Any thoughts on this engine issue

[Bulldozer]

Demon,

As I read throught the thread I did not see where you had bypassed the filter using the gravity feed option. So that certainly rules out the filter.

Way past my paygrade, but it sure seems like something is causing the idle circuit to go nuts. But what? That is the big question.

You did say plugs indicate rich. So what can you do to lean it out? Rich charge burns faster, so at idle that can not be good. Once off idle all is OK. So idle circuit is the focus. I am no carb expert, but what does one do to lean out an idle circuit? When I watched the video it does not appear that changing the idle screws had much impact. Just like many throwing stuff out there.

my very first thought was the carb or fuel pressure. he states he has had 4 different carbs and tried everyway to sunday with pressure and filters. he has a rock steady 5.5 psi fuel pressure. im convinced it is not a fuel or carb problem at all , but a timing problem. there have been 2 distributors and new box and all new ignition parts, i would also rule that out. in fact , i have ruled out everything outside the motor, i believe it is something internal. been wrong before, and i will again.

 

[412 Stroker]

How about the dampner?? is it one that uses an Elastomer?? could it have slipped??

 

[Bulldozer]

Abodee,

Can you really refer to this as a surge? A surge to me is an engine that is searching. Like a gradual increase and decrease in RPM. But this engine is bucking and unless I am mistaken I think I saw where they have observed the timing and it shows no fluctuation. Now perhaps if the damper does have full degree markings they should hook the light to each cylinder and observe the timing. If they have marks at 90 180 and 270 they can at least see if any funky stuff is going on other than #1. What do you think?

he stated the engine timing is fluctuating. maybe not a full blown surge so to speak, but it seems like it is severely out of time. i would manually bring it back up btdc and see where the balancer is, then try to re-time it and see if it is jumping around. it would seem to me with a brand new chain, the timing should be rock steady.

 

[demon34071]

this is a mystery and i will not rest until this is solved. if you have exhausted and replaced everything outside the engine, its time to dig in. i would start right at the timing cover.

what causes a surge?

vacuum leak (s)
a stretched chain or timing has jumped
any kind of fluctuating fuel pressure

because you have eliminated the fuel pressure and any vacuum leaks , that really leaves only the timing. everything is coming back to the timing. you say it is jumping around?

are you sure the mufflers are full of mud? lol

Being that the engine was built 100% with all new parts -- NOTHING USED except the crank and rods, and they were all handled and the engine builder... Which I am not...So I have a hard time seeing how the steel chain would have stretched with just idle time on it. Only actual driving time was about 40ft to put it on a trailer 4 years ago... Since then its only been pushed...

The only place it could be leaking vacuum would be under the intake were we can not get to.... and the puzzling part is when we un cap the vacuum for a direct leak at the carb it runs a little better. Doesn't eliminate the issue but does run better.

Fuel pressure is solid right in the range of the pump. Pump is 5.5-6.5 psi rated and the gauge reads 6psi all the time.

Definitely confused.... But I'm not engine guy either..so it didn't take much.

 

[demon34071]

he stated the engine timing is fluctuating. maybe not a full blown surge so to speak, but it seems like it is severely out of time. i would manually bring it back up on tdc and see where the balancer is, then try to re-time it and see if it is jumping around. it would seem to me with a brand new chain, the timing should be rock steady.

That same logic of being a brand new build (that is finally making it into the car) we are extremely hesitant to open this motor up just to do some trial and error work.

 

[demon34071]

How about the dampner?? is it one that uses an Elastomer?? could it have slipped??

Brand new -- only idle time on the motor... Everything was 100% brand new on this motor when I built it. Granted then all the mother nature issues, but as you can see in the video it has life, just shaky... LOL

 

[67Dart273]

I gotta tell you demon, I'm not a pro engine builder, but I've built a few, and been into a few. Ya have me baffled. Next step, if you have not, is a compression check. I'd suspect something holding valves open, IE pushrods too long, sticking valves, broken springs,

Was this rotated with water in it?

 

[Bulldozer]

That same logic of being a brand new build (that is finally making it into the car) we are extremely hesitant to open this motor up just to do some trial and error work.

i dont blame you. i wouldnt want to rip into it either. honestly though, you've done about all you can do outside of it. use a piston stop in the number one hole, bring it up btdc, and see where the balancer is. pop the cap and see if the rotor is sitting about on number one.

