New engine, won't run!

[tonyscustomrides]

the little contact that comes out below the coil, make sure its fully exposed so it can touch the spring on the rotor. my 64 impala ran weeks before i changed the engine wiring harnnes and i couldnt get it to fire. took the cap off, and noticed the contact was pushed up to far/ broken so some of the plastic of the cap was in its way. the little flat spring on the rotor was only touching half the time... just another possiblity.

[Dieselwrencher]

It is amazing to me how many people will tell you a TD dist. is different than a standard deck big block. The only difference I know of is there are 2 different styles of drive shafts. One is a hex and one is slotted. His is slotted and in correct. I am going to dump oil in the cylinders for him and let it sit so we can try that. By all rights this thing should fire right up. I know it has cast rings and has been rebuilt sitting inside for atleast 2 years. I know what parts went in it and I know even if the cam was installed 180* off once you relocate the dist. 180* it should fire. This thing tries to fire but as soon as you put gas to it it quits trying to start. It has good spark, good compression, good everything. It is a real PITA! I did just think of something...... I highly doubt it matters though. This engine did have open chamber heads and it now has closed chamber heads. It shouldn't effect anything except maybe more compression, but maybe only by 1/2 a point if anything. For those of you that have never had a tall deck apart, the pistons are flat top. I have seen semi-closed, closed, and open on all different tall decks, so that shouldn't matter. I'm just thinking out loud here.

[Restrorob]

Do you KNOW this engine is firing PROPERLY under compression ?

This is a tall deck engine, Doe's it have the proper intake ? IE, Non seating on the lower inside intake ports causing loss of vacuum ?

[Dieselwrencher]

Yes, it is a stock cast iron tall deck intake manifold. Do I know it is firing properly under compression? Uh apparently not because it won't start. It is timed right, it has compression, fuel, and nice spark. See why it is a PITA?

[glock35ipsc]

All I can offer is the fire triangle from my firefighter days... fuel, heat, oxygen. Take any one of them away and the fire goes out.

If fuel is squirting into the intake, that problem is eliminated. Even if it's not metered properly, it should run. Rough, but run nonetheless.

If you have spark at all the plugs, that problem should be eliminated.

That leads me to believe that it is a timing issue. After reading everything here, (if you haven't already) I would be pulling the timing cover and verify with my own eyes that the timing marks are dead on (crank mark up, cam mark down, both pointing at each other). From there, I would loosen every rocker and readjust them. Then reinstall the dizzy. Double check the plug wires for proper order (clockwise 18436572). Doesn't matter at all where the #1 wire is on the cap so long as that is where you set the dizzy up to be at. Double check all the cap and coil parts and that they are assembled right. While it shouldn't affect it starting, check plug gaps, see if any are slammed shut completely.

[Dieselwrencher]

I need to verify the valve settings for this cam. It is an L-88 cam and is solid lifter.

Even if the timing is 180* off it would be cured by turning the dist. 180*, that still didn't help. It has to be something simple I'm guessing.

[glock35ipsc]

I'm not suggesting that the timing set is 180° out, I'm thinking more like 1 or 2 teeth off. I have been 1 tooth off before and when trying to start, it would just spit and sputter but never fire.

[MR .T]

I had a problem like this once and it was a bad ground from the engine to the chassis. Im assuming your sure the valves are lashed properly and not hanging open at all?

[68GMC454]

my problems usualy lead to a bad ground from the engine ot chassis, most of the time forgettign to put it on in the first place....

[Dieselwrencher]

Originally Posted by MR .T

I had a problem like this once and it was a bad ground from the engine to the chassis. Im assuming your sure the valves are lashed properly and not hanging open at all?

I assuming they are set right. The guy I got the cam from told me they were supposed to be set at .024 intake and .026 exhaust. I'll have to check them because Mathew set them. IDK, the truck is back outside until we can get a stall opened back up to mess with it some more.

[Dieselwrencher]

Originally Posted by 68GMC454

my problems usualy lead to a bad ground from the engine ot chassis, most of the time forgettign to put it on in the first place....

I have had this happen before too, but usually when you have a bad ground, there is no spark and this has spark.

