93 454 Upgrades

eddinger · July 9, 2010

Hello everyone. This is my first post in the HD forums. I have a 1993 GMC C2500 with a TBI 454. I just got back from my first RV camping trip, loved it. I just had a few snags coming back. On the way down it pulled fine, temp was good, then I found a small crack on the top side of the radiator. Put some bars leak in it and it was fine, for a while. On the way back it was getting really hot. I had to turn off the AC so it wouldn't over heat. This didn't bother me so much, but the wife and kids were none to happy. I am going to either fix or replace the radiator soon. Now, my first question is should I look into replacing the oil & trans cooler too? Second, I don't expect good MPG with this burb but is there any thing I can do to improve it at all? Everything is stock. I have just done a complete tune up, including a new fuel pump. Would intake, K&N filter, and/ or exaust help at all? I'm open to suggestions.

96chevy7.4L · July 9, 2010

Well there are a few things that you can do. An aftermarket muffler like a magnaflow will help things a bit. The stock muffler is very restrictive. A TBI mod as described in this site in many places and a Throttle Body spacer will help also. I would put a 180 degree thermostat in it and perhaps a bigger transmission cooler if it is in the budget. A stacked plate cooler such as a B&M super cooler will help the most in my opinion.

yukon25008.1 · July 12, 2010

hey mike besides all the easy bolt-on stuff, couldnt he install vortec heads and a decent cam, or maybe a new intake(vortec) style and lose that tbi.. although doesnt someone offer a replacment tbi that flow almost double the fuel/cfm, a freind of mine has a 95 454 tbi, and his runs pretty good for 186,000 miles

96chevy7.4L · July 12, 2010

The 454 vortec heads never had carburation. The only intakes are the original intake on the trucks or the marine intake. You can modify an oval port intake and adapt to the throttle body but not really worth the cost. If i were to go through that trouble I would put the factory vortec intake and wire harness and make it an OBD-II that way its tuneable. His easiest way would be to upgrade the throttle body to a higher flowing unit with a camshaft. I think the OP wants bolts on's.

yukon25008.1 · July 12, 2010

10 4. So what are you thinking..

Intake,exhaust,blackbear ?

eddinger · July 13, 2010

I don't want just bolt ons. I just don't want to spend so much on it that I find out that I could've bought a newer modle for about the same as what I have put into mine. I knew the MPG would be low, but I didn't plan on 6-7MPG. Maybe I should be looking at newer models with vortec 350 and HD towing?

jro909 · July 13, 2010

if it were me, i would get something a little newer whether a late 90s 454 or the 8.1 or even the 6.0....gmt-800s aren't too expensive and they are reliable...and retire the old girl from towing and just enjoy the ride

96chevy7.4L · July 13, 2010

Well in my opinion a cold air intake, exhaust and a tune from TBI chips.com would help a lot. I would do the TBI upgrade as indicated in alot of places on this site. Also a throttle body spacer. Also what gear are you running in the rear. A gear change might be in order if you are having MPG issues towing. If you have anything but 4.10's I would re-gear for sure. I have 4.10's and a big block like you and I can get 10 pulling a 35 foot 5th wheel. Weighing around 15K.

eddinger · July 13, 2010

Thanks for the info. The shop that runs TBI chips is local for me so I might just drive up there and talk to him one day. My wife wants me to sell it as of now, but I like it. It's the first full size truck/ suv I have ever owned. I looked up the codes, had 2: GQ1(std ratio) and GT4(3.73) so now what does that mean? Is it hard to change? I'm new to "working on engines" so a lot of the terminology(sp?) is new to me> I also like to know why I'm doing it. This site has been a great help so I appriciate all your help.

yukon25008.1 · July 13, 2010

most of us can physically change the ring & pinion, but its one of those things..i might just be better to pay a professional, who know them in an out, especially with the spacers theres no room for error, pay a little,have a warranty and get alot of piece of mind

uh6tdrvr · July 14, 2010

if TBI chips are local to you, start with the additions! He seems to be one of the most knowledgeable guys on the web for TB engine...plus he is local to you! He can give you alot more info that you will probably want to hear about, btw, Lets see some pics of it.

96chevy7.4L · July 14, 2010

Well if you re-gear you get your big block into its power band a bit more. Basically you will make better use of the engines available torque. But if you re-gear you will have to get the speedometer re-calibrated and the shift points in your transmission may need adjusting but perhaps not. IF you were to do things in a certain order. Get better mufflers or bolt on exhaust which ever fits your wallet. Go to TBI chips and get a chip burned for your truck. I think you will like the results with just those two mods. Then Re-gear and it will make your rig come to life. Just my opinion.

eddinger · July 14, 2010

would you also put a new intake on it? They're not that expensive, until you add all the mods up together. but I'm in no rush, it's my extra toy, not a daily driver. I'll get some pics up by Thursday.

EZDAAR · July 14, 2010

Wow, cant beleive noone said anything about getting rid of that POS clutch fan for some quality electric fans.

A good complete exhaust system (header back, Long tubes), CAI, Tune and fans will net you the most bang for the buck

Cheap Hooker headers, true duel (3chamber flowmasters) with X pipe. Is the cheapest setup that will perform Very well on that 454. Small primarys 1 5/8's?, and small exhaust, say 2 1/4"

keep up the backpressure and help that scavenging.

You could probly toss it all on there for around 1200. Estimate aprox 3MPG better or more and a NOTICABLE increase in Torque and pure drivability.

Install a Vacume guage in cab and use it correctly, aka Drive with Trottle position that maintains the highest manifold vacume possible while maintaining your desired MPH.

Do the seafoam treatment, Syphon it up through a manifold vacume port alil at a time (just enough to make it smoke like a mad mofo out the tail pipe), this cleans off valves combustion chamer, piston tops etc...

Then do another tuneup.

You WILL see a dramatic change in that 454.

EZDAAR · July 14, 2010

Another Tip for ya, Go get 2 spacers that go inbetween the TBI base plate and injector tower.

Install all 3, old, and 2 news, you will need longer screws. and sligtly file down or remove the casting that wraps around behind and below the injector tower, above the fuel lines.

This coupled with a TBI spacer will dramaticly increase your airflow through the TBI and into that engine.

If you have access to a machine shop have the raised lips around the trottle bores milled off. This is another racers secret to the TBI's. No holley TBI units have the lips.

Bolt on a MSD high output coil and the MSD ingition pickup inside the distributor (it is a 15min swap useing 2 screwdrivers) for another increase in MPG.

These mods in both of my posts are standard issue mods I do to all my vehicals that use the old OBD1 GM FI setups and to my buddies vehicals when they are not to cheap to do bolt ons correctly.

Make shure your PCV, EGR and idle control solinoid are working correctly, are clean and the passage ways aswell.