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Topic Review (Newest First)
04-04-2013 12:53 AM
Project89 well took the truck on a 130 mile round trip today and i am dam surprised
filled up before i left set the cruise control at 82mph and cruised the whole way, stoped did my grocery shopping and filled the tank back up with 64 miles on the odo, took 3.3 gallons.
did the same thing on the way home but with alot of truck traffic i set the cruise control to 75 got home with 67 miles since i filled up and it only took 3.1 gallons.

so the truck is averaging about 19.2 mpg on the highway which is alot better then i thought it would do

hell the only reason i checked though is to figure out how far i could go on a tank of gas since the fuel gauge is no were near accurate.

anyways i ordered a gt45 turbocharger, 50 mm wastegate and some ex tubing to start a turbo setup on it. i just need to figure out how to fit a decent sized intercooler up in front of the radiator but it dont look like theres a whole lot of room.

the plan fo rnow is going to be to replace the engine driven fan with an electric unit to clear up some room infront of the motor, then im going to flip the stock cast iron manifolds and build a merge pipe off of those to the turbocharger

im going to have to watch the boost level carefully as the stock tbi injectors wont handle much power over stock but im just looking to increase mileage just a tad and pick up some tq for towing, the first 4 psi will bring me back to stock powerlevels at sealevel , and im prolly going to set it up for 7-8 psi total
03-31-2013 11:57 AM
Project89
Quote:
Originally Posted by Northern Chevy View Post

Others may have different idea's on this but I would hesitate to install an open style element that sucks in hot air from the engine compartment/heat rejection from the rad and towing would make it even worse. Bringing in air from the factory fender system or grill ( I'm not sure how that year was set up ) is better simply because of a cooler air charge but if its restrictive ... I don't have the answer there.

Unless you see different, most likely a spark plug, wire, dist cap and rotor change are in order, or at least anything that appears suspect at all, basic tune up parts although I realize you would already be on the ball in having those items on your list.
it has the fender air system but its missing the hose from the air cleaner to the fender box , have to see if i cant get one .

the camaro guys witht he tbi engines swear by the open element filters.already did a tuneup on the truck as when i got it it was pinging pretty bad between 1,500-2,200 rpms, turns out it was just bad gas from sitting

i stared at the engine bay for about 30 minutes yetserday brainstorming
if i replace the engine driven clutch fan with an electric fan , and replaced the fan shourd , there would be tons of room for a turbo install.

my twin turbo kit off my camaro would spool up way to fast, but for the price of headers/mufflers and dual ex stsem parts i could build a suitable single turbo system


the stock manifolds lend themselves very nicely to being flipped upside down from which i can make a merge pipe from them to the driver side fender well,
if i did this the turbo i would choose would be a t4 gt45 this turbo has a 83mm turbine wheel with a 1.05 turbine housing and a 70mm compressor wheel

on a typical light weight car with a stock 350 this turbo spools around 3,200 rpms. in the heavier truck i expect it to sppol around 2,900 which means during non towing and just driving around town it will never make boost , as i shift the truck around 2,300

when towing i expect it to spool up even earlier which is fine as it will help get everything moving

im thinking about just using the turbo to run about 7 psi , this would be like running 3 psi at sealevel would would be totally safe, this would give me about 30 hp more then stock but a butt load more tq



i have everything i need for the most part to turbocharge it id have to buy the gt45 turbo which is 299 shipped and some oil lines which is about another 100 bucks, the big thing that would concern me would be an hat for the tbi units as the carb hats wont work ( atleast that i know of )

so im going to price up headers, tubing for the dual ex system and a set of mufflers and see which way ill go with it
03-30-2013 02:11 PM
Northern Chevy If the truck has fairly high miles on it, I would suggest an "excellent idea", is to replace the fuel pump in the tank at the time of changing out the fuel sender. I just know from having replaced the sender myself a couple of times, in the area I live we have corrosive products poured on the roads during the winter and without fail the fittings at the sender unit won't swivel on the outlet tubes and it twists the tubes right off in the process of removal even if it was just to drop the fuel tank for other reasons. You may have a totally rust free unit and not have those sorts of issues. If you did decide to change the fuel pump then, make sure you install a quality one as the last thing you need is to swap out a Delco unit for some off beat Chinese garbage pump that will let you down !.

Of course everything that could be seized was when I did drop the tank, from the tank strap bolts twisting off and having to get new straps to rivet on to the brackets, to the threaded insert in the box cross member breaking up its holder and spinning up inside because of the bolt seized to that internal nut.

Change the frame filter and should be good on that end of the fuel system.

Others may have different idea's on this but I would hesitate to install an open style element that sucks in hot air from the engine compartment/heat rejection from the rad and towing would make it even worse. Bringing in air from the factory fender system or grill ( I'm not sure how that year was set up ) is better simply because of a cooler air charge but if its restrictive ... I don't have the answer there.

