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Engine Troubleshooting Help

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AmbitiousButRubbish Avatar
AmbitiousButRubbish Chris Argue
Tempe, AZ, USA   USA
Hi all I am looking for some help on a problem I have been chasing on my engine build for my Bugeye.
I'll try and be as thorough as I can in describing the build and the steps I have taken so far but this is my first build so bear with me please.

The Engine is a 1275 with a serial number that starts with 12 CD. The engine is a complete rebuild. The block was overbored 0.020 over stock. The head is off of a Mini Cooper S and was built and shipped complete with valves and springs by MED engineering out of the UK. They also supplied the pistons (OMEGA 10cc dished) as well as crank and cam gears, camshaft (Piper RS with duration of 264), balancer and 1.5 roller rockers.

The car is setup negative ground with an electronic ignition. The ignition consists of a MSD 6AL along with Pentronix Flamethrower coil and distributor, cobalt wires and NGK 6BPR6ES spark plugs. The carbs are Dual HS4 carbs that were rebuild recently by a shop and have ACC jets in them.

The issue I am having is that the car will start up and idle at around 1000rpm but will not respond to any throttle or choke inputs at all. When I do the lift test on either carb nothing happens. If I advance the timing even slightly the rpms shoot up to between 2000 and 2500 by themselves and will start to "backfire" out of the carb intakes and will die. If I retard the timing at all the car will not start. When The car is idling I can see a slight mist of fuel that is coming out of the intake on the rear carb which becomes more pronounced when the timing is advanced.

I think it is worth noting that during the build I had to shim the roller rocker pedestals up 0.012" in order to allow for the valves to complete a cycle. If I did not re-shim the pedestals, using the stock followers and pushrods the valve springs would bottom out. After shimming I measured valve lift at approx 0.450 on exhaust and 0.0425 on inlet which once I converted the numbers provided by the cam manufacturer using the new 1.5 rocker ratio where inline with what they should be. I did a bunch of research on this and there were definitely people saying there was no need to shim and some saying that it was an absolute necessity. For mine not shimming wasn't an option, not sure what everyone elses experiences are with this.
What I have check so far:
- I did a compression test on all 4 cylinders, they are 180 psi across the board.

Chris
- I did a leak down test on all cylinders and they are 94%, 96%, 94%, and 91% for cylinders 1 through 4 respectively.

- I have rechecked the the crank/ cam timing. The crank and cam were installed with the two manufactured dots facing each other with the number one cylinder at top dead center on the combustion stroke. The key way on the crank was at the 12 o'clock position while the one on the cam is at the 1 o'clock position. See attached picture. I verified that I am not 180 out by looking at the vales, the #1 cylinder intake valve had just closed before coming around to top dead center. Also when at top dead center on the combustion stroke all valves are as follows: Rockers are free on valves (from front to rear) 1,2,3, and 5. the #4 valve (Cylinder #2 exhaust) and #6 valve (cylinder #3 intake) are both partially open. Finally both valves on the number 4 cylinder are almost fully closed but the rockers on either do not turn freely.

- I have double checked valve lash on all valves and set them to 0.014" for exhaust and 0.012" for the inlet per the cam instructions.

- The distributor gear was installed while at TDC at the roughly 2 and 8 o'clock positions with the larger offset side to the bottom per the manual. See attached picture.
- I then rotated the engine to the 12 degrees BTDC position and installed the distributor. Due to the electronic ignition I could not use a indicator light to set the static timing so it was eyeballed for now. I do have intentions of trying the method of pulling the #1 spark plug and grounding to the engine to see if I can set the static timing that way.
- The rotor on the distributor is facing the front of the engine, between a 2 and 3 o'clock position.

- Spark plug gaps are at 0.030"

- Check the firing order is correct at 1, 3, 4, 2

- Fuel pump is a Facet electric pump running 3 psi I believe with fresh 91 octane.

- Carbs were freshly rebuilt HS4's done by a shop. I have the jets adjusted down 12 flats on the front carb and 16 flats on the rear carb so that the measurement for each jet is 0.053" down on both carbs.
- The idle screws have been set 1 and a half turns down.

