Hey all,
have a 87 c4 with the L98. There's 120k miles on the motor.
My question is. I'm looking for performance.
I've scoured the internet and Facebook with c4s trying to get my answer
Was originally looking into 5.3 swapping it. But I like the motor in it. Would like to keep it.

Also was looking into heads . I know the stock are aluminum. Where it gets iffy with searching.
Some talk about how the aluminum heads are one of the best heads for the L98. While others say go vortec heads.
The searching is literally bouncing me back and forth

What I ultimately want is 300hp. Nothing crazy I would think. I've already started dissecting the egr equipment and TB coolant bypass. And installed a 160 thermostat to help her run cooler.

Abg suggestions to help me out with this journey would be a massive help.

 

The intake manifold on the L98 is the major choke point. If you want to make more HP change that. It is expensive though. There's also a way to use an LT1 intake. It takes some machining though.

 

Well you don't need the 160, certainly not in Long Island.

87 heads are casting '128. They aren't bad heads, the '113s that followed in 88 had a redesigned exhaust port that made them a bit better. You can have yours ported and worked over to achieve your goal. Add 1.6 RR when this is done.

The main restrictions to that goal are the intake and exhaust. I'm not sure what you can do with headers in NY, but if you don't have to pass emissions thats the route to take. Replace the main cat with a new one and add whatever catback exhaust you like for sound preference only (they make about the same power).

On the intake side, you need to look for a TPiS base manifold and heavily port/siamese your TPI runners, port match everything else as well.

Altogether you would then be just below 300. To go further, a cam change would get there, along with the custom tune required for the cam.

An alternative route would be go with the Miniram, port out or replace the heads, add a cam, chip tune, and then you could be at or well over 300 depending on what cam choice and head choice you made.

 

You've gotten some odd and not that helpful info.
1. The material that the heads are made from doesn't make 'em "the best". There are shitty aluminum AND cast iron heads...there are great aluminum AND cast iron heads.
2. EGR delete does nothing for power.
3. 160 stat MAY help it run cooler, if you cooling system has the capacity to drive the temp all the way down to the stat opening point, which most do not due to poor maintenance.

Vortec heads are a FANTASTIC choice for a mild build, but require a different lower or base intake manifold. That's $, that you may as well put toward a lighter set of aluminum heads that are also fantastic....if you buy heads. You do not need heads to get 300 hp.

You can get to 300 with good, dual exhaust, headers, and a mild to medium cam. ~$1500 should get you there....less if you can do work yourself.

 

Thanks for the reply,
Question in regard to mid cams. They would require new springs in heads and a tune?
If I can hit 300 without ripping the heads out as well. That would be a plus.

Im just removing the egr equipment because its shot and I fear its going to cause leaks and such in the future. I threw a 160 in due to my car runs real hot for my liking. But i see these now that these cars generally run hot,

 

Thanks for the reply,

I dont have emission checks on this car due to the age. Which helps me out inregards to performance upgrades.

I ran the 160 due to the high temps my car runs in general. Also the fan takes forever to turn on. Which im not use to.

 

Sounds good! I read the later tpi when extensively modified approaches the power of a decent 4BBL! How about the throttle body system is there a site prefferably with dyno results on what's been done? The shorty headers probably aren't tuned like the long jons are but does one gain enough power to justify their hassle? the early C-4's have low compression, chopping the heads would probably be a BIG help wouldn't it along with pocket porting and matching?

 

With no emissions checks Id do long tube headers, dual exhaust and a cam for sure
You can get an intake when you find a deal on one, most are overpriced. You can get the fans to turn on much earlier, mid america has the kit its cheap.

 

I think that you'd want spring appropriate for any upgraded cam.
A tune would be ideal, but not necessary since it's mass air. I have an '89 that I did exhaust and an intake and it made 276 at the wheel which is ~300 crank. No tune...runs great.
you can keep the 160 -it could allow you to run more timing for more power/tq/mileage...but you may need to upgrade your cooling system to exploit the benefit of the stat -to get it to run that cool.

