GMC Truck Forum banner

1 - 20 of 34 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter #1
Hey guys! i hope someone could help me out with this. I have a 95 serria with the 350 TBI motor. I recently just rebuilt it (will post pics) with vortec heads that are now 1.94/1.6 and gasket matched port polish etc, and im using the GMPP vortec TBI intake. now i think i may have made a mistake on picking out the right cam. it is as follows; valve lift .447/.447, cam lift .298/.298, SAE duration 291/291, .050 duration 223/223. ive been told this cam is usually used and works well in the 327 motors. Other mods to the truck are MSD 6AL, Blaster2 coil, Full length hooker headers into true dual 2.5" pipes with equilizer. Mufflers are Flo-Pro (dont like them, any suggestions for new ones?? these ones are to loud!!!) Its apparent that i need a custom chip made for my truck but what are my options or what else do i have to do?? Fuel pressure is at 12psi, stock injectors to small ?? Its weird how it runs, it feels like its starving for fuel , its very hesitant and very boggy. My air/fuel guage tells me that its lean while on my on gas but yet sometimes its rich, its really inconsistant. it seems smooth at idle but you can hear the ecm try and bring it down but goes to far and speeds it up again. Any info would be great!!!
 

·
Chevy Owner
Joined
·
1,364 Posts
Are you still running your original fuel pump? if so, how many miles was one your truck before the rebuild? Whats the fuel pump sound like when it is running? Not saying that's your problem, but the hole inconsistant fuel pressure makes me wonder :think:...Being a TBI, I'm almost positive it doesn't need as much pressure as the Vortec's...so 12 psi sounds about right. It may need a new Fuel Pressure Relay like my 94' Blazer needed. It did the same thing that your describing, great pressure, but ran weird and felt really boggish. Turned out that the relay would work fine at idle, but at mid-range when gas would be needed, it wasn't "telling" the pump to pump enough fuel, leading to the bogging down. Sounds very similar to my problem so I hope this helps ya out.
 

·
Registered
Joined
·
1,895 Posts
There are several things wrong here.

1. 12psi is nowhere near enough fuel if you still have the 55lb injectors.
2. What is the LSA of the cam?
3. Why did you chose a single pattern cam?
4. You should be using the 65lb injectors from a 9C1 car, at close to 14psi. To verify this monitor you BLM count at the 02 sensor, and adjust the FP accordingly.
5. The vortec heads will run like crap on a stock TBI tune. I would not be at all surprised if a bone stock TBI was quicker than this truck with a stock tune and that cam.
6. You will also need to bore out your TBi unit, or find one from a 454 truck. The 1-11/16" throttle bores can't flow nearly enough air to support a pair of stock vortec heads.
 

·
a.k.a. turbodan
Joined
·
3,220 Posts
in my 95 tbi 350 i put in a cam too big for it, it was a 440,440 lift, but i dont remember the other numbers. it sounded good at idle but was rich and boggy. hesitated off the line. a computer reflash solved the problem and i changed my fuel filter at the same to be on the safe side. my fuel pressure was at a constant 13.
 

·
Registered
Joined
·
36 Posts
Discussion Starter #5
Fuel pump i think is the original, i never changed it, trucks at 158,000 KM, (around 98,000 miles) and im the second owner of the truck, and have had it for 3 years. fuel pump is very quite too, ive heard some other trucks fuel pumps and they are annoying!!. Doesnt the fuel pump just "turn on" when it needs too, pump a steady pressure, and let the fuel pressure regulator maintain positive supply pressure to the throttle body? And/Or is it a variable fuel pump that is adjusted to maintian a supply pressure? Eg. runs at a variable Voltage (5volts-12volts) depending on the fuel pressure ? ive seen the modualting type in alot of newer cars/truck, but i didnt think my truck had it. I tought the pump just turned on, put out 15 pst MAX or so, and the regulator on the t-body bled off pressure to maintain 9-13psi depending on what it was set to at factory. Im wondering if my regulator might be screwed up now, cuz it doesnt seem to change the pressure on the supply line when i increase or decrease the setscrew on the bottom of the regulator. i also just rebuilt it replacing all gaskets and screens. and a new diaphram for the regulator!!

