I have made some changes to this page after learning a lot the hard way of course with my 1991 454SS project truck. After messing with my brothers 1992 454 TBI dually truck and now my 1991 TBI 454SS, I am going to say, I am not a big fan of the 91-95 GEN V big block engine. However, they can be improved.
First I start with a new Fuel pump, STOCK 75lph TBI fuel pump will only support about 230hp before the fuel pressure drops like a rock. I recommend upgrading to the 1996 Vortec 155lph fuel pump which can support up to 450hp and plugs right into a factory TBI sending unit. https://www.summitracing.com/parts/ado-ep381 So I begin every project with a new upgraded pump. Stock TBI 454 makes 230hp and 380tq so stock fuel pump is maxed out right off and a typical 454 will run better with a fuel pump upgrade even with stock chip.
GAS MILEAGE. Always a big complaint with 454 TBI trucks. 90 and older is particularly bad and that is largely due to NO OVERDRIVE. Nothing is going to help that fuel mileage more than overdrive. Whether you drop in a NV4500 5spd manual transmission or you get a 4L80E with a TCI EZ TCU transmission controller, overdrive is only way to get those rpms low enough for reasonable fuel mileage. the other things, I recommend for mileage is electric fan conversion which I have a dedicated page for and a underdrive crank pulley to turn those accessories 25% slower and that regained power can go towards turning rubber (tires). fans, pulley, exhaust and a towmaster chip change, I consider the 2nd most important changes to get fuel mileage from your 454 engine and will gain nearly as much as the overdrive. The 2 KEY problems with a 454 engine is GM built it with a terrible low 7.75:1 compression ratio which is not only not good for performance but also causes poor fuel efficiency so if you rebuilding, put some 18cc domed pistons in that motor or better yet a nice 496 stroker kit from https://www.skipwhiteperformance.com/catalog/category/rotating-assemblies/bbc-496505-assemblies_7237/
As with the other TBI and most vehicles in this era, the exhaust is terrible restrictive. the 1991 454SS that I have does at least have a true dual exhaust setup under it from the factory which is why those trucks made 20 more horsepower than the standard 454 and the 1990 SS trucks. So I recommend upgrading to dual 2.5″ exhaust. As for headers, you could if you want but at that power level your just going to give yourself headaches with exhaust leaks and burnt plug wires. So I am not going to recommend that. Now when you do open up that exhaust with true duals, you need to look into doing a 3 wire heated o2 sensor conversion to keep the o2 sensor good and hot so that it reads accurately and gives you better fuel mileage.
ignition. People either skip this entirely, or skimp on the parts used or go crazy. TBI is a simple injection system. KEEP IT THAT WAY. No MSD or other ignition boxes. That just makes diagnosis harder and have yet to see any gains on this system from adding one. First, if the distributor is out for cam swap or engine replacement then change the pickup stator with a new AC Delco D1987 pickup stator. you can order those from nearly any auto parts store. I only use AC Delco electrics as most all others is poor quality chinese parts. AC Delco still chinese but have better handle on quality control. If your distributor has over 100k miles on it. REPLACE IT. You just asking for a headache that neither of us need. So what to use. GM performance parts division now offers a performance replacement distributor. AC Delco 1103952 you can get it from either GM Dealer or Jegs or Summit racing. Plug wires, if your running a stock engine then stock replacement wires are typically fine but any decent peformance engine USE A BETTER WIRE. I like the Accel 5000 and 9000 series as they are not only nice low resistance wire but the outer casing of the wire is tougher than any other wire I have used and the price isn’t bad. For coil, up to 4500 rpms stock coil just fine. If your going to rev her on up then I recommend a Pertronix D3002. Good coil for the money. Too many issues with the MSD and Accel coils to recommend them lately. For plugs AC Delco again seems to give me the best plug coloring.
Next is the air cleaner, when I dyno tested my bone stock 454SS truck when I was done with the tuning and such, I wanted to see just how restrictive that stock air cleaner was so I just did the classic lid flip which most of us have done back in the old days and made a pull and sure enough, I gained 8hp at the wheels with just a lid flip so either flip the lid or go a step further with a nice open element air filter or you can search ebay for 95 TBI AIR INTAKE and for around $52 you can get a more cold air intake type setup which seems to work fine.
Here are the summit racing air filters that I use and recommend.
SUM-239421 14 in. diameter, chrome, flat base, 2in. element, air cleaner assembly for tight clearance hoods
SUM-239431 14 in. diameter, chrome, flat base, 3in. element, air cleaner assembly
SUM-239441 14 in. diameter, chrome, flat base, 4in. element, air cleaner assembly
To get a GEN V motor that nothing is available for to run a GEN IV cam you need to make the valvetrain adjustable. Here is the parts list needed to accomplish that.
http://www.summitracing.com/parts/cca-1401b-16/overview/ for ball pivots
http://www.summitracing.com/parts/cca-4514-16 rocker studs.
As for what cam to run, my recommendation is a Summit Racing SUM-K1300
208/218 duration @ .050 .475/.500 lift on a 112 lobe separation angle. Cam is really what GM should have put in that engine from the factory although they shouldn’t have been so cheap and put roller cam in. Power peaks at a low 4500 rpms which is about all you can run off stock valve springs and pushrods and if your going to upgrade valve springs and pushrods then just CHANGE THE HEADS.
Intake manifold. On the 87-90 Mark IV blocks that have the crappy iron carb intake. yes change that to the Edelbrock 3764 especially if your upgrading that cam. On the Mark V 91-95 engines. With stock cam, nothing to be gained from that change. But if your upgrading cam and especially with larger throttle body (cheaper/easier to bore the aluminum intake) change to the edelbrock 3764 intake. Its got to be 50lbs lighter than that iron chunk which will make putting it back on that engine MUCH easier. That was a royal pain putting that iron intake back on my brothers dually truck.
Larger throttle body. www.rvmorsemachine.com and www.tbiparts.com both offer a 54mm bored 750/800 cfm throttle body. unless you change out the tiny cam your not going to get a benefit from a larger throttle body. Also not going to get any benefit unless the intake is bored to match the throttle body.
For you guys looking to make big power with your 454’s and stay fuel injected check out Jims project at