Power lagging

[MadOgre]

Doesn't that cam want something like 12*-14* BTDC ?

 

[firebane]

Doesn't that cam want something like 12*-14* BTDC ?

I was just coming to post that. With a cam of that nature your going to want to start at least at 12* timing and work up from there.

My current 12-300-4 cam is running at almost 16* timing and could probably do more if I wanted.

 

[Brandon777]

Okay I'll try that, was trying to find if the cam wanted a specific timing in the instructions, I must if missed it

 

[chengny]

It certainly won't hurt to try advancing the timing some, just don't lose focus.

I'm am not a hotrodder by any means, but re-read the problem - as you initially described it:

Sometimes it performs pretty good but up a hill or when I make a turn it feels like I'm losing fuel. I stalled when I took my foot off the gas just after I went up a hill and I was in level ground.

That doesn't sound like something that would result from the ignition timing being a few degrees retarded.

 

[Brandon777]

I'm gonna check the fuel pressure and I'm also going to advance the timing and look for any other problems like vacuum and such.

 

[350runner]

Hold on. Find out if you have a fuel supply issue first. Make sure there isn't an issue with that first. Then start adjusting the timing after the fuel issue is resolved. Don't want to end up with burnt valves.

Sent from the dust in front of you!

 

[Brandon777]

Will do

 

[Brandon777]

Thanks for all your help guys, hopefully this can be resolved

 

[MadOgre]

YA Jerry and Ceasar are right start with the basics first! I wouldn't doubt though if there is some slag or something in side your carb from the factory and that the floats may need to be adjusted as well. But start with first things first. Ensure that your fuel delivery is in order. That the fuel pump is working good. If that checks out. I would disassemble the carb. If that is to daunting then I would place a warranty call to where you bought the carb. Once you have that checked out and the vehicle runs stable in all conditions then adjust the timing.

I wasn't suggesting that your problems are caused from 4* timing, it just struck me as a low # for that cam.

 

[Brandon777]

First of all I would like to thank all of you for your help. I checked to see if I was getting the correct amount of fuel, and I was, I also checked all the fuel lines and they looked all good. I didn't disassemble the carb yet but I might in the soon future. So I needed to advance the timing anyways so I did and everything seemed to be good at idle. So I figured why not drive it. I took a short trip to a friends house and everything seemed to be responsive just like normal driving. So on my way back up to my house it's fairly steep and I was just giving it my regular throttle. It seemed fine and all but I did hear back firing, it wasn't load. Now I do have headers so I don't know if that normal. But I figured I'd tune the carb idle mixture screws, so I hooked up the vacuum gauge and I wasn't getting the reading I thought I should get. I was getting around 10-12. Now I don't know if that's a normal reading with my cam and carb and intake. All the vacuum lines were tight. And I didn't hear any vacuum leaks. Any ideas why it's that low? Or is that just the nature of the beast with the upgrades?

 

[firebane]

You are wanting a steady vacuum idle. Depending on your setup the vacuum reading can vary quite easily.

Use this as a reference for your vac gauge...http://www.secondchancegarage.com/public/186.cfm

Also just out of curiosity how are you reading your timing? This can be changed out from vehicles and you should be 10-12* BTDC

 

[Brandon777]

I am at 12 * BTDC, and my vacuum reading is steady it's not fluctuating or anything maybe just a flickering. I just thought I would be getting around a 20 for my reading, but I was getting 10-12 on the gauge

 

[Joe383]

I would start at the distributor and adjust your base timing with your car idling around 750 RPM and the vacuum to the distributor disconnected and plugged at the carburetor. Adjust your timing to get the highest vacuum reading. Next adjust your idle mixture screws tell you get the highest reading and go back and check timing again. My car back fired a few times when I first got it together and it was not enough timing. I am running lean too so have to replace my jets also. If you cant get a better vacuum reading then do a compression check of all cylinders and make sure you did not flatten a cam lobe. I do my valve adjustments with the motor running on hydraulic flat tappets. I back them off tell hey start to clatter than turn them 1/2 past were they get quiet. Don't ever do that to a roller motor though. Your cam card should give a ball park of were your vacuum should be and I would expect at least 15" After you get the motor running at the highest vacuum you can drive the truck for a few days and check plugs to see if your running lean or not.

 

[350runner]

I am at 12 * BTDC, and my vacuum reading is steady it's not fluctuating or anything maybe just a flickering. I just thought I would be getting around a 20 for my reading, but I was getting 10-12 on the gauge

With this cam you should be pulling a solid 20- 22 inches of vacuum in park 15+ in gear. There should not be any back firing regardless of the timing. Check you plug wires and make sure none are touching metal and the condition of the plugs. Are you positive you do not have a fuel supply issue? You stated when turning or going up a hill is when the engine acted differently.

Sent from the dust in front of you!

 

[Brandon777]

I drove it today and I wasn't having any problems with power or any kind of turning. My vacuum read low last night and I don't know why, but driving today felt really normal