PUZZLER!!! My new motors a dog! what did I miss?

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mbaird

mbaird

mbaird
Joined
Dec 10, 2005
Messages
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Location
Boise, Id
rebuilt 360
KB107s
J-heads /2.02s / bowls cleaned up and blended / good springs / Hughes rollers / Smith Bros pushrods
Lunati 262 cam (voodoo) Checked the degree on install
MP Electronic ignition (orange box) / new jacobs coil
Dougs 452 Headers
LD 340
Eddie 1405 ( Have used a 3310 750 and 650 DP as well)
Timing 36 total/ 20 initial (have tried various combos)
checked reluctor phasing
15-16" vacuum at idle
Cylinder pressure 140-150 ... ( a little weak..)

Engine idles at 750-800 sounds fine
Drives smooth

Runs like a decent /6 ! with a lot of rumble... wont even spin the 3.55's and P205/70r14s.
doesnt seem to want to rev past 4500... yet cruises real nice down the hiway.

plugs look lean no matter what jets and rods I throw at it ! Finally went to .107s and smallish rods just to get some color showing ! Way rich now ..Eye burner !

The machine shop installed cam with both dots at 12;00 so I checked it out and unless I screwed up it was dead on...which surprised me !!
But it shouldn't run decent if that was the case....would it ?

I want some input before I tear this thing apart again !


Go for it GURU's !! What's your take ?
 
Both dots at 12???? Cam gear at 6 crank gear at 12. Should really be degreed and that cam is a mite small.would go at least the 268* version.
 
mod5v said:
Both dots at 12???? Cam gear at 6 crank gear at 12. Should really be degreed and that cam is a mite small.would go at least the 268* version.
Click to expand...

he claims he degreed the cam. Maybe he made a big-*** mistake right there

Where are the pistons height wise?

"Simple stuff' is the throttle opening the carb? Secondaries opening?

AND DID YOU actually check the timing mark for accuracy?
 
Sounds like the cam is not in properly. dot-to-dot is not accurate enough. Cylinder pressure is a little low IMO but not fatal. If the carb settings don;t change stuff, you could have an issue there. How many miles on it?
 
installing the cam and degree the cam are two different operations. the first thing that jumps out at me is the marks on the timing gears. the cam gear should be at 6 o'clock and the crank gear should be at the 12 o'clock position. I would start with this. also i would verify the top dead center mark on the harmonic balance r.
 
I corrected the dampened for tdc...
I actually checked the cam degree with wheel and dial indicator....doesn't mean I didn't make a mistake.
I questioned the machinist about using the 12/12 install procedure....I have always used 6/12...

I have thought about the secondaries opening on Eddie...but I know my Holley DP was opening...and it ran sluggish with it...
 
Where are the pistons? With that combo, the pistons need to be pretty much at zero deck, or even out of the hole a hair, depending on the head gaskets. That cam and those heads would work better together if you had left the 1.88 intake valves in it. Those open chambers, big(ish) valves, relatively mild cam, and carb are just not a good match for a combo, unless the heads were shaved and pistons are zero'd. Not sure about the degreeing of the cam, but I think it would be rather anemic even if it is degreed properly. Might try backing the timing off about 3 or 4 degrees, too. I doubt it will do much, if anything, though
 
Help me wrap my head around this 6/12 vs 12/12 deal.

If I install using the 6/12 method then rotate crank 360.... won't they both be 12/12?
 
mbaird said:
Help me wrap my head around this 6/12 vs 12/12 deal.

If I install using the 6/12 method then rotate crank 360.... won't they both be 12/12?
Click to expand...
Yes. I always found if I line up 12 and 6 it is easier for me, closer. :burnout:MT
 
I don't think the 12/12 or the 6/12 install of the cam makes any difference at all. Remember the crank goes around twice for every time the cam goes around so it is a moot point. The next time around it would be at 6/12 if it was installed at 12/12. The thing I would be looking at is, was the correct mark used on the crank gear to time the crank and cam. There are to many marks on a Mopar small block crank gear and the wrong one can be used very easily.

Jack
 
Pistons are pretty much zero deck...you are right about the 1.88s..
I have a 268 voodoo sitting here as well.
This build was supposed to be just a decent runner...nothing exotic... but not a noisy /6...lol
 
Actually, the 12/12 positioning of the crank and cam gears is correct. But as mentioned, probably not the issue. Put a degree wheel on it.

