BBC thoughts

General engine tech -- Drag Racing to Circle Track

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F-BIRD'88
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Re: BBC thoughts

Post by F-BIRD'88 » Wed Sep 27, 2017 2:42 pm

That is a smooth car.

I like the 750's you chose. Good play. I like the purple metering blocks ha ha .

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Re: BBC thoughts

Post by statsystems » Wed Sep 27, 2017 4:45 pm

GARY C wrote: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!

You never double the airflow through 2 carbs.

You double the jet area, double the needle and seat area and also double the emulsion and air bleed area.

If someone is telling you up the difference between a single 4 tune up and a TR is some jet extensions...well common sense should tell you that is incorrect.

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Re: BBC thoughts

Post by cjperformance » Wed Sep 27, 2017 7:08 pm

prairiehotrodder wrote: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.
Yes this is what im getting at, TR (sideways ) carbs dont need extensions, and if the jet/bleed spec is the same then what is it about them that they are charging more $for? Did you ask?
Craig.

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Re: BBC thoughts

Post by prairiehotrodder » Wed Sep 27, 2017 7:27 pm

i asked what the difference is. He said the jet extensions. I asked if i could just remove them and save the $50 and have the same carb. He said "pretty much".

Thats all he told me. Maybe he didn't know either and maybe i should have asked more questions. I'll leave it alone. I'm gonna take an educated guess that if there is a difference it is in the emulsion jets (is that the ones in a vertical row on the metering block?) Because the QFT wesite says the MJ and the PV and the Air bleeds are the same.
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Re: BBC thoughts

Post by cjperformance » Wed Sep 27, 2017 7:29 pm

prairiehotrodder wrote:i asked what the difference is. He said the jet extensions. I asked if i could just remove them and save the $50 and have the same carb. He said "pretty much".

Thats all he told me. Maybe he didn't know either and maybe i should have asked more questions. I'll leave it alone. I'm gonna take an educated guess that if there is a difference it is in the emulsion jets (is that the ones in a vertical row on the metering block?) Because the QFT wesite says the MJ and the PV and the Air bleeds are the same.
brian
Yes correct on emulsion jets, vertical row in metering block.
Craig.

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Re: BBC thoughts

Post by MadBill » Wed Sep 27, 2017 8:32 pm

Given that the G forces are 90° to 'normal' for a sideways drag carb, do they use circle track-type cutaway floats?
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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Re: BBC thoughts

Post by statsystems » Wed Sep 27, 2017 9:10 pm

MadBill wrote:Given that the G forces are 90° to 'normal' for a sideways drag carb, do they use circle track-type cutaway floats?

They should have slanted floats but most guys don't use them and it causes issues.

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Re: BBC thoughts

Post by prairiehotrodder » Sun Oct 01, 2017 12:25 am

Here is the update on my last race of the year. I made 2 changes to my car
1 - advanced cam from 108 to 103 ICL
2 - installed electric water pump / electric fan

Air today was no better than any other day.

first pass of the day was 9.972 at 135.61 which was my best pass ever barely and i had the exhaust on.

it was a street legal event and traction went away as street cars with radials began to dirty the track. Made a few 10.1 passes with terrible 60' times.

then they re-prepped the track and i had dropped my exhaust (about 50 pounds) and i went 9.964 at 136.62 which is my new best ever. All my 60' times today were terrible and if i could have had a better 60 i could have done much better. Overall i had hoped for more improvement but i'm happy that i made two 9 second passes and my motor and car treated me good this season.

I have 3 major things that will happen for next season:
-the tunnel ram with two 750's
- the erson cam
- change tires from 28 x 10.5 to 29.5 x 10.5

Brian
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Re: BBC thoughts

Post by cjperformance » Sun Oct 01, 2017 6:28 am

Good results so far, nice work.
What is your exhaust setup? Looking at mph results on v off it seems line its working quite well.
Craig.

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Re: BBC thoughts

Post by F-BIRD'88 » Sun Oct 01, 2017 12:26 pm

Very nice......