Unless you see different, most likely a spark plug, wire, dist cap and rotor change are in order, or at least anything that appears suspect at all, basic tune up parts although I realize you would already be on the ball in having those items on your list.
03-30-2013 12:35 PM
Project89 truck tows nice , i towed our 18ft camping trailer today u didnt even know it was hooked up to the truck when going down the road.

i didnt get it on the highway but im thinking i may have over worried about the power dropoff at such a low rpm so for now i think very basic mods are in order

headers, dual ex system , and some decent mufflers , along with an open element air cleaner , and a seafoam treatment of the engine

after that ill start dataloging and send them over to a friend to burn me a new chip for the ecm to help with mods and mileage

very first thing on the list is replaceing the fuel level sender as right now the gauge will read full until its only got about a gallon of fuel left then drops to e
03-29-2013 03:36 PM
oldbogie
Quote:
Originally Posted by Project89 View Post
while im a big fan of turbocharging , i do it on the cheap with mostly stocvk bottom ends , and havenever grenaded one. i would worry about doing it on a tow viechal as it would be under heavy load all the time, good intercooler and meth injection could solve the heat issues im worried about.

but m,y question is if i have to tow up a 5-7 mile grade eventually that intercooler is going to heat soak and at that point the meth can only cool things down so much

my camaro will be around 2.900-3,200 pounds + a small trailer so its really not much wieght but id still be afariad of it without getting atleast some forged pistons in the engine and i really really dont want to get that far into the shortblock.

on the other hand i do have the twin turbo kit off my iroc before i upgraded to tubular headers and twin 76mm turbos that would bolt right on.

at my altitude its about 4 psi of boost to get back to seal level air density so a 7 psi setting would give a nice boost back in power
I'm thinking not so much to make a high power engine out of it but basically restore the factory rated power. That and a small amount more if desired shouldn't tax the cooling system or driveline any more than it would operating it as the OEM built it at sea level.

Bogie
03-29-2013 01:36 PM
Project89
Quote:
Originally Posted by oldbogie View Post
You hit on what may be the magic answer, turbo. At your altitude there is about a 20 percent loss in air density which relates to a 20% loss in rated the engine's power. So you'd certainly feel that. A 200 horse engine would be down 40 horses. That can be made up with standard hot rod techniques but getting there will mostly make the performance at modern and legal cruise speed worse at while the poser can be recovered it will show mostly on the top end at the sacrifice of the lower end. A form of supercharge simply gets around all that as it eliminates the need for a long winded cam with tons of compression which would become a pain to deal with at lower altitudes. A turbo with an barometric bypass valve gets around the whole mess keeping the boost at a steady rate above the atmospheric so that would automatically adjust the boost pressure for altitude and other causes of air density changes.

Bogie
while im a big fan of turbocharging , i do it on the cheap with mostly stocvk bottom ends , and havenever grenaded one. i would worry about doing it on a tow viechal as it would be under heavy load all the time, good intercooler and meth injection could solve the heat issues im worried about.

but m,y question is if i have to tow up a 5-7 mile grade eventually that intercooler is going to heat soak and at that point the meth can only cool things down so much

my camaro will be around 2.900-3,200 pounds + a small trailer so its really not much wieght but id still be afariad of it without getting atleast some forged pistons in the engine and i really really dont want to get that far into the shortblock.

on the other hand i do have the twin turbo kit off my iroc before i upgraded to tubular headers and twin 76mm turbos that would bolt right on.

at my altitude its about 4 psi of boost to get back to seal level air density so a 7 psi setting would give a nice boost back in power
03-29-2013 12:14 PM
oldbogie
Quote:
Originally Posted by Project89 View Post
yeah its not a floating axle, i do have a friend who will be burning me some new tunes for the truck and if that fails i have a psare standalone ecm i can install same stuff i run on my twin turbo iroc

i have to move my 18ft camping trailer with it tommorow so ill see how it does as is

the good thing is when i tow to vegas elevation only goes down , and the slat flats is 1000 or 1,500 ft lower then here maybe more
You hit on what may be the magic answer, turbo. At your altitude there is about a 20 percent loss in air density which relates to a 20% loss in rated the engine's power. So you'd certainly feel that. A 200 horse engine would be down 40 horses. That can be made up with standard hot rod techniques but getting there will mostly make the performance at modern and legal cruise speed worse at while the poser can be recovered it will show mostly on the top end at the sacrifice of the lower end. A form of supercharge simply gets around all that as it eliminates the need for a long winded cam with tons of compression which would become a pain to deal with at lower altitudes. A turbo with an barometric bypass valve gets around the whole mess keeping the boost at a steady rate above the atmospheric so that would automatically adjust the boost pressure for altitude and other causes of air density changes.

