BBC thoughts

General engine tech -- Drag Racing to Circle Track

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statsystems
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Re: BBC thoughts

Post by statsystems » Fri Aug 11, 2017 10:02 pm

prairiehotrodder wrote: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.

Yup. You can use more CR than what you have on pump gas.

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Re: BBC thoughts

Post by prairiehotrodder » Fri Aug 11, 2017 10:14 pm

What was i supposed to learn from that video F-bird? Don't take my motor to those guys? You may well be right n what you are saying about compression. What would you say is max CR for pump gas?
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Re: BBC thoughts

Post by statsystems » Fri Aug 11, 2017 10:28 pm

prairiehotrodder wrote:What was i supposed to learn from that video F-bird? Don't take my motor to those guys? You may well be right n what you are saying about compression. What would you say is max CR for pump gas?

I watched half the video. When they couldn't remember the first pull they showed went to 6500 and the second went to 6800 I clicked it off.

Sad to say they talk like a bunch of stoned teenagers.

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Re: BBC thoughts

Post by F-BIRD'88 » Fri Aug 11, 2017 10:30 pm

Watch the whole thing to the end. The point is right at the end.
This is typical Toronto "dialect" but that is not the point... watch the video.

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Re: BBC thoughts

Post by GARY C » Fri Aug 11, 2017 10:35 pm

prairiehotrodder wrote: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.
BBC will tolerate more than an average SBC, DV targets 10.8 to 11.2 on his street builds and dynos them on 87 octane to prove the point, 92/93 would be preferred in the car due to heat.
Here is a real world example of whyI think Fbird is wrong on his gear theory.
2 virtually identical builds, both 421 SBC dynoed 20 horse different both 3150+ lbs both run glides, same converter, same shocks, mono leafs and caltrack bars.
So why is the heavier under powered car with less gear, both trans and rear 2 tenths and over 2 mph faster?
1st car in this video...
https://www.youtube.com/watch?v=TTi71uG5BL8
VS this car
https://www.youtube.com/watch?v=6RgKOCo0GhU
Watch the end when it replays in slowmo...

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Re: BBC thoughts

Post by statsystems » Fri Aug 11, 2017 11:00 pm

F-BIRD'88 wrote:Watch the whole thing to the end. The point is right at the end.
This is typical Toronto "dialect" but that is not the point... watch the video.
I watched it to the end. The music sucked out Loud. They were testing 2 different fuels. I've spent a bunch of time testing fuel. I didn't learn anything from that.

What does this have to do with the OP and a pump gas build?

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Re: BBC thoughts

Post by F-BIRD'88 » Fri Aug 11, 2017 11:15 pm

Fuel matters... ya it is two different fuels. This Pro Fuels fuel is better fuel.
It is better than Sunoco and VP.. This is typical of other dyno tests
using this fuel. The MARK V fuel used in this test on this SBC was probabily over the top
but the Mark II (110 unleaded and street legal in Canada) would have shown a
real power gain too. It is GREAT for blending with "pump gas"
so your expensive 11:1cr BBC does not eat it self.
And it also makes more power too, even when blended. ( it really improves pump gas)
Fuel matters.... USe the correct fuel for the job...you will go faster for a lot longer too.

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Re: BBC thoughts

Post by KnightEngines » Fri Aug 11, 2017 11:27 pm

With shortish gears & loose converter you'll be fine at 11:1, don't sweat it.

Change the pistons to get the comp up & freshen it up.
Get someone who knows what they're doing to tweak the heads a little & supply a cam to suit, get them to look over the intake at the same time.

I'd switch to a 3 speed before I bothered with any more cubes - $ spent on more cubes can go towards a trans with the sale of the glide making up the difference.

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Re: BBC thoughts

Post by VMC » Sat Aug 12, 2017 10:44 am

My $.02 worth;

Stop looking for the one magic widget that will put the car consistently into the 9's.

Pull the engine and dyno it as-is with the headers you use on the car (and the exhaust if you can make it fit on the dyno).

You're pretty much past the point of picking the "low hanging fruit" in your hunt for power now, what you need to do is refine what you already have. You'll never see a ~5HP gain on an e.t. slip, but you will on a dyno. Find 5 places to pick up 5 HP and what do you have?--find 10 places to pick up 5 HP and what do you have? THAT you WILL see on an e.t. slip.

