BBC thoughts

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
vortecpro
Guru
Guru
Posts: 1067
Joined: Fri Apr 24, 2009 11:10 pm

Re: BBC thoughts

Post by vortecpro » Wed Sep 06, 2017 6:43 pm

prairiehotrodder wrote:1500 feet with notoriosly bad air.
I'd be raising the compression, cutting the heads are not the best way, but it could be done, you will affect the flow flat milling. What is your piston to head clearance and the type of piston and RPM?
Racing a NA NHRA stocker should be mandatory before any posting.

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

Re: BBC thoughts

Post by prairiehotrodder » Wed Sep 06, 2017 8:46 pm

MAHLE pistons with 10cc dome. Pistons are between .005 and .007 in the hole. Crosses the finish line at about 7200 rpm.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

vortecpro
Guru
Guru
Posts: 1067
Joined: Fri Apr 24, 2009 11:10 pm

Re: BBC thoughts

Post by vortecpro » Wed Sep 06, 2017 9:27 pm

prairiehotrodder wrote:MAHLE pistons with 10cc dome. Pistons are between .005 and .007 in the hole. Crosses the finish line at about 7200 rpm.
Bore size, head gaskets?
Racing a NA NHRA stocker should be mandatory before any posting.

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

Re: BBC thoughts

Post by prairiehotrodder » Thu Sep 07, 2017 12:07 am

4.5" bore
4.54 bore gasket .039 thick
4.25 stroke
121 cc head
10 cc dome
.005 - .007 deck clearance (can't remember but i know i measured it.)

All that adds up to 9.99 or 10.0 CR
I never actually measured the head, just going by AFR's advertised number.
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 » Thu Sep 07, 2017 8:17 pm

Picture 312.jpg
Here is my new-to-me Weiand tunnel ram sitting on a low buck 454 that i put together for a RAT rod.

Combo :
Bone stock 454 out of a motor home with 781 heads.
comp 11-600-4 thumper cam and lifters
looking for a used intake

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: 5657
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Sep 08, 2017 4:37 am

A Rat Rod Bbc engine is ideal for the dual Q-Jet induction.

You can even use the stock cast bbc intake for this.

F-BIRD'88
Guru
Guru
Posts: 5657
Joined: Tue Mar 27, 2007 6:56 pm
Location: Ontario, Canada

Re: BBC thoughts

Post by F-BIRD'88 » Fri Sep 08, 2017 8:31 am

You probabily also did not actually measure the piston dome
true volume.

Milling the heads reduces vtp clearance.

You can also consider a custom thickness head gasket to max cr while still keeping piston to deck clearance @tdc sufficient. If the pistons are below deck there is room to play here.

You should have bought a cam that is speced-designed
with the low cr in mind. (special closing side)
You can see the effect by testing at various lash and cam phasing +/-.

In thin air you'd want to max the tuned runner inertial ram effect of the tunnel ram..

(extra large carb capacity, correct valve timing, max use of hood scoop flow aid, )

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

Re: BBC thoughts

Post by prairiehotrodder » Thu Sep 21, 2017 7:47 pm

Interesting experience looking for tunnel ram carbs. I've emailed all the big carb shops to get a price and see what they recomend for my combo

Chuck Nuyetten
CSU
Braswell
Pro systems
CFM
AED

maybe more that i can't remember.

Most suggest around 800 - 850 cfm carbs up to dual 1050 dominators. Prices have ranged from $1380 pair to $3400 for the dominators (race only).
I can also buy QFT tunnel ram carbs for about $1700 canadian dollars for a pair. They are calibrated for a TR but not custom built to my app.
I know there is cheaper ways to do it but i'd like to start with something in the ball park for tuning and not leave to much power on the table.
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 » Tue Sep 26, 2017 11:15 pm

I seem to recall F-bird telling me not to waste money on fancy carbs.
Today i learned the difference between a regular quick fuel carb and a dedicated quick fuel tunnel ram carb. Pay attention :

regular carb # Q-850
$749.95
has jet extensions.

tunnel ram carb #Q-850-2
$799.95
does not have jet extensions.

i learned this straight from holley. This doesn't mean that carbs from other builders are the same.

I think this is what i have decided on:
https://www.holley.com/products/fuel_sy ... /0-67200BK
Brian
The Word of God is quick and powerfull
www.therocketshop.blogspot.com

GARY C
Guru
Guru
Posts: 3391
Joined: Tue May 14, 2013 10:58 pm

Re: BBC thoughts

Post by GARY C » Tue Sep 26, 2017 11:22 pm

From what I have seen over the years is that T Ram carbs are metered different from single carbs due to the fact that you are dealing with twice the air and fuel.

Call QF and I bet you find out more!

cjperformance
Guru
Guru
Posts: 2487
Joined: Tue Aug 19, 2008 7:20 am
Location: South Australia

Re: BBC thoughts

Post by cjperformance » Tue Sep 26, 2017 11:43 pm

Now did you ask QF why those TR carbs dont have jet extensions and are more expensive???
Are you hoping the holley/s you linked will go straight on the TR and work fine??
Craig.

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

Re: BBC thoughts

Post by Old School » Tue Sep 26, 2017 11:49 pm

For your application I would do 2 750's. I have ran tunnel rams and Holleys since 1982 and they are very user friendly.

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

Re: BBC thoughts

Post by prairiehotrodder » Tue Sep 26, 2017 11:52 pm

The QFT carbs don't have jet extensions because they are meant to mount sideways. I expect to have to fine tune any carb i buy. If you look at the spec sheet on the QFT carbs, all the jets and bleeds are also exactly the same.
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 » Tue Sep 26, 2017 11:53 pm

thanks old school. I think you are 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 » Wed Sep 27, 2017 11:41 am

one more track day coming up. Here is a picture from my last race
malibusir.jpg
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

Post Reply