Small Block Timing Issues Have Got Me Stuck

Here goes nothing,

To start I was called over to a friends house to help him get his fresh engine fired in his 48 Plymouth so off I went. This is what I found when I got there......318 mopar stroked to 390, iron X heads, comp XE275HL-10 cam & vlv train and 9.5:1 comp

First I spun the motor over to TDC no 1 and wired the dist correctly, problem one that he had, second he had way to big of a elec fuel pump kicking out somewhere in the range of 8-9psi flooding the engine so in went a fuel regulator. After doing the basic initial timing on the engine and correcting the fuel issue(he has a carter 750 which needs no more than 5.5psi) I was able to get the engine fired and did the initial 30 min break in run for the cam at 2000rpm. OK I thought I was done but....

He calls me over to help tune the engine so I go to hang out and drink a few beers and help. Heres the problem
1- I was not able to get the timing dialed in because the cam was installed 2deg adv on the timing set and the cam had 4 deg of adv already built in for a total of 5 deg adv on the cam(2deg at the crank is 1deg on the cam) which would not allow the engine to idle down below 1500 rpm nor could I get it come in on the balancer (but more adv on the cam means more cylinder pressure at low RPM)
2- Re-installed the timing set strait up 0deg adv, and still could not get the timing to come in on the balancer and the eng was flooding/ loading at low RPM and dieing at 1500rpm
3- Re-set the timing TDC no 1, dist & balancer all line up at zero. checked and re set the floats at 7/16" closed and 1" open while giving 1 1/2 turns out on the idle screws.
Engine fired up but still would not idle below 1500 rpm and timing would not come in on the balancer

So I am stuck does anyone have any ideas that I can pass to my buddy? any info would help him out and save me the headache. I have never had this much trouble with an engine!

 

Is the dist vacuum advance? Is it getting vacum from manifold or ported ?Could be that it is getting manifold vacum and there by advanced on start up?Have seen this before,Jusy a thought.

 

Yeah I forgot to mention that the dist is a vacuum adv and I had it disconnected while I was attempting to set the timing. There are no external ports on the intake manifold and I leak checked the intake and no leaks at all. all the vacuum ports on the dist were plugged off including the vacuum port for the brake booster. I am getting around 19- 20 in hg at 2000RPM and about 16 in hg right before the engine dies at 1500RPM.

From the way the engine sounds and the vacuum I would say that the timing is in the neighborhood of 32-34 with the dist vacuum line hooked up but still wont idle below 1500RPM

 

Anyone got an idea? I'm sure this is something simple I may have missed.


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I installed a timnung gear advanced w/o knowing there was advance built into the cam. wasn't a problem. Sounds like carb or ignition timing, vacuum loss, ect.

 

Couldn't be something as simple as a lean idle condition, could it? You have to kind of think outside of the box sometimes for these kind of problems. Do you get any sense of it running either too lean or too rich? Does it respond to adjustment of the idle mixture screws?

 

Since this sounds like an engine you did not build, from parts that you can't verify, I would go back to finding T.D.C. (piston stop) and verifying that the marks on the balancer are correct.

 

Yup. Virity that what you think is TDC really is TRUE TDC. Don't trust anyu factory tiing tabs/ marks to be correct on a modified engine.

 

Wrong balancer/timing cover combination? There are a couple of different ones for 318's.

 

Yes you are right as far as timing covers go and here they are if memory serves me correct
1965 without timing tab
1969 with integral timing tab on passenger side
1972- present with integral timing tab on driver's side
1976 without timing tab

 

Based on your user name, I would assume that you know FOR SURE which cylinder is #1, on that engine. No offense, I would have to look it up. It sounds like you are not on #1 TDC, at least, at the balancer. It also sounds like you have the experience to figure this out. Verify #1.

 

I did not build this engine but can verify the parts installed as I have pored over his folder with all the receipts and install papers that came with all the components and the eng is a solid combo, thats what is so hard about finding this little gremlin. This is a mid 90's magnum block with the X casting RHS heads and converted back to a flat tappet cam(tossed the roller lifters and retainer or spider as most call it) with a factory harmonic balancer and electronic dist.

I have personally verified that the No 1 is at TDC on the comp stroke (had the valve covers off and spark plugs out) the timing marks line up exact on the balancer at the zero adv mark and the dist is electrically aligned firing on that cylinder,....

The eng will fire and run but loads up and dies below 1500RPM still pulling around 16 in hg on a vacuum gauge and 19-20 in hg at 2000RPM. I have set and timed my fare share of engines but this one eludes me.