Bogie
03-28-2013 07:59 PM
Project89
Quote:
Originally Posted by Northern Chevy View Post
That to me sounds like the light duty 3/4 ton as all heavy duty 3/4 tons came with 8 lug wheels and a full floating rear axle { large hub sticking out } . So with that in mind I have a feeling it "should" be the 193 heads but don't assume anything and take a peek under the valve cover to confirm !.

By the way my truck has been up to 14000 feet a couple of times and the word gutless and quitting at idle comes to mind !.
yeah its not a floating axle, i do have a friend who will be burning me some new tunes for the truck and if that fails i have a psare standalone ecm i can install same stuff i run on my twin turbo iroc

i have to move my 18ft camping trailer with it tommorow so ill see how it does as is

the good thing is when i tow to vegas elevation only goes down , and the slat flats is 1000 or 1,500 ft lower then here maybe more
03-28-2013 07:45 PM
Northern Chevy That to me sounds like the light duty 3/4 ton as all heavy duty 3/4 tons came with 8 lug wheels and a full floating rear axle { large hub sticking out } . So with that in mind I have a feeling it "should" be the 193 heads but don't assume anything and take a peek under the valve cover to confirm !.

By the way my truck has been up to 14000 feet a couple of times and the word gutless and quitting at idle comes to mind !.
03-28-2013 07:38 PM
Project89 sorry its also 4x4
03-28-2013 07:26 PM
Project89 its an ext cab short bed 2500 /tow package 6 lug wheels i dont know the wieght of hand as the sticker is unreadable ill have to look on my other truck as there identical minus the engine swap on the one

and yes its the nv 4500 trans
03-28-2013 07:09 PM
Northern Chevy It wasn't mentioned if your truck is a heavy duty 3/4 ton or one ton { 8500 GVW or higher rating } as I gather from what I have seen that they used the 191 heads with the lower compression and the standard transmission code MT8 which is the NV 4500 and had a non synchronized low first gear. Your comment about a granny low instantly had me guessing its the heavy duty engine/trans drive line but you can clarify that and if its a two or four wheel drive, what cab and box length it has. The reason I ask is for others to see how much or little weight your already lugging down the road just in truck weight, never mind pulling a load.

I am NOT the engine expert speaking up so keep that in mind but just to relay info on my own truck which is a 1995 half ton extended cab 4x4 with auto trans. It has the 193 heads and has no problem running regular fuel as its been to the coast and so on. What it lacks in a big way is power and lately due to the internals of a lifter failing and leaking down, I swapped in a new cam which happens to be a Comp 12-249-4 and a few other companies make similar spec cams under the so called "TBI compatible" listing. I installed that and right away I knew I had problems with lack of fuel delivery so I ordered a custom chip { actually a MEMCAL } which took care of those issues. The burning question, did I gain any power and the answer is ... precious little. Keep in mind that I am running the stock throttle body, stock cast exhaust manifolds, stock Y pipe, the Cat is removed though and uses a 3" pipe to a low restriction muffler. Would this cam have woken up had I created a better breathing engine from end to end, that I don't have an answer for. I can see from my own experience and in reading a variety of what others have gone through and some real hair pulling experiences if they modified a lot in the way of larger TBI and boosting the fuel pressure, getting the GMPP intake to bolt onto Vortec heads and bored the manifold inlet for the larger TBI, adding EGR to it, headers and so on ... then trying to get it programmed and never getting it right. If you have access to a shop that programs these older computers and has a dyno would be great and pretty much plan on that expense if you change a lot of parts.

Not that I mean to pour cold water on your idea of upgrading the power but there seem to be some pitfalls if not going by a tried and proven match from end to end that has been able to be tuned. I realize I might get razed a little on here by saying that but its just a friendly reminder to get it all planned out on paper before you buy one part or turn a wrench AND price it all out to see if it even makes sense for a budget you may have in mind.

To be honest, with altitude being an issue in your case and planning the vehicle to be used as a tow unit, I personally would be ether looking at a bit more updated truck that would have a larger engine with substantial power in ether a gas or .... I bet you would be smiling power wise sitting behind the wheel of a 2009 or newer Duramax with 6 speed allison that had the factory particulate exhaust thrown and reprogrammed if they allow that down there. You know yourself what a turbo can do and altitude is where a turbo diesel blows the doors off a naturally aspirated gasoline engine. I know, a truck like that may be out of reach price wise but didn't think it would hurt to pose the thought.
03-28-2013 01:22 PM
Project89
Quote:
Originally Posted by oldbogie View Post
It has swirl port heads it's just a question of whether it's the low compression 191 or the higher compression 193. Aside from chamber volume 76 or 64 cc it's the same head. But 3200 seems a bit early to crap out even for Swirl Ports.

