hi everyone I have a question, when you put a new cam in and you advance it from stock timing to say straight up I've heard some people talking about it causing a lean condition. How does it do it and why? I am wanting to build my 460 and I want to get a new cam and chain with the 3 way key. also how lean does it end up? I am going to get a holley 750, headers and dual flowmasters. I also know that I need to get a dual pattern cam because the exhaust side is alot more restrictive than the in take right? Just thought I would do some research before I do any thing to it and screw it up. I am one those people that like to do a job right the first time instead of beating around the bush. this web site is really a good place to go and get advise. thanks in advance for your replys thank you.

 

Never heard about a lean condition when changing out the timing set, nor have I experienced this with my own motors. As for the cam, I always go for a cam with more lift and duration on the exhaust side. Hope this helps, I seen your post was hanging out there with no replys.

 

hey. maybe I was thinking to much I heard someone on here talking about his truck ending up lean but maybe his carb just craped out and changed his meters. o well thats why this web site is here right? thanks

 

Yeah, this web-site is better than any book you will ever read pretaining to these trucks.

 

When you advance the cam timing with gears or a performance cam, the engine acts like it has more compression and improves performance. I am not a physisist ( I can't even spell it) but it does creat a lean running condition. Headers will contribute to this as well. Now many hotrodders like a lean condition, but too lean can be a problem.

My Edelbrock 1411 (750cfm w/electric choke) comes out of the box with meterring rods that are the leanest they make, and in most circumstances, runs great. But start messing around and creating a leaner condition than stock, and you may run into problems with backfiring through the carb. Not a big deal though, I just stepped up the meterring rods to enrichen the mixture until I found the right combo. Cost me $7 to fix the problem, once I figured it out.

Most of the time, the lean running from changing gears or cams is good for performance, and you have no problems at all. I had more problems than most, and why I do not know, but I think my combo, and mostly the carb I chose was the reason. Now this things runs fantastic!

 

wow thanx very much!! I have to say that I learn something new every day. Do you like your edelbrock? I have heard alot of mixed opions between edelbrock and holley. Also is it better to time the cam striaght upor maybe 1 degree retarded for daily driven performance? just trying figure out what would be best for the street. thanx everone for the help!!

 

Set the cam timing straight up period, unless otherwise advised by the cam manufacturer.

Edelbrocks seem to be less hassle to get and keep tuned. I like mine, I have a 1411 also.

 

are the meters easier to change on the edelbrock as opposed to the holley ? I guess I will set the cam straight up. thanx

 

With the changes you are making to your engine the air/fuel mixture is going to need to be tuned. Each engine will respond a bit differently and one carb to the next will perform somewhat differently, especially carbs from different manufacturers.

As Dan noted he had to richen his mixture after installing the pre-emissions cam gear, but I have done the same to my `85 and did not have to make any changes to my fuel mixture. I have an Edelbrock 1406, which is 600 cfm and a pre-emissions carb. So, after you have the work done check the fuel mixture to get it optimal.

Since you are going to be having a lot of exhaust work done you may want to consider having an oxygen sensor bung welded in as close to the headers as possible but also where both sides of the exhaust will be “seen” by the sensor. O2 sensors read the amount of oxygen in the exhaust and are used by late model vehicles to adjust fuel mixture continuously by way of the fuel injection system.

Use a generic sensor (they are about $25) to read the voltage after the motor is good and hot. To read the sensor you should use a digital multimeter and if it has a capture function where it will store readings and give you back an average then that would be best. The sensor readings will swing a lot so getting the average is what you really want. The readings should be taken while driving the car in your typical style and under a lot of different speeds.

Most sensors generate between .01 to 1.0 volts. The higher the number the richer the mixture. You are shooting for an average of about .450 to .550 volts for optimal mixture. After a test drive and the capture of the readings call up the average and see if you need to go more rich or lean. Make the changes in the jets (or jets and metering rods if you decide to go with the Edelbrock) and go two steps at a time. After each mixture change capture another set of readings. If you have gone too far then take them back one step. Also, it would be a good idea to write down each reading and the jets used for that reading so if you have to go back you will know where to go.

When not testing the mixture remove and plug the hole using an old spark plug so the O2 sensor does not get carboned up.

Good luck,

Mark

 

That seems like a really good idea!! I will probably try that because I have all the time in the world and after all the hardest part is tuning. its just a project so I can play around with it till she is in perfect shape and running like a raped ape!! thanx very much everybody has been such a great help and I have learned alot so more questions to come thanx yall!!!

 

I LOVE my Edelbrock Carb! I hear that if you are running for high RPM power, the Holley is the way to go, but for ease of tuning go with the Edelbrock. Drag racers love the Holley, but guys like me love the Edelbrock.

The metering rods are changed from the top of the carb and takes five minutes and about $7. EASY!!! I am not a carb man, so this was perfect for me.

Check the condition of your spark plugs to determine the fuel/air mixture, if your running too lean or rich. I am running a bit rich now and will pick up some performance if I lean it out a little.

I agree with setting the cam timing straight up, unless you are running an aftermarket cam, then follow the recomendations. If you are going to go through the hassle, set it straight up.

 

thanx . My girlfriend has one on her chevy 350 600 cfm and it not to bad worked for her straight out of the box. and runs alright though but I am more of a ford fan( too many chevys out there) and I want to do something diffrent. maybe just to watch my chevy friends in the rear view mirrors. Thanx for everybodys help

 

also, if you are really concerned with the air fuel ratio, you could get a air fuel ratio guage from someone like auto meter. weld a bung for an 02 sensor hook it up and get real time af readings and can tune accordingly.
mike

 

sweet, that almost seems like it would work even better. I am not to concerned about it but I want to do something right if I am going to do it.