Carb for 408
- Thread starter zsn0w
- Start date
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j par
Well-hung Member
WHAT? You bought it off the shelf and it worked just fine? But but Yellow Rose said you can't do that...
James Clews
Well-Known Member
Hi Rumblefish! I am in Australia and have a 1974 Valiant charger with 410 stroker,five speed tremec and 3.91 ratio borg warner diff with true track centre and 31 spline billet axles. My engine specs are as follows. forged crank, I beam rods, SRP forged pistons, edelbrock heads with home porting and 2.05 valves, harland sharp roller rockers,hughs roller cam 234 @ 50 th, Try why pacemaker exctractors into three inch system.edelbrock 800AVS carb, edelbrock air gap intake. Car runs very mild, idles at 750 rpm with 14 lbs of vacuum. It is a joy to drive until you put the peddle to the metal then turns into a beast. By the way our valiant chargers only weigh 1400 kgs about 3100 lbs. and have a 105 inch wheebase. not much bigger than an early barracuda!
yellow rose
Overnight Sensation
I was going to ask him to post some pictures of his plugs but then I thought why bother.
What I think is dead rich most guys think is perfect. And they'd be wrong.
James Clews
Well-Known Member
The best thing I ever put in my car was an air fuel ratio guage. Most people run there carbs pig rich. Get a air fuel guage you will be suprised.
j par
Well-hung Member
That's what I do...
EXcappa
Well-Known Member
EXcappa
Well-Known Member
I ran a custom 750 holley on my 565hp 408 and it was perfect.
I now have an 850QF on it making 600hp with bigger cam and better heads
Made an extra 9hp with a 950QF but lost too much torque
I now have an 850QF on it making 600hp with bigger cam and better heads
Made an extra 9hp with a 950QF but lost too much torque
James Clews
Well-Known Member
EXcappa ! mine weighs around 1450 kgs but when I drag race it I remove bumpers , sway bar , driving lights rear seat and passenger seat and rear seat, all jack spare wheel & tools. and sometime put a fiberglass seat in. I can shed nearly one hundred klgs, over two hundred pounds and this is worth at least two tenths in the qtr.I only gain about eighty klgs as the driver so I am not big and fat so it helps with my qtr mile times.
zsn0w
Well-Known Member
Thanks for the suggestions everyone. Sorry I haven't replied, been a busy weekend. I think I'm going to use the normal Edelbrock heads for now, no porting. I've got a 8 1/4 with 3.21 gears in the back with a 3 speed manual on the floor. Going to be switching those out after the engine swap as money permits, though, to an 8 3/4 and an A833 OD. I do plan on tuning it all myself. Don't have much experience with carb tuning, but I'm looking forward to learning. That's part of why I started looking into edelbrock and street demon carbs, because that style seemed more interesting to me compared to the holley style. Also, the idea of having vacuum secondaries seemed like it could be more streetable, but I guess I'd be able to tune a holley double pumper to be the same? Part of what made me start looking into different carb options again was reading about how thermoquads worked. Kind of made me feel like that style of carb belongs on there.
edit: one other thing, bad fuel economy isn't a deal breaker, but I'd definitely prefer a higher mpg if possible as I plan to drive it a lot. So, if one carb is going to give me equal cruising power and much better fuel economy at the cost of a little bit of top end power, I'd prefer that for sure.
edit: one other thing, bad fuel economy isn't a deal breaker, but I'd definitely prefer a higher mpg if possible as I plan to drive it a lot. So, if one carb is going to give me equal cruising power and much better fuel economy at the cost of a little bit of top end power, I'd prefer that for sure.
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yellow rose
Overnight Sensation
Actually, the Holley style carb with changeable brass is much easier to tune and has more tuning capabilities than the Edelbrock has. It also doesn't have float bowls that sit over the hot intake manifold.
zsn0w
Well-Known Member
Would a phenolic carb spacer fix that? or the Street Demon with the polymer bowl?
Yes, but no matter which one you use, use a thicker gasket under the carb like Edelbrock sells to help combat the carb from getting to hot and boiling the fuel. The gasket is about .333 thick.
The carb spacer should be left for tuning the engine combo and the phenolic resin carb centers help keep the fuel cooler but can combat the intake heat to keep the fuel cooler by its self.
Any carb can suffer from an intake to hot .