I have already considered the fact of an low RPM air leak that would richen up the air/fuel mixture and choke out the eng. I have already checked for vacuum leaks too and I thought the carb was at fault which I still kinda think it has a role to play in this but not entirely. Thats why I set the inlet PSI to 5.5 for carter, checked and verified the float open & closed measurements of 7/16" & 1" and did the initial idle mixture at 1 1/2 turns out for both banks. I have also gone and checked the needle/ jet sizes and the vacuum spring rates that were installed( Metering Jets - Primary .110, Secondary .107; Metering Rods - .075 x .047; Step-Up Spring - orange (5" Hg) and there all right in the ball park for a 400ci engine with a radical cam so this is why I am stumped on the poor or better yet lack of an Idle.

Believe me when I say that I have mulled over this quite a bit before I even thought about starting a thread and have considered all the angles I can think of, talked to the Comp tech guys & Edelbebrock to no avail. To be honest I just want to figure it out to say that this engine did not get the best of me as it would be the first that has

 

Well I am about to get out the degree wheel and degree this cam in the car which would be a first for me as I have always done it before set the heads up and I using checker springs on the No 1 int/ ext. The other weekend I went through and verified all the cylinders were opening and closing in sequence with the valve covers off and all of them were right where they needed to be with respect to the balancer and the timing marks on it. Its the craziest thing I tell ya.

I am slowly working more toward the conclusion of the carb/ something funky with the dist. Maybe off vacuum canister or mechanical weights and springs are all wrong for the combo.

 

Get it running, and look for a serious vacuum leak..... That would go with the above suggestion of running too lean..... Are the heads or manifold aftermarket? if so, check for possible mismatch....

4TTRUK

 

Thank you all for the input guys and I truly am grateful. As far as I gather from the responses I am just going to start back from the begging & work from there, it has to be something silly and simple and I will keep ya all posted.

 

Yeah the heads are the RHS X casting and the intake is a ProComp single plane. I do know that the magnum and LA series engines had different intake to cylinder head angles and the bolts were slightly off but I am most certain this is not the case, as they are matched and of the LA series on the Magnum block.

 

I will go over and check again as it never hurts to check twice or even three times to find a vacuum leak

 

Not knowing your wireing is your box a full 12 volts ? then look at your wire to dist and check your signel there. sounds more like a week spark issue to me. also remember as a mopar guy i am sure you have seen this, when LA motors are milled they tend to open at the lower side of the head to intake couseing a bad Vacum leak at the vally area. good luck

 

X100
& before you chase your tail anymore.

 

Idle it down until it starts tripping, then spray a little carb cleaner down the carb. If the engine picks up, you are lean and I would REALLY start hunting vacuum leaks (remember it can leak air in around the bottom edges of the manifold flanges as well.

It really doesn't sound like an ignition timing issue. Even with the dist way out of whack, if it STARTS, the engine should still want to run below 1500, right?

 

Yeah I forgot to mention in the last post but I had metered the dist and checked for 12V going in and it good

 

Your post triggered a thought of mine, when I first got the engine to fire on the break in run I noticed that one of the intake bolts was not installed and some coolant was leaking out. I wiped it up and was oily so I killed the ignition and checked the oil and sure enough it was milky. I poked and looked around and the only thing I could think of was the intake fwd coolant passage was leaking so off cam the intake and it was in fact the pass bank passage leaking. Got that sealed back up and have run the engine multiple times working the lack of idle issue and no oil in the water so that is fixed. Now I am beggining to think that there is a real possibility of an air leak in the valley under the intake, but the engine is not running lean if anything it is running rich because the plugs are somewhat sooted up and not coco brown. My buddy is running a ProComp single plane intake, I am not familiar with them at all. Are they cheap overseas junk or American made? I have not been able to really find anything on them. Well this weekend I am going to give it another whack and see what I can not drum up or possibly find the solution. I will keep you all posted of my findings and again thanks for the outside thoughts.

 

I had an issue before where the advance spring in the distributor was really weak and would kick in full advance around 800-1000 rpm causing the engine to run really fast. If you did dial it down then the timing would spring back 20 degrees and stall the engine. In my case I could see it happening with the timing light. Harder to tell for sure if you can't see the timing marks. You could wiggle the rotor with the engine off, compare the spring pressure against a known good engine.

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I mean the rotor inside the distributor.

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The carb cleaner will tell the story. Remember that if you go lean to the point of misfire, the fuel will soot the plugs or wet them from poor combustion.

 

I believe Procomp is Chinese.....and with quality problems.

 

Did you figure out the problem yet?

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Its worth a shot, next time I am over there that will be one of the things I check.

 

Your absolutely right, I have the carburetor based at 1 1/2 turns out on the idle screws and the floats are set correctly at 7/16" closed and 1" hanging open with the jets, metering rods and springs all set up for a 400ci engine.

 

I have never heard of them before till his engine had one sitting on top and I am not impressed with the quality either for that matter. If I can dial it down to a bad vacuum leak at low RPM I am going to suggest to him bite the bullet and by a new intake manifold, an Edelbrock, Offy anything other than whats on there now.