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TBI Mods:Snake oil or worthwhile??? Updated 5/19/12 AFPR and Pod Spacer!!!

S

smier

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***(5/19/12)The first group of posts in this thread are grouped together to show the majority of the mods I did to the TBI system and Exhaust in the quest for a great running, dependable, and somewhat economical fullsize 4x4. I have gone back and edited, as well as added photos to try and make the thread as informative as possible to someone looking to do similar mods to a TBI Blazer. I planned this thread to be a one stop tech source for these setups, and will be going back and adding and editing in info as I make further progress. Enjoy!!!***


So over the past year and a half I've been working on not only getting my '91 blazer running perfectly, but also trying to improve it's performance and fuel economy. Overall I've had pretty good success, and I thought I'd start a thread to share what has worked, and what hasn't. Here's the old girl right after I bought her:
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First a little background on my truck, it's a '91 Blazer 4WD with the TBI 350 and an automatic transmission rolling on 31" tires and the stock suspension. When I bought it 6 years ago I thought it ran great, but it had a stuck IAC and a bad oxygen sensor throwing codes, as well as an intake manifold leak I was unaware of. I have since replaced the intake manifold gasket, cleaned and rebuilt the throttle body with a new gasket and O-ring kit. Cleaned the fuel pressure regulator and installed a new diaphragm, then installed a new throttle position sensor, IAC (Idle Air Control), oxygen sensor, new plugs, wires, distributor cap, and rotor. I also had a bad EGR valve. I had to adjust my idle back to stock settings because the previous owner had messed with it because it was stalling occasionally due to all the problems. I also had to adjust my timing back to 0* base timing with the EST wire disconnected. It was set at 8* advanced and would ping slightly under load. All of this brought me back to stock from the factory, and not only did I gain drivability, but my fuel mileage went from 10 to 12 mpg, to 16 to 17 mpg commuting back and forth to work. I mention all of this to stress how important it is to make sure your truck is running well before you start any modifications. Now onto the Mods!!! My long term goal is to swap a 383 I've been collecting parts for in my basement, but I wanted to really learn the TBI system first, so I figured why not see what this stock 350 could do?
 
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Flowmaster Cat-Back Exhaust kit $209 from Summit Racing

I replaced my roughly 6 year old Flowmaster Cat-Back 3" exhaust setup with a new one today. Comes with a 50 series muffler. Flowmaster guarantees their aluminized setup for 3 years, and after 6 salty winters, mine was showing some rust around the welds. I was getting ready to finally install the high-flow 3" Maganaflow Catalytic converter, so I thought I might as well replace it since I needed to disconnect it anyway... I love this kit, it fits perfect on the stock setup, sounds great, and for $209... how can you go wrong? Both times I have installed this kit, it took me longer to cut the old one off than to install the new flowmaster setup... Easy!!! Flowmaster Part #17161
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So a few months ago I purchased ($45.00) and installed a K&N filter part# E-1500 into the stock snorkel setup, quick and easy install, but I'm not sure if I gained anything. It seemed to have slightly better throttle response, but maybe I just needed a new air filter anyway... I will say that I gained fuel economy on my '96 F-150 with a 5.0l and also on my '03 Durango with the 4.7l engine, so I'm not willing to call them a Snake oil dealer, but if this were my first time dealing with them I probably wouldn't buy it again based on the performance in my Blazer. It may have also been bad timing, because I put it in right around the time we start running winter fuel blends here in my area, which normally will drop you fuel mileage a bit.... I will say I like the quality of the K&N filters, they seem well built, and I've had one in my '99 Mustang for almost 12 years with no problems, just don't over oil them after you clean them.
 
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I installed CFM Technologies throttle body spacer kit yesterday. This is one item I thought for sure would be a waste of $83... Was I wrong!!! Holy crap what a difference!!! It took a bit for the ECM to get used to it, but definately a noticable difference in throttle response and low end power. I really had a hard time spending the money on this one, I've read reviews of other spacers and really thought it wouldn't help. What sold me was their design, they've machined the center out to allow the motor to draw incoming air and fuel from both throttle bores instead of just one side. The kit came with all necessary gaskets and longer bolts for mounting the throttle body.
The only difficulty is that I had to bend and move the fuel lines to accommodate the spacer, which caused a rattle and the fuel lines to contact the body of the truck at first, not a big deal, but it took me a bit to figure out. Second problem, it changed the angle of my TV cable for the trans and threw it out of it's proper setting, so it will require you to reset your TV cable so your trans will shift when it's supposed to. Pics to follow, it makes the rest of my engine bay look really ugly... I'm curious to see how it affects my fuel economy, I'm really enjoying romping on this thing now!!!
 
