frank carlson

I have an completely stock 88 vette with auto trans and 150K miles. The engine is tired and I would like to do some smog legal upgrades as I live in Calif and use this vehicle to attend car shows and rallies. It has to pass emissions testing every 2 years. The stock HP for these engines is approx. 250. Is there a cam, intake runners and exhaust package or a combination of these parts that will increase HP to approx. 300 and still pass these strict Ca emissions tests. Thanks for input.

Rebel Rev

I have heard that the actual horse power of a 1988 C4 is closer to 300 than 250.

Could be wrong of course... but as I have a 88 as well ... this is what I have heard.

vl5150

I don't think the 88's were at 300 RWHP. More like 210 or to with 20% loss from drive line friction.

There's posts here with California L98 California recipe. If I recall correctly, 300 wasn't really achievable.

A full bolt on L98 with 113 heads may touch 300 RWHP, but not quite. And most of these cars would absolutely fail any kind of California inspection.

Just my $.02, but other's will have way more experience than me. I recommend trying some different searches to try and mine the information you need.

C4in mesa

Drive a stock 1988 C4 and you will think different.

vader86

Um, no.

Assuming the OP doesn't want to open up the engine. You can port the stock plenum, add new AS&M Runners and a TPiS base to open up the intake side. You could go for a port job on the '113 heads and swap the cam out for something a little bit bigger, like an Accel 211 or ZZ9.

On the exhaust side all you can do is replace the main Cat with a new one, and the catback exhaust. Most catbacks give about the same ~10 hp increase so pick based on sound preferences. There are no shorty headers with CARB numbers to pass emissions out there.

Any cam change will require a custom tune to pass emissions.

vl5150

...and I will add the standard Vader line to check his website.

http://temp.corvetteforum.net/c4/vader86/

And 300 RWHP out of a stock C4 is...

cv67

AFRs 180 L98 head is Ca legal
Getting a cam sniffer friendly is no issue
Ditto on working over some aftermarket intake parts or a Superram if you can find one.
Youll have to run stock manifolds which are puke but noone says you couldnt change them out every2 yrs for some headers.
Guy on thirdgen I believe Dyno Don makes some real passable looking ones. If you can do some clean work you can use some Dougs LT1 shorty headers. Passing visual is hit and miss with them but its been done.

If you dont want to spend the money on heads do what you can wiht the 113s use the stock manifolds and call it a day. with a stock valve you can still pick up power just a matter ofhow much. (porting valve job springs seals surface etc).Adds up.

cadmaniac

This should get you there.

113 heads unless your rich,
port the stock intake and plenum,
oversized stock looking runners from TPIS,
LT1 exhaust manifolds, and exhaust.
Cam that will meet emissions.

That'll pass the visual, and the sniffer.


Good Luck

fl_799

What's the consensus of having 150K on the clock guys? Might have to go 'stealth' on this.

Maybe start with a ZZ4 shortblock, mildly ported 113 heads, roller rocker arms, ported intake/plenum, cleanup of stock runners, port the factory Tri-Y manifolds, a high flow cat, and a good tune. This might be good for around an honest 250 at the wheels 300 at the crank, pass emissions and still look 'stock'.

C4in mesa

Vader86 I totally respect your knowledge regarding the L98. However you say any cam change will require a tune to pass emissions. That is false. I have the Comp Cam 08-501-8 which gives me a 25-30 horsepower gain. I might add it gives me that gain along with the other upgrades. I strongly feel that they all work together and that is why I can run a 13 sec quarter mile and go from 0-60 in 4 seconds. In fact I have the stock ECM chip and when I tried a mail order custom chip it couldn't even allow me to put the car in gear. I just put the stock chip back in and my car runs great. I pass emissions and am at the top of the chart for acceptable pass or fail. I checked on line to see if it passes California standards and it squeaks by.

DinoBob

Nice. Can you list your mods?

C4in mesa

1988 base model C4
Ported the heads exhaust some and gasket matched and ported the intake.
Comp Cam 08-501-8 new springs, rods and steel guide plates were required (Summit Racing)
This cam gets zero kudo's on this Forum and I don't understand why ? I didn't have to do anything but turn the key when the motor was finally all plugged in.
Roller rocker arms 1.5
Adustable fuel pressure regulator (turned the key and set the fuel pressure at 45)
Hypertech coil, 8mm wires
Balanced motor
Gasket matched and ported stock plenum, SLP runners ported, Edelbrock 3860
Open lid air intake K&N filter
Hedman long tube headers, Magnaflow cats, Flowmaster 44 mufflers, true dual 2.5" exhaust
(I will install a X pipe before Christmas just after the cats)

DinoBob

Cool. Have you dynoed or timed it?

C4in mesa

I have only had a buddy with a stop watch to count the 0-60 and quarter mile times. So an official drag strip tree lights and off to the finish I have not. There is a drag strip that I will go take some runs on this winter. My engine really loves 70 degree air over the 105-110 and hotter air she's getting these days.

canuck buick

0-60 in 4 seconds sounds awfully fast what rear end do you have?

C4in mesa

It's a 700R4 with a B&M shift kit. Dana 36 2:59. The key is start in 1 gear then 2nd gear. I know a guy who has a 1993 C4 automatic with a 450HP LS motor in it and he had a stock Dana 36. This notion that the Dana 36 us weak is ridiculous. It may not be capable of running the quarter mile again and again but for a daily driver who enjoys the occasional blast off its fine.

vl5150

I do not think Vader's advise is misguiding anyone. He's probably referring to having a regular street tune to richen up normal driving to match the cam's increased fuel requirement and then a lean tune to pass emissions.

I have both a Moates APU-1 and a Wideband sensor to know exactly what my car is doing. After just my headers and 1.6 roller rockers, my car ran great from SOTP, but the logging showed very dangerous A/F ratios (16;1+) and very high knock counts (in the hundreds) after just a few minutes of driving. I could not hear the knocking. Mine is a 1990 so it's a speed density car and it's a bit more sensitive to change. I'm sure I would have passed California emissions as well since mine was so lean it wasn't burning as much fuel.

C4in mesa

Email can sometimes be vague as far as the intended meaning of my post. I just wanted to point out that a mild cam upgrade along with improved air intake and exhaust no tune is necessary. A couple members on here have been in my car and seen how well it drives. If my MAF sensor is part of the reason I don't know ? I've been told it offers more leeway for modifications. I only wish now I had stroked it and bought AFR heads. At the time of the rebuild I was waiting a year for the car and the cost of course was the biggest factor. The shop charged me just over $3000 in parts and labor. The cost to pull the engine and put it back in another $1500. The exhaust system $1100. All the sensors and plastic connectors that broke during the removal and putting it back in plus the new injectors $500-600. At every turn there was more money being thrown at it. Upside is I have a strong motor with 13,000 miles and counting.

vl5150

So you're 100% sure that after a cam upgrade the BLM's are close to 128 then?

C4in mesa

Block Learn Multiplier (BLM) is the long term fuel adjustment that the ECM "learns" to keep the air/fuel ratio within acceptable parameters. A BLM of 128 is considered the ideal, while anything higher shows Lean condition and anything lower shows Rich condition..As long as the blm is fairly close to 128 the computer can compensate by adding or subtracting fuel using a short term correction called an Integrator, this works at a faster rate ( many times per second ) to correct the A/F ratio and help keep the BLM at the correct number. . Hope this helps...WW
I can only hope that based on how the car performs and the fact my gas mileage is over 20 miles per gallon on the freeway I am at a acceptable number. Maybe a dyno test and a check to see whether or not it's running rich is in order ?