- I have installed an air fuel ratio gauge in the exhaust and readings were in the high 12's to low 13's

- A new timing indicator and timing strip were installed (6" diameter balancer and tape were used) when the #1 piston was verified to be at TCD on the combustion stroke.

Here are some of the more confusing bits:
- When using the timing light at idle. the light is showing that the engine is so far retarded that it is actually off of the timing tape. I have double and triple checked that the tape is in the correct position. Again any bit of advancing causes the revs to up and backfire our of the carbs.
- From this I then wanted to set static timing using a vacuum gauge. Peculiar part here is that if I put a vacuum gauge straight off of the intake manifold, I get a reading that essentially bounces slightly around 1. When the engine is off and I just crank the car again I get just a slight bobble of the vacuum gauge. The only time I see any reasonable vacuum is when the RPM's jump up to 2000 then I see about 10. I have verified that the gauge is not bad and that there is nothing clogging that port on the manifold. I sprayed started fluid in an around the carbs and intake manifold on both sides and the rpm's did not pick up at all so I do not think I have a leak.

The next step
- I plan to put a full degree wheel on the balancer and check that the valves are all opening as they should be to confirm that this is not a cam or cam gear issue.
- I plan on putting an inline spark plug tester to see if I can detect any irregularities on the ignition system. It is all new components but that doesn't ensure that I didn't get a bad part, it does happen.
- I will also try and set the static timing a little more accurately using the method outlined in a separate thread of pulling the #1 spark plug and grounding to the engine.
- I will also try and rig up a home made smoke machine just to verify that I do not have a manifold leak.
- I have not tried to balance the carb flows yet but having read a few threads I know people say that instinct is to blame the carbs but it typically isn't the issue so I have devoted my attention elsewhere.

For me the head scratcher is the vacuum, but I am looking for some direction on if I have missed anything to check or if I should be checking anything else next other than what I just listed. I read a recent thread on here that had a similar sounding issue and it turned out to be a bad points system and going to an electronic ignition fixed that. Probably should have went with a stock build for my first one to eliminate some of these variables, live and learn as they say.

I have uploaded 3 pictures of the engine, crank/cam gears installed, distributor gear install @ TDC, and the rocker pedestal shims.
Thank you for reading all of this, your help is much appreciated.

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Attachments:
Engine.JPG    64.2 KB
Engine.JPG

Timing Chain-1.jpg    41.3 KB
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Dist Gear at TDC.JPG    80.3 KB
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Rocker Prdestal Shims.jpeg    33.6 KB
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Perdido Avatar
Perdido Gold Member Rut Rutledge
Tuscaloosa, AL, USA   USA
Chris,
My first thought it to check your cam installation since that’s what it sounds like to me. Before taking it apart I would put a degree wheel on the crank and make sure.
Rut

Dave at OldSchool Avatar
Dave at OldSchool Dave Perry
Battleground, AL, USA   USA
I agree with Rut. " No" vacuum here sounds like cam and/or valve issue

I assume you have Pertronix 142 in the distributor... double check your coil and be sure it is not their v8 coil, and is their correct ohm coil for a 4 cylinder

Dave Perry OldSchool Restorations... North Alabama

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AN5L8016 Avatar
AN5L8016 Mark Haynes
Nederland, CO, USA   USA
I've got to agree, I managed to time the cam on my MKII in to the #1 valve (stupid, I know), rather than the #2 (intake) and had the same "stand-off" of fuel mist outside of the carbs. Double check with a dial indicator and a degree wheel being sure to use #1 intake (valve #2 from the front)..



'58 Bugeye
'66 'Stang

AmbitiousButRubbish Avatar
AmbitiousButRubbish Chris Argue
Tempe, AZ, USA   USA
I like the consensus here... looking into it further I definitely didn't take the proper steps when degreeing in the cam. Nothing like doing things the hard way to learn a lesson. I'll be attacking that over the next couple days and will report back in.

Dave you are correct on the 124, I'll double check the coil as well.

Thanks for the responses, much appreciated.

