BBC thoughts

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
F-BIRD'88
Guru
Guru
Posts: 5655
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Wed Oct 04, 2017 1:37 pm

It is too bad you could have not gotten more passes that day. Would have been interesting
to try looser valve lash to see if it liked a "smaller cam"

Every Big Block chev I have ever played with.... mine and others over the years have all wanted 38° BTDC
ignition time. Excessive hungry for spark timing @WOT tells me something is slowing down the combustion burn time
on 1 or more cylinders.. EG: Exhaust reversion EGR effect, lean or rich running cylinders (1 or more)...something like that. slow burning racing fuel..... Head gasket water leak.....
Carb air flow disturbance....

When you run the tunnel ram with no hood using a (forward facing) areo scoop on the carbs is a good idea.

cjperformance
Guru
Guru
Posts: 2482
Joined: Tue Aug 19, 2008 7:20 am
Location: South Australia

Re: BBC thoughts

Post by cjperformance » Wed Oct 04, 2017 6:12 pm

prairiehotrodder wrote:
Wed Oct 04, 2017 12:22 pm
it has a trans brake, i have the chin spoiler and a 4" cowl hood. I will run without a hood untill untill i decide if i am gonna commit to the tunnel ram. Then i will likely just cut a hole in it. I'm sure you are right about the gears. The car would likely work good with 4.30 or maybe even 4.56 with those taller tires. After i get a few passes in next summer i will consider it.


My 60' on saturday was 1.467 1/8 was 6.369 at 109.3 and 1/4 was 9.972 at 135.61 on my first pass with exhaust
later run was 1.481 6.375 at 109.73 and 9.964 at 136.62 without exhaust.

Also i was playing around with the timing and i think i finally noticed that with the cam at 103 the motor finally didn't need 40 degrees of advance.

Brian
You may have missed but back a bit i was wondering about your exhaust combo, what are you using for an exhaust system?
Also do you know air conditions/DA from run to run?
Craig.

prairiehotrodder
Expert
Expert
Posts: 612
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Wed Oct 04, 2017 6:15 pm

exhaust is lemons 2.25" into 4" headers with 4" exhaust pipe into 4" magnaflow race mufflers and no tail pipes. I think the only thing that helps when i take the exhaust off is losing the 50 pounds. I do not know the air conditions from run to run.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

cjperformance
Guru
Guru
Posts: 2482
Joined: Tue Aug 19, 2008 7:20 am
Location: South Australia

Re: BBC thoughts

Post by cjperformance » Wed Oct 04, 2017 7:00 pm

prairiehotrodder wrote:
Wed Oct 04, 2017 6:15 pm
exhaust is lemons 2.25" into 4" headers with 4" exhaust pipe into 4" magnaflow race mufflers and no tail pipes. I think the only thing that helps when i take the exhaust off is losing the 50 pounds. I do not know the air conditions from run to run.
60' & 1/8th was faster with exhaust , just lost 1mph at the 1/4 stripe. Thats very good, would be great to know air conditions!
Craig.

prairiehotrodder
Expert
Expert
Posts: 612
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Oct 06, 2017 1:58 pm

this is what happens when you work at night in my shop with the door open. Muskrat. Caught him in my shop the next morning. Released him into the wild.
Picture 363.jpg
Back on topic. I pulled the old Lunati cam out of my motor and am preparing to install the new Erson cam

http://www.pbm-erson.com/Catalog/Erson/ ... ERSE129894

The card calls for it to be installed at 108 ICL. Since the LSA is also 108 does that mean it is at 0 advance or retard ? Does that seem like a good place to start?

Brian
You do not have the required permissions to view the files attached to this post.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

F-BIRD'88
Guru
Guru
Posts: 5655
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Oct 06, 2017 2:50 pm

Yes when the LSA is 108 and the ICL is 108 the cam is "straight up" 0 degrees advanced...

Many racing cams are made like this and it is up to you the end user to find the best installed cam phasing.
It is not intended to be optimum. It is up to you to find optimum....

With the low compression ratio I'd advance that cam. Your last cam test drag test session showed this.
Advancing the (big) cam improved top end power (higher MPH) therfore overall power was better with the cam advanced...
Not unexpected (to me)

That long duration cam really want 14:1cr.. Advance it.....generously,,, if VTP clearance allows.
Start testing it (generously) advanced. Move it , test it.

You could do simple very short WOT stations stall tests with the trans brake to see which cam position give the highest observed trans flash stall rpm. Keep the stall tests short.
Allow plenty of time and air flow to cool the transmission and allow the trans fluid to recover
( air bubbles and temp) between stall tests.. Find a average. Find the best average stall test of a group of tests ( short time duration stationary stall tests should not hurt the trans)

Essentially you are using the trans as a load dyno.

A digital laser mechanics tach is better as it has much better rpm resolution than your tach unless it has digital readout or a USB port. If your spark box has a USB port or tach output it is usefull for this too.

You could also consider getting (build your own) a stationary test stall transmission where the trans output shaft is physically locked and using another test torque converter say with a disabled stator so it does not multiply torque at stall. It just acts like a high stall fluid coupling as opposed to being a "torque converter".
This allows you to test the motor under a controlled load, at home.
A crude dyno. Could use any GM trans for this. Got a spare GM transmission kicking around?

