I currently have 75 jet in the driver side and 74 on passenger side (stager jet) for my B4B and Cliffs .044 rods. Runs great on warm days. On a 40 degree day, I get stumble and pop and carburetor icing problems. I have 3/4 turn on the secondary, to apply good strong signal to secondaries and have .041 cliff tappered rods. Air flap is limited to 80 degree maximum, as I am not convinced 90 degree opening is as efficient. "COLD" means this: 1. TA heads have heat blocked from the B4B manifold. 2. I have been using a 1/2 " phenaulic spacer under the carb. 3. I draw cool intake air straight from the firewall into the air cleaner (100 percent). 4. Headers are jet hot coated, and I never feel a heat blast when I open the hood. (much cooler under the hood) SO...The current plan is: Swap in my 1/2 inch aluminum spacer with thin gaskets to reduce insulation under the carb. Jet richer 76 and 75 primaries like you would in cooler climate anyway? ....I would like to hear from some of you who have used cold air and cold intakes and coated headers.
"On a 40 degree day, I get stumble and pop and carburetor icing problems." "1. TA heads have heat blocked from the B4B manifold." This will be the problem more than anything else. Since you have blocked cross-overs the intake will be cold and require a much richer mixture until it warms up/heat soaks. With anything street driven there will only be superficial improvements to power output with a cold induction system combined with blocked exhaust crossovers in the intake manifold. The engine and all related parts still need to heat up enough in a wet-flow system to prevent atomized fuel from coming out of suspension on it's way to the combustion space. A choke or richer jetting will be required during the warm up period to compensate. My Pontiac 455 has aluminum heads w/o any existing cross-overs, so I experience some power loss and cold-blooded running symptoms until the intake heats up some. The colder it is outside the longer this takes. I've also done considerable drag strip testing in this area as well, and have found that the quickest ET and MPH is obtained with a hot engine and engine parts combined with cool/cold outside incoming air vs heated engine compartment air. IF I tune for that scenario the engine runs quicker than trying to run it cooler or cold with cold engine parts (intake mostly) and then trying to "flood" it with fuel from the carburetors to compensate. I'd also add here that in it' quickest state of tune for ET and MPH, the engine will actually "stumble/hesitate/bog" on full throttle starts with traction if the intake isn't fully warmed up/well heat soaked. It's also DEADLY consistent tuned and raced in this configuration because it's simply much easier to keep it fully warmed up round to round vs trying to cool it way down, especially in later rounds when the Officials start "hot lapping" you back to staging so they can finish up the evening of racing. I also LOVE it when my competition in later rounds has the bug sprayer out to cool the intake and other engine parts, and all his buddies pushing his car in staging while they attempt to cool it back down to where it was in the previous run......which seldom if ever happens. Anyhow, I have zero issues in warmer weather, but when temps fall below about 40 degrees it simply takes much longer till the intake heat soaks well enough that the engine performs like it's supposed to. Not a big deal because I never drive the car in the Winter months, and very seldom run the engine if it's below 40 degrees anyhow. Tuning specifically for this scenario is not a good idea, as the engine parts will eventually heat up enough for the problems to disappear anyhow. So in basic terms the "problem" you are having is not really a "tuning issue", but related to the fundamental laws of physics instead, and why the engineers equipped these engines with a working heated intake system in the first place........Cliff
Thank you Cliff. I'll leave the jetting alone now. The aluminum spacer (vs phenaulic) should help bring the heat up to the carb. Last night was 40 degrees or so... * I drove the car about 10 minutes and got out my laser thermometer. Manifold was 120 and carb 100 degrees.... Car had whimpy power. * Let the car sit 10 minutes with closed hood. Manifold was 170 and carb 125 degrees.... Gained a ton of HP!
