racprops

As above?

And what compression ratios can be run with these heads??

Rich

Fast355

iTrader: (2)

65cc

GM had flat top pistons in cars with them and had them at 9.6:1.

For your heavy van especially with TPI, I would suggest using a dished piston and run about 9.3:1.

I ran a 383 at 10.5:1 but it had vortec heads, very tight quench distance and a huge cam as well as ran on 91+ octane only.

For a purely low rpm build I would consider using the 395' Marine cam.
196/206 @ .050,
.431/.451 lift,
109 LSA, 106 ICL.

racprops

WOW Thanks, I am impressed that you are aware of my research into using a TPI in my van.

Did you also see I am trying to use a 383??

Rich

racprops

Houston we have a problem:

Cannot find it.

Thought I had but the numbers are all wrong...sorry.
Rich.

racprops

OK Here is what I am trying to build:

A Chevy 383 with an aftermarket Scat 383 crank, stock 400 5.565 rods with new bolts, my heads are cleaned up #14102193...Swirl port 64CC 87-up...305/350......1.94"/1.5" valves

My pistons are KB Piston Style with a D-shaped cup Piston Material: Hypereutectic aluminum: Block had been prepped for them.

I plan on running an 86 up TPI with MAF.

Everything is stock, no hot rod performance changes. Note I do have a set of cast aluminum samisen intake runners, just in case using them will improve low end torque.

My aim is to make the highest torque at as lowest RPMs possible. I know this set up TPI and Heads will not run over 5000 RPMs.

My plan is to gear the van for fewer than 2000 RPMs at cruse speed of 75MPH. I plan on doing that by adding a second Over Drive. Current transmission is a 4L60E and the stock 343 rear end.

Thanks to this site I have learned a ton of things.

So two major questions remain:

The cam?

And how to piggyback a TPI PCM on top of the Vans original PCM: to control the Transmission.

Thanks.

Rich

Fast355

iTrader: (2)

I would not piggy back ECMs nor would I use the factory 3rd gen MAF stuff. Either use the vans stock TBI PCM moded for multi point EFI or switch to the newer underhood 0411 LS PCM. I did a 94 TBI van to TPI swap years ago with 1997 Vortec electronics. Look into EFI Connections 24x setup with coil near plug ignition. Good engine management will get you closer to your fuel economy goals than the second OD. If you are not towing I would recomeend using a taller rear gear (2.73) and use a higher stall speed to get you rolling from a stop. The net effect would be lower cruise RPM with the same performance. I have an 87 G20 that I swapped a 6.0L/4L80E into and kept the 3.08s. 70 mph @ 1,850 rpm. Using the factory high stall 4L80E converter that stalls at 2,400 rpm you can stand on the throttle and it burns the P295s off the back. Its a stock 6.0L LQ4 short block with ported and milled 5.3 heads and a 2004 LS6 cam. Trailblazer SS intake manifold and shorty headers with a 2.5 to single 3.5" exhaust.

racprops

There are three reasons I want the older PCMs, One) I have a number of them, and in this very site I learned of Highway Mode and am counting on it as well, and I seems nearly impossible to get in any newer systems.

Two they are simple and ONLY concerned with fuel management unlike the newer systems that can even see a burned out tail light...

Three there is a add on board that will allow super tuning everything including even Highway Mode so I can get the most out of it and it now allow flashing the chip so I do not need an eprom burner.

Later I will find a aftermarket Transmission controller to replace the TBI's old PCM.

And I have looked in one newer PCM, a 2003 unit that has synced injection, but all those newer systems need a special spark control. And again NO highway mode.


My number crunching shows my use of am OLD B&W overdrive will do a big RPM drop giving me low RPMs at 75/85MPH and I get to keep the street performance I have already, only more as the new motor will crank out power. And I now have 8 forward gears IF I want them, not a good as a full 8 speed auto, but say I am climbing a hill, I can use gear splitting to shift into 3rd with over drive and use a nicer RPM range that 3rd alone will give, ETC on all four auto gears, although I don't think I will use anything other than 3rd and 4th + overdrive normally.

I would like to see pictures of your install and what kind of MPG you got.

Rich

racprops

There is a guy on Chevy High Performance who claims these heads will: "detonate with over 8.5:1 compression and a 114 to 117 lobe separation cam. Because: The air speed increases to a level that makes the engine operate as a higher compression engine. Venturi effect in the narrow port runner at higher speeds fills the cylinder to make it respond as an 11:1 motor."

Ever heard of that??

Personally sounds like what we WANT!!

Rich

Fast355

iTrader: (2)

0411 has highway mode if you use the Holden platform as the platform ID.

The newer ignition system delivers a much hotter spark and the timing advance is more accurate since it is sensed off the crankshaft.

The 6.0 87 G20 gets about 18-20 mpg running 75-85 mph with the cruise set and the a/c blasting. It is DBW. If I had used a newer 5.3 with DOD that shuts down to 4 cylinders on the highway the fuel mileage would have been about 15-20% better.





.
I had actually considered putting a 5.7 Hemi and 5spd Automatic in it before I stumbled across the 6.0L. The 06+ Hemi engines had the 4 cylinder mode and the transmissions have a 0.67 OD. The a/c compressor was also mounted on the top in the middle with the alternator. They also have no plug wires to burn on the headers. Powerwise the Hemi and LQ9 6.0L are the same at 345 hp and ~380 TQ. I had an 06 Ram that ran 13.20s in the 1/4 with a small cam, headers, 2,800 stall and 4.56 gears but still got 18 mpg highway. 2,500 rpm @ 75 mph. It would accelerate well at light throttle on 4 cylinders in town too.

racprops

How do I switch to the Holden ID?? I looked up the 0411 PCM and it does control a 4l60E transmission, but from the look of your engine, it also needs a coil pack per spark plug and a does it need a vortec crank pick up , painful to install.

This is interesting an article about using a 0411 as a standalone transmission controller...https://sites.google.com/site/sloppy...ans-controller

There are hotter coils I and get for the older engine, and I have a little more control of the base timing setting.

Your MPG is about where I hope to start...

From what I have read a Hemi running in 4 cylinder mode does not get a lot more MPG than it gets running in 8 cylinder mode, I think pumping loses cut into the savings.

Rich

DynoDave43

iTrader: (11)

I have never heard of this. Not once.