Lunati Cam / Torque Converter Pairing

[CV355]

Hi guys,

I believe I have a Lunati 10503, 114, stock intake and exhaust lift.  It's a cheater cam- previous owner installed it and there is no documentation (I am judging by specs given).  Right now it's also running a ~3500rpm stall torque converter through a C6, 4.11's in the back.  Not very "cruise" friendly.  There is also an Art Carr reverse manual VB that kicks you in the rear every shift- might be swapping in a gentler auto vb.

I'm looking at putting in a 2300rpm converter and 3.50 gears to make the car a little friendlier on the street/highway.  I was advised that this combo may not be good with the Lunati cam that is in there.  What are your thoughts?  I absolutely love the lope and would like to leave the cam alone if there are no major red flags in doing so.  Again, I do not want performance out of this car; driveability is my main goal.  The performance it gets from inherent efficiency is all I care about.

[chilly460]

If I have the correct specs, that's a 224/232 cam on a 114lsa.  Assume this is a 390 or larger combo?

2500 and a 3.50 gear should be fine with that cam, I'd likely advance it 4-6* to make sure it's happy down low especially in a heavy vehicle. 

[CV355]

If I have the correct specs, that's a 224/232 cam on a 114lsa.  Assume this is a 390 or larger combo?

2500 and a 3.50 gear should be fine with that cam, I'd likely advance it 4-6* to make sure it's happy down low especially in a heavy vehicle.

It's a 428 at 11:1 compression. 

[1968galaxie]

How did the 428 run with pump gas and the 3500 stall converter?
Any detonation issues?

Lowering the stall speed and lowering the gear ratio will make the combination much more detonation sensitive.
Advancing the cam will only make detonation more of an issue.

That being said was the 11:1 CR actually measured? (CC combustion chambers, CC valve reliefs, measure deck height, etc.)
Many times CR is less than we think.

[CV355]

How did the 428 run with pump gas and the 3500 stall converter?
Any detonation issues?

Lowering the stall speed and lowering the gear ratio will make the combination much more detonation sensitive.
Advancing the cam will only make detonation more of an issue.

That being said was the 11:1 CR actually measured? (CC combustion chambers, CC valve reliefs, measure deck height, etc.)
Many times CR is less than we think.

I haven't experienced detonation issues but then again my driving experience in the car has been minimal.  The previous owner said the heads were decked 0.030 or so, and the internals are original part numbers (rebuild).  11:1 would be the max based on my calculations.  I only run 93 with a full bottle of octane booster.  Should run fine on 93 otherwise.

I ran calculations based off known values and estimates (don't have how much the heads were decked).  I'm coming up with ~10.5-11.0 at max/min values since the block was bored 0.030"

[chilly460]

If it's truly 11:1, I'd likely not advance the cam too much, as stated it'll be more sensitive to detonation with the longer gear and tight stall. 

It'll run fine with that cam and the 3.50 gear with a 428. 

[CV355]

If it's truly 11:1, I'd likely not advance the cam too much, as stated it'll be more sensitive to detonation with the longer gear and tight stall. 

It'll run fine with that cam and the 3.50 gear with a 428.

Kinda stinks, I don't know what the cam is degree'd to right now.  I wish there was better documentation on it.

[Falcon67]

If I have the correct specs, that's a 224/232 cam on a 114lsa.  Assume this is a 390 or larger combo?

2500 and a 3.50 gear should be fine with that cam, I'd likely advance it 4-6* to make sure it's happy down low especially in a heavy vehicle.

That is not a big cam for a 428.  You're problem with "11:1" is that the 114 is increasing cylinder pressure.  I'd run a compression check to see what the static PSI readings might be.  Agree with not advancing it at all.  Read your octane boost bottle carefully - "1 point" means you're going from 93 to 93.1.  The fuel has gotten crappy enough here that I won't run 10:5:1 with a good size roller cam on anything but 110 leaded race fuel.  91 is crap, 93 has all but disappeared.  Any "93" is loaded up with Toluene which makes for very sooty fuel.

[plovett]

That is not a big cam for a 428.  You're problem with "11:1" is that the 114 is increasing cylinder pressure.  I'd run a compression check to see what the static PSI readings might be. 

I'm not following on why a 114 LSA means more cylinder pressure?  Why do you say that?

paulie

[Falcon67]

Upon review, I have that backwards - vacuum is increased and cylinder pressure is actually reduced, probably because the intake valve closes later.

http://www.hotrod.com/articles/camshaft-shootout-lobe-separation-angle-tested-explained/

[1968galaxie]

I still think an iron headed (unless it has aluminum heads?) 428 without attention to quench distance and having actual CR near 11:1 is asking for issues on pump gas.
The loose converter and low gear ratio helped so the engine was less "loaded"
Changing to a tighter converter and higher rear gear will load the engine much more.
Detonation a very likely result - taking away ignition timing to reduce detonation will just kill power.


Just my opinion.

[scott foxwell]

Find out what your cranking compression is.