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5/19/12, I finally installed the Pod Spacer!!! I know, I know it only took me a little over a year...
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I started by pulling the throttle body off the intake.
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I originally had high hopes of trying each item out individually, but at the rate I'm moving, it'll never get done... To my surprise, my fuel pressure regulator was leaking around the diaphragm gasket. I guess that explains the occasional gas smell I was smelling but could never find! Here's some pics I took along the way to show the difference between the stock gasket and the pod spacer.
Stock gasket:
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CFM's Pod Spacer:
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I also went ahead and installed my Adjustable Fuel Pressure Regulator and my fuel guage and adaptor at the same time.
 
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***(5/19/12)***I also finally installed the AFPR (Adjustable Fuel Pressure Regulator).
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It was easy, and thankfully my throttle body injector pod assembly already had an access spot for the adjustment knob so I didn't have to drill. You can see where the fuel was seeping down the fuel pressure regulator and down the back of the throttle body, you can also see the thin, stock Pod gasket that I replaced with CFM's Pod Spacer gasket:
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It's a real pain to adjust the fuel pressure because you have to be a contortionist to turn the knob after you have the throttle body reinstalled... I ended up setting the fuel pressure to 13psi, it really idles beautifully at 13psi. I took it for a quick spin and it seems to run great, but I haven't driven it enough to see any other improvements yet...
 
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I finally got around to installing the Magnaflow High-flow Catalytic Converter (part# 59929) today, I went ahead and replaced my 3" Cat-back exhaust setup from Flowmaster while I was working under there... Simple and quick, I had to go and buy a 3" exhaust section to make up the difference in length, the Magnaflow is much shorter than the stock Catalytic converter, and about 50 pounds lighter!!!! I just exhaust clamped it on, but I'm going to have our mechanic at work weld it together for me next week and ditch a couple of clamps to clean it up some. $105 at Summit, qualified me for free shipping for my entire order!!! :waytogo:
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Haha, I just thought it would be cool to put a lot of it together in the beginning, I've got all the parts, and I've been putting them on one by one to see if they really perform as claimed, or if it was a waste of my time and money. It's a work in progress, but it's going to take a little while to put it all together... Flame away, I can take it.
 
Honestly, I have a TBI 383 and with all the $$ I spent on it I wish I had just gone either carb or picked a 6.0 out of a truck at the junkyard.
 
I hear what your saying about the 383, let's save that debate for another day... This is going to be about modding a basically stock, emissions friendly, daily driver for hopefully the next few years. I want this truck to be a grocery getting, family friendly, very mild trail use, camping and fishing outdoor rig. If it can't fit those qualifications, I can't justify keeping it. Oh, and let's not forget the top comes off!!!
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Did you get the cfmtech salad bowl (power charger) as well? I've been eyeballing the whole cfmtech setup for a few years now, just always had other stuff that took priority.

I will say that even with the stock manifolds and no mods to fuel/intake, just a single 3" from the y-pipe back with a high-flow cat and a flowmaster super 40 really woke mine up.
 
I actually didn't get the salad bowl yet, but I have come across a few threads on a couple different sites where guys seem to like it. In hindsight I probably should have, but I had already spent a small fortune on all the parts I bought already. I will seriously consider it if everything continues to work well.
I tried to fill up my tank after work to do a mileage comparison, but the pump kicked off at $75 just before it would have been full... D*** fuel prices!!! Finally got the TV cable for the transmission set correctly after the spacer install this afternoon as well, shifts like a new truck now. I forget to mention I have the flowmaster 3" catback exhaust kit with a 50 series muffler on the truck already, I put it on about 5 years ago when the original exhaust rotted off at the muffler not long after I bought the truck. I love it, it was cheap, fit great and sounds good. It's not too loud, but it has that nice flowmaster rumble when you get on it. I would buy the same kit again, it's held up well for me.
 
Subscribed. I have a "new to me" 91 with the same goals. Except the 383. If I end up keeping this thing as long as I plan to, eventually I'll do an LS swap.
 
i just got a '90 from my friend. 165K, stock except for the Flomaster cat back. i pretty much got all the main crap done and working. runs strong, but it's got a tad low compression on 2 cylinders. the same mods you are doing now is what i'm up to next.....how cool is that for me :D. everything i do needs to go on the next motor too. i'm going to order the spacer and bowl and get a K&N, although my air filter is new.

lately i'm considering a mildly spiced up 305 due to gas prices, i had a good 305 in my '85, so i think a TBI version will suit me just fine.

i need to read up on the TV cable adjustment.....i never did it. also i'm going to send my injectors to Witch Hunter, figure that can't hurt either way.

what gears and tires do you have? this is perfect timing for me :rolleyes:
 
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