Good tips, agree 100 percent. My pet peeve, the Targa Top. I have the front gasket to replace. Want to take the original clear top, make a mold and make a carbon fiber instead. As well as do my own paint, just have not settled on a theme or dedication scheme. I was a purist in keeping it original, but I need something that brings eye to the neglected, overlooked, unloved C4 Corvettes.
I apologize if it's been said already, but the reason for the coolant going through the throttle-body/ EGR plate is to cool the EGR to have a cooler intake charge.
Negative. The coolant-bypass thru the throttle body is to eliminate throttle plate/IAC icing. Any air flow restriction causes a air pressure drop [this is how a carb works]. With any pressure drop causes a corrosponding temp drop. This causes humidity [moisture in the air] to freeze and block the IAC passage along with the throttle plates (min idle speed). This happens on cool, moist days and the outside temp doesn't have at/below freezing.
I did the throttle body coolant bypass long ago akso, I learned that tip reading in some magazine, for sure never hurt a thing and yep being I drive it summer only it's for sure no bother
I have a 5.7 l98 in my Camaro they ran hot when idling from new I had my ECU set to turn my fan on at 185 it made a big difference. Just to give another idea for running them cooler.
The coolant flowing through the tb is to heat is quicker to heat the air and get it up to a constant temp asap so when the old non heated o2 sensor heats up and comes online it can go to closed loop and make fewer emissions. The "coolant bypass mod" is keeping the throttle body and intake cooler so you can make more power. The intake and tb will eventually heat soak either way but just not quite as much without hot coolant heating the tb. So you will use more fuel and make more power with the cooler more dense air. Anyway, I did it to my LT1 also and never changed it back. IDK if I would do it again for the 2 or 3hp but it adds up. My M6 LT1 Z went 13.8@100.4 on an easy launch with hypertech programming, 160 stat, tb bypass, k&n filter only and of course a flowmaster (muffler only). I think it would go like 14.1 or so before the way it felt but never tried. Oh, short throw hurst shifter too since stock is bs. There's my 2c $2 or whatever I did there.
what I did to my car was a custom cut a square cut under the air filter were the cover of the radiator underneath of the filter I cut a sayings diameter and length of the filter that cool it down so much better since you live in a dry area and there ain't hardly no problem with water getting in I live in California it rains but no problems the water Gordon might be a tip to help you out to keep the car cooler and it did it really did it runs so much better and getting the cool air from the bottom and it keeps the motor cool at all times
+Richard Hernandez I'll look into that. I live in Tennessee now, so water could be a problem...but I do everything I can not to drive it in wet weather.
one more thing when it does rain the car comes with a thin plastic Shield on the bottom of the filter just in case any water gets in I put it on when it does rain pretty sure yours has one too and that blocks the water from going in the filter thank you very much replying back I have a 1987 I'm slowly restoring it it's fine you have a excellent great condition car in your hands take care of it great videos you should put more
How is it cooler when it's sucking ambient temperature from outside anyways. Well how can pulling 70 degree air vs 90 keep your internal engine temperatures lower?
to reduce temps, wrap the exhaust, run actual dex-cool antifreeze, you might look at replacing the water pump. As old as that car is she might be gettin a little tired
I just got done with doing my heads and cam so a few more items to add Amazon USB endoscope camera with the the LED lights. I ripped a oil pan gasket and couldn't inspect it without dropping the pan which is a huge pain. To do the oil pan and get the car high, I picked up the super huge 12 ton jack stands from Harbor Freight and that gave me plenty of room to suffer under the car. They had a small snail fan there too and that was a life saver. Also I put the Magnaflow bolt on cat on mine and it doesn't give up much power and the exhaust smells much better. The test pipe that I use at the track makes the aftermarket exhaust too loud.
+Vince L Hmmm...my oil pan gasket has been seeping since I bought the car, but only recently started actually leaving drips on the floor. I havent done a very close inspection but was sure I'd have to drop the mounts and lift the engine to get the pan off. Maybe I'll stop puting that repair off...
