'51 GMC,4200 Vortec DOHC - Turbocharged

[efi-diy]

Re: '51 GMC,4200 Vortec DOHC - Turbocharged

Quick update... chassis dyno last week - not fully tuned - session was aborted due to a drive train issue.

numbers are at the rear wheels in direct & lock up through a 3.50:1 9"

HP 510
TQ 500

At 4500 rpm, 11 PSI

its amazing how much power this 256 ci engine will make on so little boost. Anyone have a good 9" power loss number?

[horsewidower]

Re: '51 GMC,4200 Vortec DOHC - Turbocharged

That is stunning.

Hmmm, E class engine for Bonneville...

[Darren N.]

Re: '51 GMC,4200 Vortec DOHC - Turbocharged

:o that is some serious torque comin' outta that 6! I bet the truck is a complete riot to drive. ;D

[efi-diy]

Re: '51 GMC,4200 Vortec DOHC - Turbocharged

:o that is some serious torque comin' outta that 6! I bet the truck is a complete riot to drive. ;D

Yep it is ... 40 to 100 MPH goes fast. At 60 MPH if the boost comes on hard the horizon disappears for a bit. Ease into the throttle to much (like 30%) in 1st/2nd below 40 and the tires break loose... Really starting to consider a speed sensitive boost controller to make this more driveable.

Its still not fully tuned.. and the turbo is far from maxed out.

These engines are still dirt cheap - they are starting to catch on but not in a big way - yet. Rods, '60's GM chassis that came with 230/250's, a couple of supra's ( ;D) and Jeeps are starting to get these engines.

A stock 4200 makes either 275 or 290 HP, add a GT37 turbo off of a duramax, at 8 psi there is 425 HP to be had. the only kicker is the early (pre-06) PCM are not boost friendly. So either go aftermarket or '06 or later PCM.

A rear sump oil pan is available to make swaps easier.

[SuperBuickGuy]

Re: '51 GMC,4200 Vortec DOHC - Turbocharged

I wonder if you could have similar results with the 3700? a smallish turbo on my H3 might be a lot of fun.

[efi-diy]

Re: '51 GMC,4200 Vortec DOHC - Turbocharged

Same engine with a bigger bore and minus 1 cylinder - so yes you would get a % increase of what I have.

My engine has 3 performance differences from stock:

- 8.2 CR vs 10.2 stock
- ported head and slightly bigger valves
- 60* @0.050" more camshaft

If you live in an area that doesn't need periodical emission checks the first thing I would do is to get another head and port the exhaust side - flow testing shows its at least 40% choked off to generate passive EGR. Do a re-tune after the port work and I bet there is 20+ HP locked up.

My '06 was rated by GM at 290HP - after the mods before the turbo the bare engine made 350HP stock exhaust mainfold and free flow exhaust. 320 HP with normal NAPA mufflers.

[efi-diy]

Well believe it or not we still have freakin' snow on the ground here.. uggh 5 1/2 month of this shiht is enough....

Since last time - the 4L70E got repaired after it shattered the tailhousing on the dyno.... the master cylinder is now under the floor from on the firewall - mucho better for engine access and providing room to finally re-wire the truck...

So starting with a '99 steering columm which allowed the wonky steering sector shaft to be gone and a full harness extracted from a 99 truck at the local pnp in mid-Jan at -30*F - yep it was officially cold.. but that best time to get un-molested parts, only the hard core go part diving when its that cold...

So the old wiring is now gone and the '99 harness is slowly migrating into the truck starting with the lighting harnesses... The dash harness has undergone a strip to punt the DTRL head lights and other none essential items. Some new features have been added to the harness and its almost ready to go in.

In addition to the 2 '99 fuse/relay panels that came with the stock harness, we're adding 2 more fuse/relay centers under the dash to ease wiring hook up of non-standard items like line-loc, trans-brake, boost control, & manual shift control for the trans (select either full computer mode or full manual using the internal fluid pressure switches and some electronic logic to control the shift solenoids) move the shifter and the trans shifts just like a th350/400 would. Hit the full auto switch and the megashift does its thing..

Once the dash harness is installed, the under hood harness for engine sensors will go in. We're striving to have all the electrical to the front clip, engine, transmission and inter-harness connections done via dephi connectors so if the front clip has to come off the electrical is undo 2 connectors and unbolt it. Ditto for the engine & transmission.

Then the MS3 will be wired in via 4 disconnects - the dress plates are shown in the picture... buddy ooops on one of the plates when laser etching it.... good free help is hard to find.. flat black paint will help...

The plates were water jet cut then anodized and laser etched.. should help make for a cleaner install... The original wiring job was done when the truck was built and I caught flack - it was butt ugly but functional... so this year it was time.....