[68 TT]

Originally Posted by Dieselwrencher

It is amazing to me how many people will tell you a TD dist. is different than a standard deck big block. The only difference I know of is there are 2 different styles of drive shafts. One is a hex and one is slotted. His is slotted and in correct. I am going to dump oil in the cylinders for him and let it sit so we can try that. By all rights this thing should fire right up. I know it has cast rings and has been rebuilt sitting inside for atleast 2 years. I know what parts went in it and I know even if the cam was installed 180* off once you relocate the dist. 180* it should fire. This thing tries to fire but as soon as you put gas to it it quits trying to start. It has good spark, good compression, good everything. It is a real PITA! I did just think of something...... I highly doubt it matters though. This engine did have open chamber heads and it now has closed chamber heads. It shouldn't effect anything except maybe more compression, but maybe only by 1/2 a point if anything. For those of you that have never had a tall deck apart, the pistons are flat top. I have seen semi-closed, closed, and open on all different tall decks, so that shouldn't matter. I'm just thinking out loud here.

The chamber size change should really jack the compression up well beyond half a point. I went from 180 pounds of cranking compression on an LS-6 cammed 454 with 11 to 1 compression up to 215 pounds with a head change to closed chamber heads. I couldn't even run av gas in the thing, it needed race gas to run right. On 100-low lead it would pop and miss at anything under 8 degrees advance and rattle horribly from detonation at anything more than that. It was a complete dog with the av gas and barely ran at all that way. WOT was completely out of the question.

I had an L-88 crate motor in my Camaro back in the late 80's. The L-88 cam is pretty big and probably builds more cranking compression than the LS-6 cam does as it was more of a street cam. Even with flat top pistons this engine may have 11.5+ to 1 like cranking compression with the cylinder pressure it probably builds with the L-88 cam. It may not have the spark energy needed to fire that much compression. When you add fuel with the throttle when cranking it just makes it worse. The static compression would work fine in an engine with a different cam.

Did I read that right that this engine has the tall deck iron truck intake on it with the L-88 cam? All the tall deck motors I have seen have the very small port heads on them for building low end torque. That cam is designed around the air flow of rectangular port heads and the power band is out of reach of a stock valve size oval port head motor, even the large oval ports.

Peak torque on mine was over 5000 RPM and the HP curve was still climbing when I told the dyno operator to let off at 7000 rpm.

[Dieselwrencher]

This engine has heads off a 69 396 so they aren't your typical tall deck smog head. And this intake has the same port structure (Large Oval) as the GM marine intakes that seem to make decent power. This cam isn't huge, and there is no way this thing has more than 10.5:1 compression. They only had 7.5 or 8:1 stock. At most it may have 9:1 with the closed chamber head. Think about this. The 396 that these heads came off of were raised top pistons, aka closed chamber pistons, with the closed chamber heads, and was 10.5:1. Take that area away from the closed chamber piston and add in the fact it has flat tops and what do you have? Less compression. The tall deck pistons aren't even reallt flat tops, they have a recess across the whole top. I highly doubt this thing needs race gas to fire.

[britnjc]

Correct me if I'm wrong but the motor is firing. It is igniting but will not sustain combustion...

[68 TT]

Originally Posted by Dieselwrencher

This engine has heads off a 69 396 so they aren't your typical tall deck smog head. And this intake has the same port structure (Large Oval) as the GM marine intakes that seem to make decent power. This cam isn't huge, and there is no way this thing has more than 10.5:1 compression. They only had 7.5 or 8:1 stock. At most it may have 9:1 with the closed chamber head. Think about this. The 396 that these heads came off of were raised top pistons, aka closed chamber pistons, with the closed chamber heads, and was 10.5:1. Take that area away from the closed chamber piston and add in the fact it has flat tops and what do you have? Less compression. The tall deck pistons aren't even reallt flat tops, they have a recess across the whole top. I highly doubt this thing needs race gas to fire.

My point was that the L-88 cam creates much more cranking compression than what a typical cam would on the same engine. This engine may have 10.5 to 1 static compression but the cranking compression is that of an engine with much higher compression due to the cam design. It was meant for maximum high RPM HP in a race motor so the cam design builds as much cranking compression as they could get it to. It was never meant to be used in a street car.

The LS-6 cam by comparison lowers cranking compression due to its design so it could run on lower octane gas. What numbers do you get out of a compression test? Stock the LS-6 made 160 psi with 11:1 static compression as a point of reference.

