I get my 327 back tomorrow from the dyno. They said my carb it to big,750. What would you guys recommend. 68 block, 11.1 pistons, 67 327 heads, stealth intake. Thanks.
If it's a vacuum secondary, and the car is geared and cammed to work with those parts, then it will probably work ok?
What do they recommend? Normally you use dyno time to sort these things out....ok, now for an answer - not sure of the cam your running or your gears/trans or vehicle weight.....but if it's a light car with a stick and suitable gears a 600-650 double pumper - if it's an automatic and/or a heavier car a 600 vac secondary or afb
I had a .030 over 327 back in the days backed by a 4 speed a 4.88 gears. Ran a 600 DP Holley on it. Thought it was a good fit.
A 3310 is vac secondary......a dp is mechanical - ill ask again - which one - a 3310 can definitely work in your application with some changes, but I would run a 600dp
An engine is just an air pump , air in and air out . A 327 should operate best with max 650 CFM . Bragging rights were the worst killer of good running engines and drivability . Don’t over do it .
Where's the air inlet for your PCV system ? Doesn't have to be dp to be Mech secondary , like a list 9776
Those are tunnel ram carbs - no place on a single application - when you say double pumper most assume carbs like list 4779
Depends on what your max expected rpm is. A 570 street avenger (vacuum secondary) is plenty for a mild small block in a cruiser. If you want a little more I'd go with a 670 street avenger, but no bigger.
Carb doesn't care what it's used on , by that token , you can't use a Q-jet on a four banger or a 2 bbl on a big block . You can say what is generally used , but you shouldn't pigeon hole equipment . NASCAR made 700+ hp with 390 CFM ..bet I've seen hundreds of magazine 350 tests using 750 CFM carbs , they appeared to have worked
That 'thumper' cam will be a problem with a vacuum secondary, best go with a double pumper and 4 corner idle, those cams make things 'difficult' to get things right, if you are buying one I'd go with a QuickFuel 650cfm; if you want a little more 'period correct' then I'd be looking at the Holley Classic 650 double pumper with 4 corner idle.
Do you have a copy of the runs on a dyno sheet and what was the air fuel ratio with the 750, it may be a tuning problem, I feel your healthy 327 with the 2800 stall and .411 gears would handle a DP 750 just fine.
I have a 327 bored to 337. I used a 3310 750CFM and it was too much. I now have a 4150 DP 650CFM and it is just right! I have fuelie heads and the short block was blue printed and balanced.
Those tunnel ram carbs have no accelerator pump on the secondaries......when used in a single application its bog city when they open with no pump shot - the AFBs and Q-jets (which also have mech secondaries with no acc pump) control the bog by having secondary "air doors" - so yes, the holley tunnel ram carbs do care what they are used on...
Had a 60 over 327, 202 heads a turbo 400 with shift kit w 3.08 gears 375 HP factory cam and 650 double pump it ran like a scalded cat I can't imagine what it would have been like with 411s
http://portandpolish.ca/carburetor_size.html Be realistic. How often are you going to be WOT at 5000 RPM asking for more? How much are you going to be tipping in from under 3000 RPM, expecting it to respond well?
You have an interesting combo of 11:1, dual plane intake, thumper cam, mild-moderate stall... What's the intended usage? A 750 is too much, a 750 vac sec would work, a 600-650 vac sec should be ideal for street usage, maybe loose the tiniest bit of peak power that you wouldn't even notice. With that compression, you could probably step up the cam quite a bit... -rick
The shop who ran your engine is correct; that 750 double pumper is too much carb. If it was a vacuum secondary 750 Holley it might work OK, but a 650 DP, or 650 Vac. sec. carb would both work better. I'm running a 650 Quick Fuel DP on a 350 SBC with Dart heads, and a bigger Howards roller cam, and it works great. But even it needed some tuning to change idle bleed jets, and primary and secondary jets to get the air fuel mixture right and eliminate stinky idle.
For street use, under carbureted means that you get beat out on the back roads at top end, but stop light to stop light, good off the line punch. 600-650 cfm, and vacuum secondary. But take the finished car to a chassis dyno, not one of those inertia rigs, but a real power absorbing dyno, and get it tuned by an expert. And it needs to be someone who has a handle on carburetors, not efi. There's a lot of adjustability in most carburetors, and it's easy to mess one up.
Does the dyno sheet provide a CFM curve and/or air flow efficiency number? If you believe the dyno numbers and paid for the info, use the data and the guy's suggestions.
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