BBK Throttlebodies

[Fastbird93]

Anyone have trouble with them before? Mine seems to have a "sticky" point right before the blades close, which keeps it from closing, cauing me to have a slightly high (about 200-400 RPM) idle and my IAC counts to bottom out at zero.

I also have some kind of hard residue right behind the blades, and am thinking one of two things: Either it's there for a sealing purpose, in which case BBK needs to take a look at their tolerances instead of putting gunk to seal at the blades, or it's not supposed to be there and I can grind it out.

Sorry, no pics as I don't have a close focus feature on my digi camera.

[Injuneer]

I seriously doubt they would put "gunk" behind the blades to seal them to the body. It is very common to get carbon buildup behind the blades, because of the "recycle" from the PCV vent system. If you have excessive blowby on the pistons, or a fualty PCV valve, crankcase vapor can flow the wrong direction in the line from the TB to the passenger side valve cover, fill the top of the TB with oil, and then let it spill back into the vent hole, which is in front of the throttle blades. Might want to check the cover plate, and the area behind the TB for excessive carbon buildup.

If the blades are starting to rub on the throttle body bores, you need to look at why. Is the shaft bearing worn? If it worked fine for a while, and only recently started to hang up, something has changed recently. It is possible to lightly sand the edges of the blades, to allow for additional clearance, but I'd find out why it started hanging up, before altering anything.

I have some problems with my Holley 58mm TB, and borrowed a BBK 58mm while I "massaged" the Holley. The BBK came off an LT1 that made over 1,100HP, and never had any problems. Although the BBK seems to have a problem with the IAC passages having casting flash in them, and doesn't "look" as good as the Holley, it seems to be built as well, or better.

[Fastbird93]

I seriously doubt they would put "gunk" behind the blades to seal them to the body. It is very common to get carbon buildup behind the blades, because of the "recycle" from the PCV vent system. If you have excessive blowby on the pistons, or a fualty PCV valve, crankcase vapor can flow the wrong direction in the line from the TB to the passenger side valve cover, fill the top of the TB with oil, and then let it spill back into the vent hole, which is in front of the throttle blades. Might want to check the cover plate, and the area behind the TB for excessive carbon buildup.

If the blades are starting to rub on the throttle body bores, you need to look at why. Is the shaft bearing worn? If it worked fine for a while, and only recently started to hang up, something has changed recently. It is possible to lightly sand the edges of the blades, to allow for additional clearance, but I'd find out why it started hanging up, before altering anything.

I have some problems with my Holley 58mm TB, and borrowed a BBK 58mm while I "massaged" the Holley. The BBK came off an LT1 that made over 1,100HP, and never had any problems. Although the BBK seems to have a problem with the IAC passages having casting flash in them, and doesn't "look" as good as the Holley, it seems to be built as well, or better.

Problem is that this build up/gunk was there from the factory. The TB has maybe, at the absolute most, 1000 miles on it. It's clean as a whistle inside and out. The blades don't appear to be rubbing on anything other than this build up as there's no abrasions or scoring. I've noticed the hang up since day one, but at first attributed it to me being over cautious, but now am absolutely certain that it's an issue.

[Injuneer]

Mikght be worth a picture.... sounds like a major design issue.

Fred

[Kevin - Blown 95 TA]

Mine is doing the exact same thing. I think that it has something to do with the black plastic cover, but I can't seem to determine where it might be touching. With the cover off, the prob doesn't seem to occur. I verified it by checking the throttle angle with the logging software. I also pulled over one of the times when it was idling at 1300 or so and physically pushed it closed a little which brought the idle down to normal. Then I removed the cover and continued driving without the problem. Now. I have the cover on again and sometimes have the problem. I can get it to idle down by tapping the gas pedal. Anyway, my plan is to add a light auxilary spring until I can figure out what it is causing it or where it is rubbing on the cover - it might be the cruise control cable barely touching ot something. I have a spare cover, so I might paint one white inside and see where or if it is rubbing. The blade shaft pivots on ball bearings, so I have faith that there's no wear, and I don't have any carbon deposits. I read once that there was a reason for the grey coating on the back side of the blades, but I can't remember what it was.

[fastTa]

It seems like BBK is aware of this problem. It is in there FAQ section on their website. There solution to the problem is an idle setscrew adjustment. I've seen alot of threads with the same problems on ls1tech.com as well.

http://www.bbkperformance.com/tech.shtml

[Kevin - Blown 95 TA]

Thanks for the link, but that seems to describe a problem of it sticking closed, not open like we are experiencing.

[fastTa]

Thanks for the link, but that seems to describe a problem of it sticking closed, not open like we are experiencing.

I wondered the same thing myself, but it is a little hard to discern given the way the question is worded.

I would give BBK a call. They might have fixed the problem and might be willing to do a swap given the broadness of this "sticking" problem. You never know, BBK might be willing. It would be a good test of their customer service!

[Injuneer]

The coating on the back of the blades is an anti-carbon coating. The stock TB blades have it too.

[Fastbird93]

Well, got the TB issue taken care of. The Throttle stop was too far open. Did some playing, got a pretty solid 800 RPM idle.

BUT!!!!! I've stil got a VERY nasty LTerms split at idle and everything checks out with that TB, including the pipe mod.

My rockers are a bit out of adjustment, but they're getting the 1/4 lash treatment tomorrow, as well as a check of the O2 wiring harness'.

Any thoughts or ideas?

[Kevin - Blown 95 TA]

BUT!!!!! I've stil got a VERY nasty LTerms split at idle and everything checks out with that TB, including the pipe mod. Any thoughts or ideas?

Maybe you got a leaky intake gasket or leaky exhaust gasket. Either one could cause an imbalance. Some guys adjust the throttle stop screw until the LTs even out because they found that the LTs would actually switch at a certain point of adjustment. I have never verified this - my splits are about 4 or so and nothing to worry about. I HAVE been running for the last 4 years with a homemade extended O2 harness on the driver's side. I don't know what, if any, effect that has. I wouldn't have done it, but I was stuck trying to get it together & didn't know about the available O2 extenders. I suppose a poorly done job would affect the readings.