Dave at OldSchool Avatar
Dave at OldSchool Dave Perry
Battleground, AL, USA   USA
.
Chris, You are mistaken to think you can not static time the distributor .

With Pertronix, it is easy to do.. here's the link to the system I have used for many years. http://www.ttalk.info/PertronixStaticNeg.htm

Also, put a mark on the pulley at 30 degrees advance, and check with timing light at 2500 rpm's... it should be close.

Be careful not to leave the power on any longer than needed....

Dave Perry OldSchool Restorations North Alabama U.S.A.

Perdido Avatar
Perdido Gold Member Rut Rutledge
Tuscaloosa, AL, USA   USA
Dave,
I haven’t been thru Battleground in years...has the highway gotten any safer?
Rut

Dave at OldSchool Avatar
Dave at OldSchool Dave Perry
Battleground, AL, USA   USA
you mean 157 that we are on ?? it's a divided 4 lane , heavily patroled at 65, and pretty decent

Perdido Avatar
Perdido Gold Member Rut Rutledge
Tuscaloosa, AL, USA   USA
Last time I traveled 157 it was a combination of 2 and 4 lanes with mobile homes on the road...lots of mobile homes. Glad to hear it’s better!
Rut

AmbitiousButRubbish Avatar
AmbitiousButRubbish Chris Argue
Tempe, AZ, USA   USA
After pulling the engine and running through the timing and verifying everything I’ve refired the engine and I’m still in need of some help. The major issue is that the engine will not idle down. I fire it up and the engine runs up to about 2000 rpm. The throttle cable is disconnected, springs are attached, the Choke cable is also disconnect and the idle screws are out all the way. When it is running the carb pistons are about half way up and I can see fuel coming up from the jets.

The carbs are HS4s and we’re rebuilt by a shop. I have got the jets centered quite nicely but I haven’t played around with them too much else.

I’ve read that some people have had similar symptoms to mine when the throttle plate isnt installed correctly. There does seem to be excessive room around the bore and the plate. In the rebuild book it shows a bevel on the plates and that they are installed with the upper half pointing towards the engine instead of out as mine are. I’ve attached a couple pictures for reference. Do these look to be installed correctly? Am I on the right track thinking this could be the issue?


Attachments:
BE970E97-6F6E-485B-8AE9-D031913BC9DB.jpeg    30.7 KB
BE970E97-6F6E-485B-8AE9-D031913BC9DB.jpeg

8789F893-E061-44B8-BF73-E4F88578F733.jpeg    19.9 KB
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AN5L8016 Avatar
AN5L8016 Mark Haynes
Nederland, CO, USA   USA
It looks like the throttle plates aren't centered in the throats and are staying too far open at idle. You may want to loosen the screws on the plates to allow them to recenter, then tighten them up again. As to the taper on the plates, those should interface with the throat of the manifold, if they are reversed, the plates won't close up to the wall and you'll get a high idle condition.
Personally, I think the HS4s are too much carb for a 1275 with a mild cam, JMHO.



'58 Bugeye
'66 'Stang

AmbitiousButRubbish Avatar
AmbitiousButRubbish Chris Argue
Tempe, AZ, USA   USA
Thanks for the response Mark, much appreciated. I'm definitely going to try and recenter those plates. A follow up question, Can those shafts/plates be installed backwards, meaning should those plates have the bottom closest to the intake side of the carb instead of the top as mine are. I haven't been able to locate anything definitive that shows the orientation or if that matters.

As for the carb sizing, that was the recommendation that I got from MED Engineering whom did the work on the head and provided the cam, although that isn't to say it's correct. The thought has crossed my mind that they may be too large after talking with a couple of local club members. I'm new to all this so I appreciate the input. I have attached a picture of the cam specs for reference if that helps. Could the sizing be responsible of the issues that I am having?



Chris



Edited 1 time(s). Last edit at 2019-01-30 10:31 AM by AmbitiousButRubbish.