The early 396 closed chamber heads like this motor has can flow pretty well but the 100 cc chambers shroud the valves a little when you punch them out for the 2.19 & 1.88's. I ran them on a 396 for a while and it made pretty good power. It put a 3900 pound 70 Chevelle into the mid 12's with a peg leg 3.31 geared rear end on street tires.

The L-88 cam is pretty big for a street truck. Way too much duration and a power band that builds little to no torque where you need it most.

Cam Style Mechanical flat tappet
Basic Operating RPM Range 4,400-7,000
Intake Duration at 050 inch Lift 264
Exhaust Duration at 050 inch Lift 269
Intake Valve Lift 0.560 in.
Exhaust Valve Lift 0.580 in.
Lobe Separation (degrees) 112
Intake Valve Lash 0.024 in.
Exhaust Valve Lash 0.026 in.

A cam like the Comp XS282S will sound just as mean as the L-88 cam and build a ton more usable power with the oval port heads. I have run it in several oval port big blocks and it is down right incredible with these heads.

Summit Racing Part Number CCA-11-678-5

Cam Style Mechanical flat tappet
Basic Operating RPM Range 2,400-6,800
Intake Duration at 050 inch Lift 244
Exhaust Duration at 050 inch Lift 252
Advertised Intake Duration 282
Advertised Exhaust Duration 290
Intake Valve Lift 0.590 in.
Exhaust Valve Lift 0.598 in.
Lobe Separation (degrees) 110
Intake Valve Lash 0.016 in.
Exhaust Valve Lash 0.016 in.

Lobe designs and valve spring technology has come a long way in 40+ years.

[Dieselwrencher]

The reason this engine has this cam was price. It was cheap and that is what my brother could afford to spend when rebuilding it for his 84 K20.

[68 TT]

Originally Posted by Dieselwrencher

The reason this engine has this cam was price. It was cheap and that is what my brother could afford to spend when rebuilding it for his 84 K20.

I hear you there. I am running a less than optimal cam (too big) with the wrong kind of intake for the application due to my nonexistent budget for the Camaro. I used what I had sitting on the shelf rather than spend money to get better parts. $1000 to spare and I could be making far more power and have a much more streetable car too. Way too many far more important things to spend money on at the moment to even think about putting money into the Camaro.

[Dieselwrencher]

A friend of mine removed this cam from a 468 and sold it to him for $50 with the lifters. It had 300 miles on it. I didn't think he could go wrong. He didn't need a crap ton of power because I knew the truck would be on its top anyway if he did have.

[Mr.Chevy4x4]

Ok, here's another line of thinking. Did the person who rebuilt the engine know the difference between a tall deck and a regular passenger car 427? If they used standard passenger car 427 pistons it would be .400 down in the hole which would give you like 3.5 to 4:1 compression ratio. It would never fire off and run at that compression ratio. My very next move would be to run a compression check on every cylinder.

Just my $.02.

Mike

[Dieselwrencher]

Yes, we know the pistons are different. It has .060 over stock replacement 4 ring pistons in it. When ever it gets brought back in from the cold and snow, we will check some more things.

[brothers69c-10]

Originally Posted by britnjc

Correct me if I'm wrong but the motor is firing. It is igniting but will not sustain combustion...

This is correct. It pops and acts like it wants to run, but won't. No backfiring, just noise of what an engine sounds like when it fires.

[glock35ipsc]

Originally Posted by glock35ipsc

I would be pulling the timing cover and verify with my own eyes that the timing marks are dead on (crank mark up, cam mark down, both pointing at each other).

I'm curious if this has been checked yet?

[68 TT]

Pull all the plugs, squirt a little oil in each cylinder then do a compression test.

If you feel up to it do a compression test first then squirt the oil in and do the compression test again to see if there is any change.

Let us know what the compression numbers are either way.

It may just start after the oil trick but if the compression is too high it may not have enough spark energy to light the mixture.

What ignition system is on this motor? Any chance of swapping on a known good ignition system from another rig?

[Dieselwrencher]

The thing is, it won't even run on ether. Any gas engine will run on ether weather it has weak spark or nice hot spark. When we get it back in, we'll report compression numbers.

[russgt]

Just out of curiosity, what do you guys have on it for exhaust?