Discussion in 'The Venerable Q-Jet' started by hgiljr, May 24, 2020.
Thanks for info guys. So next steps? New intake or get a rebuilt QJ carb? Look at something else?
In order for the idle air bypass to work, it needs the cutouts in this picture,
Photo from Cliff Ruggles' book.
Since you are using a thick 1/4" gasket, I wonder if you can notch the gasket???
I still think you can pitch the metal plate and use the gasket in your picture. What is the yellow stuff in the chamber in holes next to the primary holes?
From what I saw, seems to be epoxy or something. As if they have been eliminated at some point. @LARRY70GS I can notch the gasket to match up with the new bypass air holes, but it is the only unique gasket that I have as I have not been able to find a duplicate. I wonder if someone at some point had such gasket custom made.
Just talked to Ken,
Notch that thick gasket so the idle air bypass holes are exposed. look at the picture I posted. Notching the bottom of the carburetor would be a lot harder. The gasket would be easier.
Thank you Larry. Do I notch the gasket to expose the new bypass holes that Ken did on the carb and the one that is on one of the primaries as shown in my carb picture or just notch to expose the holes that Ken did?
No, the bottom of the carburetor would be notched, but you would need a dremel tool to do that. Those holes are there to provide extra air at idle so you can close the throttle. When the throttle blades are open too much, the primary nozzles start to drip fuel. The engine idles on the primary circuit INSTEAD of the idle system. That's why the mixture needles are unresponsive.
I also think you may have a vacuum leak from the intake not fitting well. If you take an intake bolt out and sight down the hole, you may be able to see the threaded holes in the head not lining up well with the intake bolt holes. What happens is the intake sits too high on the heads because of block/head milling.
Just the holes Ken drilled. The other hole is already exposed because the bottom of the carburetor is notched for that hole.
The epoxy is to seal the plugs, which often leak. That's SOP for most all rebuilders, I'm sure Cliff and Ken both do that.
Did the additional holes on the gasket to expose the holes Ken drilled on the carb and results now are high idle even with idle screws completely closed. Lower idle when the holes in the gasket were not present and idle screws closed. back to the drawing boards. Any suggestion on what to use to cover such holes in gasket that I drilled?
So you backed the throttle speed screw all the way out? The throttle is nearly closed?
Yes throttle screw is all the way out. BUT, improvement. I went ahead and drilled the holes a bit larger and now things are beginning to look better. I also reconnected the spring to pull the throttle bar forward. Just need to adjust idle screws a bit more as I didn't have time this afternoon. Should I reconnect vacuum advance or leave disconnected?
Leave it disconnected. If it doesn't detonate, then you can reconnect it.
Please post a picture of the modifications you made to the gasket.
The problem is the camshaft, everything else is being done to help with the collateral damage.
I get more complaints from folks who have installed those cams than any other. 107LSA is used in a street engine for one reason...."bling". Well, actually two reasons, it helps fill my wallet modifying carburetors and distributors to give these engine the timing and fuel they need at idle to compensate for a piss-poor cam choice!
You can make more power everyplace with a "big" cam in one of these engine even with moderate compression, just have it ground on a much wider LSA. Over the years I've found without exception that with the big 455's, Buick, Olds and Pontiac that the wider we go with LSA, higher with the compression and longer seat timing the MORE power they make and vehicles are faster on the street and at the track.
Of course we do get a few complaints from customers when we go that direction with their engine builds.........they idle too smooth and folks don't turn their heads when they idle thru the local Dairy Queen car cruise!...........LOL
Below is an example of what I'm talking about. Pretty cool story but the short version is that the engine builder had Comp Cams select a cam for his 455 Pontiac build. They sent him an XR276HR cam, 224/230/110 LSA. It idled "rough" and didn't make chit for power on the dyno with his custom ported 250cfm iron heads. It also pinged as the cam was too small and LSA too tight for the big 455.
Anyhow I spec'd him out a cam with 289/308 seat timing, 236/245 @ .050" and 114 LSA. I told him to install it at 110ICL. He did exactly that and no other changes.
About a week later I get a call, and emailed me the dyno charts. He says it idles much better, improved throttle response, and made even better power than they were shooting for. Even better it no longer pings on pump gas!.......Cliff
Did you drill holes in the gasket or did you notch the gasket to provide a path to the primaries?
Holes were drilled into the gasket. It’s definitely a custom made gasket. Today I made a lot of progress. A local Buick gear head, Jim Haas, visited my house and and assisted. He tuned the carb and timing. We also found a vacuum leak on the intake gasket area which he tighten al screws. Car timing is currently at 15-32 and there is no detonation. It was completely off. It did idle a bit high after a 20 minute ride but lowered throttle screw a bit. Next steps are to:
1. Appears PCV valve is not doing anything as if there is nothing inside it. Need to see which is correct PCV valve for such car.
2. The fuel line appears to be a bit kinked. Need to get a new fuel line.
3. Reinstall the choke as that was never installed. Need to find the choke arm for it.
4. Distributor seems to be a off a couple of teeth. Need to remove and reinstall correctly.
I want to say thank you to everyone that has been assisting me through this process, on and off forum. I know I eventually have to change the cam but want to enjoy the car a bit as I have hardly enjoyed it since originally purchased.
A hollowed out PCV valve would be a HUGE vacuum leak, so for sure get one installed that has the guts in it.
I can tune these engines to run well with those cams, they just like a LOT of timing and fuel at idle and at lower RPMS. I would carefully put a couple of "channels" in the baseplate to allow the bypass air to enter the intake without notching or cutting up the gasket.
The power range with those cams is quick and narrow, so once you get all the idle nonsense sorted out it will feel pretty impressive at heavy and WOT when evaluated by the "seat of your pants".
Some of my customers who went to the Thumper and Thump Your Mutha cams kept them despite the stinky exhaust and poor street manners. Others swapped them out for something more user friendly. Certainly nothing wrong with a bad-ass sounding engine, if you can deal with a few negatives associated with that deal.........
I may be picking at a scab but it sounds like the bypass air is still blocked from the primaries. With holes drilled straight into the gasket under the holes Ken made the only place to get air is the heat riser channels( I think without seeing it). Do what Cliff or Larry said to make a channel for air to get to the new holes from the primaries. Did Jim Haas see that issue? Did he think it was ok?