 

Well its designed to run hotter, if the space between the radiator and condensor is clear - it usually isn't, it should stay close to tstat opening temps (195F) during most use. Heavy traffic it'll get to fan on temps, 228F, pretty quickly. You shouldn't worry until coolant gets to the 245-250F range. At 260, shut it down.

If you want to run cooler, I'd tell you to change the radiator to a DeWitt and never have to worry about it again.

Go with the 1 3/4" TPiS headers on the car first. Yes a cam change of any kind means you should do the springs and valvetrain, especially given the age.

 

I agree with most on here. Long tube headers and true dual exhaust is going to give you the most seat of the pants increase. Also remember that an engine is basically a big air pump. The more you put in, the more you can get out.
make it breath better and you will probably be satisfied

 

IF you don't already have a set be sure to get a set of the Factory Service Manuals for your specific Year Corvette. They come in hard copy for about $85 and on DVD from RockAuto for about $35. They are critical to have when you own a Corvette, especially a C4. On the 1988 set there are two separate books, one is for the mechanical side and the second covers the electrical system and the EFI system. There is no other manual worth having when working on a C4, I have experience with Clymers, Haynes and others and they don't compare to the FSM's.

Is this your first Corvette? Corvettes are such a Blast when you first get them, I loved driving my own Corvette the "first" time. It wasn't long before I found things that needed attention. I took my time and fixed each one before driving the Corvette on the public roads. I learned my Corvette and had a Blast getting to know the Car personally. I fixed the Emergency brake before I made the car go faster...

I would strongly recommend that you get the Corvette running "properly" and drive it for a year or so and make a list of what "needs" fixing. Taking your time to get to know the 1987 Corvette should be a rewarding experience, the performance is not like a tesla but they are Fun, reliable Corvettes. I understand the need for speed and it is a whole lot easier to achieve on a newer generation of Corvette. I have an older C3 with a 427 and I have the speed when I feel the need. The C4 is so much better driving than the earlier Corvettes were. I have my C4 basically stock and it has been able to break into the low 30 mpg range. It is my comfortable cruising Car when I am by myself or with another. The C3 I have will scare the heck out of me and many others as it is. The engine is a copy of the L88's minus the Aluminum heads, the 12.25-1 Compression ratio really woke this engine up.

By the way I see you removed the EGR or disabled it. The EGR is a important part of the engine's operating system. When the EGR is removed the engine will run at Higher Combustion Chamber temperatures and the potential for detonation increases. The engine will also run Hot enough that it will produce NOX which is not a good thing. The EGR can NOT be "disabled" without a change in the software code used by the ECM. Otherwise the ECM will continue to try and work and you will need to use premium fuel to keep it from detonating (pinging).

I would personally go back up to a 180* thermostat at least, the 160* is a tad low for this L98 engine in the C4. Like mentioned above the fans don't come on until 228* or something close. The engine should "Operate" around the 195*-205* (F) range when running normally.
Buy a roll of the vacuum hose and start replacing the original hoses, on my 1988 C4 the hoses were in really bad shape.

As far as running too hot I would be sure that your radiator is clean, the coolant is fresh and replace the radiator cap with a fresh new one. I would be very careful not to run too much anti-freeze in your coolant, max should be 50% or so and the rest Distilled Water. Old Hoses and Radiator caps need to be replaced on a schedule.

IF looking for information on C4's, THIS is the right place. There is so much knowledge available here that it is almost scary at times. I came to learn and get help and after a few years I found myself returning to the community and that is a good feeling. I love the Corvette Forum as it helps a lot of folks with our common interest keep their Corvettes on the road affordably.