LT1 cam with a chip will help whether you change the heads or not. Headers with duals are another good band-aid with these heads. The big thing Swirl port heads respond to is more cam timing, but the speed density metering measurement system needs 10 inches or more of idle vacuum, preferably more, so this greatly limits duration and timing profile of the cam.

Vortec heads are certainly a decent and popular change and will add about 20-30 hp but require an intake change because of a different bolt pattern from the intake you have. The iron L98 head casting 14101083, in part number 10125377 will fit your current intake, it is the same head as the Swirl Port sans the swirl vane. It was used on the Impala version of the Z-28's L98 engine, a pretty good modern head that's greatly under appreciated.

Your TBI is undersized both in CFM and in fuel delivery for much power. The OEM 350 TBI will flow about 450 CFM, the 454 TBI will flow about 600 CFM and Holley offers a slightly bigger 2 barrel unit at 670 cfm. TBI injectors can be had up to about 90 pounds per hour where the OEM 350 will do about 60 pounds per hour on average. These are based on an 80% duty cycle and about 11 PSI fuel pressure.

Bogie
ive never messed with tbi much, hence why my other truck has a tpi swap on it . vortec head swap would be nice but do they mayke a votec tbi manifold ? or do i have to get a carb manifold and run the adapter?

im going to pull a valve cover this weekend and check the casting number but im going to assume it has the low compression heads since the truck will run on 85 gas and not ping

how will the vortecs compare to the swirl ports in off idle power and tq ? i do love the amount of power the truck has down low , i am willing to give up some though as if i need to the transmission does have a granny gear to get things moving when towing. ive never had to use it as is though

i should mention the early fall off could be because i am at 6,500 ft above sealevel
03-28-2013 10:24 AM
oldbogie
Quote:
Originally Posted by Project89 View Post
i just purchased a second silverado 350 tbi with the nv4500 trans ( might be a 3500) i always get it mixed up

my other silverado is the same except it has a tbi to tpi swap on it

im going to use this new truck to tow my twin turbo car to the track in vegas and also out to the salt flats to race instead of just driving the camaro there since either trip is 600+ miles round trip

my first thoughts were to do the tpi swap with the lt1 cam

but i dont wanna really do that , im going to assume the 92 tbi engine has swirl port heads , i havent pulled a valve cover to verify casting number yet

my only gripe with the truck is it falls on its face around 3,200 rpms and thats without towing anything , anything under that its great

im thinking maybe something a lil larger on the cam to shift power up just a lil bit , the bb 454 tbi swap and maybe an edelbrock manifold with th e carb to tbi adapter plate and a set of heeaders

if this was a truck u were going to tow with which way would u go with it
maybe even a cam recomendation

btw gears are out of the question speed limits out here are 80mph on the highway and in the truck i will cruise at 75-80 , while towin id obviously go a lil slower then that
It has swirl port heads it's just a question of whether it's the low compression 191 or the higher compression 193. Aside from chamber volume 76 or 64 cc it's the same head. But 3200 seems a bit early to crap out even for Swirl Ports.

LT1 cam with a chip will help whether you change the heads or not. Headers with duals are another good band-aid with these heads. The big thing Swirl port heads respond to is more cam timing, but the speed density metering measurement system needs 10 inches or more of idle vacuum, preferably more, so this greatly limits duration and timing profile of the cam.

Vortec heads are certainly a decent and popular change and will add about 20-30 hp but require an intake change because of a different bolt pattern from the intake you have. The iron L98 head casting 14101083, in part number 10125377 will fit your current intake, it is the same head as the Swirl Port sans the swirl vane. It was used on the Impala version of the Z-28's L98 engine, a pretty good modern head that's greatly under appreciated.

Your TBI is undersized both in CFM and in fuel delivery for much power. The OEM 350 TBI will flow about 450 CFM, the 454 TBI will flow about 600 CFM and Holley offers a slightly bigger 2 barrel unit at 670 cfm. TBI injectors can be had up to about 90 pounds per hour where the OEM 350 will do about 60 pounds per hour on average. These are based on an 80% duty cycle and about 11 PSI fuel pressure.

Bogie
03-28-2013 04:50 AM
454C10 Swap in a used 96 to 2000 350 vortec engine. factory roller cam and votec heads. These engine are cheap at engine salvage stores and will bolt right in using your current throttle body injection.

If the vortec swap isn't enough then add some bolt ons. (headers, rv cam, intake, better efi tune, etc...). Should be able to make 350hp and close to 400 ftlbs of torque and while retaining a good idle and low speed torque.

Could also do a top end vortec swap but not as good due to the flat tappet cam.

Some how, get rid of those 92 heads.
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