Reply With QuoteI was told I have real nice secondary linkage. I can adjust when my secondaries come in. I can cruse at 3k, on 2 barrels. My milage is great, until I bury my foot!!
Holleys list # 6109 are 750 double pumpers made to mount inline on a tunnelram, and they work great. I've used them on a drag car and boats, they also have progressive linkage and are ideal for cruising. The inline mounting makes the linkage very simple also.
I was told I have real nice secondary linkage. I can adjust when my secondaries come in. I can cruse at 3k, on 2 barrels. My milage is great, until I bury my foot!!
If you want to be able to day cruise and have good fuel mileage with snappy throttle response with multible carbs stay at or below 600 cfm each. With anything else you are simply dumping raw fuel and potentially contaminating the oil. This is especially true with a tunnel ram which are all designed for upper RPM power. I ran for years a pair of 450 competitions on a mild 454 with a TR-2X tunnel ram. No one could touch the hole shot but with an A impeller it ran out of breath just short of 5000 RPM. Up to 5000 RPM the pull was very good. Larger carbs drop the vacuum signal too much and now you have to tune the carb over rich to make up for the loss of signal. With stock or near stock valve train there is no reason, or even an capability, to go above 5500 RPM anyway.
660's ARE A CONSIDERATION, FOR...SOME ECONOMY WITH THEM, A MOD WE DID...WAS TO NOTCH OUT THE SECONDARY OPENING CAM SO THEY OPENED LATER INSTEAD OF 1to1 WORKS PRETTY WELL,...
The problem with this modification, when done by itself, is that the accelerator pump's centrally located discharge nozzles still dump fuel into the closed secondary throttle plates. It puddles up until the secondaries are opened.
If you want progressive primaries/secondaries, these days you are better off buying carburetors designed as such. Fact is that the double-pumper superceded the center squirter.
LO
On the jet boat, 466 with Holley 660's
http://www.***boat.com/image_center/...erhead-med.jpg
Generally speaking, if you have standard 600 vacuum secondary carbs, it may be possible that you need more than two 600's at 5000 rpm. I may being upping my cam and going to a pair of 850 Center Squirters myself.
LO
Never heard of an 850 center squirter...what's the list no?
I'm running a set of 850 center squirters on my blown bbc...
Hey Heatseeker, where'd you find the 4223's? I saw mine on Ebay, freshly remanufactured and with a "Buy It Now." I jumped on 'em.
850 Center Squirters are relatively rare carburetors. They may not be top-of-the-line by today's standards, but the "rare, classic & retro-bling" is where they have additional appeal.
LO
Never heard of an 850 center squirter...what's the list no?
660 Center Squirter: List #4224S
850 Center Squirter: List #4223S
850 Center Squirter:
http://www.***boat.com/image_center/...00/350Carb.jpg
http://www.***boat.com/image_center/...b_Over-med.jpg
Cool, huh?
LO
The problem with this modification, when done by itself, is that the accelerator pump's centrally located discharge nozzles still dump fuel into the closed secondary throttle plates. It puddles up until the secondaries are opened.
I've heard that you can hog out the primary accelerator squirters causing more fuel to flow to the primaries than the secondaries, somewhat negating the effect? Never actually tried it but it sounds somewhat reasonable.
If you want progressive primaries/secondaries, these days you are better off buying carburetors designed as such.
I believe you're right there Paul. All these tuning tricks are exactly that.........tricks. I think the design of the modern dp is far superior to the 660s (850s center squirters too apparently........cool stuff there) if cruising somewhat economically is the goal.
LakesOnly,
Paul have you come across any 950 3 barrel Holley carbs ?????
I know they come as vacuum secondaries and have heard that they also have some that are mechanical.
Jim
Holleys list # 6109 are 750 double pumpers made to mount inline on a tunnelram, and they work great. I've used them on a drag car and boats, they also have progressive linkage and are ideal for cruising. The inline mounting makes the linkage very simple also.
Those are about the best "all around" TR carbs Holley makes. Took off a pair of 660's that were highly modified, and installed the 750's...tjhey were unreal! Never realized how much smoother the motor could run untill we changed. Problem with the 660's is they're really only meant to run wide open. The transition between idle and WOT isn't made for cruising at all, that's why they get such poor mileage. It's not because of the linkage...your motor at any given rpm is asking for the same amount of air and fuel, weather it's through a two barrel or all eight barrels. The 660 is just not made for part throttle, and really inefficient. Some try and use metering blocks off the 1850's and run a power valve...that sort of works, but the metering is still different. The 6109' 750's had much better throttle response...partly due to the progressive linkage, but also due to a much better calibration, cruised like a sewing machine, and got way better mileage, even though they were larger carbs. Holley dosen't make the 6109 any more, but my advice would be to stick with any of the std. double pumpers (4176, 77, 78, etc.) They have good calibration and easy to work on. I know 660's are the typical carb, and everybody's got them, and say they work...but I would venture a guess that if any of those guys switched to a plain 650 dp they'd be AMAZED at how much nicer their boat ran. PLEASE...not trying to start anything...
BTW...any pair of Holley carbs can be run inline on most of the common tr's by doing a little parts swapping. Turning them sideways helps eliminate fuel starvation to the front jets under acceleration. Also makes jet changes easier.
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