BBC thoughts

General engine tech -- Drag Racing to Circle Track

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vortecpro
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Re: BBC thoughts

Postby vortecpro » Wed Sep 06, 2017 5:43 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?
NHRA Stocker Cranks
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prairiehotrodder
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Re: BBC thoughts

Postby prairiehotrodder » Wed Sep 06, 2017 7:46 pm

MAHLE pistons with 10cc dome. Pistons are between .005 and .007 in the hole. Crosses the finish line at about 7200 rpm.
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Re: BBC thoughts

Postby vortecpro » Wed Sep 06, 2017 8:27 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?
NHRA Stocker Cranks
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Counter Weight Cutting

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Re: BBC thoughts

Postby prairiehotrodder » Wed Sep 06, 2017 11:07 pm

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.
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Re: BBC thoughts

Postby prairiehotrodder » Thu Sep 07, 2017 7:17 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
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Re: BBC thoughts

Postby F-BIRD'88 » Fri Sep 08, 2017 3:37 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.

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Re: BBC thoughts

Postby F-BIRD'88 » Fri Sep 08, 2017 7:31 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, )

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Re: BBC thoughts

Postby prairiehotrodder » Thu Sep 21, 2017 6:47 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.
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