New Project and need some advice.......

**Gene Thompson** · 12-07-2022

I am still very new to the programming world of PCM's. I have successfully converted a 99 Tahoe from the "Black Box"
to an 0411 PCM. This got my feet a little wet. Now I am wanting to put a L21 454 with a 4L80 into my 1965 Impala. The L21 uses a
24X Crank Reluctor and a 1X Cam signal which allows for CNP. From what I understand this engine used a "special" PCM.
Since I do not have the PCM I was thinking I could go ahead and upgrade to a P1 or P59. Is anyone familiar with this upgrade?
Any suggestions on what file to start with? I have played around with different base files such as starting with an 8.1 and
segment swapping the transmission along with swapping around the bank for cylinder so I can repin the harness for the correct firing order.
I am sure there is a lot more that I will need to do but I was just curious if anyone else has done this? I am open to suggestions on which PCM,
OS, and which base file to start with. Any guidance is greatly appreciated.

**In-Tech** · 12-07-2022

Hiya,
It seems you are on a good path. Is the L21 still stock and will remain so? If not, you should either start with a 6L 4l80e file DBC(Drive by Cable) and correct or deal with a 8.1L 4L80e file which I have not seen a DBC file for. I have always been curious about this L21 file and I will have one from a TopKick tomorrow. Sucks it has an Allison transmission according to the VIN. The computers are the old LS1A computers(that is what efilive calls them). If not familiar, they are '97/98 corvette or '98 camaro style. Neither came with a 4L80E so a seg swap is unlikely and also you said you don't have that pcm anyway.

If stock, I think we should be able to transpose the VE table and some other things to get you close. Again though, a 2001 6L dbc 4l80e would be a better starting point. Adjust the cu in constant as well as the VE table from the L21.

Tell us more of what your final intention is so we can better advise.

**Gene Thompson** · 12-08-2022

Thanks for the info Carl.
I am actually in the building stage right now. The only thing I plan to do beyond stock is use a ZZ502 camshaft.
Camshaft Specs.....
The duration at .050" tappet lift (intake/exhaust) is 224/234
Lift with 1.7:1 rocker ratio (intake/exhaust) is 527/544.
Valve lash is zero/zero
Lobe centerline is 110 degrees.
So nothing drastic at all. Just sounds real good to me.
I have been debating DBC or DBW. The L21 is factory DBW so I have the throttle body with intake.
However, with all that said I have also kicked around the idea of using an aftermarket intake and a 4150 style throttle body to keep
the under hood appearance some what correct. I believe that this can still be done using the OEM PCM but it may force me to use speed density not sure???
Would this be a bad move in your opinion?

**Fast355** · 12-08-2022

Originally Posted by Gene Thompson

Thanks for the info Carl.
I am actually in the building stage right now. The only thing I plan to do beyond stock is use a ZZ502 camshaft.
Camshaft Specs.....
The duration at .050" tappet lift (intake/exhaust) is 224/234
Lift with 1.7:1 rocker ratio (intake/exhaust) is 527/544.
Valve lash is zero/zero
Lobe centerline is 110 degrees.
So nothing drastic at all. Just sounds real good to me.
I have been debating DBC or DBW. The L21 is factory DBW so I have the throttle body with intake.
However, with all that said I have also kicked around the idea of using an aftermarket intake and a 4150 style throttle body to keep
the under hood appearance some what correct. I believe that this can still be done using the OEM PCM but it may force me to use speed density not sure???
Would this be a bad move in your opinion?

Single plane intake will cost you alot of torque compared to the truck manifold or a port fuel injected dual plane.

**Gene Thompson** · 12-08-2022

Fast355 I agree. I want to use a port fuel injected intake. I have a Pro Flo 4 system on my Chevelle and it works really well but I
want to try and use OEM PCM on this build. So I guess what I am saying is I would be using the same basic setup as the Pro Flo 4
except with the OEM PCM.

Edit.....
maybe I spoke out of turn. I thought that I had seen a dual plane multi port injection intake on summit but it appears I did not.
So maybe I will need to stay with stock intake.