Also, that's a tiny little cam for a 360 with KB107s. Again, probably not the issue. The cylinder pressure to me is way low......but what the heck do I know?
 
mod5v said:
Both dots at 12???? Cam gear at 6 crank gear at 12. Should really be degreed and that cam is a mite small.would go at least the 268* version.
Click to expand...
I agree, the cam is a bit small for the rest of it. The 268 would be much better, along with a 700-750 cfm carb, but if that thing isn't decked, it's still not going to be great. IIRC, my deck height varied almost .030 front to back before I got it decked, with the deepest one being over .030 in the hole. After decking, they are all something like .002 out of the hole.
 
The 12 to 12 should work as well if done accurately (using a straight edge). (Turn an engine over one full rotation after aligning the dots at 6 and 12; the dots will be at 12 and 12.) The 12 to 12 seems to have more possibility for error. Dot-to-dot can get off if you don't use a straight edge.

The cylinder pressures are fair to middlin'; SCR should be in the low to mid 9 range with this piston/head combo. I would expect maybe 150-160 psi? Being low could mean a later intake closing.... could be from a cam retarded 1 tooth. Proper degreeing should catch that but it sounds like the OP is not confident. Did you have the heads off when degreeing so you could check TDC with an indicator? Did you use a dial indicator?

And did the shop know that the crank key does not align up with dot on the crank sprocket? Just checking everything.... a lot of timing problems have shown up suddenly.

That 262 should run pretty lively. Vaccum is good; makes sense with the good idle.

How were the pushrod lengths determined? Block decked or heads shaved? Anything plugging up the exhaust system? Full dual exhausts? Manifold types?

The lack of revving beyond 4500 indicates something plugged or the valvetrain falling apart. Waht valve springs are being used and what closed valve spring height?
 
64physhy said:
Where are the pistons? With that combo, the pistons need to be pretty much at zero deck, or even out of the hole a hair, depending on the head gaskets.
Click to expand...
They work out to be .012" in the hole with no decking and 9.600" deck height. So pretty close to zero deck.
 
All I can add is years ago I had a 440 built and the cam degreed in.He wasn't a mopar guy and he degreed the cam in on the exhaust valve.Ran smooth and like a 318.Degreed the cam in properly and it finally felt like a 440.
 
Say with .030 pistons at zero deck, the Scr Should be a tic under 10/1.This is how I got that; swept(CV) is 748cc, head chamber, plus gasket, plus eyebrows,(cv) = about 84cc.
Scr =(CV+ cv) /cv ; Scr = (748+ 84)/84 = 9.90. That's a pretty good number.

The 262 voodoo when installed at 108LDa should have an ICA of59*. Plugging that into the Wallace calculator shows a Dcr of 8.23(very good) and cylinder pressure of 165 psi. Since your pressure seems to be down, I would get a second opinion and if still low, likely the cam timing is off, or erroneous data has been given or assumed. You know the saying "garbage in/garbage out"

If the cam-timing is right that motor should smoke the tires with 3.55s, and 275s, right through first and most of second, on the street. Mine did with a Hughes HE2330cam, and Eddies.
You didnt mention, or maybe I missed it, what tranny/TC are you running?Not that it's a big deal with that size of cam. Mine was just dump the clutch and drive away. That size cam makes tons of torque down low. It would break the tires loose at any speed below 5000 in 2nd gear. I absolutely loved that cam!
 
Just checking everything.... a lot of timing problems have shown up suddenly.
Click to expand...
Seems like a lost art, timing chains and degreeing cam shafts. All belts now and computer controlled VV timing. :burnout:MT
 
I have all the propped tools for degreeing...cam came out to Lunatis recomendation. ....doesn't mean I didn't have senior moment.

9.90 CR is what I was aiming for on build.

It's funny you mention blocked exhaust...I was thinking about that a few mins ago... but it's all brand new 2.5" system after Doug's headers.-

Why the persistent lean condition? Would wrong cam timing cause that?
 
Used them....Eddie ran better. Engine runs good to about 1800 but goes flat after that....just runs like a low power 318...seems to have trouble breathing up higher..
 
An intake restriction would present, the same as an exhaust restriction.Faulty camtiming is a restriction.
The, will not rev past 4500, and the 14/15 inches at idle,when coupled with the possibly low cylinder pressure,points to bad cam timing. But I've never had a combo like that to diagnose.I'm a little stumped on the persistent lean,tho.
 
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