I'm using this one with a 750 DP after having to modify it by cutting a slot for the secondary pump arm, as well as cutting out the middle making it open. Helps, but the primary pump does percolate some after shut down. Never had any heat issues with the Street Demon with polymer bowl, running or parked. That's in my van with the engine under a doghouse which traps heat after shut down, if I don't raise the cover to let it vent.
Krooser
Building Chinese Free Engines since 1959...
While I can do my own carb work I have an old buddy do my Holley stuff... when I have him do my core(new or used) I wont even have to adjust the idle speed... he gets them perfect.
I paid $275.00 to have him do the last 4412 I took to him.
It pays to use a professional.
I paid $275.00 to have him do the last 4412 I took to him.
It pays to use a professional.
No, I have not used Braswell, because I just can't see spending double the price of an off the shelf unit (or in this case, over double the price). I built my carb and tuned it myself. A wideband helps, but is not required.
By the way, there is nothing wrong with off the shelf cams and carbs. I really don't understand why some folks think you MUST have a custom cam or carb to make your car go....it absolutely baffles my mind because its just plain false. Throwing money at a problem is a way to do it, but its not THE way.
zsn0w
Well-Known Member
I don't have a lot of time right now, but I've definitely got a lot more time than money. I don't really mind putting some hours in to learn how to tune a carb myself even though I definitely see how it's probably more effective to have someone who knows what their doing do it for you. I just enjoy doing things myself for the most part, even if it takes screwing it up a couple times before I get it figured out. I guess one of the main questions I have here is if the things I read about the edelbrock and street demon style carbs being better for cruising and fuel economy than the holley DP like I'm reading. I have very, very little experience with the edelbrock style carbs and haven't read near as much about them as the holleys, so it's hard for me to compare. I'm not super concerned with how easy one or the other will be to tune, as I have to learn either way.
BUT! It’s the US governments way!
yellow rose
Overnight Sensation
Then you don't know what you are missing, unless you are damn good at tuning a carb.
Must just be morons who have people like Braswell and BLP build their carbs. Or Mark Whitener to Dom. Just plain morons, when they can buy an off the shelf carb, which is calibrated for who know what and have it be perfect.
Working with a guy right now who bought an off the shelf Pro Form 750. By the time he gets done paying me, he could have bought a BLP B4X and been done. He's already wasted two weeks chasing down brass, buying a pin vise, buying drill bits and replacing them when he breaks them because he has the touch of a gorilla.
And he said to me yesterday "I'd have been money ahead to buy something else" and I said no **** Sherlock.
Live and learn you hope, but I doubt he's learned anything.
yellow rose
Overnight Sensation
If you want to learn to tune, then buy a carb that's at least fully tuneable. I just made a post about a Pro Form 750. Great little carb for the price. OOTB it's jacked up. Why they let it out the door like that I can't say.
But, you can buy brass and drill bits pretty cheap and you can change and learn all you want.
Before you jump into the deep end I suggest you go over to that forum that was either started by or is now run by Mark Whitener. Can't think of it but it's a my fun forum deal. Read all you can over there before you start, or you'll be doing things like setting power valve opening from idle vacuum.
Also, David Vizard wrote an ok beginners book on Holley carbs that's worth reading.
zsn0w
Well-Known Member
I know the basics of how the holley carb tuning works. You pull out the metering blocks between the bowls and body and replace the jets, and you can change the power valve right? That's pretty much the extant of what I know. On my current carb, I have vaccuum secondaries, so I also know you have to swap out the spring for that, but that won't apply to whatever I get next. For edelbrocks and the street demon I just know there are jets somewhere and that you unscrew a cover to replace metering rods and springs. I know they all also have the idle mixture screws and I know how to adjust those. What makes one more tunable than the other? are the metering rods a less precise way of doing things than the metering blocks of the holleys? I know the DPs have 4 idle screws as opposed to 2, but isnt that just because the others run on two smaller barrels to save on fuel until the secondaries open?
yellow rose
Overnight Sensation
You can change the idle feed restriction. You can add T slot restriction (everyone should). You can change idle and main air bleeds easily. You can change emulsion easily. You can change power valve channel restriction easily, and when you understand why that is so important, you can make a Holley get fuel economy like an Edelbrock and make more power.
That's the short of it.
So, in other words, unless your one of your recommended carb wizards, no one here has a chance at tuning a carb unless there extremely lucky, because we’re dumb ***’s.
Just where are these wizards located?
Just where are these wizards located?
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