Just rebuilt my 400 cid sbc .10 over new crank 6" rods,rings.New camfrom Bullet cams[gross lift >573I >590E duration .050 267I 275E lobe separation 106.Now my dragster is 3/10s slower,and gets slower with each 1/8mi run!I run alcohol with stack injection.It used to print time slips! Do I need more break in runs? Running 30* timing.

Why the cam change? What was the old cam? Was the old combo on alcohol also?

Are you sure you got good oil pressure? I am concerned you said it slows down each run. What about crank and rod clearances?

Is this a flat tappet cam? Seems that way with the low lift. If so, you might have wiped a lobe or two off.

better look for metal in the filter or screen
or pull pan and check bearings

Cam change was based on Bullet Cam advice.Oil pressure at70 psi at finish line.Have run alcohol for last 18 years.Checked lift at rockers,all good.Just took fuel system apart all was clean.Can not remember old cam spec,Comp cam 12-515-5.Have same RHS 220cc heads as before.I am lost,Just may need to tear apart to recheck engine inside.

Did you check crankshaft torque as each one of the main cap went on? Then after each rod assy. went in? Although anything detected there should pretty much be a constant and not deteriorating. Unless it was a ring problem, which should show up in you filter opening. Believe I'd open it up before major repercussions and expenses vs. time and gaskets.

Have you verified you crank damper outer ring isn't moving? Have you had to re-time it to keep it at 30*? Just basics, but you never know.

Maybe your engine wants more timing with the new cam . My sbc runs best e.t. and m.p.h. at 38-39 deg. on alky.

Valvesprings not enough pressure for the new cam?? Or springs are fading away and need replaced maybe??

Assuming it is NOT a mechanical problem what do the plugs say?
Was the injection flushed out when put away for the winter? If in doubt pull the nozzles and check for blockage.

Was the intention of the new cam to pick up power?
Does it need more fuel due to the new cam and whatever else you changed?

quote:

Originally posted by spookie:
Just rebuilt my 400 cid sbc .10 over new crank 6" rods,rings.New camfrom Bullet cams[gross lift >573I >590E duration .050 267I 275E lobe separation 106.Now my dragster is 3/10s slower,and gets slower with each 1/8mi run!I run alcohol with stack injection.It used to print time slips! Do I need more break in runs? Running 30* timing.

No idea why they spec'ed a cam with more ex lift than intake! Timing is low. Bu neither should cause the car to slow up run after run. Something is wrong! Find it. Check all the stupid stuff, fuel, fuel filter, ignition etc.

I have never had a sbc that run that little of timing with a 23 degree head usually around 40. But that doesn't explain slowing down each pass.

quote:

Originally posted by rs72z:
I have never had a sbc that run that little of timing with a 23 degree head usually around 40. But that doesn't explain slowing down each pass.

My 454 SBC with AFC 235 CNC 23* heads runs best at 28*-30* timing on track and dyno.

Still as you say it should not slow down each pass and that is why I asked about the oil pressure and clearances.

Crank trigger or dist PU? Key sheared on crank will not have the actual timing displayed by light and will usually continue to move towards retard.

If it's slowing every run, he'll switch converters eventually, typically the problem if the engine oil filter is clean. I'm sure it has higher ratio rocker on the intake.

Your talking about a big inch engine with some really good heads with very good chambers. Although i don't see where he posted what heads he's running.

quote:

Originally posted by Curly1:
[QUOTE]Originally posted by rs72z:
I have never had a sbc that run that little of timing with a 23 degree head usually around 40. But that doesn't explain slowing down each pass.

My 454 SBC with AFC 235 CNC 23* heads runs best at 28*-30* timing on track and dyno.



Still as you say it should not slow down each pass and that is why I asked about the oil pressure and clearances.[/QUOTE

My concern is why is it slowing down every pass? That makes me think there may be a mechanical problem such as a bearing close to seizing.

As for timing mine does not like that much but no matter what I do not think the timing is the cause of it slowing each pass.

The cam and timing are killing your power. Terrible cam choice for alcohol. It's blowing all your power ( heat) out the exhaust. Gas would be better, but not alcohol. Your also about 8-10 degrees short on timing for alcohol. But even that will not overcome the cam overlap. Rejet and put it on gas and see for yourself.

This message has been edited. Last edited by: Ron C.,

The first thing I would do is pull the valve covers off. Check each spring and have someone bump it over while you watch the rockers go up and down. It is possible a lobe has went down. If it all looks great then I would run the valves again and see if anything changed.

I went through fuel system,all was good.rechecked rackers ,all good.reset timing where my old engine dis liked 38* as per suggestion. Went out sunday 60ft times back down to 1.24 with a 5.66 1/8mi.Thanks for all the help.Setting timing that high would have the last thing I would haved tried.But it worked! Thank you all.