OK, before my cam swap, i was running 15.11@90mph. I installed the XE256 cam and I slowed to 15.30's@90mph. I have an 83 LG4 T/A with 80,000 original miles. My mods include Edelbrock headers, 3" y-pipe into the cat, 3" SLP catback, 3.73 posi, "G" hanger, "DR" rods, bumped timing, open element air cleaner. My 60' times are the same...2.08-2.15 range...with no tire spin. It seriously pulled better with the LG4 cam in it. I was hoping for high 14's at least. My question is: it feels like it is running out of fuel at higher RPM. Is there a way to check this with a carb? Also, should I step the rods up a little bit to richen it up for the new cam? I have a Tech1 scanner and I set up the IAB and M/C so the dwell and everything is right on the money. It also idles VERY rough. Did any of you carb guys run into any problems like this with a wee-05 and this cam? Please help me out here. I cant figure it out. Thanks in advance.

 

The first thing you should do is go back over what you did and check the basics. Badly set valve lash, off timing, and vacuum leaks cover about 95% of all post cam swap problems. Check all the plus and wires to make sure there are no problems there too.

What are the specs on that cam again? I left my Comp Cataloge in my other life...

 

I had that cam in mine with vortec heads, cc carb with "B" hanger and "DR" rods.
Smooth idle, ran 14.4's @ 99mph.
'86 LG4
3.42 open rear with lots of tire spin at launch.
Stock heads are gonna kill you above 4,500rpm.
Check the float level, valve lash.

 

Which is the preferred way as far as setting up the rocker arms? Is it better to do it while the motor is off (zero lash, plus 1/2 turn), or while its running (loosen till clatter, tighten till it stops, then 1/4 turn)? I called Comp cams and they told me the same thing. Also, there are no vacuum leaks. But as far as hanger, is there much of a difference between "G" hanger and "B" hanger as far as performance?

 

I like to set lash with the spin the push rod method, then 1/2 a turn. Seem to have better results that way. Besides its alot less of a mess. I usually set 'em like that cold, then warm up the engine to operating temp and go over them again.
The B hanger will get the thin end of the rod up quicker, I think my stock hanger was a K, the B hanger and the DR rods made a HUGE difference. Also adjusted the tension spring and the vacuum can as per the tech articles on this board.

 

Thats cool. I do howeve have the oil deflectors that clip on the rocker arms, and I have a valve cover with the center of it cut out to allow access while catching all the oil. My lifters werent pumped up at all and they were very soft when I set them up so Im sure thats my problem. Im going to check the vacuum at idle to see if I have a valve hanging open or not. What should it be around? 17-20?

 

lol yeah that might have somethign to do with it. Run them once with the engine running. It's extremly difficult to set hydraulics with the engine off reliably.

 

Keep us up to date on your engine, TP89. I want to use the same cam and am really curious as to why you are having such fits with that setup.

 

OK, i just checked my vacuum at idle. It fluctuates from 14-17in. Not very fast, but regularly. I am going to adjust them with the car running tomorrow. What is the best procedure when it comes to doing this? Back the nut off till it starts to clatter, tighten it till it stops, then 1/4 turn? And do that on each one? I have the little clips to put on to deflect oil, and my nifty little home-made valve cover. Do I have it right though?

 

Yes, you got it right. Exactly how I do mine: rocker clips, cut-up vave cover and all.

I suspect that you were hanging a valve or two open before. That cam should idle real mellow- almost like stock.

Make sure all your pushrods are spinning while you're adjusting stuff in there. Look for one that's "wobbly" looking while it spins- could be a bent one in there somewhere. Might as well check everything while you're in there.

 

Well, I did it. I backed 'em off one at a time till they started clattering, tightened them till they stopped, then an additional 1/4 turn. Runs unbelievably smooth, and is very responsive. Itll take the rpm now but it still dosent seem to pull like it should. Ill try some more timing, but do ya'll think I need to fatten up the secondaries a little bit for the new cam? Im just glad it runs smooth now. Thanks for the help everyone.

BTW, I could use some advise on those secondaries. :hail: wee-05

 

Where is the lack of "pull"? If it is in the upper rpms you will have to retard the timing and vice versa for low rpms.

If you run a vacuum advance distributor be sure to install the Crane vacuum advance kit. The best $15 you'll ever spend on your engine

 

I am not going to run a vacuum advance. I have to keep all my emissions "poo" intact. Ill run it this friday though and see what the wee-o runs. If it runs a tenth faster than my stock cam...so be it. Im saving up to build a 327 for it. I should be able to get it moving pretty good with that. But if anyone else has any ideas for my 305 to break into the 14's, im all ears. But anyway, I apperciate all the fast input.

