Ready to purchase some carbs today for my engine.. this is a standard bore/stroke 454 with flattop pistons with oval port heads. Thumper cam, lakester style headers, auto with 3000 stall. Purely a street car with an occasional trip to the strip maybe a couple times a year. My question is the difference between the Holley 450 tunnel ram carbs and a couple plain ol' Holley 600 Vac Secondaries. Obviously I know the 450 are mechanical secondaires vs. the vac secondaries of the 600's. My thought was with running the 600's the secondaries will only open when the engine needs it..whereas the 450 will have everything open under full throttle. I'm i looking at this wrong and what carb direction should I be looking? Not looking at fuel mileage or pure track performance, just streetability. Thanks!
The 450s have everything open off idle. What you really want is 660 center squirts, uh how much do you want to spend? Maaan have I got a deal for you.
Nah, I'm with Waddayacare - 450's will do you better - the looser converter will allow the engine to handle the mech secondaries without bogging (assuming it's a fairly light car and not a truck) Cheers.
LOL...fairly light, 2500lb range model A car, 4.56 gears. Yea...not trying to do on the real cheap, but think those 660 would be the real ticket based on everything I've read! a friend of mine has some 1850 600 vac secondaries on his motor...runs great..They have been tuned just for a tunnel ram (pumps, cam, vac secondary balance tube...) I may just borrow them to see how something like those perform before dropping $600+ !!
If you can try a pair on for free it will help you decide without throwing money at it. That is sometimes a good route.
I would suggest the 600 or the 660 that tunnel ram is a big intake. Would take a lot of carb too fill it up IMO.
Good thinking, a manifold will not operate efficiently of you don't keep the plenum full. The problem becomes if your engine can use that much air. If you run a big intake on an engine that is not built to handle it then when you use enough carb to keep the plenum full you have to really jet down which screws up your air fuel ratio. Sometimes it is catch 22 you are damned if you do and damned if you don't.
That's a good move and I wouldn't be surprised if you just buy those after running them. I run 450's on my tunnel ram but would do the 600 vacuum secondaries for just a street car. I run a pair of 600 Carters (vacuum type carbs) on a low profile 2 x 4 intake on another small block I have and they run great all around. My vote for the 600's for ease of the drivability the vacuum features provide.
already called him...he's yanking them off now!! I'll throw them on tomorrow (maybe tonight!!LOL) and see how they do. If they work halfway decent..I'll just go that route. I can get a couple used 600's from different friends and rebuild them to the same specs as these one I'm trying out. Luckily his motoe and mine are nearly identical..I'm just running a deeper gear!
As a person who just went through this whatever carbs you choose are going to have to have some tuning. Especially with a thumpr cam. I used 450's on my small block and don't think I'd buy them again. If I had the money I'd get a good pair of the 390s. They are a little pricey though. My engine is a 355 double hump 2.02's 10.5 to 1 comp. big mutha thump hyd. Standard shift 4:33 rear and lake style headers. With the 450s I drilled 3/32 holes in the primarys went to a 3.5 power valve and a 41 squirter. I'm sure it will need some more tuning when I get the body on the frame and drive it but that put me fairly close for now. I am able to close the primary throttle blades where they belong and it's not eye watering rich and there isn't any stumble when you crack them wide open. Also I am using a edelbock tr1y ? Tunnel ram. The upper plenum has had a 1 1/4 slice taken out and welded back together to reduce plenum volume.
heres a friends A coupe running a 302, the carbs are 500 edelbrock's, i'm not sure he even changed the jets and it runs great, idle is nice and smooth and lots of pull.
Oops for some reason I was thinking it was a small block. I'd Definatly go with 600's or even better if you want to spend the cash 660's I would not buy used. All too often there is slop in the throttle blade shafts causing vacume leaks.
I would go 450's but with progressive linkage. So primaries on both carns open till half throttle, the secondaries follow, or vacuum secondaries, for simple drive ability.
Never a fan of the Edelbrocks..don't know why, never had one. must be that quadrajet crap I delt with 30 years ago!! LOL Definetly need to check over any I do buy used..think new they run around $290 each that that may be an option as well. Really leaning towards the 600 vacs...I know they work well on my friends setup, but then again my cousin ran 450's when he had his car and it wa a monster! Think all he did was check/set float level and that was it..right outta the box onto the engine!
600 will work, no dought. But which ever you choose do progressive linkage. I ran Dual 660's on a Built 350. In on of my high school car, an OT 69 camaro. It ran 8:10s in the qrtr. 168 mph. On the street it was a bear, between the spool and the engine. Forget any fuel economy. I had the carbs reworked for progressive linkage Out of the box it was all 4 open at the same time. Either way, you probably gonna wonder if the other is better. LoL If your runnin a tunnle ram, vac is gonna be low from the start. Do you have Power brakes? The high stall converter will help with vacuum anyways a little.
Interested on the outcome. That sounds like my set-up. I've got 600's but it'll be a little bit before road ready.
No power brakes, 3000 stall (maybe going to 3500), 4.56 gears..maybe going to 488's..oh so many things to do!! LOL
I've run 635 cfm and 750 cfm carbs on a 454 with oval port heads and Weind tunnel ram. No problems with either one of them. I don't think the 600's would over carb your setup. I always run a tunnelram with direct linkage on the primaries. I don't see how progressive linkage could work very well with small plenium and long runners without fuel distribution problems to the front cylinders.
read imfo........by holley&edelbrock........... for incar gopro on how it works: youtube at a30gasser Model A vs Henry J Eagle Field 2012 i know this is only a sbchevy but at 10,000 rpm it thinks itis a big block?!?
I agree, personally on my 450's I've jetted up, power valved down, squirted up, accelerator pumped up and accelerator cam to red number one hole. No holes drilled in any throttle blades and it comes on like a raped ape when the pedal is down. When I bought the used tunnel ram it did have a pair of 1850 600cfm carbs on it. I figured I'd have enough to do with the new combination without dialing in vacuum secondaries but often wonder about the difference those 600's would make ha ha
I have to chime in here as I am having a REALLY hard time believing you had a 3000 plus pound vehicle with a small block that ran low 8's at almost 170 back when you were at high school age and also claim you drove around on the street.
Don't mess with the 450s or the 390s. Get the 660s. They are designed to be used on blowers and tunnel rams. 4-corner idle, the right linkage progression for a dual carb set-up, and center squirters. The perfect carb for a tunnel ram. NO, it's not too much fuel and cfm, and YES, your 454 will love 'em.
I totally agree 660's are the best bet for sure. I had a set I gave away they had sloppy throttle shafts and every used pair I found did also. They can be fixed but IMO I'd rather have new ones. You never know who has done what to used ones. I would recommend against 450's for anything. Forget progressive linkage in my opinion. One big factor is the thumpr cam series. With the tight lobe centers they have a little different learning curve especially with a tunnel ram. I would not do it the same again but the money is spent now so I'll live with it until its time for a tear down.
Installed the 600's today...ran awesome!! I know what route I'm going now!! Thanks everyone for the help!!
I'm not running a bbc, but I am running dual 450's on my 289. As mentioned earlier, whatever you get you'll want to tune to the engine.
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