Well I'm back gents, with many fewer dollars now. Started with an 817,400 GM block, decked .010. pistons are -18cc dish hypereutectics with 6" rods and a custon cam with 221 degrees dur and .465 lift with 1.6 roller rockers and 114deg. separation. Then a pair of 200cc Dart Iron Eagle Platinum heads. (aprox. 10.2:1 comp) then Edelbrock performer EPS (2701) manifold and headers.
This thing is being built to pull a travel trailer through the mountains, So torque is important. T350 tranny (with shift kit) and 3.08 posi in the rear. Now I do want to have some fun.....(he he he) 8) with it too.
My big question is what kind of Carb should I put on it. I was thinking about a Q-Jet but I'll have to get an adapter to put it on the Performer EPS. I have also considered using a 1411 Edelbrock (EC). After reading some previous threads, some think that I don't need to stay with a 750 cfm Carb. What would y'all suggest for a carbeurator?
Thanks, It's great to be back
Loren

By the way, I went with the airbags and gas shocks (great suggestion!) and I got that SS cluster (tach and guages) installed replacing those idiot lights. (thanks for all the help and pin assignments)

I recommend an Edelbrock Thunder series 650 AVS (1806 carb). Sure, you could get more balls-out performance with a larger carb, but it would cost you both mileage and torque. I run this carb on my slightly modified 383 Mopar, and am extremely happy with it.
Whatever you finally choose, DO NOT buy ANY "DEMON" CARB! Demons have had so many quality control problems, summit Racing stopped selling them because of all the returns. The brand new 650 Demon I had on my car was a total POS, and bolting the Eddie on felt like I picked up 50Hp immediately.

I would also strongly recommend upgrading your gears to 3.42s. This will make it much easier to pull your trailer up hills and let your (great sounding) engine combo really come alive when you don't have the trailer behind it. Cams, intakes, and headers all like aggressive gearing.

Loren, something tells me Kettbo and you have a lot in common. He's building a SBC 406 w/6" rods too.

As far as the carb, I don't think 600 CFM will be enough. I'd suggest either a Holley 750 with vacuum secondaries, or the Edelbrock 750 which has a similar type of mechanism to minimize bogging when the secondaries are opening. Personally, I'd shy away from Q-jets, not because they won't work, but because getting them adjusted just right for your application usually takes a whole lot of work and expertise.

Holley used to have a page on their website where you could calculate approx how many CFM you'd need for different applications. Last time I was there I couldn't find it.

Here's two reference points,
A) I used it to estimate the CFM's on my 462 with headers, a moderate cam, big free-flowing heads. I came up with about 800 CFM at 6,000 RPMs. Assuming same RPM range your setup would be about 75-80 percent of that figure (I'd think) which would be greater than the 600 CFM level.

B) I have a 396 with a stock to mild cam that strains to turn 5500 RPM. It has a #1406 Edelbrock 600 CFM carb with headers and stock heads. At WOT it sounds and acts as if it's sucking air through a straw.

Hope it helps.
Mike

Get a 770cfm Holley Street Avenger.

Sounds like an interesting engine...long rod 406....
Hmmmmm,plans for one tooooooo.
Unless I swap the 406 out for a BIG BLOCK!!
Think a 650 will give great throttle and power to common usable rpms.
Avoid double pumpers for a car used for towing or daily driving unless you have your own refinery. 3310 Holley w/vacuum secondaries should work fine. Q-Jet should NOT be ignored if you have tinkering skills.

My 68 427 RatVette's 3310 Holley gave up the ghost last year after years of service and several rebuilds..... Got me an Edelbrock Thunder AVS 800. RatVette needed some calibration changes which I did....had been years since I did this sort of thing...was a breeze. RatVette runs like a scalded-ash dog now.

Guess what I'm saying, carb type is a matter of preference. Go no bigger than 750, no less than 650.

A vacumn secondary 750-770 will work perfectly; your engine is stout enough for a 750cfm. Holley vacumn secondary carbs are very forgiving, you will get good throttle response from the primaries and good airflow from the secondaries without restriction.