Mine is a 6M so I had to loosen the flywheel plate, remove starter, and those diagonal K braces up front. Also that cooling lines that run into the oil filter housing I had just enough room to do the job. I'm not exactly sure if the automatic's housing will cause any issues out back. I'd say if there's interference anywhere it would be easy to remove the motor mounts and lift it an inch or so. I was going to violate my own prime directive and have a shop do it since I spend so much time doing my heads, cam radiator, etc, but I'm glad I did it myself. The shops I took it to didn't want to tackle it. One more thing.. Putting it back together was interesting because the flex of the frame made putting those K frame braces back on.
Quick update..So I've been tuning my 90 Vette's computer over the past few months and I'm about finished now. I have an LS3 in my Camaro with intake, headers, and tune and the modified L98 is just brilliant in comparison and much more fun. The Camaro feels soft around town and needs a downshift (or two) to get it to where it's making power so in normal driving it feels soft. The Vette is making power everywhere. On the highway, 1mm of pedal is needed to maintain 80 MPH. 2mm's of gas pedal starts a slow acceleration to 100MPH. This is on a 6 speed on a 3:33 rear that wouldn't pull for squat in 6th at all. I think building up the L98 TPI is very rewarding for a street car as long as the cam stays low duration and high lift.
Sir thank you for the smog pump bracket suggestion!! hahahah ive owned my vette since 1991 and always hated removing that to work on the intake/fuel injection or replace valve cover gaskets
+fred smith You're quite welcome. Its the little thungs that help the most. I certainly didn't come up with the idea, but testing it myself and passing on the knowledge is my duty as a Corvette owner!
+BiggerHammer hmmmmm upon closer inspection my smog pump sits back towards the valve cover more than yours...so close in fact that the vacuum hose that runs between the two is a wedge fit...wonder what the deal is
Great video. Can i remove the smog pump assembly and etc and plug the line at the cat and still run the cats for now , on my C4 ' 90 Convertible. Any information is greatly appreciated.
I daily a 1987 Z52 year round, rain, snow, or shine. The L98 is a good motor, but it seems ridiculous to me that if one sensor is off, even if it’s the slightest amount, the thing goes into limp home mode and runs like absolute garbage.
you should lose the vent hose on passenger side from valve cover to throttle body....when you park the car fumes from crank case make their way up into the throttle body/idle air control port and deposits carbon which will make it idle poorly in time...
It doesn't matter if a little Carbon builds up, you can spray it off every 20k or so with a can of seafoam spray or throttle bottle spray lubricant. It's venting for a reason.
I really like the red that you painted on the plenum. What kind of paint did you use there. Was it high temp and what was the name of the red. Thanks engine looks great
I can't remember where I got the covers...I want to say Napa online? They came in black, brushed and polished and they're probably close to twice the height of the factory covers. They'd probably fit a backhoe. Thanks for the comment
Is this car emissions exempt in your state? If yes then secondary air system (air pump, air diverter valve and all tubes/lines ) can go into storage ( save in case move to new state or need emissions test ) . Including air tubes welded on to exhaust headers you have been fighting for spark plug access to all these years.
im thinking of getting one of these as a first car are there replacement parts readily available and would it be a good reliable car i actually want the l98 over the more powerful lt1
+michael28701 GENERALLY speaking...theyre quite reliable, as most of the mechanical parts are parts bin...which also makes them mostly cheap and readily available. Corvette specific parts on the other hand are usually quite a bit more expensive than your average car. Like door seals and interior panels. It is possible to find decent used parts for them at a better price...but they werent exactly mass produced, so really clean used parts are rare.
+michael28701 Seals are the most expensive part of a Corvette. So if you're going to daily an older one, make sure they are in perfect condition or you have the budget to replace them. Interior second.
James Laiola removing the air pump won’t help gas mileage as it spins freely and puts no load on the engine. Now if you’re able to remove it, it depends on if your state does emissions inspections and testing. Here in Oklahoma they don’t
+Amopro 22 I'm all for it. But there are probably better alternatives unless you plan to swap out the injection with a carb...as I've mentioned before, these cars were at the beginning of the computer era and they still had a ways to go to perfect it. But anything is worth a try!