Until you've dialed in the lash, carb tune, timing, etc. and maybe tested a few peripherals (headers, carb spacers, etc.) you're not likely to see the full potential of what you already have.

Take this for whatever it's worth;

My personal 496 has been on the dyno 3 times--once when I first built it in 2006, and twice in 2014. The first pull in 2006 resulted in a dismal 477 HP. With tuning and changing the headers, the carb, and milling out the plenum divider on the intake I picked it up to 534 HP and 546 lb.ft by the end of the first dyno session. I had to pull the engine down in `14 due to a ring seal issue (poor machine work from the 1st build), and the only change was to drop the compression from 11.2 down to 10.5 and switch from a 1/16-1/16-3/16 to a 1.5/1.5/3 mm ring package. I re-baselined the engine in the exact same state of tune it was in during the first session and the power figures were within a couple % of where I'd left off.

I tested the following things during the 2nd session:

-carburetors
-intakes (OEM 163 with plenum divider removed and heavily ported & epoxied Holley Strip Dominator)
-carb spacer
-distributor
-jetting
-lash
-spark plugs (standard vs. projected tip)
-timing
-headers (3 sets)
-header collectors
-engine temperature

At the end of this session it was over 580 HP and 590 lb.ft. However, the engine was exhibiting oil pressure fluctuations despite a pan swap from the first build, so I pulled a pan off of another project and scheduled a 3rd dyno session. I also built a new 1000HP carb to test as well.

At the end of the 3rd session, the engine had made 616 HP and 616 lb.ft with a single plane and 614 HP and 610 lb.ft using the dual plane.

Think about that...from 477 HP to 616 HP changing only peripheral items.

Spend your $ wisely. Dial in what you have now.

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Re: BBC thoughts

Post by prairiehotrodder » Sat Aug 12, 2017 12:28 pm

I agree with you on the dyno idea. Its just not that easy because of my location.

Sold my old Straub cam last night, got good money for it.

Bought a Meziere electric water pump and an electric fan to replace my edelbrock mechanical water pump and clutch fan. Might be 5 or 10 hp there. I'm not done with this motor yet. When i do freshen up the motor it will get higher CR pistons and stay with my 4.25" crank and 6.385 rods. Maybe i'll just go to 4.560 bore instead of all the way to 4.6. I calculate a 18 cc dome would be necessary at 555 cubes. At that point i would also change cams. the Lunati cam i bought was used (on its 3rd motor at least) and has seen better days. I appreciate all the input i have received on speed talk. I have definitely used some of the advice.
Next summer the car will get the 29.5 x 10.5 tires so that should help my 60' as well but hurt my gear ratio. I think it will be worth it though.
Brian
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Re: BBC thoughts

Post by rmyauck » Sat Aug 12, 2017 1:19 pm

Melfort! Not too far away as I'mm near the border in Flin Flon!

How about trying a bit of an RPM increase made safe by destroking to say 3.76 so rod angle improves a lot. Less wt. flying around also! Doesn't reduce the displacement too much, and keep your bore size for strength and maybe do only necessary reboring. Your heads will still be great also and maybe will work better at higher revs. I had a 427 then a later 454 and really liked the 427!

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Re: BBC thoughts

Post by rmyauck » Sat Aug 12, 2017 2:39 pm

Down to 478 CI with the original BB stroke and they built them down to 3.47 for road racing.

Maybe you would need a turbo with the destroker to get the power also with 62 less CI, but who knows! I always wondered what a stock 427/454 destroked to 3.0 or less so it could rev like a SB with much greater built in strength! Would it get the efficiency of an LS due to the BB heads?

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Re: BBC thoughts

Post by MadBill » Sat Aug 12, 2017 6:32 pm

Unless one is running in a lb./c.i. class, making an engine 60 + cubes smaller is not usual the path to better performance. (and keep in mind there are drag engines turning 8,500 RPM with almost 6" strokes...)
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Re: BBC thoughts

Post by pdq67 » Sat Aug 12, 2017 9:24 pm

Remember that by juggling main bearing spacer's, you can install a 348", 3.25" stroke "W" engine's or the 409 "W" engine's 3.5" crank in our BBC's.

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Re: BBC thoughts

Post by prairiehotrodder » Sat Aug 12, 2017 9:48 pm

How did we get on to the topic of building a smaller motor? Thats not happening.
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