Try this: max RPM (desired) x 406 cubes/3456 = recommended CFM ex: 5500rpm x406 cubes/3456 = 640cfm ex: 7000rpm x 406/3456 =772cfm unless your 406 is REALLY well built, you will not attain 7000 rpm

Thanks guys, I doubt this torque baby will ever see 4,000rpm. The stock rear end was a 2.56 !!!! :cry: I went with the 3.08's trying to stay down mainly for mileage purposes. I was thinking that the gearing on a TH 350 and the bottom end torque from the 406 would be adequate for pulling up the Smokies, I may have miscalculated. I sure hate going in again and to change the rear end as it is always such a pain getting them adjusted just right. I'm kind of an "Old Fart" now and really don't want to spend a lot of time tweeking a carb. I believe in the "KISS" principle (keep it simple stupid!) and I guess I'm a simple kind of guy. If I go with a 750 Edelbrock, do you all think the 1411 with the leaner jets would be a good idea or go on and put in the bigger jets like a 1407? Also, whats the skinny on the "Thunder Series"
Thanks again,]
Loren

Thanks guys, I doubt this torque baby will ever see 4,000rpm. The stock rear end was a 2.56 !!!! :cry: I went with the 3.08's trying to stay down mainly for mileage purposes. I was thinking that the gearing on a TH 350 and the bottom end torque from the 406 would be adequate for pulling up the Smokies, I may have miscalculated. I sure hate going in again and to change the rear end as it is always such a pain getting them adjusted just right.

I'm kind of an "Old Fart" now and really don't want to spend a lot of time tweeking a carb. I believe in the "KISS" principle (keep it simple stupid!) and I guess I'm a simple kind of guy. If I go with a 750 Edelbrock, do you all think the 1411 with the leaner jets would be a good idea or go on and put in the bigger jets like a 1407? Also, whats the skinny on the "Thunder Series"
Thanks again,]
Loren

I think your drive train setup above with a carb in the 650 CFM range would be just fine, particularly since it's a low to midrange RPM engine. Only thing I would tweak is get a torque converter for towing heavy loads. It'll slip less on the highway under low-loads (better mileage) and will not heat up as much when pulling all that Budweiser and ice up the mountains. Talk to the "Aces" at B&M etc about which converter would work best. A trans fluid cooler would add extra insurance against heat damage.

Regarding carb jetting, once you've figured out which ones to use, changing needles/jets on the Edelbrock are a snap. Just did it for the 1st time ever on my 600 CFM #1406 in about 15 minutes with happy results.

Thanks guys, I doubt this torque baby will ever see 4,000rpm. The stock rear end was a 2.56 !!!! :cry: I went with the 3.08's trying to stay down mainly for mileage purposes. I was thinking that the gearing on a TH 350 and the bottom end torque from the 406 would be adequate for pulling up the Smokies, I may have miscalculated. I sure hate going in again and to change the rear end as it is always such a pain getting them adjusted just right. I'm kind of an "Old Fart" now and really don't want to spend a lot of time tweeking a carb. I believe in the "KISS" principle (keep it simple stupid!) and I guess I'm a simple kind of guy. If I go with a 750 Edelbrock, do you all think the 1411 with the leaner jets would be a good idea or go on and put in the bigger jets like a 1407? Also, whats the skinny on the "Thunder Series"
Thanks again,]
Loren

A 650 CFM carburetir would suit the engine up to 6100+ RPM @ 90% efficiency. I have a Edelbrock 1806 AVS on my 350 and it has been great. The "AVS" stands for "adjustable valve secondary" which they claim:


... The Thunder Series' unique AVS feature allows for limitless calibration of the secondary circuit with simple hand tools while on your vehicle. It's quick. It's simple. It's effective. Counterweighted secondary carburetors utilize a heavy, non-adjustable "counterweight" that relies solely on the velocity of the air coming through the secondary venturis to roll open the secondary air door. Under certain conditions, a delay or stumble can occur when transitioning between the primary and secondary circuit at Wide Open Throttle (WOT). This is due to the velocity not being able to roll the air door open fast enough. This condition is virtually eliminated with the AVS feature.

I hope this helps you decide! :-D

I'm getting some good info to mull over. I'll check into the converter issue since when I install this thing in the car would be the choice time. I do run a pretty big tranny cooler and put in a tranny fluid temp guage under the dash (rarely gets to 170-80 even pulling the trailer). For about $100 more, I can go with a holly.. I'm now thinking maybe the Street Avenger 670 cfm. I don't think it's a double pumper which I really don't want with the price of gas.
What is the down side to "over carburating". and does anyone have a guess what kind of milages the Holly 670 or Edel,1411 (750)? I appreciate the "spoon feeding" you are giving me on this issue.
Loren :oops:

I don't think a 750 is really oversize. I believe it will supply your engine just fine without a loss of cylinder preasure and low end torque. A 750 will easily let you run up to 7000 RPMs @ 90% efficiency. That's what I think! :-D