BiggerHammer no I wanted to keep the injectors so I can pretty much daily drive the car I have the brain the wiring harness fuse box and I'm going to wire it all in
+Amopro 22 I'm not one of those negative Nancy's. Go for it! These engines are nice and torquey. They're infinitely adjustable for hp and torque with minimal spending. Easy to maintain and stout.
Nope. Throttle body coolant flow is to reduce icing on the throttle blades from high velocity /humid air passing over the smaller throttle blades of a multi port throttle body. This freezing has nada to do with the temp outside. Lol In a high torque engine configuration like the l98 it's all about velocity. Filling the cylinders as quickly as possible . The coolant and the entire engine come to equilibrium at some point no matter what. If that mod worked, why not run an intercooler line on it? Cause it doesn't work. It would worsen the icing issue. Will it hurt the car bypassing it? Maybe. If the icing gets too bad it could potentially jam the throttle blades. At the least it blocks airflow and increases velocity over the blades exacerbating the icing problem. You are getting icing , you just aren't looking for it. TB bypass is a useless mod. On a side note. I Never try to get high rpms out of an l98 tpi. It's just designed to do the opposite and be a strong, fun, daily, stump pulling, yanking you around everywhere without screaming it's head off muscle engine. Tpi on a zz4 with stand alone EFI and a beefed up lowly world class t5 five speed with short shifter is my favorite daily street setup of all time. So much fun for so little.
Yep, that's why when your carb or throttle body ices up, the solution is to shut the engine off, although the cold outside temp is a factor, it's not the entirety of the problem as the video suggests.
hulagan808 I had a 91 Z28 Camaro TPI and still have an 85 corvette TPI. Both have the Throttle body coolant bypass mod. Never had a problem, it may not help but it for sure doesn't hurt.
You totally forgot to mention how to remove the valve cover on the passenger side of the car. Well, I dare you. Because that annoying EGR pipe is totally in the way!. NO WAY that valve cover simply slides of the head..... I know, I've been there....
Good tips, agree 100 percent.
My pet peeve, the Targa Top. I have the front gasket to replace. Want to take the original clear top, make a mold and make a carbon fiber instead. As well as do my own paint, just have not settled on a theme or dedication scheme.
I was a purist in keeping it original, but I need something that brings eye to the neglected, overlooked, unloved C4 Corvettes.
I like the Vette, man! Great tips as well! I have an IROC 5.7 that I adore, but for me the C$4 is what I think of when I think of Corvettes.
I apologize if it's been said already, but the reason for the coolant going through the throttle-body/ EGR plate is to cool the EGR to have a cooler intake charge.
Good point, the egr fumes are much hotter than coolant. It's probably hotter without the coolant running through the throttle body.
Negative. The coolant-bypass thru the throttle body is to eliminate throttle plate/IAC icing.
Any air flow restriction causes a air pressure drop [this is how a carb works]. With any pressure drop causes a corrosponding temp drop.
This causes humidity [moisture in the air] to freeze and block the IAC passage along with the throttle plates (min idle speed).
This happens on cool, moist days and the outside temp doesn't have at/below freezing.
I did the throttle body coolant bypass long ago akso, I learned that tip reading in some magazine, for sure never hurt a thing and yep being I drive it summer only it's for sure no bother
I have a 5.7 l98 in my Camaro they ran hot when idling from new I had my ECU set to turn my fan on at 185 it made a big difference. Just to give another idea for running them cooler.
The coolant flowing through the tb is to heat is quicker to heat the air and get it up to a constant temp asap so when the old non heated o2 sensor heats up and comes online it can go to closed loop and make fewer emissions. The "coolant bypass mod" is keeping the throttle body and intake cooler so you can make more power. The intake and tb will eventually heat soak either way but just not quite as much without hot coolant heating the tb. So you will use more fuel and make more power with the cooler more dense air. Anyway, I did it to my LT1 also and never changed it back. IDK if I would do it again for the 2 or 3hp but it adds up. My M6 LT1 Z went 13.8@100.4 on an easy launch with hypertech programming, 160 stat, tb bypass, k&n filter only and of course a flowmaster (muffler only). I think it would go like 14.1 or so before the way it felt but never tried. Oh, short throw hurst shifter too since stock is bs. There's my 2c $2 or whatever I did there.
