kingtaling

what if I wanted to disable the knock sensor to run a huge cam??? how do I do that?? Would it work? If not, Why, and how would i make it work? I've got a stock 305 with catback exaust and i wana run a nice lumpy cam but Cant with all the Knock Retardations and O2 sensors and Vaccume Crap this and that. I dont care about the horsepower the cam makes, I just like the sound! I will add Headers later as well, I beleive it is critical to sound ALOT and breaks up the exaust gasses instead of stock manifolds mashing them together.

Guest

One doesnt have anything to do with the other. If you want a lopey cam the knock sensor wont care.

kingtaling

that cant be true. a knock sensor will detect the cam as a knock and retard my timing. I've seen it happen. besides, with a cam like that other computer controlled crap will have to be changed as well I'm sure. For instance the O2 sensor will have to be moved up closer to the headers, or a heated O2 sensor will have to be installed. Headers will FRick up the O2 sensor's readings otherwise.

8Mike9

Sure it does, if it's a really high lift cam, you'll want to know when the valves are knocking on the pistons.

Xenodrgn

If you wanna run anything more than a compucam 2030, then ditch all the CC stuff and go carb. The computer won't work with anything more of a cam than the 2030.

Once you go carb, you can run whatever cam you want all day long (as long as it's within the mechanical limits of the motor (valves slapping pistons = bad))

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1985 Camaro SC - 2.8L, auto.

http://www.xenodrgn.f2s.com/Frontright.jpg

kingtaling

and that is what i was tryin to avoid! i like my fuel injection and cant spend the money on a non CC carb and intake and distrib and fuel pump etc... not to mention i still need the Computer for my tranny... Ahh i hate CC cars. Say...
can a PROM be burned to disable the knock sensor?? can i disable the knock sensor?

Guest

Um ok. I guess the lack of knock on an engine I built with a 224/232 cam is my imagination. I know people running bigger cams and no problems either.

Maybe you'd like to explain how exactly the knock sensor picks up a cam as knock? This should be interesting....

JoelOl75

I plan on running 334/334 duration on a modified TPI setup. I'm sure the chip will be off on the fuel, but I don't see any reason to not run a knock sensor. It doesn't hear misfire from the long duration, only detonation.

Damon

Back to original question: How to defeat the knock sensor?

Instead of plugging the wire into the knock sensor itself, simply connect it to a 3900 Ohm Resistor (3.9K Ohms) like you would buy at Radio Shack and then on to a good ground. The ECM will think the sensor is out on the end of the wire (avoiding the dreaded check engine light) but it will never register knock under any conditions.

What will follow this post is a rash of replies saying not to do this, you'll ruin your engine, etc, etc. BS. I've done it more than just once or twice and verified it's safety and effectiveness with a Diacom scanner and thousands of miles of real world driving/racing.

Just remember there is no knock sensor to "save you" if you drop in cheap gas or run lean after you do this.



[This message has been edited by Damon (edited August 08, 2001).]

Xenodrgn

Damon's got it right. And so does Madmax.

The knock sensor isn't going to be your problem, it's the fuel tables and such in your ECM... you could either ditch CC stuff and go carb (out of the question as you mentioned) or get a custom prom.

The only reason why the knock sensor would be a problem is if you put in the cam and didn't correct mixture, you'd run lean and have alotta detonation, but defeating the knock sensor isn't going to help that problem.

Hope we've helped.

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1985 Camaro SC - 2.8L, auto.

http://www.xenodrgn.f2s.com/Frontright.jpg

kingtaling

OK basically what I'm gathering is I can put in a big cam but will have to correct the mixture... And this is done through... the PROM? WHat I'm trying to accomplish here is a car that may not be super fast but at least sounds good, and this means a change in the cam to me, not just loud exaust.

I assume when people mention cam durations they are refering to @ .050 not just max duration, because 234/234 @ .050 is pretty lopey compared to 234/234 @ .000 lift. I'm running a .255/.265 @ .050 In my other camaro and it took fast bleed lifters to get it to idle at 1400 Rpms.

I want to run about 214/224 @ .050 with under .500 lift to get a mild Idle (305 CiD Engine, that should be pretty borderline / radical), but only want to change the cam, lifters, and possibly timing chain and springs and pushrods if they need it. What I DONT WANT TO DO is Frick with the ECM, Knock Sensor, electronics, distributor, etc... to get it to run like this.

Basically the question NOW is, If i replace the CAMSHAFT with that cam, and the lifters with stock-type roller lifters in my little 305 CID engine, will I have to frick with anything else? ANd do you beleive it is NECESSARY to change the pushrods and springs in an 80K mile engine with the cam change...
If not what kind of lift should I target with these old springs...

