Modified L31 with a Proflow 4 system

[Fast355]

I built a budget L31 with flat top LT1 pistons, 305 nodular iron marine crank, lightly worked heads, a GM 6492 roller cam, 1.6 full roller rockers, hooker 2.5" exhaust manifolds and was all set to put a truck intake on it with an 0411 or P59 running it. Then I walked in to the bargain cave at Summit saturday morning. Ended up picking up a brand new Edelbrock Proflow 4 4150 style EFI system for $1200. I hope to get it dropped in and running in the next week or so.

[TriumphR3]

Nice Fast, hope it all comes together.

[Fast355]

Nice Fast, hope it all comes together.

The engine is in and runs, but I am taking the time to rebuild the front suspension, brakes, ac and other stuff.

[tayto]

been waiting to hear your opinion on the Holley exhaust manifolds. i like the heat shields on the exhaust manifolds, looks good!

[TriumphR3]

I like those heat shields too. Did they come with the manifolds or are they custom?

[Fast355]

I like those heat shields too. Did they come with the manifolds or are they custom?

They are L31 350 manifold shields. Still available new from GM for about $5 ea. The dipstick and tube are also for a L31 truck or Tahoe. I looked up many of the part numbers on Nemiga parts.

The one thing I have not been able to find yet is a G-van 454 air duct. The 454 air cleaner and duct has an air inlet that is 2x the size of a stock small block.

[Fast355]

been waiting to hear your opinion on the Holley exhaust manifolds. i like the heat shields on the exhaust manifolds, looks good!

I know they will be down a bit on HP and substantially on torque to headers, but they fit very nicely and I can easily get my hand into the space left over to access the spark plugs and wires. I can get to all the plugs with a standard spark plug socket and 3/8" flex head ratchet.

[Fast355]

Just thought I would add it does run fully on its own fuel system now, TBI tank &sending unit with a vortec pump.. It literally started very quickly and easily considering the timing was a bit retarded and nothing has been messed with on startup fuel. I ran the engine independent of the vans harness, save for the fuel pump relay and fuel pump wiring I had already connected to the Proflows fuel pump output in the process of getting the wiring sparted.

1st start
https://youtube.com/shorts/pN8rTQVkP-4?si=1wuKOreS6DbHoHLx

1st warmup, base timing adjusted to the specified 12 btdc with the set timing mode enabled
https://youtube.com/shorts/RCqewqzyYHs?si=kUCnS_HpZFLTcJG9

Warmed up, Idle air flow screw adjusted.
https://youtube.com/shorts/q6WOUPrYwDg?si=nSpXAcUwvlrc1Uu6

[Fast355]

https://youtube.com/shorts/pJWi1-9njU8?si=eZCuuTd-YbIcK6MR

[Fast355]

Pulled it out of the shop and made a brief test drive. Running well enough already that it stalls the OE TH400 converter ~2,500 rpm and hazes the right rear P275/60R15 even with the 3.08 gear lol.

[Kitch]

Hi Fast,

Always interested in your progress on this.
Whats up with the 12.3V battery voltage on the dashboard display, isn't that a bit low?

Cheers,
Andrew

[Fast355]

Hi Fast,

Always interested in your progress on this.
Whats up with the 12.3V battery voltage on the dashboard display, isn't that a bit low?

Cheers,
Andrew

I need to replace the alternator and finish wiring it up.

[Fast355]

Hi Fast,

Always interested in your progress on this.
Whats up with the 12.3V battery voltage on the dashboard display, isn't that a bit low?

Cheers,
Andrew

Put a 145 amp AD244 on it and wired it up. Charges perfectly now. 14.5 on a cold start and settles down around 13.8-14.0 when it is hot.

[TriumphR3]

Awesome Fast. Everything looks spot on.

[Fast355]

Awesome Fast. Everything looks spot on.

Thanks and they do. Bit of a mystery why long terms and short terms are as far off as they are, but they are correcting in opposite directions and the actual air/fuel ratio is close to the commanded, so does not concern me. The PF4 does not activate the long term correction updates until 165F. I think with more run time and mileage it will all even out.

[TriumphR3]

Yes sir I believe they will. That is really a nice setup.

[Fast355]

I found a NOS, discontinued Spectre air cleaner housing I have had my eyes on. $250 at Summit when Spectre last offered it for $150 on Ebay and it comes with the re-useable 14x4 air cleaner. Seller still has 8 showing available at this time, just FYI. I found some large scoops listed for saw dust collection, that I plan to fit into the front core support on each side of the condenser. Also found some 4 layer, insulated flexible 4" duct that looks like the single layer plastic intake tubes GM used on the 70s and 80s vehicles externally. Thus it is getting a dual 4" cool ram air intake system. Should help out the intake air temps a lot on a hot summer day preventing hp loss.

My plan is to tape off the lid and paint the sides and bottom with universal semi gloss black engine paint, leaving only the lid shiny like the old LT1 or Z/28 350s.

[Fast355]

Yes sir I believe they will. That is really a nice setup.

Thank You

[TriumphR3]

Nothing like keeping the factory look.

[Fast355]

I do like keeping things under cover as much as possible.

