BBC Camshaft LSA question

[prairiehotrodder]

Big day for me.

Ran my licencing passes today to get my NHRA competition licence. It was a street legal day with no track prep and i ran a best of 10.15 at 133.9. The DA was at 2600 ft and my best 60' of the day was a 1.47 on a slower pass. My car was 2 mph slower than my last years best but i'm not worried about it. I'm kinda stuck with what i'd like to do to the car now. I was hoping to have it solidly in the nines this year. The car now weighs 3400 race ready. I've been told that according to pipe max it really wants bigger headers. Currently i have 2" tubes to 3 inch exhaust with flowmaster super 44 mufflers. This car honestly runs the same with and without the exhaust. It does not care. I'd also like shaft rockers. After attempting to adjust the valves hot with the stud girdles on the other day i really noticed how i wasn't doing a very good job. The lash changes a huge amount when you tighten the lock.
brian

[MadBill]

It actually results in a more precise setting if you get the engine hot, peel off a cover and just measure/record but do not adjust the lash. (you can even do one bank at a time and run it a bit more between before tackling the other side.) Let it cool completely and then take your time to measure the cold lash. You can then calculate and adjust to the cold lash that will result in the proper hot lash. (It's best to hot check all the valves in case the expansion varies a bit from cylinder to cylinder, but I for one don't see the need for fanatical precision except for the purpose of tracking any changes over time that could signal a problem.)

[GARY C]

Big day for me.

Ran my licencing passes today to get my NHRA competition licence. It was a street legal day with no track prep and i ran a best of 10.15 at 133.9. The DA was at 2600 ft and my best 60' of the day was a 1.47 on a slower pass. My car was 2 mph slower than my last years best but i'm not worried about it. I'm kinda stuck with what i'd like to do to the car now. I was hoping to have it solidly in the nines this year. The car now weighs 3400 race ready. I've been told that according to pipe max it really wants bigger headers. Currently i have 2" tubes to 3 inch exhaust with flowmaster super 44 mufflers. This car honestly runs the same with and without the exhaust. It does not care. I'd also like shaft rockers. After attempting to adjust the valves hot with the stud girdles on the other day i really noticed how i wasn't doing a very good job. The lash changes a huge amount when you tighten the lock.
brian

When you ran it without exhaust did you just disconnect it from the header or did you have collector extension?

[prairiehotrodder]

i made collector extensions. 3.5" x about a foot. I always use them because the sound is a little farther back and deeper. Not as deafening.
brian

[MadBill]

Without searching back for specs, I believe PipeMax would suggest a little longer, say ~ 15-17"...

[prairiehotrodder]

my collector exstension is 14" with the total length including whats on the header of 19". I'm not thinking there is much to gain here.
brian

[GARY C]

my collector exstension is 14" with the total length including whats on the header of 19". I'm not thinking there is much to gain here.
brian

That should be close enough to eliminate that as a possible problem, 18" total is a pretty good fail safe, 1" more or less probably wouldn't register on the dyno.

[prairiehotrodder]

Here is an interesting bit of info. I had set my timing at 40 a few weeks ago when i pulled my car out of winter storage. At the track on saturday my mph was down about 2.5 from last years best. It felt like it was struggling a bit on the top end. I forgot my timing light at home so i decided to just take a guess and back off the timing a tiny amount. It got slower. Therefore i decided to just pull it ahead a tiny bit. Ran my best pass (10.15 at 133.9) . Checked the timing when i got home and it was at 47.
brian

[MadBill]

Time to check the damper OD for slippage and verify TDC.

[prairiehotrodder]

its not that there is a problem with the balancer, it was my bad guess at advancing the timing that was the problem.

[MadBill]

But you said it ran its fastest with that advance..

[prairiehotrodder]

Well i scored a nearly new set of Lemons headers this week. 2.25 " tubes into 4" collectors. According to Pipemax these should be worth 30 hp. Dan Lemons also told me that the reason my car didn't care whether the exhaust system was on or off was because my headers are to small (2" tubes into 3.5" collectors). I'd love to put this motor on a dyno and find out how much power its really making. But the track will tell. I'll post an update when i get the headers on the car. They are being shipped from Houston Texas. I should really start a new thread to follow my progress if anyone cares to read. Its actually quite helpful to me to post on here because it helps me follow my own progress and many of you have spotted things that i didn't notice or wouldn't have thought of.
Brian

[BrazilianZ28Camaro]

Good progress OP!

The CR is in the low side for the cam duration, that might explain the best ET with all that timing, but 47° is excessive.

Look for fuel delivery problems if the car best mph only comes with over advanced timing. (assuming the timing mark alignment was checked against true TDC.)

Jets and timing might need further adjustments with the bigger headers. This beast will breathe now.

[prairiehotrodder]

My new to me Lemons headers showed up today. They are 2.35 tubes and fit better than the old hooker 2" tubes. They are also set up for pan evac hoses. Is there anything to be gained by using that?
Brian

[MadBill]

There are a number of variables that affect the effect of pan vacuum, e.g. ring 'tension' & RPM range. Since the system is already in place, if you're going to dyno it anyway a back to back test is worth doing, For engines without a system, a quick way to find out that David Vizard mentions is to hook up two shop vacs in series to the breather. Plumbed this way, they can usually pull 5-8 "Hg., which is as much as you can expect from exhaust vac. Based on results you can decide if they are worth the effort.