 

[demon34071]

I agree that you seemed to have done all of the basic and easy stuff. Last easy thing would be to check the vacuum hose connection to the correct port (I am sure that you did this on the carb swap) and inspect the valve springs for integrity.

Then it is pulling the intake and check the condition of the cam and lifters. Check the distributor bushing/gear as suggested above.

Next, pull the timing chain cover and remove the cam and inspect for corrosion of the bearings.

Then, pull the heads and inspect the cylinder walls for pitting.

Finally, pull the crank and pistons. Hot tank the block, and reassemble with new rings and bearings.

That the same basic advice an engine builder told... Tear it down and eventually you'll figure it out.... Well that is way out of my talent level, hence Y I paid to have this done for me years ago... Its just a shame like most of us it took till now to get it running... But you have to jump when you have the money in this hobby or they never end up finished.

I just can't see why any of this would be an issue since the motor and the bucking goes away when the motor is under throttle??

 

[demon34071]

I gotta tell you demon, I'm not a pro engine builder, but I've built a few, and been into a few. Ya have me baffled. Next step, if you have not, is a compression check. I'd suspect something holding valves open, IE pushrods too long, sticking valves, broken springs,

Was this rotated with water in it?

I think I posted last night that we did a compression test and it was good on the gauge they all ready in the 150-155-160 range and held tight..... We also cranked the motor with the valve covers off to make even more sure the valve train was all moving... That checked out too....

Thats' when we stopped for the night puzzled as hell...

 

[demon34071]

i dont blame you. i wouldnt want to rip into it either. honestly though, you've done about all you can do outside of it. use a piston stop in the number one hole, bring it up btdc, and see where the balancer is. pop the cap and see if the rotor is sitting about on number one.

That's a good idea.... Its one of the things we have not tried... I will talk to Al and see when we can try this one. Thanks...

 

[Bulldozer]

That the same basic advice an engine builder told... Tear it down and eventually you'll figure it out.... Well that is way out of my talent level, hence Y I paid to have this done for me years ago... Its just a shame like most of us it took till now to get it running... But you have to jump when you have the money in this hobby or they never end up finished.

I just can't see why any of this would be an issue since the motor and the bucking goes away when the motor is under throttle??

if it is out of time, increasing the rpms will sometimes make it sound like it is running better and it will smooth out because the pistons that are firing are working faster.

 

[spinman_1949]

Demon,

Did you indicate the timing is fluctuating? If it is then you need to find out why. If the diss is correct you should not be seeing any advance at idle. And I know you do not have any vacuum hooked up correct? So if the diss is not providing any advance at idle and there is not vacuum advance to deal with, then if the timing is moving around more than a degree or two at idle then something is not right. And keep in mind that you are only seeing what is happening at # 1 TDC.

I understand that everything is new in the engine, but unless you happen to have all bad carbs. All bad diss. All bad ECU's, Or have an electrical problem beyond any level of understanding, you need to look at what you do know. So is the timing moving around? If it is then something is not right.

 

[Bulldozer]

If the diss is correct you should not be seeing any advance at idle. And I know you do not have any vacuum hooked up correct? So if the diss is not providing any advance at idle and there is not vacuum advance to deal with, then if the timing is moving around more than a degree or two at idle then something is not right. And keep in mind that you are only seeing what is happening at # 1 TDC.

XS2 exactly why i think the chain is coming into play or the balancer has slipped giving a false timing reading

 

[spinman_1949]

Demon,

Have you driven the car yet? An engine under no load may not show issues off idle. Maybe you should drive the car and see how it acts under load?

 

[spinman_1949]

Abodee,

Yup I got a piston stop to check my damper. My TDC mark is right on. But I do get a 10 degree fluctuation which leads me to figure I have a chain issue. Of course I am not experiencing the same problems. I think my issues are valve related. Especially due to the big swing on idle vacuum and even at higher RPM's. I am guessing a tight valve or two or worse burnt valves. I did have that severe pinging issue.

As far as this engine is concerned, Demon has moved the timing from 22 down to 14 and the problem follows to a greater or lesser degree. So I kind of question that the damper not displaying correct TDC. Unless it is so far off, that even at 22 degrees BTDC indicated it is really down near zero or retarded. That might explain the off idle improvement, especially if the diss is providing advance early. The standard light spring and heavy gap spring setup does give advance right at 1000 RPM. I know cuz I tested it. Of course if 22 BTDC is not enough, then one would figure the engine would not even run at 14 BTDC.