To help your Corvette breath better get a "higher flowing" catalytic converter and a cat back exhaust system. My C4 gained almost 14 HP when I did the Cat back exhaust system and new Catalytic Converter. Don't try and get rid of the Catalytic Converter as it helps the car run so much cleaner exhaust. It is also against Federal Laws to tamper or remove any of the required Emissions Equipment that came on the Corvette. Not that many people pay attention to these laws anymore. I do and I keep both of my Corvettes legal to drive anytime I want.

Merry Christmas to you and your Families!

 

Says who?

Coolant temp is a personal choice. Read THIS

 

I disagree that "Coolant temp is a personal choice". We have had this discussion before and engine manufacturers specify what operating temp the car should run at.

Running an engine too cool is going to get more condensation (water) in the oil and not be able to boil it off. Too much water in your engine oil is a bad thing.

Other thoughts besides my own.

1.) "What's the danger of running an engine cold?

Total engine failure.

Well, that may seem a little extreme, as certainly all of us have run a engine that was cold, hard. We probably even got away with it due to the amazingly good engine design we have today. However, it's an extremely risky thing to do and can easily result in catastrophic engine failure. ESPECIALLY in highly tuned, built engines.

If the engine is way too cold (ie, the coolant hasn't even come up to temps), it's not making its ideal power either. VTEC engines actually do not engage VTEC unless the coolant is up to temperature, for example - this is true of many other variable valve timing technologies as well. Think of it as Honda trying to save you from yourself.

In all engines, the engine's clearances are significantly tighter, creating extreme amounts of stress on the engine's internals and the piston rings will not have properly sealed with oil temps too low.

In short - it's really bad for your engine to run it hard until it's OIL is completely warmed up. Coolant temperature is a false indicator."

2.) "The problem with a low temp thermostat then for regular driving is that there are times when the car will be running at a temperature lower than it's design intended. The result is increased wear on the engine's internals. It's essentially the same as if you assembled the engine with clearances tighter than designed for because you didn't follow the directions or your tools were not calibrated properly."

3.) "The biggest misunderstanding about thermostats is that people believe they make the engine run cooler. They don't necessarily do that. The cooling system and load on the engine determines how hot the engine gets, the thermostat fully open will still be the mercy of the coolant system's ability to remove heat."

4.) "The thermostat can only determine when the cooling system is allowed to start cooling the engine. It sets a floor, not a ceiling on engine temperatures."

5.) If you're chasing more power, this isn't a place to look. Any power gain would be circumstantial (ie, only under certain conditions), incredibly negligible, and at the risk of accelerated wear on your expensive engine internals (especially in street cars).

6.) Never try to get a better time at the drag strip by running with cold engine oil and never try to warm a car up by reving (sic) the engine.

Points number 1 thru 6 came from the following source: https://www.tuneruniversity.com/blog...l-temperature/

7.) In all cases, less than 100C (212F) will cause water buildup in the crankcase.

I think that these point should be enough to show that the Low Temperature Thermostat is not the way to go on a street driven C4.

Merry Christmas to all!

 

Did you even LOOK at the thread that I posted? I don't see how it's possible that you did, based on the cow **** that came from your keyboard?? Wow.


Ayuh. WHY IS THAT????
It's b/c the OEM's have to meet requirements that we don't care about.
You can disagree all you want....which is EXACTLY what makes choosing your operating temp....a "PERSONAL CHOICE"! But don't spew complete bullshit like the following:

Ayuh. You didn't read the thread I linked....did you? Water doesn't need to reach any particular made-up, magical number to evaporate. Water evaporates at room temperature, doesn't it? Yes it does. In fact, water evaporates at 33F. In fact, water even evaporates when it's in a solid state; ice! Albeit slowly. But water evaporates rapidly at higher temps and doesn't need to be any particular, made up magical number, in order to evaporate. Spray water on your driveway...come back in an hour. Where'd the water go? It evaporated and some how, it did it w/o getting up to "212F".



BULL ****.


BULL ****. Did you even LOOK at the thread that I posted?? Engine Master RAN, "highly tuned, built engines" on the dyno at temps in the 130's!!! and, in fact, that is a very common practice on the dyno....with "highly tuned, built engines". You don't know WTF you're talking about, unfortunately.