I also noticed that i have little droplets of water running down the sides of the throttle bores, its been like that for a long time even beofor the rebulid, figured it was normal., but never thought it might be a problem.
 

·
Registered
Joined
·
36 Posts
Discussion Starter #6
fullthrottledan said:
in my 95 tbi 350 i put in a cam too big for it, it was a 440,440 lift, but i dont remember the other numbers. it sounded good at idle but was rich and boggy. hesitated off the line. a computer reflash solved the problem and i changed my fuel filter at the same to be on the safe side. my fuel pressure was at a constant 13.
did you adjust your fuel pressure?? or just leave it the way it was from stock ?
 

·
Registered
Joined
·
36 Posts
Discussion Starter #7
91_bowtie said:
There are several things wrong here.

1. 12psi is nowhere near enough fuel if you still have the 55lb injectors.
2. What is the LSA of the cam?
3. Why did you chose a single pattern cam?
4. You should be using the 65lb injectors from a 9C1 car, at close to 14psi. To verify this monitor you BLM count at the 02 sensor, and adjust the FP accordingly.
5. The vortec heads will run like crap on a stock TBI tune. I would not be at all surprised if a bone stock TBI was quicker than this truck with a stock tune and that cam.
6. You will also need to bore out your TBi unit, or find one from a 454 truck. The 1-11/16" throttle bores can't flow nearly enough air to support a pair of stock vortec heads.
The Lobe Centers of the cam are 110int/118exh. I got this cam because the machinist i delt with suggested it, since he has used it sucessfully in alot of 350's. ( its a melling performance cam, 22200, WG-996)
As for the vortec heads and everything else i figured id need to boost of the fuel pressure a lot but figured it would still be somewhat driveable.
As it sits sleeping in my garage right now, it sure isnst something i want to drive everyday for work,
As for the 454 TBI unit, is this a Must?? or just recommending it? i was told mine would surfice, just wouldnt produce as much power.

I guess my options are open. if i have to change the cam i will. if i have to get new injectors i will!! What ever i have to do i will, just not exactly sure what to do!! Im not looking for all the power in the world out of the motor, just better gas mileage, good towing, and some good highway passing speeds, (and the ocasional burn out on cruse nights =] )
 

·
Registered
Joined
·
1,895 Posts
brando said:
The Lobe Centers of the cam are 110int/118exh. I got this cam because the machinist i delt with suggested it, since he has used it sucessfully in alot of 350's. ( its a melling performance cam, 22200, WG-996)
As for the vortec heads and everything else i figured id need to boost of the fuel pressure a lot but figured it would still be somewhat driveable.
As it sits sleeping in my garage right now, it sure isnst something i want to drive everyday for work,
As for the 454 TBI unit, is this a Must?? or just recommending it? i was told mine would surfice, just wouldnt produce as much power.

I guess my options are open. if i have to change the cam i will. if i have to get new injectors i will!! What ever i have to do i will, just not exactly sure what to do!! Im not looking for all the power in the world out of the motor, just better gas mileage, good towing, and some good highway passing speeds, (and the ocasional burn out on cruse nights =] )

You don't HAVE to do any of the things that I listed, but it would run 1000 times better if you did. A vortec head swap is not a plug n play deal; and you complicated even further by adding a cam that is not very TBI friendly. With that much overlap, you have basically moved the powerband up so high that you will have little power from idle up to 3000rpms. In a light car, this would be a nice combo, but not in a truck that weighs 4200lbs. After you get it running, the first thing I'd do is get a higher stall convertor. It won't be able to get out of its own way without one.

The 454 TBI and 9C1 injectors would be nice, but they're not necesary. If you stay with the 350 TBI unit and 55lb injectors, you are really limiting the top end, which is where this motor should produce the most power.

What do you consider good gas mileage? I doubt you get over 9 with this combo.

