well, a friend of mine, more like an acquaintence was telling me about his chevelle and it's dilemmas yesterday. it's a '69 with a 454 that ran mid 12's until he put a 200 shot of nitrous on it and ran an 11.1. something broke. it's backfiring for sure. any ideas where to start looking. we're assuming it's a carburettor issue.

jason

Could be a carb issue, what kind of carb is he running? Is he running a cam button, if he is and its broke or slid off, the cam timing will change and it will run like shit until you get some r's and then it'll clear up. But be careful you dont want to tag a valve.

pretty sure it's a holley double pumper. 790 or 850 or something slightly bigger than my 750. honestly, i wasn't listening too well when he mentioned it yesterday. i could have sworn he said 790, but i don't recall that holley makes a 790...

yeah i think he's learned his lesson. mid 12's is good enough. the nos ain't worth the risk until he can get an msd digital 6 plus or a barry grant adjustible timing computer.

i don't know about the cam button. pardon my ignorance, but what is that?

jason

A cam button holds a cam in place so it dosent shift off of the cam lobes and scatter your valve train. Some cams are cut at an angle and don't need them. Most do use a button.

check the head gaskets... nitrous likes to blow them out. especially if there was to much timing or not enough fuel. may also want to run a compression check just in case the rings burnt up.

come to find out, he blew his power valve to pieces and rounded off an exhaust lobe on his cam.

how the HELL could nos round off a lobe on the cam? that seems like a faulty cam or somebody badly adjusting the rockers to me. i dunno if it's a roller system or a flat tappet setup. i'd assume flat tappet hydraulic, and that somebody adjusted them like they were solid lifters...or vis a vis.

the tech he took the car to said that the holley 850 (yes, it's an 850, not a 790. i have no idea where that number got into my head) was toast. that he would have to buy a new one.

any thoughts, comments? trying to help this guy out a bit, he's been immense help to me with the el camino...

jason

So he had nitrous backfire. Is he running egr heads, cause if he is and the seal started to leak it would cause the middle lifters on either side (which ever is leaking) to expand and tear the lobe up on the cam cause of lost clearance.

Wow, am i glad that ive never even been intrested in no2. i would probably have the same problems. i thought about cooling my supercharger with no2 but i see all the problems with it and it dosent seem like its worth the risk.

yeah, i don't care what the ricers say, that shit is the devil.

if it runs so damn well, why is it that over 50% of the people who run it at the track break something??? i can't believe that it's ignorance. i think it's more an issue of you have to be a genius to get the conditions right to successfully use it without breaking something. or that the 50% who don't break stuff are running a 30 shot!!!! lol!

as for cooling your blower, why not just run a cool can upstream of your fuel injection rail? they sell them in summit for dirt cheap, fill em with ice and it cools your fuel. sheesh, run two, one on the return to prevent vaporlock.

that and wrap your exhaust with thermotec wrap to keep the heat out of the engine compartment. then again, if the heat can't get out of your manifold, it might stay in your engine a bit more, which would counteract said benefit...

ever contemplate an intercooler/aftercooler (i don't know what that is, i just have heard of them in reference to superchargers)?

jason
whose el camino is in desperate need of a tuneup. why does time have to be so darned limited!!

would a cool can work to cool the s/c that well? ive looked into an intercooler but its $1700 for my car. i dont think thats worth it really.

i've been running nitrous for years and i have never had anything break from it, it's how it was set up that caused the problem. probably leaned out when it was turned on. as for the cam lobe he could have had a rocker that was adjusted improperly but he could have also stuck a valve. its odd that just 1 lobe went flat.

yup, i'll say...and yes, he did have the timing advanced a bit too much and a bit too lean on the fuel. still, when you follow the instructions they give you in hot rod or some other magazine telling you how to go a step up in the jets and 7 degrees back per/x hp shot, you'd think it'd work. would have been better to have a barry grant timing box, or msd dig6plus, and an extra nitrous controller that runs a squirt of extra fuel.

jason

2* retard per 50 hp gain of nitrous..thats the rule of thumb. i have MSD igniton system with a multi step retard just for the nitrous. works like a charm, i also have a seperate fuel system for the nitrous that is set at 5.5 psi. i also use a plug thats 1 step colder than stock. the nitrous fuel setup only gets 110 octane leaded race fuel.

Thats the way nitrous is supposed to be set up. One of my dad's friends had an alcohol injected flatty that had 600-800 fogger running a seprate fuel system injecting vp c-14 to cool the charge and stabilize the burn but only a single stage retard, still worked great for Drag Racing. It ran in the 8 second index.

i read somewhere in a magazine the best way to use no2 is to have it computer controlled to increase as the rpms increase.....just what i read dont remember where