Thanks!

kingtaling

OK basically what I'm gathering is I can put in a big cam but will have to correct the mixture... And this is done through... the PROM? WHat I'm trying to accomplish here is a car that may not be super fast but at least sounds good, and this means a change in the cam to me, not just loud exaust.

I assume when people mention cam durations they are refering to @ .050 not just max duration, because 234/234 @ .050 is pretty lopey compared to 234/234 @ .000 lift. I'm running a .255/.265 @ .050 In my other camaro and it took fast bleed lifters to get it to idle at 1400 Rpms.

I want to run about 214/224 @ .050 with under .500 lift to get a mild Idle (305 CiD Engine, that should be pretty borderline / radical), but only want to change the cam, lifters, and possibly timing chain and springs and pushrods if they need it. What I DONT WANT TO DO is Frick with the ECM, Knock Sensor, electronics, distributor, etc... to get it to run like this.

Basically the question NOW is, If i replace the CAMSHAFT with that cam, and the lifters with stock-type roller lifters in my little 305 CID engine, will I have to frick with anything else? ANd do you beleive it is NECESSARY to change the pushrods and springs in an 80K mile engine with the cam change...
If not what kind of lift should I target with these old springs...

Thanks!

Xenodrgn

I was correct in my thinking, however I missed some of it... read this post for more info.

https://www.thirdgen.org/messgboard/...ML/012312.html

kingtaling

well that helps a little i guess. I just dont know how big those engines they are refering to are. mine is only a 305. I think Ill just leave it stock as it is, why take the chance? when the engine blows, Ill make some serious changes. For now, screw it.

kingtaling

maybe ill add somthing a little less noticable and a little more worthwhile... like a shift kit. :-)

Scott 87 IROC-Z

I just got my solid roller 377 running about 2 hours ago. So far with no tuning it does not trigger the knock sensor. The specs on the cam are 242/248 deg and 570/576" lift on 112. If you kick the idle up enough, you shouldn't have any problems.

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87 IROC-Z 305 TPI gears, exhaust, converter
14.70 at 94.1 mph
Solid Roller Minirammed 377 - It's Alive !!!

TRAXION

I'm running a 230/245 cam (yea, those are the 0.050" lift values ) and I have no extraneous knock.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

Guest

The ones I listed above are at .050" too... I even have the 'sure to set off the knock sensor' Pete Jackson "Quiet" gear drive and it doesnt bother it either.

That other post I was referring to a 305. It for the most part covers a 350 as well. I have run a 204/214 .420/.443 (110lsa?) and 212/212 .444/.444 112lsa cam in a 305, and both worked ok with the stock ecm. I think I could have run a 212/218 or 215ish with no problems with the ecm at all, although in any case a custom chip (see diy prom) will certainly make things better. I figure that 218 is probably about the limit on a 305 without touching the chip, and I would guess it would take a little effort to get it running just right.

kingtaling

Eh.. like what kind of effort? you cant even turn a distributor on these cars :-|

I cant even check my timing.. no timing mark! whats wrong with GM in the 82-92 era? what happened?

Ok to clarify myself and make sure I've got it right:
My STOCK 305 can take a 204/214 .4** / .4** (110* - 112* LSA) Without changing ANYTHING EXCEPT THE CAM not LIFTERS not SPRINGS not ANYTHING.... NOt even the oil... and it *should* work fine??? what kind of adjustments are needed if any? i DO HAVE A CATBACK AND A gutted cat already, so that should help things. my O2 sensor sets off the Check Engine light I think.
Keep in mind this car has 85000 MILES on it from 1989 up on the same crap.

Trigger84

Man I'm glad I dont have a computer anymore. Anyhow, although I am an opposer of computer controlled engines, you should probably not use a major cam on the engine. You could do it, and get rid of the knock sensor, but then youre gonna have to worry about engine damage, either that or run 100 octane all the time. (its currently over $3.00 a gallon here)

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---Grady---
1984 Berlinetta.
LG4 305
Holley #1850 600 c.f.m. carb.
Edelbrock Performer intake.
TH-700R4 tranny.
Flowmaster 80 series/ 3" cat-back pipe.
Accel Superstock Coil.
7.5 10-bolt rear/ 3.08's.
Edelbrock Pro-flow air cleaner.
Pioneer head unit, Pioneer front 4X6's, Cerwin Vega rear 6x9's.
Daily Driver.

Personal Quote: "The Rice-Boys all tremble with fear when the old American V8 draws near."