BBC thoughts

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
prairiehotrodder
Expert
Expert
Posts: 620
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

BBC thoughts

Post by prairiehotrodder » Fri Aug 11, 2017 7:13 pm

Considering my options for the next step of the evolution of my 540 BBC.
This is what i have:

Dart big M with cast caps 4.5" bore
K1 forged crank 4.25" stroke regular weight
Eagle 6.385 rods
Mahle 10 cc dome pistons with 1.270 compression height.
CR is between 9.9 and 10.0

IF anyone has been following my other thread and seen my progress trying to run consistent 9's with my NA 540 it seems like its not gonna happen. Just barely running a 9.99 occasionally. Need more compression but want to stay pump gas. The motor has 3 seasons of racing and some street driving. It seems as strong as the day i built it.

What i'm considering:
1 - re-use my crank and rods, bore to 4.6 (565 cubes) and about a 20 cc dome piston for around 11 CR.
2 - re-use my crank, buy 6.535 rods and pistons (1.12 compression height) (i notice a few big name builders do this combo)
3 - buy 4.375 crank, re-use my rods, 4.6 bore and new pistons (582 cubes)
4 - another thing to consider for any of the above combo's is a light weight crank, are they worth it?

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

Orr89rocz
Guru
Guru
Posts: 1566
Joined: Sun Sep 28, 2008 9:25 pm

Re: BBC thoughts

Post by Orr89rocz » Fri Aug 11, 2017 7:31 pm

Have your heads and intake ported. Install 2.125 or 2.25 headers. Abit more cam. Bit more gear and stall. It will do what you want at 10:1

statsystems
Guru
Guru
Posts: 1143
Joined: Sun Apr 03, 2016 1:17 am

Re: BBC thoughts

Post by statsystems » Fri Aug 11, 2017 7:32 pm

prairiehotrodder wrote:Considering my options for the next step of the evolution of my 540 BBC.
This is what i have:

Dart big M with cast caps 4.5" bore
K1 forged crank 4.25" stroke regular weight
Eagle 6.385 rods
Mahle 10 cc dome pistons with 1.270 compression height.
CR is between 9.9 and 10.0

IF anyone has been following my other thread and seen my progress trying to run consistent 9's with my NA 540 it seems like its not gonna happen. Just barely running a 9.99 occasionally. Need more compression but want to stay pump gas. The motor has 3 seasons of racing and some street driving. It seems as strong as the day i built it.

What i'm considering:
1 - re-use my crank and rods, bore to 4.6 (565 cubes) and about a 20 cc dome piston for around 11 CR.
2 - re-use my crank, buy 6.535 rods and pistons (1.12 compression height) (i notice a few big name builders do this combo)
3 - buy 4.375 crank, re-use my rods, 4.6 bore and new pistons (582 cubes)
4 - another thing to consider for any of the above combo's is a light weight crank, are they worth it?

Brian

You don't need more inches. You need more compression and the correct cam to go with it. You are a full point off on compression.

I'm never against a bigger bore. You don't need more stroke. Work on the heads.

prairiehotrodder
Expert
Expert
Posts: 620
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Aug 11, 2017 8:00 pm

Heads are the best part of this motor. AFR 335 CNC . Don't want to touch them. The intake is an Edelbrock super victor i bought used. I wouldn't be afraid to get something different and i was considering a t-ram but the thought of twice as many carb problems isn't good.
Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

statsystems
Guru
Guru
Posts: 1143
Joined: Sun Apr 03, 2016 1:17 am

Re: BBC thoughts

Post by statsystems » Fri Aug 11, 2017 8:08 pm

prairiehotrodder wrote:Heads are the best part of this motor. AFR 335 CNC . Don't want to touch them. The intake is an Edelbrock super victor i bought used. I wouldn't be afraid to get something different and i was considering a t-ram but the thought of twice as many carb problems isn't good.
Brian

I'd be willing to bet someone could easily make more power working on the heads.

GARY C
Guru
Guru
Posts: 3669
Joined: Tue May 14, 2013 10:58 pm

Re: BBC thoughts

Post by GARY C » Fri Aug 11, 2017 8:15 pm

prairiehotrodder wrote:Considering my options for the next step of the evolution of my 540 BBC.
This is what i have:

Dart big M with cast caps 4.5" bore
K1 forged crank 4.25" stroke regular weight
Eagle 6.385 rods
Mahle 10 cc dome pistons with 1.270 compression height.
CR is between 9.9 and 10.0

IF anyone has been following my other thread and seen my progress trying to run consistent 9's with my NA 540 it seems like its not gonna happen. Just barely running a 9.99 occasionally. Need more compression but want to stay pump gas. The motor has 3 seasons of racing and some street driving. It seems as strong as the day i built it.