Tested the ram air function earlier with the filter in place. With two scoops in place should be even more effective.

https://youtube.com/shorts/MLogcEp7gkA?si=5SWi9iDfGFzOoyL9

[Fast355]

Ducting arrived today, re-tested with the full lengths of 4" ducting. It will be cut to proper length when it is fitted.

https://youtu.be/s6MIf4ckeAE?si=JnvdC8_HneXgL0L5

[TriumphR3]

That is definitely something I’m going to look into, as I’m running a 14” open filter. I had always wondered about heat sink and what kind of affect it would have my 88 C1500

[TriumphR3]

The air cleaner assembly has actually come down even more now. The filter element is actually standard for my C1500

[Fast355]

Just an update on this. I swapped the PF4s single plane manifold for a Mercruiser MPI Dual Plane using the rest of the PF4 system and installed old TH315Y Thorley Tri-Ys and put a mandrel bent dual 2.5" exhaust on this. I have been driving it since last week daily. Runs very strong for what it is. Actually had it pull down a 5
9s 0-60 on my GPS performance app which is fairly accurate. Stall the stock converter a bit, walk it off the line and send it and it moves pretty darn good. 60 mph is about 5,600 rpm in 1st gear. With the GM 6492 roller cam, 1.6 full roller rockers, aftermarket vortecs thw dual plane, 4bbl throttle body, tri-ys and 2.5" free flowing exhaust this little 350 happily and easily rwvs to the 5,800 rpm rev limiter. It does not really fall off up stairs just pulls.

0-60 PF4 Data screen capture with audio
https://youtu.be/UjEKGehu1M8?si=vv7HNWoAbrkuwYSU

~60-65 mph cruise with a 3-2 kickdown and acceleration to ~85 mph

https://youtu.be/BjKfFEwvVKA?si=RqVgVX5j0vO_-Qyi

What it sounds like with the headers, dual 2.5" mandrel bent exhaust using the dual in/dual out magnaflow built turbo muffler. Unkowingly the tail pipes were welded up with a chunk of shreded brake lathe silincer band inside one of the, they had been laying around my friends muffler shop for years before we cut them up and made the fit. XP5033/XP5034 tailpipes for a GM A-Body modified to fit the van.

https://youtube.com/shorts/AP9oFP9kMyk?si=vUluyWGMnH-6m_AD

[Fast355]

When I bought the old girl, the previous owner had removed all the rear seating. I love that it looks like a heavy conversion van on the exterior but it only has the front swivel buckets inside and the walls and headliner. All the heavy rear seating was already removed to turn it into kind of a plush cargo van. I am about to build out the interior and take it on the Hotrod Power Tour in June.

That 10.25:1 mildly cammed 350 with aftermarket vortecs, the port fuel dual plane, 1,000 cfm 4150 throttle body, and headers is a potent combination even with the stock TH400, the stock GM "high stall" TH400 converter that was behind the TB 305 and the 3.08 rear. I can launch it with the open differential fairly hard too. Bring it up against the converter, walk it off the line and get all the way into it at 10-15 mph. Gpes like a bat out of hades for what it is. I need to mess with the TH400 governor a bit more as it tends to bounce the 5,800 rpm rev limiter a couple of times after I drilled the outer weights to make them lighter and swapped the inner weights and springs for lighter TCI ones from an old governor recalibration kit I had laying around. I would like to get it shifting at 5,500-5,700 at WOT leaving the 5,800 rpm limiter. I think I am going to try the drilled outers and stock inner weights and springs. I have all the stock weights inclusing outers and inners and the stock springs in a ziplock in the top drawer of my toolbox.

I have scoured the junkyard listings, ebay and the like for the past year to try to find a 454 TBI G30 air cleaner duct and I have yet to find one. I have the much larger 454 air cleaner that is van/rv specific and hope to find the darn rubber intake duct someday that matches the larger air cleaner with its 2x as large snorkel. The stock TBI SBC air cleaner and ducting is pulling about 1.6 in/hg vacuum at 5,500 rpm.

I decided not to run the aftermarket setup, it is a very tight fit in the van engine bay and I do like the more stock look underhood.

[Fast355]

Edelbrocks base tuning is extremely rich out of the box and their AFR targets were insanely rich. With the cats on it, I am targeting 14.7:1 at idle and cruise and 12.5 in power enrichment they call acceleration. With this mild near stock like 6492 cam it burns very cleanly and is getting excellent fuel economy cruising around even turning ~2,750 rpm at 70 mph. The gear ratio calculator shows it should be turning 2,600 rpm @ 70 but with the TH400s non lockup converter it is a bit higher. ~150 rpm slip cruising at 70 mph is not all that much for something that is flash stalling nearly 2,800 rpm. On level road it is pulling about 18 in/hg vacuum cruising along at 70 mph, plenty of torque in reserve to climb grades and accelerate in high gear.

Oh I also ran it on 87 to start with 14* initial and 29* total timing at 4,000 rpm. I put 93 in the tank, bumped it to 16* initial and 34* total at 3,600 rpm and it woke it up like crazy. With 34* total commanded initially it was showing 36* total. Ended up that it was due to the vacuum advance adding timing with the air cleaner restriction. Pulled it back to 32* commanded and it now runs 34* total that I had initially wanted it to. 10.25:1, 0.038" quench, aftermarket iron vortecs, tiny cam giving 195 psi cranking compression, 93 pump gas, 34* at 3,600 is seeming to be about perfect.

The Proflow 4 out of the box also had the deceleration fuel cut-off set for 1,200 rpm as a minimum, it was not overly happy with that setting. Idled tended to dip a bit and it would try to stall before it recovered coming to a sudden stop. I copied the GM L31 tunes and set it for 1,500 rpm. It is much happier with that RPM value.

I also have a theory to try out on the throttle body minimum air idle screw. It has a tendency to stall going into reverse when it is cold as well as when it has been driven and sat a while with the coolant temps between about 100F and 140F it tends to flood a bit on restart. If I crack the throttle it starts much more easily. If I crank it over without throttle, tends to flood out and have to open the throttle a good bit on the second cranking attempt and it blows some grey fuel smoke when it lights off. I have the crank fuel set at the minimim value allowed. I am going to open the throttle plate up enough to make it idle about 50-100 rpm over the commanded idle speed in Park/Neutral thus getting it more air when cranking and right after startup.