I guess TPIS doesn't know what they are doing? they sell a kit to get rid of the coolant passage
what I did to my car was a custom cut a square cut under the air filter were the cover of the radiator underneath of the filter I cut a sayings diameter and length of the filter that cool it down so much better since you live in a dry area and there ain't hardly no problem with water getting in I live in California it rains but no problems the water Gordon might be a tip to help you out to keep the car cooler and it did it really did it runs so much better and getting the cool air from the bottom and it keeps the motor cool at all times
+Richard Hernandez I'll look into that. I live in Tennessee now, so water could be a problem...but I do everything I can not to drive it in wet weather.
one more thing when it does rain the car comes with a thin plastic Shield on the bottom of the filter just in case any water gets in I put it on when it does rain pretty sure yours has one too and that blocks the water from going in the filter thank you very much replying back I have a 1987 I'm slowly restoring it it's fine you have a excellent great condition car in your hands take care of it great videos you should put more
+Richard Hernandez More will come. I'm in the process of moving so its been difficult, but they're coming 😉
great to hear that there's more videos coming can't wait to see them
How is it cooler when it's sucking ambient temperature from outside anyways. Well how can pulling 70 degree air vs 90 keep your internal engine temperatures lower?
to reduce temps, wrap the exhaust, run actual dex-cool antifreeze, you might look at replacing the water pump. As old as that car is she might be gettin a little tired
I remember when my 91 had a very messy engine bay. It looks a lot better without so much of that unnecessary emissions garbage in it
I just got done with doing my heads and cam so a few more items to add Amazon USB endoscope camera with the the LED lights. I ripped a oil pan gasket and couldn't inspect it without dropping the pan which is a huge pain. To do the oil pan and get the car high, I picked up the super huge 12 ton jack stands from Harbor Freight and that gave me plenty of room to suffer under the car. They had a small snail fan there too and that was a life saver. Also I put the Magnaflow bolt on cat on mine and it doesn't give up much power and the exhaust smells much better. The test pipe that I use at the track makes the aftermarket exhaust too loud.
+Vince L Hmmm...my oil pan gasket has been seeping since I bought the car, but only recently started actually leaving drips on the floor. I havent done a very close inspection but was sure I'd have to drop the mounts and lift the engine to get the pan off. Maybe I'll stop puting that repair off...
Mine is a 6M so I had to loosen the flywheel plate, remove starter, and those diagonal K braces up front. Also that cooling lines that run into the oil filter housing I had just enough room to do the job. I'm not exactly sure if the automatic's housing will cause any issues out back. I'd say if there's interference anywhere it would be easy to remove the motor mounts and lift it an inch or so. I was going to violate my own prime directive and have a shop do it since I spend so much time doing my heads, cam radiator, etc, but I'm glad I did it myself. The shops I took it to didn't want to tackle it. One more thing.. Putting it back together was interesting because the flex of the frame made putting those K frame braces back on.
+Vince L Hmmm...Good to know. You've put another thought in my head. I think I'll hold off for a bit and drop a new cam in at the same time.
Quick update..So I've been tuning my 90 Vette's computer over the past few months and I'm about finished now. I have an LS3 in my Camaro with intake, headers, and tune and the modified L98 is just brilliant in comparison and much more fun. The Camaro feels soft around town and needs a downshift (or two) to get it to where it's making power so in normal driving it feels soft. The Vette is making power everywhere. On the highway, 1mm of pedal is needed to maintain 80 MPH. 2mm's of gas pedal starts a slow acceleration to 100MPH. This is on a 6 speed on a 3:33 rear that wouldn't pull for squat in 6th at all. I think building up the L98 TPI is very rewarding for a street car as long as the cam stays low duration and high lift.