BULL ****! The three different Engine Masters tests I shared in the thread I linked, PROVED that engines make MORE power when cold, than hot. MORE POWER, COLD. Go read the thread. READ it.

Here....I'll post it again for you. Ready? It's RIGHT HERE! CLICK HERE FOR THREAD.


Dead assed wrong. Engine's clearances are LARGER, when the engine is cold. Pistons expand faster than cylinders b/c they're aluminum (and get much hotter than the bore), so cold = greater clearance.



WRONG, on the clearances....PROVE IT, on the engine wear. I've looked and looked and other than BSer's on the internet, there ain't NO evidence of early wear from cooler running. In fact, boat engines (which are V8 Ford and Chevy CAR engines, run at ~150F....and last for decades always "going up hill". How can that BE???


Those two are right. Good job, there.


Wrong, wrong, and WRONG. Look at the dyno results that I posted. LOOK at them. With your eyeballs.....


Coolant temperature ≠ oil temperature. I guess that you didn't know that? Note, that NO ONE, who chooses to run a 160 stat is going to be running their oil "too cold" -in the realm of that that article is warning about, unless they make short trips, which is a separate issue that no t-stat can solve. (see below)


Absolutely NOT. Short trips are what will cause "water build" up in the crank case. That is called "severe conditions" and requires proper oil changes to manage.


They might....if any of them were correct. Too bad most of it is totally wrong.

You're right that the stat sets the min temp. You neglected to address that most cooling systems should be able to "drive the temps down against the stat"...so, a cooler stat could/should result in a cooler average operating temp.
You're right that beating on your engine when it's cold, or when the oil is cold, is not good. That was a good copy 'n paste, but neglected to point out that water temps do not equal oil temps, and no one in this or any thread, is talking about running an engine w/oil temps so low that you'd risk "total engine destruction". That is absurd hyperbole in this thread.

Merry Christmas to you, too.


.

 

This has gotten out of hand.
the truth is that chevrolet was entering into the 80’s and new smog regulations.
they ran the engines hotter to try to comply with the current smog laws back then.
thermostats don’t regulate engine temperature.
air temperature, quality, condition and airflow through the radiator,
antifreeze content, condition of the engine, type of water pump, and fuel all mix together to control temp.

 

The thermostat, and the fan regulate engine temp. Stat manages the low end, fans regulate the high end.

...In a properly functioning cooling system, on a C4.

 

I hope you have a Wonderful and Merry Christmas as well, Tom!

Yes Tom, I DID read your attachment. I just don't agree with running engine "too cold". When they make oil that lubricates as well when cold as it does when hot the issue might be resolved. I would NEVER take off in my Cessna 172 when the engine oil was not up to operating temperature as I risked damaging the engine I was taught. Same works for car engines or even Boat engines.

That is absolutely right, the Thermostat will only control the LOW end. The Fans, engine Loading, Coolant makeup (% of anti-freeze) and radiator cap (pressure) control the High end of the temperature spectrum.

A Merry Christmas to All!

 

Right. The really, REALLY important thing that needs to be recognized here though, is this:
1. NO WHERE, have we discussed operating an engine where the oil temps are low enough to be a risk. Keeping things in perspective here, a 160 stat isn't going to affect the oil protection in any meaningful way, vs. a 180 stat....evidence that is backed up by 1000's of dyno sessions run on "high performance, built engines" at (water) coolant temps in the low 100's.....and millions of water cooled boat engines.
2. Oil temps are not coolant temps.


I HAVE to ask this, too: If you actually read the thread that I linked, as you claim, how it the world did you come up with and why did you post this gem!?

...when my thread documented three separate tests where significantly more power was made by nothing other than running the engine colder?

 

Thank you for educating us! Am sure I was sleeping in automotive shop class when they covered engine cooling. Or I was paying more attention to the only girl in our class with some very large hooters!