I have a Holley 650 on my Buick 350. In WOT it seems like it’s running very lean until about 3k rpms. Before I got the motor rebuilt and this new carb it would do a burn out no problem but now it struggles to make any power before 3k rpm
It has a Ta sp3 intake, comp cam, 10 to 1 compression, and headers. It’s the Holley 650 brawler with vacuum secondaries.
should be a quick fuel #BR67207 ? that's got a 6.5 p/valve , 68 front jets and 31 pump nozzle according to summit info . first thing is you will hear you need a bigger cfm double pump carb . bigger yes , 750-850 ? I have good luck with the vac secondary carbs . that should have the adjustable vac secondary correct . be sure you review/understand the instructions for that and test drive before making adjustments . that comes preset with a purple vac sec spring I believe . I've run a couple - never had to adjust , run fine . jet size etc looks pretty good , not too lean . but , if it ran ok before engine work - - - - - ? also new engine combo = adjustments needed probably . 2 cents .
Did the machine shop tell you that the engine has a calculated 10:1 compression, or did you just use pistons rated at 10:1, and assumed that the compression was 10:1? It might not be. What comp cam? What are the specs? You might have over cammed the engine. The carburetor is undersized at 650 CFM. In addition, the Holley vacuum secondary carburetors are not as good as the double pumpers. Are the rear gears and torque converter appropriate for the cam? You will also lose some low end torque from the single plane intake. You may have a mismatch of parts. Lots of questions.
It does have a calculated 10:1 compression. Stock converter and I believe it has 2.73 gears, comp cams recommends 3.40-3.70.
Not the best cam to choose. It's a straight pattern cam, Buick engines like a dual pattern cam with more exhaust duration than intake duration. If you truly do have 10:1 static compression, that cam will give you close to 8.3 Dynamic Compression. That is close to Race Gas territory. Does it ping? I don't say this very often, but you could use a bigger cam. Seems like your problem is a mismatch of parts. You need a bigger carburetor (Q-jet), more converter and more gear.
Would it be worth it to get the Holley efi system and any recommendations for new gears? And I’ll look into possibly getting a cam from ta performance. It seems to run fine on pump 91 it doesn’t do anything that would make me think it needs race gas, just the problem under WOT
Have a Q-jet built for your engine by one of the 2 guys on V8. http://www.everyday-performance.com/ http://v8buick.com/index.php?forums/everyday-performance-llc.172/ www.quadrajetpower.com Get a converter built for your car, http://v8buick.com/index.php?threads/tsp-9-5-street-strip-converters-lifetime-warrantee.147066/ Maybe 3.23-3.42 gears And TA 212 cam
just reread post info . "no power/lean before 3000 rpm" . just thinking out loud - that's about the time the secondary's are starting to kick in . so maybe primary side problem ? non functioning power valve , lean ? and what carb was on there originally , that was running good ?
It was the original Rochester carb but that was also with the stock motor before it was rebuilt, I’m going to have my motor guy check it before I think about buying a new carb
In my experience the Holley vacuum secondary carbs are garbage performance wise compared to a Q-Jet. The Q-Jet is a mechanical secondary carb WITH AIR DOORS. Also from experience, the Q-Jet doesn’t seem to like a single plane(SP3) I had horrible bog. I switched to an 850 AED double pumper on my SP3, all was right with the world again
Air flow or CFM. Pretty sure Holley carbs are Wet flowed when rated. Don't know about Q-jet...think they are dry flow rated. A wet flow rated carb would produce anywhere from 8%-16% more cfm if you would dry flow that same carburetor. That is why you should just give the engine what it likes...
i know it's the opposite Holley flows less then there ratings on two barrel carbs for sure, not sure on four barrels but i think your right.
Does it bog real bad when mashing the pedal to the floor? I have got extremely good results from tuning my 600cfm double pumper. I am running the sp3 with around 9.01 compression. I can give you some advice and suggestions. In my case a bigger carb wasn't better. My 350 with the Sp3 and 256 rear gears really responded well to my small carb. Burnout power and good drivability is possible. Your carb might just need jetted up a bit. Your brawler might even have power valve jets that are changeable. They will effect the amount of fuel channeling through the power valve...maybe bump them up a couple sizes. You could also try a 4 door power valve with a higher number like a 9.5. If your cam makes alot of vacuum you'll want a power valve with a higher number. I don't have much experience with vacuum secondaries but all of my suggestions can be done on the primary barrels.