With enough fuel pressure, and a higher stall convertor it should be drivable, but you really need to get it to a dyno and have it propery tuned and scanned.
 

·
Registered
Joined
·
36 Posts
Discussion Starter #9
91_bowtie said:
You don't HAVE to do any of the things that I listed, but it would run 1000 times better if you did. A vortec head swap is not a plug n play deal; and you complicated even further by adding a cam that is not very TBI friendly. With that much overlap, you have basically moved the powerband up so high that you will have little power from idle up to 3000rpms. In a light car, this would be a nice combo, but not in a truck that weighs 4200lbs. After you get it running, the first thing I'd do is get a higher stall convertor. It won't be able to get out of its own way without one.

The 454 TBI and 9C1 injectors would be nice, but they're not necesary. If you stay with the 350 TBI unit and 55lb injectors, you are really limiting the top end, which is where this motor should produce the most power.

What do you consider good gas mileage? I doubt you get over 9 with this combo.

With enough fuel pressure, and a higher stall convertor it should be drivable, but you really need to get it to a dyno and have it propery tuned and scanned.
Interesting. I guess i screwed up!! Not really a good idea to have let my machinest pick out a cam for a computer controlled truck. Any recommendation on a Cam for a TBI setup if i stick with the Vortec heads??

As for the Gas mileage, the whole reason for the rebuild was to get better gas mileage. I was getting about 12-14 mpg on the old motor. And again i went with vortec heads based on "being told" id get better flow and better gas mileage. I figured id need a computer chip to get the best out of the setup.
 

·
Registered
Joined
·
601 Posts
91_bowtie said:
You don't HAVE to do any of the things that I listed, but it would run 1000 times better if you did. A vortec head swap is not a plug n play deal; and you complicated even further by adding a cam that is not very TBI friendly. With that much overlap, you have basically moved the powerband up so high that you will have little power from idle up to 3000rpms. In a light car, this would be a nice combo, but not in a truck that weighs 4200lbs. After you get it running, the first thing I'd do is get a higher stall convertor. It won't be able to get out of its own way without one.

The 454 TBI and 9C1 injectors would be nice, but they're not necesary. If you stay with the 350 TBI unit and 55lb injectors, you are really limiting the top end, which is where this motor should produce the most power.

What do you consider good gas mileage? I doubt you get over 9 with this combo.

With enough fuel pressure, and a higher stall convertor it should be drivable, but you really need to get it to a dyno and have it propery tuned and scanned.

:word:

As for mileage, DON'T GO WITH AN AGRESSIVE CAM IF YOU WANT MILEAGE! I really think the cam is killing you.

For performance, the crane 2030 is highly reccomended. Even with a milder cam I'd still reccomend a tune to account for the vortech heads.
 

·
Registered
Joined
·
601 Posts
Oh, and I don't know that you'll be able to do much better that 14-15 city, that is all I could ever get with my 95. My dad had a 305 stick c1500 and was able to get 16-17 (he babies it, gets 17 with his '03 sierra 4x4 4.8 where as I get low 16 high 15).
 

·
Registered
Joined
·
36 Posts
Discussion Starter #12
jebx said:
Oh, and I don't know that you'll be able to do much better that 14-15 city, that is all I could ever get with my 95. My dad had a 305 stick c1500 and was able to get 16-17 (he babies it, gets 17 with his '03 sierra 4x4 4.8 where as I get low 16 high 15).
If i could get 14-15 in the city, and more on the highway, that would be great!! im starting a job out of town (about 4 hour drive) and i wanted to get the better gas mileage for the travel. I was also lacking the highway passing speeds on the old motor since i was pretty bagged out.
 

·
Registered
Joined
·
601 Posts
Might want to look into a 4 cylinder s-dime for that kind of driving (assuming you are dead heading there). I don't know if you are lifted or anything, that hurts mileage. I would expect 13-15, that is what I have always gotten in the ole 95. I never took it on trips unless I was towing, too expensive so I can't tell you accurately highway mileage.
 