Attachments:
Cam Spec.jpg    15.9 KB
Cam Spec.jpg

Poundingsand Avatar
Poundingsand Silver Member Peer Ebbighausen
Los Angeles, CA, USA   USA
Hi Chris. If the throttle plates are oriented the wrong way they wouldnt move when you pull the throttle cable, it would seem. Just a thought...

refisk Avatar
refisk Rick Fisk
Frankenmuth, MI, USA   USA
If the throttle plates are installed backwards they won't close properly and the idle will be high. In your top photo it looks like the plate is backwards. They can only open one way. When you open the throttle the shaft turns and the top of the plate moves away from the engine and the bottom towards the engine.

Of more concern is the huge gap around your plates. Something is holding the throttle open. Are the choke fast idle screws backed off?

MKIISpriteGuy Avatar
MKIISpriteGuy Richard H
Kent, WA, USA   USA
Chris:

Looking at your photo of your timing chain sprockets, you have noted the 2 dots lined up adjacent to each other. This is the Cylinder #4 firing position. Rotating the crankshaft until both dots are at the one o'clock postion will get you to the Cylinder #1 firing position, and the reference point for installing the distributor. I once spent several hours trying to determine why my distributor was 180 degrees out of alignment, and my Haynes manual was no help.

I wrote in my old Haynes manual a few notes on this, including the position of the low-lift rockers when the motor is at #1 firing position:
Rockers no. 1, 2, 4, 6 are fully closed. Rockers no 3 and 5 aqre fully open. Rocker #7 is beginning to open. Rocker #8 is almost closed.

There are several posts on the MG Experience site covering this topic. Both the A-series and B-series motors have this issue. I have pasted below some statements for an MGB (B-series) thread in 2015 entitled ""Correcting Timing Chain position":

". The Workshop Manual is misleading, Haynes is actually incorrect. Both say to fit the chain and gears the dimples must be in-line and adjacent. But that puts No.4 piston at the top of its compression stroke, not No.1. That's fine as far as crank to cam alignment goes, but there is a problem when inserting the distributor drive gear. Haynes says to have the crankshaft in the same position to insert the gear, but that puts it 180 degrees out. The Workshop Manual still says to have the dimples in line, but this time misses out the crucial word 'adjacent', i.e. the crank has to be turned one revolution to put the cam dimple on the far side. If you have already put the front cover on you will need to make sure it is No.1 that it at TDC on its compression stroke before inserting the distributor drive gear, but that needs the push-rods and rocker gear to be installed."

".....the timing gears must first be positioned with the timing dimples adjacent to each other at TDC
- then the crank is turned so that the dimples are aligned at approx 01:00 - (take a long straightedge, and line up the dimples with both the turn center of the crank and the turn center of the camshaft - all four of these points must line up).
To help verify if you have this correct - the # 7 and # 8 valves should be "rocking" - that is, both of the rockers on the #7 and #8 valves should be mid-way down, between open and closed.
That's the position when to install the distributor drive gear. Failure to do this accounts why many owners live with their distributors mis-positioned by 180º."

"..Once the chain is installed dot-to-dot, as others have said, this puts number 4 at TDC in firing position on its compression stroke, not number 1 as would be the case with most other engines, especially domestic V-8s. So, assure that the chain and sprockets are installed with dot-to-dot along the centerline of the crankshaft, then rotate the engine one revolution, which will rotate the camshaft and its sprocket one half of a revolution, since the camshaft sprocket is exactly twice the size of the crankshaft. This will put the dots at the position in your photos, both at about the 1 o'clock position, and you can re-check with your straight edge. Be sure to turn the engine in its normal direction of rotation -- clockwise when viewed from the front of the car. With the chain and sprockets in this position, cylinder number 1 will now be at TDC in firing position on its compression stroke, and it is at this time that you can install the distributor drive gear with the offset per the illustration in all the manuals. "

"..Glad I found this thread; I thought I was going mad after finding my engine valve timing was 180 deg out during my strip down! Its only now I understand that when the crank and camshaft dots are adjacent to each other (like shown in the Haynes manual) its No4 cyl that's at TDC and on the firing stroke, not No 1 Cyl. The Haynes manual doesn't bother to tell you this, I just assumed it was No 1 Cyl that would be on the firing stroke; now it makes sense!"






Good luck with your 1275.
Richard

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