+Vince L The cam is where I want to go next. I think I'm going to pull my engine soon. I'm a smart guy but cam profiles elude me.
Sir thank you for the smog pump bracket suggestion!! hahahah ive owned my vette since 1991 and always hated removing that to work on the intake/fuel injection or replace valve cover gaskets
+fred smith You're quite welcome. Its the little thungs that help the most. I certainly didn't come up with the idea, but testing it myself and passing on the knowledge is my duty as a Corvette owner!
+BiggerHammer hmmmmm upon closer inspection my smog pump sits back towards the valve cover more than yours...so close in fact that the vacuum hose that runs between the two is a wedge fit...wonder what the deal is
Your engine looks great!
That car will never see a cat.con. ever again!!
Great video.
Can i remove the smog pump assembly and etc and plug the line at the cat and still run the cats for now , on my C4 ' 90 Convertible. Any information is greatly appreciated.
I've been wanting to see a 0-60 video with (stock) l98 vs (stock) lt1 c4 corvette video!!!!!!! Can't find one
WOW very kool great info.,,1st class AAAAAAAAAAA++++++++++++ again great video I liked it a lot keep up the great work.
In NJ we don’t have to inspect cars that are 1995 or before. Makes all this easy and clean.
I daily a 1987 Z52 year round, rain, snow, or shine. The L98 is a good motor, but it seems ridiculous to me that if one sensor is off, even if it’s the slightest amount, the thing goes into limp home mode and runs like absolute garbage.
you should lose the vent hose on passenger side from valve cover to throttle body....when you park the car fumes from crank case make their way up into the throttle body/idle air control port and deposits carbon which will make it idle poorly in time...
+Critical Thinker Hmm... I will look into that. Thanks for the tip!
KERMIT THE FROG
It doesn't matter if a little Carbon builds up, you can spray it off every 20k or so with a can of seafoam spray or throttle bottle spray lubricant. It's venting for a reason.
I really like the red that you painted on the plenum. What kind of paint did you use there. Was it high temp and what was the name of the red. Thanks engine looks great
thankfully we're at an age where non of the emissions stuff is even necessary
Do you have a diagram of the spark plug wires on top of the distributor cap? And, a video on how to do the valve covers?
Negative x 2. However, if you aren't in a huge hurry I'll be back to work on it as soon as I'm done restoring the house.
They're designed to run hot from the factory. It's for emissions purposes.
Only thing we had back in my day was Catholic converters
Thank you for this. What did you use to bypass the TB? I have an 88 C4.
Fantastic tips, valve cover bolt, air pump bypass, outstanding . What year is your vette ?
+Joseph M 1987
Where did you get your Valve covers? Nice car looks clean.
Summit racing has so much stuff.
they are probably GM 12497978, many stores have them. There are a few similar versions taller or shorter
Cool. Where did you find those valve covers? Niced polished, are they tall enough for roller rockers?
I can't remember where I got the covers...I want to say Napa online? They came in black, brushed and polished and they're probably close to twice the height of the factory covers. They'd probably fit a backhoe. Thanks for the comment
Low the thermostst to 160 degree F.
Why would you put cats on the Vette if you don't need them? Thanks!
Is this car emissions exempt in your state? If yes then secondary air system (air pump, air diverter valve and all tubes/lines ) can go into storage ( save in case move to new state or need emissions test ) . Including air tubes welded on to exhaust headers you have been fighting for spark plug access to all these years.
im thinking of getting one of these as a first car are there replacement parts readily available and would it be a good reliable car i actually want the l98 over the more powerful lt1
+michael28701 GENERALLY speaking...theyre quite reliable, as most of the mechanical parts are parts bin...which also makes them mostly cheap and readily available. Corvette specific parts on the other hand are usually quite a bit more expensive than your average car. Like door seals and interior panels. It is possible to find decent used parts for them at a better price...but they werent exactly mass produced, so really clean used parts are rare.
so basically when i buy one make sure the interior is good at the very least when i do find one i can go after
+michael28701 Seals are the most expensive part of a Corvette. So if you're going to daily an older one, make sure they are in perfect condition or you have the budget to replace them. Interior second.
how much are the seals lol
+michael28701 'bout six hundred bucks...
mine runs to 227 degrees then fans come on drops it to around 200 and repeats like clockwork.
do we need to have the air pump? will removing it help with mileage?