 

A couple of things you haven't mentioned:

Did you change valve springs? My stock springs would float at 5200 RPMs. Your cam may be overwhelming the springs.

Cat - you mention the y-pipe and cat-back, but what cat are you using? If it's still a stock LG4, well, no wonder!

The B hanger holds the rods up higher than the G hanger, so it will be richer quicker, and depending upon how far the AV is opening, the final mixture can be richer. You might not need that much, so something between B & G may work for you. But, nothing may be available, so the G may be the ticket.

 

The cat I have is a 3" high flow unit. Ill mess with the hanger a little bit. I also have a fan clutch that is locked up all the time...so im sure that is robbing its share of power.

 

I'll give you an all-clear on the carb calibration, at least. If it's runnign slow the DR rods are not the problem (assuming you have adequate fuel pressure at the carb all the way through redline). They work great on 95% of all V8 applications. One less thing to check on, at least.

 

I do have a question about the fuel pump issue. If it is running out of fuel up high RPM's...would the power just drop off all of a sudden and fall on its face, or would it gradually lose power? I dont have anyway of checking fuel pressure at 5000rpms when im on it, so would it be worth just getting a fuel pump to be on the safe side? Or would I just be wasting money. I just done see how a little 305 can require that much fuel.

 

The top end USUALLY just hits a wall, stumbles and then goes again when you hit 2nd gear. But not always. It can just get kinda flat and then start pulling again in 2nd gear.

How to check fuel pressure at WOT/high RPMs. Buy a remote mount fuel pressure gague and kit to hook it up (with flex line). Mount it right at the inlet to the carb (yes, you may have to tap into the hard line unless you already have an external filter in line where it would be convenient to tap in). Run the line up under the rear hood seal. Duck tape the gague to the windshield, temporarily. Do NOT mount it inside the car! Take a spin. If you're running out of fuel at the top of 1st you'll see the gague take a nose-dive. Very obvious if you have a problem. This is the ONLY way to know for sure.

I had a BIG mechnical fuel pump on my 79 Malibu and was stumbling on the top end running only 13.7s! It's the long draw from the tank combined with the hard acceleration in 1st gear that causes the problem, not that the pump itself doesn't have the volume capability.

 

Cripes...something else must be wrong then. I checked the fuel pressure and its about 6-7 psi all the way to 100 mph. I just dont understand what it could possibly be. Timing chain is on right, rocker arms are turned 1/4 turn past when they stop clattering, timiong is set ok, so its not pinging. Unless the carb just needs to be jetted up a little bit. I had the XE256 in there for a couple days when I got the car, and that made a HUGE difference. I just dont know what else to make of it. The cat is punched out so it cant be restricted exhaust. Im about to just give up here. Its just kinda frustrating...I bought a cam to quicken the car up, didnt run right, pulled it all back apart to check everything, still didnt run right, pulled it apart again and come to find out the rocker arms were way outta wack. Hell, for all the money I spent on buying parts, I almost coulda bought a set of heads. But anyway, I appreciate all the suggestions and help. Y'all are great. But im still more than willing to listen to any more ideas.

 

Sorry, I meant I had the XE262 in there when i first bought the car...but it just wouldnt idle.

 

I didnt read anything about proper cam break in,,,plus the valves too tight to start with !!! I dont know ,,,,what happens without proper break in and the valve lash being too tight??

 

I did break the cam in according to Comp Cams instruction sheet. I ran the motor for 30 minutes at an average of 2000rpm, varying the rpm according to the sheet. The one thing I am very precise on is proper break-in procedure. Anycam I ever installed always brought some results. But youd have to ride in it to believe it, I seriously think it pulled better with the LG4 cam. But I'm not going to put it back in because I threw it away. Also, I spent $100 on a cam...I'll make it work.

 

I just ran the XE 256 cam through DD2000 and compared it against the LG4 peanut cam. It says it is worth an aditional 35 hp over the peanut and is only 5 hp less than the XE 262. It's power curve overtakes the peanut significantly by 3000 rpm and is a full 35 ahead by 5000 rpm.

No matter what, you will notice 35 hp!

The only thing I can think of might be that the valve springs are cooked and just floating on you as you hit the 4000 rpm mark.

Aditional lift and duration will probably make the valve springs crap out earlier in the rpm band than what the peanut demanded.

 

I guess I can explore some new valve springs. I do need valve seals anyway...gee, its a 20 year old SBC. I found a set of CompCams valve springs in Jegs for $41.99...good to .480" lift. Those look pretty good. It makes sense though. As hard as I run this car, they very well could be weak. If it dosent fix it, at least it wont smoke anymore. Thanks again.

 

Here is the graph from DD 2000 showing you the gains in torque and HP of the XE 256 over the Peanut cam. You will definitely notice it when you get to 3500 rpm.