BBC Camshaft LSA question

[prairiehotrodder]

Typo above, should be 2.25 tubes. i'm gonna cap the pan evac for now because i don't have the stuff to hook it up. Hope to find out this weekend if these headers live up to the hype. Will build a new 4" exhaust system next week but run open headers this weekend. They have collector extensions allready. These headers may be on the big side. Dan Lemons suggested 2 1/8 tubes but these were available used for a good deal so i couldn't resist. Just gotta mount my O2 sensor then i'll be good to go.
Brian

[F-BIRD'88]

Would make a great Hot Rod mag article. 2 Shop Vacs in the back seat powered thru a 12V+ to 110V AC power converter... Hillbilly electric pan eVac..

Shop Vac's are on sale at Canadian Tire...

[F-BIRD'88]

On a more serious note...A friend here runs a pan evac system on his 700++HP pro street Big Block Mopar. The pan evac does work on the street on his car with mufflers.
When you do use a pan evac on the street as opposed to quick 1/4 mile only drag racing you need Good FUNCTIONAL valve cover breather oil BAFFLING that works.

You may even also want a oil separator catch tank plumbed in the system to stop engine oil loss. (and or capture it) Without that, (and functional valve cover oil baffles) you will quickly suck out all the engine oil and dump it on the street and oil mist coat the underside-back of your
street driven racey car, as you drive.

[F-BIRD'88]

When used on the street you want the system set up as a "hybrid" exhaust assisted (the eVac part) breather/crankcase ventilations system. Combines conventional valve cover breathers on the front of the valve covers and the pan E Vac valve cover connectors on the rear of the 2 valve covers. The in line check valves in the pan e Vac tubes
control flow via pressure differential in the different driving modes.
(idle, part throttle, WOT , deceleration)
Creates a exhaust assisted crank case ventilation as opposed to a true Pan eVac with enough vacuum in the crank case to assist piston ring sealing.
It does create a positive vacuum assist/ventilation at part throttle as you drive and at full WOT. It does work. Oil control thru good valve cover baffling is critical unless you get your motor oil for free.

[n2xlr8n]

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.

X2....plus cleaner plugs and oil.

I wouldn't run any engine I cared about without some sort of evacuation / pump.

[prairiehotrodder]

Interesting day at the track. Still trying to decode the results. With new headers

1st pass - 10.075 at 133.01 1.437 60' (this was my best 60 ever until today)
richened jetting
2nd - 10.031 at 133.05 1.436 60'
moved timing from 41 to 43
3rd - 9.992 at 133.04 1.400 60'

4th - 10.023 at 132.45 1.382 60' (best 60' ever - felt awesome)
5th - 10.108 at 132.35 1.47 60'
6th - 10.138 at 131.10 1.436 60'

Based on my first 3 passes it felt like the headers worked awesome. My 60' just kept getting better and i was make good power, but my mph was stuck at 133. My car felt like it quit accelerating 100 yards from the stripe. No matter what i did (jetting / timing) it wouldn't go beyond 133. My 1/8 mile times and speeds were very good i felt. My AFR stayed good. It didn't feel like the engine was missing or breaking up. I'm wondering if it needs a bigger cam now? Last year i went 9.94 at 135.7 but that was with a 29.5" tall tire. This year i have a 28" tire. I need the motor to rpm higher.

[F-BIRD'88]

Tighten the valve lash and test.. Is the cam advanced (a lot) maybe move it also...
Stuck at 133 mph.. Does the car need a areodynamic fix..
Body spoiler.. Air dam under bumper to keep air from onder car. etc.

Is the front end high thru the traps?

Does the steering feel light thru the traps?

If the motor needs valve duration reducing the lash may help

[prairiehotrodder]

lash is allready at .015 area ( i'm not to good at getting it dead accurate) cam is degreed to the exact specs on card. I think its advanced quite a bit. I also think retarding it from where it is may help. When i originally bought this cam i had 3.50 gears. I now have 4.10's and a much higher stall convertor. I think i need more cam but i could be wrong. This cam has served me very well and i'm very happy with it. Its a Straub cam. It just may be time to go bigger. I'd buy another Straub cam in a heartbeat but due to the time to get one and our poor Canadian dollar i picked up a used cam close to home that i may try. Yesterday at the track it seemed like the better my 60' and 1/8 times got, the worse my 1/4 and mph got. My 1/8 times and 1/4 times didn't jive as good as they should. Here are the numbers. Also the formulas that give hp based on ET and Speed show a fair difference.

6.376 - 10.031
6.337 - 9.992
6.349 - 10.023
6.406 - 10.075
6.419 - 10.138
6.432 - 10.108

i bought a used Lunati 50214 It may not be optimal. It just turned up close to home so i bought it.

[F-BIRD'88]

What was the wind direction and speed during the runs.

A head wind will rffect the top part of a 1/4 mile run more than the 1st half of the run. historical local weather data may help.

How much is the cam advanced from "straight up?
yup a bigger gear and higher stall and shorter tires
can may want a readjustment of the engines power band (cam adjustment)

[MadBill]

Don't want to shuffle through 15 pages to verify but I can't recall this engine being dynoed, however it sounds like you'd ideally be turning perhaps 7200 in the lights. It would be very useful to have dyno data to aid in gear selection. (e.g., if it's turning 7800, chances are it was all done 1,000 RPM ago..)

[prairiehotrodder]

Engine has never been on a dyno. Not exactly sure of RPM's in the traps. Tough to tell. The math says 133 mph with a 28" tire and 4.10 gear is 6500 rpm. That must be without any convertor slip. Had a mild side wind. My first thought was valve springs but i think it would have sounded rough? It just wouldn't go any faster.

[MadBill]

Yes, it calculates to 6546 RPM with zero slippage. I'd just be guessing about slip but 6% would give you 6940 RPM. You really need some numbers to work from. At the least, perhaps a video of the tach during a run. Knowing how it pulls approaching your shift points would tell you if it's out of revs in the lights.

[F-BIRD'88]

Tire size. Most "28" tall tires" are not effectively actually 28" .
Most are about 27.5" effectively. Measure yours. from ground to centerline of axle
(loaded radius x2) Converter slip 7% ish.
I get a trap rpm of 7000 to 7100 rpm for 133 MPH

What is your 1/8th MPH's VS 1/4 MPH's from time slips?

[prairiehotrodder]

Mph in 1/8 vv 1/4

108.23 - 133.05
108.32 - 133.04 this is my 9.992 run
107.6 - 132.45
107.55 - 133.01
107.56 - 132.35
106.34 - 131.1 this was my last run of the day. Not sure why it slowed down. Was worried i may have hurt something but it sounded fine.

[F-BIRD'88]

The 1/8th VS 1/4 MPH numbers look fine.

What ever happened during the last run, happened at or near the start,
not at the end.
Could have been just a hot motor or the air was not as good by that time.
(local weather service historical data for that day can revel that.)