On the mechanical side a new diff is being readied at Strange to upgrade from the 9" which is sold to another MS'er "Cadillac Dan". Later the 4L80E will be built once funds are available and the truck is running.

Ever see a flame red '62 caddy with a tremec 5 spd, custom EFI ram log intakes... with more gear the tank should get into the 12's this year.. this year its getting full EFI timing/fuel control... and I hear headers are rumored... anyway that's Dan's project...

[efi-diy]

Re-wire update.....

This job is almost as tedious as body work...

I put close to 20 hours in since Friday morning in just the engine compartment and it hardly looks like anything got done...

Front and back lighting harnesses are done/tested.
Internal dash wiring is temp installed to allow progress on the under hood wiring - needed to sort out how to run certain functions under the hood before I can finish the dash stuff.

Seems 60% of the time goes to finding the right connector or wire color & gage... Really trying hard to stay with the GM wire colors to ease future trouble shooting.... All the while modifying the '96 harness to allow fast front clip/engine removal...

Today we installed the under hood fuse/relay center after changing the main mounting surface - some time in its past life the fuel pump relay cavity got really hot and melted the plastic. Some one had relocated the fuel pump relay one slot over into where the A/C compressor relay would go... A new top plate for the fuse/relay center was just $7 from Mouser so I decided to make fix while the harness was out. This meant swapping every contact from the old main plate to the new one - one wire/contact at a time except...

Every try and remove the main buss in a fuse/relay center ?.... had to make enough release tools to disengage all the lock clips at on shot...

Worked one the main disconnect to engine harness/disconnect, got 1/2 half done the other side tomorrow...

Best guess is somewhere close to 700 splices/terminations and/or adjustments will need have been done by the time its running....

decide on routing/function approach
find terminals and/or wire (correct color/gage)
measure
strip
crimp
solder
heat shrink...
repeat

Just once it would be nice to have access to enough material to build from zero rather than rework an existing harness.. go to stores with a shopping list and come out with everything needed.... Oh well guess I'd have to work for GM to be able to do that....

wire wires everywhere....

[TheSilverBuick]

I put close to 20 hours in since Friday morning in just the engine compartment and it hardly looks like anything got done...

I hate when that happens. I cannot for the life of me achieve a clean underhood look. =/

Keep at it. Are you going to make Bonneville this year? Unless I'm mistaken I've managed not to run into you any year =/

[efi-diy]

Quick update, the engine bay wiring is progressing - 90% complete... the under dash is next up uggh....

Spent 7 hours on a road trip to Montana yesterday to pick up the new rear axle for the truck to replace the 9" with a Dana 60 .. My buddy Cadillac Dan wanted the 9" for the '62 + the rear disk brakes that I had in storage, so I decided to upgrade and get a better posi to boot.

Next up once the wiring is done is to build the 4L80e.

[efi-diy]

re-wire again.....

Well the engine side is real close to being done - just missing the wide band O2 install and tidy/tie things up. The under dash EFI/trans control harness is in progress.

Mounted the relay center that will allow full manual control of the 4L6(8)0E tonight so it can start getting wired in.

At least there is light at the end of this one.. still faint, but we're getting there...

Well it will never be hot rod wiring pretty - it is design for ease of service and redundant fuel/ignition control. Once running I'll take another run at tidy... but with spring finally here it time to drive it and leave the tools alone for a bit.

[CTX-SLPR]

Do they make boots for the connectors to hide the backs of them where the terminals press into the cavities? What range of wire sizes do they make to fit those connectors? Seriously thinking about using those on my next rewire.

[efi-diy]

wire sizes

10-20 awg (22 if you fold the wire before crimping). I could not find any boots for the back side - Raychem may have something in their MIL products catalog but expect to pay $50+ a boot.

I got mine from DIYAUTOTUNE - prices are better from DIY than buy direct from the vendor.

Delphi has a 25Amp max current limit on the pins.

[efi-diy]

Re-wire update..... engine side & EFI harnesses completed and beep tested..!

Well finally got to the point where we could beep test the EFI/transmission control harness from the load/sensor right up to where the MS3 and the 4L60E micro-transmission controller plug in.

Next up is to get the main under dash harness finished up (gage wiring etc..) and permanently installed.

The the interior cross-harness needs to be terminated on the EFI/Trans control side.

We have a 4 day weekend here so it should all be done by Monday Yeah! 7 weeks of wiring purgatory...

Then its back to finishing the Dana install and getting the driveshaft shortened.

I started this process back in Jan. with the steering column swap and its getting a bit long......

Still some wiring tidy up to be done once the truck is running - my priority now is to get it on the road.

[SpiderGearsMan]

lookin good bro