·
Registered
Joined
·
36 Posts
Discussion Starter #14
jebx said:
Might want to look into a 4 cylinder s-dime for that kind of driving (assuming you are dead heading there). I don't know if you are lifted or anything, that hurts mileage. I would expect 13-15, that is what I have always gotten in the ole 95. I never took it on trips unless I was towing, too expensive so I can't tell you accurately highway mileage.

Lol, a 4 banger!! those are the things i wanna drive over!! as for lifted, i got 2.5inch blocks in back and cranked torshin bars running on 33's.

13-15 would be nice if i had the power back, but like i said the motor needed some freshing up, she had a hard time on the highway passing, and towing anything.
 

·
Registered
Joined
·
1,816 Posts
I managed 16 mpg driving from Houston, TX to Dalhart, TX. Its amazing what driving with a lighter foot can get you. Previous to that the best I ever got out of it was 13 mpg. Then, I figured it couldn't hurt to accelerate as slow as possible and keep it between 65 and 70 instead of 70-75. Other than that my truck is stock with a fresh tuneup, a K&N drop in, flowmaster cat back, 285/75/16 BFG a/ts and 3.42 gears. Oh yeah...and 163,000 miles on a 1994 TBI 350 at about 5000 lb
 

·
Registered
Joined
·
36 Posts
Discussion Starter #16
Does anyone else have any comments or sugggestion on getting a Tune to properly work this combo? Anyone out there that does custom programing that i could talk to?? ive heard of websters and Ed wright mentioned on the fourm how do i get ahold of them ? Ive talked to nelson but he doesnt have a chip out for my model truck yet.

If i changed my Cam back to a stock one or mabey use the edelbrock 2030 (i think) but left the vortec heads on, with 65 lb injectors. do you think i could get some decent mpg out of it ?? and i guess i probley would still need a chip cuz of the vortecs right??

How many miles do you ususally get out of stock injectors ?
 

·
Registered
Joined
·
1,895 Posts
Lyndon Wester is one of the guys I'd call.

The Edelbrock TBI cam is the 3702, and it's JUNK. The 2030 is made by Crane, and I highly recommmend it. :D

Yes, the vortec heads alone require a custom PROM.

The injectors should last quite a while. There are 2 screens per injector that eventually become saturated, and cause the fuel to drip instead of spray. These screens can be replaced in a matter of minutes. If the injectors are spraying the fuel in a well-defined cone shape, then everything is just fine. If you see droplets, or any irregularities, then I'd suggest a set of flow-matched injectors from Turbo City. Make sure the tuner knows that you plan on using the 65lb injectors.
 

·
Registered
Joined
·
36 Posts
Discussion Starter #18
91_bowtie said:
Lyndon Wester is one of the guys I'd call.

The Edelbrock TBI cam is the 3702, and it's JUNK. The 2030 is made by Crane, and I highly recommmend it. :D

Yes, the vortec heads alone require a custom PROM.

The injectors should last quite a while. There are 2 screens per injector that eventually become saturated, and cause the fuel to drip instead of spray. These screens can be replaced in a matter of minutes. If the injectors are spraying the fuel in a well-defined cone shape, then everything is just fine. If you see droplets, or any irregularities, then I'd suggest a set of flow-matched injectors from Turbo City. Make sure the tuner knows that you plan on using the 65lb injectors.
Does anyone have Lyndon Westers Contact info?
 

·
Registered
Joined
·
36 Posts
Discussion Starter #20
Thanks guys, i got a hold of Lyndon Wester, Hes going to make me up a chip for my truck!! He suggested to run 80lb injectors, but im having a hard time finding any. Does anyone have for sale used or new, or know where to get decent priced 68# to 80# injectors for gm tbi??

Thanks again guys for all your help
Brandyn,

Ill post some pics soon , whats a good image hosting service, i forgot the password for my gateway server and cant save any pics on it!! Oops! dont have time to reload it ither.!!
 
1 - 20 of 34 Posts
Top