Gas- CSU or C&S
Methanol- APD

 

C.S.U. Keven will help you long after the purchase. We have one of is carbs on a BBC f1x-12r idles perfect ar is flat.

 

I'm just curious why in this day and age someone would go with a blow through carb instead of EFI on a boosted application? I'm not trying to bash at all as I am considering a procharger on my Nova.

 

I run bs3 on my car, but have to admit the right blow thru work, and are simple to tune.

 

DHR Darren, the reason I chose blow-thru was due to the fact that it's cheaper and also, I don't have enough knowledge in EFI tuning to be confident and to benefit from it. My plan is to go with a blow-thru setup and become really confident with my tuning ability in regards to a carburetor. During this time, I will be doing a lot of research and studying up on EFI tuning so if and when I do make the change over, I will be confident enough and have some knowledge to back me up so I'm not just going to the track and scratching my head.

 

joemondo, when you say your air fuel ration is flat, you mean it doesn't jump all over the place when you pull up data? What's the biggest variance in points you've seen when you look at the data?

 

joemondo, when you say your air fuel ration is flat, you mean it doesn't jump all over the place when you pull up data? What's the biggest variance in points you've seen when you look at the data?[/QUOT On the dyno thru the pull, flat 11.5 on c116 from 3000 up, from 10psi to 30+. Be honest I was shocked how close an old school carb was.

 

Ive had real good luck with my carb shop 950 on a 383sbc w/ f1r . Have made some changes to my combo over the years and help was a phone call away , good customer service . Afr is 12.0 through entire curve . Idle was fat out of the box , but car started and idled immediately , then just adjusted idle mixture screws . Idles at 16.0 now . Works well on the street too and was built for drag only .

 

Ran blown gas for about 7 years with CSU building the blow thru carb. Started this in 2005. Combination was. 565 BBC with. F3-139 ProCharger with CSU Dominator gas carb. Ran as fast as 6.30's @ 219 mph. Kevin is the master at blow thru carbs. Don't search any further .

 

How much are you spending on the carb and data logger ? Do you already have a 7531 box or are you going to have to buy an ignition box , coil , ?

EFI is not that far off if your starting from scratch .

And they have fail safes . .

 

Agree 100%. If you are talking boosted then you will need to pretty much build an EFI compatible fuel system anyway so the "cost" is the same there. For ignition you would need to buy a programmable box with boost reference for the carb setup where the EFI systems can control that themselves.

I am looking at converting to the Sniper 1250 system from my blow thru carb. A blow thru carb bought new is over $1,000 right? The sniper system is $1,500 and if you buy it from Steve Morris he will tune it for you!

So the cost difference is $5-600 for the fuel mixer. If you have to buy an MSD box for the carb setup you have a few hundred spent on the carb side so it is very close all said and done.

Will you drive on the street? That is a big consideration for my change. Yes, my carb works well at the track, but I drive it 25 miles to the track and back. At idle and cruise it is still stupid rich. Can that be fixed? Well yeah, but now you are getting into some serious carb tuning work and expertise beyond the basics. Making some software changes would be easier than messing with high and low speed air bleeds etc. imo. And like I said, Steve Morris will give you the tune anyway.

 

C&S ask for Roger
Another reason for blow thru vs EFI is the cooling effect it has on the inlet air temp. With EFI you would have to reduce timing or intercool the air charge. Or hose it down with meth.

 

Thank you everyone for all the wonderful information you're giving me . If I started from scratch, I would've went with EFI and just learned along the way. I already have the MSD Digital 6 Plus ignition box (#6520) along with the MSD Boost Timing Master box (#8762) and the entire fuel system (from the pump to the regulator) is setup for a carbureted application (mind you, some of the components could potentially work with an EFI setup but I'm very doubtful of that). At this time, I'm going to stick with a blow through carbureted setup and maybe down the road I will convert to EFI, I just can't do that right now.


The carburetor I currently have is a Quickfuel 950 which I had The Carb Shop convert to a blow-thru style carburetor. Reading my data log, the air/fuel ratio is all over the place being as rich as 10.8-10.9 to as lean as 13.3. The data log will show an inconsistent air/fuel ratio between those numbers there. I can safely say that I do NOT have a flat or linear air/fuel ratio. I calibrate my Bosch O2 sensors (I have one in each collector) before I make my first pass each outing. I showed the data log to my engine builder (he's been building engines for about 35 years now and is a guru when it comes to N/A engines, however it does admit that he might not be the best source of information when it comes to power adders) and he said that my air/fuel ratio is all over the place and should be a lot closer than what it is, and I agree with him.