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Re: BBC thoughts

Post by Bob M » Tue Oct 03, 2017 1:29 pm

prairiehotrodder wrote:
Sun Oct 01, 2017 12:25 am
Here is the update on my last race of the year. I made 2 changes to my car
1 - advanced cam from 108 to 103 ICL
2 - installed electric water pump / electric fan

Air today was no better than any other day.

first pass of the day was 9.972 at 135.61 which was my best pass ever barely and i had the exhaust on.

it was a street legal event and traction went away as street cars with radials began to dirty the track. Made a few 10.1 passes with terrible 60' times.

then they re-prepped the track and i had dropped my exhaust (about 50 pounds) and i went 9.964 at 136.62 which is my new best ever. All my 60' times today were terrible and if i could have had a better 60 i could have done much better. Overall i had hoped for more improvement but i'm happy that i made two 9 second passes and my motor and car treated me good this season.

I have 3 major things that will happen for next season:
-the tunnel ram with two 750's
- the erson cam
- change tires from 28 x 10.5 to 29.5 x 10.5

Brian
Have you considered a drag radial tire? I found better all around times switching from a 28 x 10.5 slick to a 275/60 DR. Not to mention a much better "feel" down the track then the bias ply slick.

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Re: BBC thoughts

Post by prairiehotrodder » Tue Oct 03, 2017 2:54 pm

i've considered drag radials but i;m scared to take the risk and buy a set and find they won't work. My car is always on the edge of traction as it is. My track surface is easily polluted by radial tire cars dragging up sand and rocks and ripping up the rubber. I'm not saying they won't work but i may leave that idea for another time. I've been thinking about my combo lately and i know i've made some mistakes. I never should have put in a glide but now that i have it i don't think i'll change it. I need to do things to my motor to make torque. That will make my car faster with the glide. I think the Erson cam i bought and the tunnel ram will both help in that department. Its crazy how certain things virtually did nothing.
the crank trigger
the lemons headers
the lunati cam
moving the cam around.
mini tubbing my car
the exhaust on or off

all of these things did next to nothing. Maybe just shifting the torque and hp rpm range around a bit. I'm real curious to see what the t-ram will do.
Brian
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Re: BBC thoughts

Post by F-BIRD'88 » Wed Oct 04, 2017 11:14 am

One thing I noticed that might want to llok at is the big outlaw style tall cowl induction hood scoop.

The GM factory ones 2" ish tall on a stock flat hood work. They do create a high pressure cool air pick up point at the base of the wind shield. But the real tall outlaw cowl hood tends to let the air go right over the roof of the car and creates a low(er) than ambient pressure at the base of the wind shield ( relative )
and or the air comes thru the radiator (heated air). The result is like a negative supercharger where the engine is recieving air that is at a less relative pressure than the ambient air is and much less pressure than
say a ram air or forward hood scoop or true functional cowl 'induction"

This can be solved by a sealed carb pan with air duct that picks up the air in front of the radiator, all under the cowl hood.
Looks the same but functions a lot different.
Another path is a forward facing hood scoop ( also best of sealed to the carbs with a carb pan)

This can be the limiting factor ( "the cork") that will limit or stop other engine upgrades ( cams, headers etc) to not show a performance gain.
this may not be the only factor that is limiting further car performance gains but it is a area that needs addressing. Another is the Chin spoiler that goes under the radiator support. If it is missing a lot of air gets trapped under the car at high speed, creating excessive body air drag. The faster you go the worse it gets
when the critical front chin spoiler is missing.

Whats going on with the 1/8th mile time slip data compared to the 1/4 mile time slip data?
Can show you what if and where and how the car is performing as it goes down the track.

With the glide and now planed taller new tires you may want to swap the rear gears too.
The higher you rev up the motor with the tunnel ram and long duration cam the better if with a glide.

You could evaluate that by just doing 1/8th mile test drag passes or limited 1000 FooT passes with steeper gears
to see if the car likes it especialy with the tunnel ram. ET MPH
Then decide based on that for running the whole 1/4mile trap while buzzing the motor higher thru the traps with steep(er) gears.
It will either react to the change or it won't. The more gear, (mechanical leverage) the better the weight transfer on launch to get all the cars weight on the (limited size) back tires for traction.....Especially with a Power glide.

The taller diameter tries you have planed tend as a rule to "grow" a bit more than a short diameter drag tire does at higher speeds
thru the traps acting a bit like a "overdrive" in effect and allowing more agressive gearing.
This is how you make a heavy(er) weight, power glide car with small tires work.

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Re: BBC thoughts

Post by F-BIRD'88 » Wed Oct 04, 2017 11:33 am

Does your 'Glide have a trans brake or are you "footbraking it" ?

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Re: BBC thoughts

Post by prairiehotrodder » 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
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