This can help you dial in the cam position and lash and dial in the carbs at home, under load.
before hitting the track next spring.
A th350 or th400 or even a th700r4 could be modded for this.
(make the trans be locked in high gear only and physically lock the high gear planetary or out put shaft)
A GM 8" to 10" torque converter could be modded for this.
(Disable the stator so it just spins)
if you do build this stationary stall test transmission be sure to build a full trans shield for it too.
Just in case it does come unglued.
This test trans could save you a TON of TIME and MONEY in getting the new combo dialed in
compared to multiple trips to the track or multiple dyno sessions.
You can even make money testing other peoples race cars with this test stall transmission/fluid coupling combo.

Got another glide transmission kicking around? or any other GM auto trans?
junk yard?

F-BIRD'88
Guru
Guru
Posts: 5655
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Oct 06, 2017 3:12 pm

That lil guy just wanted to find a warm spot and give you a bit of "MuskRat LuV" ha ha .
Could have been a Moose.

F-BIRD'88
Guru
Guru
Posts: 5655
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Oct 06, 2017 3:53 pm

With your previously stated welding fabrication trade skills
it should not be much for you to rig up an engine/test trans stand with colling etc over the winter.

Long long cold Saskatchewan winter. .

Yiu could even dial in that 2x qjets on a 1 4bbl adapter
scheme for your single race dominator intake too.
See my other posts about using 2 qjets inline but in a "Six Shooter" configuration... It is 1340 cfm @1.5". And very street car friendly.

Old School
Pro
Pro
Posts: 315
Joined: Sun Feb 13, 2005 11:27 am

Re: BBC thoughts

Post by Old School » Fri Oct 06, 2017 4:47 pm

i would put it on 106.

I would like to see you run the car with the cam change only if you have time this year.

prairiehotrodder
Expert
Expert
Posts: 612
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Oct 06, 2017 5:22 pm

Hey Billy. I just stabbed it in and with the timing chain in the zero position i get an ICL of 105.5 . Sounds like a good place to start. Racing is done this year. I know you are right about testing the cam change by itself but thats not gonna happen. I have the intake off of it and i need to sell it. New carbs are on the way. Tunnel ram is ready to go on. I know it will be impossible to know what helped and what didn't when i start racing next year but thats a problem i'm gonna have to live with.

F-bird - i'm also sure you are right about building the tranbrake dyno but thats a ton of work. There is no way i have the time or money or ambition to do all that. I would just buy a adjustable cam drive such as a Jesel setup and test it at the track. Moving the cam around doesn't seem to make much difference. This new Erson cam should make more torque than the old Lunati because of the 108 vs 110 LSA. I moved the Lunati from 108 ICL to 103 and its tough to say if it made a big difference.

Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

statsystems
Guru
Guru
Posts: 1106
Joined: Sun Apr 03, 2016 1:17 am

Re: BBC thoughts

Post by statsystems » Fri Oct 06, 2017 5:41 pm

prairiehotrodder wrote:
Fri Oct 06, 2017 5:22 pm
Hey Billy. I just stabbed it in and with the timing chain in the zero position i get an ICL of 105.5 . Sounds like a good place to start. Racing is done this year. I know you are right about testing the cam change by itself but thats not gonna happen. I have the intake off of it and i need to sell it. New carbs are on the way. Tunnel ram is ready to go on. I know it will be impossible to know what helped and what didn't when i start racing next year but thats a problem i'm gonna have to live with.

F-bird - i'm also sure you are right about building the tranbrake dyno but thats a ton of work. There is no way i have the time or money or ambition to do all that. I would just buy a adjustable cam drive such as a Jesel setup and test it at the track. Moving the cam around doesn't seem to make much difference. This new Erson cam should make more torque than the old Lunati because of the 108 vs 110 LSA. I moved the Lunati from 108 ICL to 103 and its tough to say if it made a big difference.

Brian
It is 100 times harder to test and evaluate cam ICL at the track than it is at the dyno. You don't have a dyno within a few hours of you? It's well worth is to use a dyno to test things like that.

prairiehotrodder
Expert
Expert
Posts: 612
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Oct 06, 2017 6:27 pm

I agree but

its 3 hours away

$900 for one day

i don't have bunch of parts to test anyways.

but yes you are absolutley right.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

prairiehotrodder
Expert
Expert
Posts: 612
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Oct 06, 2017 6:29 pm

after more playing with the degree wheel ( i know just enough to be dangerous) I come up with intake opening of 31 at .050 and 64 closing at .050
Do those numbers jive with my 105.5 ICL ?

the card calls for 29 and 65 at 108 ICL.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

GARY C
Guru
Guru
Posts: 3373
Joined: Tue May 14, 2013 10:58 pm

Re: BBC thoughts

Post by GARY C » Fri Oct 06, 2017 10:02 pm

No one here or Lunati or you cam card knows what your engine wants, only a dyno will tell you that. Every thing else is SWAG!

Old School
Pro
Pro
Posts: 315
Joined: Sun Feb 13, 2005 11:27 am

Re: BBC thoughts

Post by Old School » Fri Oct 06, 2017 10:07 pm

prairiehotrodder wrote:
Fri Oct 06, 2017 6:29 pm
after more playing with the degree wheel ( i know just enough to be dangerous) I come up with intake opening of 31 at .050 and 64 closing at .050
Do those numbers jive with my 105.5 ICL ?

the card calls for 29 and 65 at 108 ICL.
Intake closing of 64 is a good place to be with your engine.

Post Reply