Boy this one is a real brain jerker.

 

[demon34071]

Demon,

Did you indicate the timing is fluctuating? If it is then you need to find out why. If the diss is correct you should not be seeing any advance at idle. And I know you do not have any vacuum hooked up correct? So if the diss is not providing any advance at idle and there is not vacuum advance to deal with, then if the timing is moving around more than a degree or two at idle then something is not right. And keep in mind that you are only seeing what is happening at # 1 TDC.

I understand that everything is new in the engine, but unless you happen to have all bad carbs. All bad diss. All bad ECU's, Or have an electrical problem beyond any level of understanding, you need to look at what you do know. So is the timing moving around? If it is then something is not right.

It was moving around... but we solved that issue... not it is only moving a couple degrees... so yes it is still moving but not as bad....

I just sent the video to the guy who built the engine Tim Bowman @ Bowman Performance... hopefully he can help shed some light on it as well.

FYI -- No I have not driven the car with this motor in it... I don't want to drive it with with such a bad bucking issue. I don't have unlimited pockets if that does more damage to the motor or the car, so I want to get this fixed before I attempt a road test.

We will definitely figure it out. I'm hoping the builder has more detailed notes than just the receipts I have. This way I can open it up with having firm details on whats in it and can check with what it should be... I would prefer this than just exploratory engine surgery....

Thanks for all the help and thoughts... they are helping us rule out things and keep our sanity at the same time.

 

[Bulldozer]

Abodee,

Yup I got a piston stop to check my damper. My TDC mark is right on. But I do get a 10 degree fluctuation which leads me to figure I have a chain issue. Of course I am not experiencing the same problems. I think my issues are valve related. Especially due to the big swing on idle vacuum and even at higher RPM's. I am guessing a tight valve or two or worse burnt valves. I did have that severe pinging issue.

Boy this one is a real brain jerker.

thats right! i remember now, did you get that sorted out?

10* is ALOT . to me , thats enough to warrant a new chain just to be sure.

 

[Bulldozer]

I just sent the video to the guy who built the engine Tim Bowman @ Bowman Performance... hopefully he can help shed some light on it as well.



Thanks for all the help and thoughts... they are helping us rule out things and keep our sanity at the same time.

thats a good idea to send the video.

please keep this thread alive until you find out something definate. this one has me on the edge of my seat LOL

 

[Inertia]

I think the answer is right before your eyes,, the plugs are showing rich,,, 2nd hint,, when pulling off vacuum hose,, it speeds up,,it needs to be leaner..

didn't catch if you had a pcv or not,

the surge is called "hunting",, its trying to find a happy place to run,,, until you lean it out,, it prob wont run any better,,

cure the richness.. clean the plugs, run it, and read the plugs,, they'll tell you ..

 

[Arco440]

Sounds like a sticky valve to me. Did you change the lifters?

I'm with him cam or lifter problem.

 

[demon34071]

I think the answer is right before your eyes,, the plugs are showing rich,,, 2nd hint,, when pulling off vacuum hose,, it speeds up,,it needs to be leaner..

didn't catch if you had a pcv or not,

the surge is called "hunting",, its trying to find a happy place to run,,, until you lean it out,, it prob wont run any better,,

cure the richness.. clean the plugs, run it, and read the plugs,, they'll tell you ..

I'll talk to Al and we will definitely try it... I know as we adjust the carb we couldn't get it to stop the bucking... But we will definitely try this... Thanks

 

[crackedback]

If you have a vacuum gauge, set the idle mix screws using it.

Have you set the float levels? Checked if fuel was dripping from the boosters?

I'd start over on tuning it. Set initial to 16 BTDC, Re-baseline the idle mix screw settings, 1.5 turns out, set float level and trying tuning it. Highest idle vacuum, leanest setting.

 

[spinman_1949]

Demon,

I think I asked this. If you screw the idle adjustment screws all the way in, the engine dies correct?

 

[demon34071]

Demon,

I think I asked this. If you screw the idle adjustment screws all the way in, the engine dies correct?

Yes -- That is what killed the motor in the video