In conclusion, the guys at The Carb Shop are very knowledgeable and have awesome customer service, I just think I have one of those "bad items" that no matter what you do to it or with it, it will just never work -the carburetor being the bad item in this case- and just have to get something different. I'm sure you guys have "all been there done that" with something through out your lives be it a car part or something totally unrelated to cars.


Thank you,
Tim

 

Do you have a way to log fuel pressure ?

Dont give up on that Carb Shop Carb .

Might need a better BRPV though .

Does it had Boost Reference Power Valves ?

What are the AFRs in boost ?

 

Yes, I do log fuel pressure.


The primary metering block does have a boost reference power valve and the secondary metering block as a block off plate. This is STRICTLY a drag car.


I took a screenshot of the AFR chart with boost and rpm:

 

Seems to me like the AFRs are right around 11.0 in lower boost and get to around 12.0 in the upper boost .

Sure it could be a little leaner in lower boost , but 11.0 should not kill any power , and 12.0 should be ok on C16 .

Could be a little richer up there , but on good gas I wouldnt be too worried .

A carb with a fuel curve from 11.0 to 12.0 through out the pass isnt THAT bad .

If you want more fuel up top , open up the PVCRs a little . And if you want it leaner building boost , use jetting and or slow down the powervalve .

If the Powervalve or powervalves are working correctly , you should be able to run very small jetting and still have enough fuel up top . With two PVs , I was running 68 squared .

Also you could block the secondary HSABs .

Have you put fresh plugs in and made a pass then looked at them ?

But Blow-thru carbs are all about the BRPVs .

 

Dragrace, what is the issue you are trying to solve? It looks like you have a pretty stable and safe afr. Is it running poorly? Stumbling? If not, you may just have information overload. Once i got mine in the range i wanted, i quit looking at the data. I was going nuts overanalyzing the data. The plugs or time slips will tell me if something is off.

 

I'm running VP Racing Q16 and increased the jet size accordingly to accommodate for the increase oxygen content. I had the car dyno-tuned back in July using the Q16 and the car made a lot of power with no issues however, the dyno pulls were only about 4.5 seconds compared to a 9.5 second 1/4mile run. The other thing that the dyno won't really show is if there's a stumble off the line since during the pull the back tires are already moving. Taking the car to the track after the dyno session, there was a stumble off the line until about the 100' mark and then the car took off like a rocket. During that weekend of racing, I made about 20 passes on the car. When I got home I took all the plugs out and brought them to my engine builder to inspect them with his spark plug viewing tool and he found some aluminum on the plugs. The other thing I noticed was that there was some seepage of water coming from the outside corners of the cylinder heads. I'm chalking this up to detonation.


I only have the one power valve in the primary metering block and the secondary metering block as a block off plate for the power valve.


The secondary high speed air bleeds came form The Carb Shop already blocked off.


I spoke to Rodger from C&S Carburetors as well as Kevin from CSU Carburetors and both guys are extremely knowledgeable and appear to have outstanding customer service. The other thing I like about Rodger and Kevin is that they didn't bash or speak ill of their competition. Speaking to both of them however, I was informed that The Carb Shop's boost regulated power valve system is somewhat older technology.


The last time I took the car out I was able to make two passes and yes, I put 8 new spark plugs in and shut the car off after the 1/4 mile run and pulled #1 and #2 spark plugs (my hottest cylinders according to EGT's). When I got back home, I removed the plugs and brought them to my engine builder so he can read them correctly. There were no traces of aluminum on any of the plugs (I think the reason for that was because I pulled huge amounts of timing out which slow the car down substantially) but, we could not get a good read on the #1 and #2 plugs because they just looked white. There was some speckling on the porcelain but my engine builder is saying it was from the copper anti-seize that may have came off the threads.

 

Yea , I wasnt impressed by The Carb Shops BRPVs .

 

Maybe one day ill get boost referenced power valves. Lol. Carb Shop built mine about 8 years ago without them.

I guess that is why my cruise is so rich? The fuel has to be there off boost so it is when under boost?

 

I have been doing some research and considering making the switch to EFI over the winter. I think I will make a new post with the correct heading to have some more people chime in.

 

For first timers , look at the Holley EFI .