TBI to Vortec Head Conversion Tuning Issues
 

Ok folks, as usual I've read multiple post's throughout the web on TBI to Vortec upgrades and tuning issues but I just wanted to see if anyone here could add any suggestions/input to this weekend warrior motorhead.

Truck Upgrades:
1987 Chevy 4x4 V10 5.7L 350 TBI, upgraded to Vortec heads, new GMPP TBI Vortec intake manifold, bored .40 over, RV cam, self aligning roller rockers, edelbrock shorty headers with smog, true dual exhaust, 700R4 tranny, rebuilt stock throttle body w/adjustable fuel reg and stock injectors. I eliminated the smog pump and all of the plumbing and capped off the port on the exhaust manifold on the passenger side. Purchased an egr tube for a 96 TBI so I can route the exhaust gases from the exhaust manifold to the new positioned egr on the intake manifold next to the thermostat housing.

Startup:
Started right up with hesitation, at first it ran rough at idle and had some backfire & popping when revved and initially couldn't set timing and idle due to vacuum leaks and had sparkplug wires 5&7 reversed, fixed leaks and sparkplug wires then set idle @ around 1500ish rpm's and advanced timing to 10 deg. Sitting at idle then increasing engine rpm's slowly then aggressively is not a problem, no missing no hesitation but when I take her out on the road there is no increased power, can't even spin the tires. At best she's sluggish with a noticeable hesitation when I open her wide up down the road. I found that the sparkplug wire on cyl #6 was burnt and exposed to arcing against the oil pickup tube <need to protect the wires from the headers>!!

Probable Fix??:
I will install a new set of sparkplug wires...I have yet to set the fuel pressure on the new adjustable regulator to around 18-20lbs?...I also have two new fuel pumps I have to replace in the fuel tanks for increase fuel flow and adjust the fuel regulator to match the increased hp. Will I need to upgrade the ECM prom to match the new mod's? And btw, the builder spec'd the motor at around 320hp without being dyno'd.

Sorry for being longwinded but wanted to know if anyone has any input/suggestions/fixes on my issue?

Thanks in advance!!

With TBI, there is an disconnect, to disable the electronic advance. Disconnect it and set the base timing at 0 degrees. Reconnect it, and it will automatically bounce the base timing 8-10 degrees all by itself.

If you have the base timing set at 10 degree with the advance connected, your going to be really far off.


The base timing on a TBI engine with the advance disconnected shouldn't exceed 8 degrees.

edit - also, I have had a lot of trouble from MSD coils and the ignition module that goes in the distributor. Better luck with factory replacement stuff.

Sorry, one more thing.

TBI's are notorious for not being machined flat on the bottom. Even with a good gasket they can suck air between it and the intake. Whenever I have one off, I run the base on my big sander just to flatten it out. Seems to stop that gasket from breaking down too.

Maybe on a stock engine, the vortec heads are going to want 10-12* BTDC to run on the stock chip. Not to mention the fueling from the injectors needs to match.

If the engine really is 320 hp its going to need a huge amount more fuel. The stock 61 lb/hr @ 13 psi injectors are good for ~230 HP @ 85% Duty Cycle. The 320 hp engine needs ~85 lb/hr injectors to stay under 85% duty cycle. The chip needs to be programmed with up to 50% more acceleration enrichment fuel from both the TPS and MAP. The vortecs swallow fuel when the throttle is opened and a lean backfire is the usual result.

Hey guys, great input and advice!!

Once I tune the fuel system i.e. replace the fuel pump in both tanks, set the fuel pressure since I installed a tunable fuel pressure reg, and purchase a custom prom chip for the new setup, guess I'll see if this will hopefully be the solution.

One other thing, I notice at idle the fuel injectors are basically dripping instead of spraying, bad injectors too or is this the norm at idle?

Thanks a bunch, guys!!

I know you probally don't want to spend any more money on this, but perhaps you should look into the ebl flash. It replaces the prom with a system to flash tunes in instead of the prom burning. If you aren't over there, go on fullsizechevy, there is a guy there named doober who is running it on his tbi vortec headed 383 and his works great

Thanks, Richard....I'll ping in and look at his setup!

**On another note in this thread, for those who read this thread please pray for those who put themselves in "Harms Way"...I ETS'd from Ft Hood many moons ago and the current shooting at Ft Hood holds close to my memory banks since leaving the Army in '76. I currently live in Waco TX and since I've lived here way too many tragedies have taken place in Central TX....Luby's massacre in Killeen, Branch Davidian compound in Waco, the first Ft Hood shooting 5 yrs ago, and now this current shooting. I remember vividly when the recruiter for our Battalion committed suicide in his car in the parking lot. He was a Vietnam Vet with apparent PTSD. Our Vet's and current soldiers needs our govt's assistance in every way, form, or fashion!!

<just sayin>