James Laiola removing the air pump won’t help gas mileage as it spins freely and puts no load on the engine. Now if you’re able to remove it, it depends on if your state does emissions inspections and testing. Here in Oklahoma they don’t
It doesn't help ENOUGH to necessitate to work required to remove it. 1-2 hp is about all you're gonna see.
"IACV" has nothing to do with ur intake freezing "idle air control valve"
what do you think about me squeezing the motor that's in your vet into a 62 Rambler American
+Amopro 22 I'm all for it. But there are probably better alternatives unless you plan to swap out the injection with a carb...as I've mentioned before, these cars were at the beginning of the computer era and they still had a ways to go to perfect it. But anything is worth a try!
BiggerHammer no I wanted to keep the injectors so I can pretty much daily drive the car I have the brain the wiring harness fuse box and I'm going to wire it all in
+Amopro 22 I'm not one of those negative Nancy's. Go for it! These engines are nice and torquey. They're infinitely adjustable for hp and torque with minimal spending. Easy to maintain and stout.
BiggerHammer Thanks
Go for it, if you haven't already. If you did, how did it go, and how does it go presently ?
I can remove my driver side rocker arm cover easily without grinding any bolt ☻
Nope. Throttle body coolant flow is to reduce icing on the throttle blades from high velocity /humid air passing over the smaller throttle blades of a multi port throttle body.
This freezing has nada to do with the temp outside. Lol
In a high torque engine configuration like the l98 it's all about velocity.
Filling the cylinders as quickly as possible .
The coolant and the entire engine come to equilibrium at some point no matter what.
If that mod worked, why not run an intercooler line on it?
Cause it doesn't work.
It would worsen the icing issue.
Will it hurt the car bypassing it?
Maybe.
If the icing gets too bad it could potentially jam the throttle blades.
At the least it blocks airflow and increases velocity over the blades exacerbating the icing problem.
You are getting icing , you just aren't looking for it.
TB bypass is a useless mod.
On a side note.
I Never try to get high rpms out of an l98 tpi.
It's just designed to do the opposite and be a strong, fun, daily, stump pulling, yanking you around everywhere without screaming it's head off muscle engine.
Tpi on a zz4 with stand alone EFI and a beefed up lowly world class t5 five speed with short shifter is my favorite daily street setup of all time.
So much fun for so little.
Yep, that's why when your carb or throttle body ices up, the solution is to shut the engine off, although the cold outside temp is a factor, it's not the entirety of the problem as the video suggests.
hulagan808 I had a 91 Z28 Camaro TPI and still have an 85 corvette TPI. Both have the Throttle body coolant bypass mod. Never had a problem, it may not help but it for sure doesn't hurt.
@@REDZ28won It helps, hilagan and Robert are clueless.
Yes it's a useless mod. But the egr is sending hot ass fumes to the throttle body and those fumes are like 900 degrees
.. you'd want the coolant flowing in the throttle body if the egr is gonna heat it up.
does the computer know if this is disconnected???
+richard mouton I haven't connected it to anything, but it runs perfectly fine. Nothing acts different from before the modifications.
Lol, yea..them valve covers gave you like 20hp lol
They can fit taller rockers so yes
You totally forgot to mention how to remove the valve cover on the passenger side of the car. Well, I dare you. Because that annoying EGR pipe is totally in the way!. NO WAY that valve cover simply slides of the head..... I know, I've been there....
you lost me when you started clipping the heads off bolts
+Jonathan Neill Clipping the heads off of bolts?
He obviously didn't understand what happened. Or just never worked on anything before.
Jonathan Neill..the bolt was just the protruding end of power steering pump to bracket.
LOL! FFS, man....
I think you were lost when you woke up because he cut the end of the bolt... the head is in the front not in the back by the valve cover!!!