugs. How did they look? A light cinamon sugar color is ideal.

This is going to be an interesting puzzle when you finally sort it out.

Good luck.
John

[Austrian455]

John,
the point is not that I need a break from the Buick. I would love to go on until it runs as it has to.
But I can´t wait with the 57 Bel Air because the body shop is waiting for the rolling chassis. And I have to finish my Fleetwood. I picked up all the chrome parts yesterday.
:D I had the door handles, outside mirror, and rear bumper rechromed. Ohh man, I love old parts with new chrome plating.

To answer your question:
I checked the timing with a timing light. And I could hear how the idle speed increased when I turned the distributor. Never heard about wrong timing marks on a Buick. I know from chevy and Fords with bolted on timing marks. But the timing marks are cast in on the Buick timing cover. How can they get wrong?
Air/Fuel ratio is a topic. 5 of the spark plugs were black and 3 were just a little bit lighter. Not much. So she´s running a bit rich now.
What do you think about the gap on the plugs? Is 0.040 correct?
It would be cool to get this engine running good enough for some cruising this summer.
I´ll start the engine build up as soon as I can effort the money to build it like I want it.
I would love to come off the line like the black Pontiac Grand Ville from grandville455 ( http://www.v8buick.com/showthread.php?t=176619 ) or the black Riviera shown here ( http://www.v8buick.com/showthread.php?t=128608&page=5 ).
I wonder what it takes?

[WDR]

The outer ring on the Harmonic balancer may have slipped. This would put the timing mark in the wrong position. You can get the engine in good tune if you use a tachometer and a vacuum gauge. Adjust your fuel mixture and timing to get the highest vacuum reading at the proper idle speed. I would set the spark plug gap to .030 to .035. Setting the engine up this way should get it back to normal.

[WDR]

One more thought, has the timing chain and gears been replaced? The nylon/aluminum top gear could be worn out. You can check it by taking off the distributor cap and turn the engine over by hand and watch the rotor. If there is a delay in the rotor rotation beyond a few degrees of crank rotation, the timing gears and chain are worn out.

[Austrian455]

Good thought on the balancer. I never had the idea the it may have slipped.
My engine seems that it never was opened yet. Yes, I have nylon gears in there.
And yes, there is some delay on the rotor when I rotate the crank.

[The German]

Peter, just now I remembered that once I read that it could be possible that the cylinder rings could become blocked by caked-on-particles so that they get fixed. This could cause that the rings let some gas pass so that the compression is lower and in the long run blocked rings cause more and faster wear which will be the reason for lower compression. Also such particles can cake on to the valves and be the reason that they don´t close as they should.
I don´t know what oil you have; if you have an oil with a high rate of dissolving agents all should be clean and okay, but if you have the normal oil I would recommend to add an additive to clean up the engine. My own experience with such an additive is very good:
- I could follow the cleaning process by looking to the oils color - it became darker within a short time after filling in the additive and I had a hard ticking hydraulic lifter for ca. 10 minutes (guess it was a cacked-on-particle which came lose and flew into the lifter with the oil stream but later was filltered out). I never had this again since I changed the oil and filled in a new mixture with the additive.
- The engine now has much lower vibrations than before - and I did nothing else with the engine but filling in the special oil mixture !

May be such a mixture could also bring some positive results to your engine - one step more to those you did until now and will do probably during the next weeks, but a step which I would not let undone because I´m convinced that it´s really worth the effort !

Also have a look to this thread :
http://www.buickcenturion.com/forums/showthread.php?t=724&highlight=Mathy

The caked-on-particles at the valves could perhaps be washed away by another additiv which is filled into the fuel tank, but here I have no experience. The producer of the Mathy-M-Oil-Additive has such an additiv also (Mathe-Schmierstofftechnik GmbH, Soltau, GERMANY).
Ask them for information first - you will get really interesting papers !

However - good luck !

[Austrian455]

Rolf, thanks for the info.
I heard of these engine cleaner additives. I never added one of them because I heard some stories about them that made me afraid.
For example, I know about a 65 T-Bird. The engine was running but had some of those caked-on-particles in the engine. He had to rebuild the engine because one of the mainbearings of the 390 was gone after adding the additive.
I will ask them for information.

[Austrian455]

Hey,

I was very busy the last weeks. That´s why I wasn´t here for so long.
I wasn´t able to get my engine running as I want it to.
So I pulled the heads some days ago.
Cylinderwalls are very good and the it´s still standard bore.
The headbolts seam to be very tired because the open VERY easy and the heads were not NOT stuck to the block anyway.
I checked the Performer intake at the machine shop for straightness.
Its junk. That´s where the vacuum leak came from.
So I bought a new one.
Yesterday I spent about 4 hours with raw porting of ONE head.
On monday I´ll do the second one. Then it will take me
some further time to get the a smooth surface in all ports.
And I had my Hooker Headers sandblasted, painted them and put
them in heats wrap.
I hope to receive my order from Greg Gessler next week.
I ordered a head gasket set, Q-jet bushing kit, calibration kit, advanced curve kit and the adj. oil preassure regulator.
On monday, when all the port work is done the heads are getting milled, valves cleaned and polished, valve job done and I´ll paint them Buick red again :)
I´m also doing little work on the intake to get the ports matched to the heads.
I´m curious to see what all this mods can do.
I´ll keep you posted.

[birminghamer]

It's a long shot but I had a similar experience with a power brakes booster, press the brake at fast idle, any change? If so you could explore that angle
Off topic I know, how is the stainless on the rear doors and quarters of the 57 Fleetwood? I have a complete set that needs a new home, let me know. It's been in storage 25 plus years, needs to go.

[Austrian455]

The brake booster is OK. I had all vacuum ports plugged off to be sure.
Thanks for the offer. The stainless on my Fleetwood is in excellent condition.