What i'm considering:
1 - re-use my crank and rods, bore to 4.6 (565 cubes) and about a 20 cc dome piston for around 11 CR.
2 - re-use my crank, buy 6.535 rods and pistons (1.12 compression height) (i notice a few big name builders do this combo)
3 - buy 4.375 crank, re-use my rods, 4.6 bore and new pistons (582 cubes)
4 - another thing to consider for any of the above combo's is a light weight crank, are they worth it?

Brian
I would mill the heads for 11.2 compression and then have someone like Chad or Tony Mamo work the heads and intake, then I would go to the dyno with the 2 cams you have and see where you need to be on convertor and gear.

prairiehotrodder
Expert
Expert
Posts: 620
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Aug 11, 2017 8:21 pm

looking for educated advice on the combo's i listed above.

It allready has 2.25" headers and they didn't help at all at my power level.
The convertor works better than what the tires will handle
The 4.10 gears are close as well.
Doesn't need more cam. allready tried 2 cams, same results.
Its easy to see that the CR is to low so i want to fix that. Don't really want to mill the heads because i wouldn't gain much there. Maybe 1/2 a point at most which would help but i would like to gain a full point.
Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

GARY C
Guru
Guru
Posts: 3669
Joined: Tue May 14, 2013 10:58 pm

Re: BBC thoughts

Post by GARY C » Fri Aug 11, 2017 8:26 pm

trying to run consistent 9's
Just barely running a 9.99 occasionally.
The convertor works better than what the tires will handle
So why are you focused on more power and possibly more cubes?

prairiehotrodder
Expert
Expert
Posts: 620
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Aug 11, 2017 8:57 pm

good observation Gary.

i'm gonna upgrade from a 28 x 10.5 to a 29.5 x 10.5 for next season. Thats as big as i can fit. My car doesn't launch as well as it should because its to heavy for the glide. Hoping to make more power down track.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

F-BIRD'88
Guru
Guru
Posts: 5728
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Aug 11, 2017 9:17 pm

Advance that Lunati cam to a 103 in C/L. Put 4.56 gears in the car and track test it.
Take another carb with you to track compare. (borrowed?)
That car with a glide will need a LOT MORE Gear. (ya that means you have to rev it higher)
RPM rev limit it at the top end 1100Ft mark to 1320ft (for initial track testing purpose) if you are afraid of overreving it.
The 1/8th mile ET MPH and 1000 ft data will tell the tale.

Car should of had a 3 speed trans. Increasing the axle ratio with the glide
will track prove this. Consider your game plan once you see this .
There are a few options... get the track data first, then consider them.

(if you can and are willing)
Before you get and try a tunnel ram get 2 carbs and test on your manifold on a 2x4 adapter.
(Humour me on this one)* the car will respond to what it likes.

What is the real true exact compression ratio ( measured) not what the machinist told you...

cuslog
Pro
Pro
Posts: 372
Joined: Tue Apr 13, 2010 9:08 pm
Location: BC, Canada

Re: BBC thoughts

Post by cuslog » Fri Aug 11, 2017 9:44 pm

"Car should of had a 3 speed trans. Increasing the axle ratio with the glide
will track prove this. Consider your game plan once you see this .
There are a few options... get the track data first, then consider them."

I'll second this -- you say you do some street driving too ?
I've run a 4L80E for 15+ years now and love it. Just as rugged as a TH400 but with a .7 overdrive -- makes the street driving quite bearable.
3.89 rear, At the track I only use the first 3 gears.

F-BIRD'88
Guru
Guru
Posts: 5728
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Aug 11, 2017 9:45 pm

If you are going to raise the compression ratio to a real 11:1 11.20:1 you will need to blend your fuel for racing. You need a real deal 100 octane (R+M/2).
(easy and affordable with 110 octane unleaded for blending)
Recomend Pro Racing Fuels Mark II for this (110 octane unleaded)
30:60 to 50:50 ratio as required.

You can putt putt around on the street fine on pump gas with a bit of timing retard
on 11.20:1cr
but at the track for max perf you will need true 100 octane blended fuel.
There is no free lunch... You will not re invent the wheel on this
so..... get your head around this if thats the path....

prairiehotrodder
Expert
Expert
Posts: 620
Joined: Sat Dec 24, 2011 10:02 am
Location: melfort saskatchewan Canada

Re: BBC thoughts

Post by prairiehotrodder » Fri Aug 11, 2017 9:59 pm

I have a hard job believing you on the compression F-bird. I have personally had a 377 SBC with 11.75 CR that loved pump premium 92 and lasted 5 years of hard racing and street driving. Aluminum heads and the right cam seemed to make the difference.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

F-BIRD'88
Guru
Guru
Posts: 5728
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Aug 11, 2017 10:00 pm

https://www.youtube.com/watch?v=IeuIHBE_5wI

Now you (and these "hosers") know what I have known for years....

F-BIRD'88
Guru
Guru
Posts: 5728
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Aug 11, 2017 10:02 pm

its not a 377 SBC and your luck will run out.

How many times you want to re-build this motor ????

Post Reply