Thanks Gary, glad you are figuring it out. Effectively insulating the carburetor is easily accomplished with a 1/4" thick factory style gasket. One has to keep in mind here that the high velocity air coming down thru the carb, especially the front of a q-jet will greatly reduce the temperature of the carbs baseplate and they "ice" up pretty easy in really cold weather. For normal driving in warmer and even hot/humid weather that incoming air still does a great job of cooling down the carburetor to prevent problems. One can still see some "heat soak" in certain conditions, but I've never had this issue with my engine and have drove and raced it in the hottest possible conditions when the only place you wanted to be was in a swimming pool, not in a muscle car! As for spacers I did some very extensive spacer testing a few years ago and found that most of them actually hurt power and vehicle performance vs helping it, at least when used on a dual plane intake. Just the opposite for single plain intakes, they pretty much require at least a 1" spacer to work well. This simply happens because the throttle plates stick pretty far into the plenum area on a single plane intake causing both air flow and distribution issues. We ALWAYS see a nice power improvement on the dyno by adding a spacer to any type of single plane intake we've tested to date. When I tested spacers they were installed and the car driven on the street to get a "feel" for how they were working, then the car was taken to the track for testing. Keep in mind when listening to my results is that they are for my engine only, and it makes a LOT of power (over 600 ft lbs torque) and over 550hp. So results with engines making more or less power may be different. Anyhow, the WORST of the spacers tested was a 4 hole variety, killed the thing everyplace. It did however improve idle quality slightly and "felt" very responsive for "normal" driving. The fully open spacer was also horrible, it induced a "stumble" going quickly to full throttle that we couldn't tune out. The car didn't like it on the street or at the track. A fully divided spacer did OK, ran a little slower in ET and MPH than no spacer at all, but not very much. A semi-open spacer ran well everyplace, but slowed some in 60' but ran almost 2mph faster on top end. Semi-open simply means divided in the front and open between the secondaries. It should some promise and with a little gearing or converter change it would probably improve vehicle performance. After all the testing the winner was no spacer at all, just one 1/4" thick open gasket. My engine likes that deal as it allows both sides to see each other but not enough to cause "reversion" or interrupt airflow/cause turbulence that hurt power anyplace. So it ran the best ET with no spacer at all just one 1/4" thick gasket. I see LOTS of folks use spacers and doubt if most have actually drag strip tested them to see if they really pick things up some. Considering the "cobbling" involved with raising a carb at least 1", I was happy my car didn't like one. I had to mess with fuel lines, throttle linkage, air cleaners, Shaker assemblies and do some pretty creative design stuff to have the carb sitting 1" higher than it usually does.........Cliff
My aluminum spacer is a 1/2" modified 4 hole (semi-open) in that I cut the divider out across the rear barrels. The front holes are fully intact. The top gasket is cut to match the spacer and bottom gasket is fully open. The Edelbrock B4B Buick intakes have distribution issues and the semi-open spacer was an attempt to minimize that problem and lift the throttle blades as well. The intake divider is lowered a little, and one jet richer on primary driver side to avoid the dreaded "lean #1 cylinder". THANK YOU CLIFF for your very informative input........ I should be close to where I need to be now with my conservitive modifications... and my awsome Ruggles Recipe Quadrajet. 1967 GS 7.52 at 92 (est. 11.80 at 113 1/4 mi) 455 -stock 70 Buick factory pistons (no notches), stock rods & rockers arms, C118 Kennebell cam, JW 3500 converter, TA stage 2 heads, factory rally wheels, ps and pb, stock appearing, full exhaust, 91 octane "no ethenol", and no trailer... 3700 lbs.
It is very important on some intake manifolds to get the carb up high enough so the difference it throttle plate depth (spread bore carburetors) doesn't hurt distribution and disrupt air flow into the plenum areas. I saw this play out once about 15 years ago on a dyno session we went to. I provided a custom 850cfm q-jet for a very stout 505cid Pontiac engine topped with KRE's aluminum heads. They had installed single plane intake and only a gasket, no spacer. The engine hated it, and would not make good power with that intake/carb set-up. It was removed after many unsuccessful dyno pulls and we installed a Victor/Dominator. The power went from just over 500hp to just over 600hp! It made 612hp to be exact. While the intake/carb swap was being made we took an aluminum 1" spacer and carefully blended it to match the intake and provide smooth flow from the Q-jet to the plenum areas. The single plane intake, spacer and q-jet was re-installed, and the very first pull it made within a couple of HP of the much larger Victor/Dominator set-up! NONE of the folks involved with that engine or dyno runs could believe how much power we were leaving on the table NOT using a spacer with that intake!........Cliff
Not a problem, in the Office today catching up on phone calls and emails, etc. That particular improvement by only adding a single part to date has topped the list, but we've tried other parts over the years that showed considerable gains in power. One of those was nothing but a set of headers being used for dyno runs on a stout 505 race engine we prepared here. The old set were "cheap" , 4 tube design and not very well made, but fit the application. The engine power was off quite a bit, and no carb, distributor or moving the cam around netted us much better. We swapped out those headers for a really well made set from either Hedman or Hooker, can't remember exactly at the moment. The new set had very smooth bends and greatly improved design just by looking at them. The big 505 had been showing up around 630hp, and it INSTANTLY jumped clear up the 670-680hp range with no other changes. Another test years back that showed NO improvement whatsoever was swapping out my stock HEI for an MSD billet with a 6AL box. It actually made about 1-2 less average power than the HEI on back to back pulls with no other changes. So much for the "bug-zapping" stuff and all the propaganda that surrounds it.........Cliff
