Hi all. I have a 383 stroker in my 55 Chevy. It has Dart 1 heads, 10.5 compression ratio, Racer Brown mild cam, BW T-10 and 3.08 rear. Just purchased an Edelbrock X-C8 cross ram manifold. I recognize that this manifold is designed for mid-upper RPM, but like the look. Am looking to put 500 CFM Edelbrock carbs on it. I have been looking for a used pair of 1904s, with the annular boosters, but haven’t had any luck. Are these a lot better for my application than the 1800 or 1400 series? Thank you all for any advice.
Having done a very similar thing years ago i can give you a little advice, i used 1400 series 500 cfm manual choke carbs on my set up. That motor was a 10.5 to 1 327, don't remember the entire cam spec, but was 480 lift on the intake and exhaust for sure, so it had a little lump to it. I did jet it down 3 or 4 sizes from stock 500 cfm jets and i messed with the metering rods too but it was 15 years ago and cant remember what jets, rods and spring numbers i used. expect to mess with it a lot to get it dialed in. The big problem is that intake was never designed or even thought of being used on the street, it was for wide open throttle at 5000 rpm and up. That makes it not great in stock form to run on the street without fouling plugs like every 300 yards. and every 3rd stoplight. but there are some things you can do to help. The manifolds biggest issue is reversion at low rpms. I quite literally had a fog of fuel vapor hovering above the carbs at idle when at a stop light the first time i drove it across town. Also the banks of the intake are separate, P*** side carb feeds drivers side head and drivers side carb feeds p*** side head. It effectively turns your 8 cylinder into two 4 cylinders as far as tuning goes. This also equates to really ****py low speed around town driving because you do not have vacuum signals from all the cylinders as the engine runs for the carbs to receive full vacuum signals that they need to operate properly. Great for wide open 6500 rpm p***es, ****py from 3000 RPM though town. What i did to help the issue was two, two inch thick aluminum carb spacers under each carb, i then drilled and used an NPT tap to put 2 3/4 heater hose ******s into both spacers. Then connected both spacers together with sections of 3/4 inch fuel resistant heater hose to the ******s. This gave both a larger plenum volume that seemed to greatly help the reversion issue, but also did wonders to drivability by helping to sync the vacuum signals from bank to bank. I would highly recommend starting out with the spacer and hose set up before tunning, it will still be a **** pot of tuning, but way easier with the banks synced as to not. Also, i ditched the vacuum advance distributor and ran a full mechanical since the vacuum wasn't that high to begin with plus before i tied the banks together with the spacers, a vacuum gauge would bounce like it was on a trampoline since the banks were separated. It looks *****en for sure, i ended up pulling it all off and putting a regular dual quad set up on it, and it ran 10 time better around town, but didn't feel like at it pulled as hard at high RPM when i would take it to the drag strip on the weekend.
I wonder if a pair of 390 CFM Holley's may not be a better choice. Summit's carb calculator says for 190 CI (1/2 of 383) @ 7K RPM, a 340 CFM for street and 425 for race. You would probably still want to tie the two sides together, but the smaller carbs would give better mixture velocity and throttle response.
Seems from @Nailhead Jason ’s reply, it’s the intake that is an issue, maybe not so much carbrueration?
Too much carb will kill your low end, and that was why he had so much trouble tuning it. At WOT it doesn't matter, but if drivability is a goal, I learned 'race' sized carbs are rarely a good idea.
I would be concerned about the lobe separation angle (LSA) on the cam. Long runner manifolds are subject to reversion, as has been mentioned, especially when the LSA is too narrow. I ran a 377 (400 block, 350 crank) back in the day, with an X-C8. Even with two 390s it was miserable, had no low end, and was impossible to tune. One of the few times that I dared take it on a longer trip, I stopped by Don's on the Berlin Turnpike, to talk to the guys that worked there. They are the ones who taught me a very important lesson, and more importantly, helped me fix it. They had me open the hood, remove the air filters, and let it idle (which it did, VERY poorly). They pointed out that there was visible fuel mist above the choke horns. The word: reversion. They hooked me up with a cam that was about the same lift and duration, but had a much wider LSA. It was 114 or 115 degrees. They said it was listed as a "blower cam". After I swapped to that cam, and some fresh lifters, it was irrationally fast after tuning. It remained in that configuration long after I got my license taken away, and sold it. Mine too was mechanical advance only, and I had a 3/4" crossover hose attached to the back side of each plenum. This type of cross ram is arguably worse than a tunnel ram, as it has two wide-open plenums, instead of just one. Even with a crossover tube, the design leads to poor fuel metering, except possibly at wide-open-throttle.
I can't comment on the use of the cross-ram as I've never had one, but I'm using two Edelbrock 500's on the Weiand manifold on the 400" Cadillac in my '40 and am very happy with them. Throttle response and low end power is great.
To answer your original question. Everything I've read on actual use to intended use on forums, instructions, information etc all state that the annular boosters work much better when running dual carbs. It's said that they react much better at idle and low speed due to the annular boosters needing less vacuum signal thru them to work properly. Many on the forums I've read stated it cured any hesitation during tip-in etc. I have infact, after 6 months of research, reading, running forums etc just bought 2 of the 1904's off of ebay from a seller called Rileys rebuilds. She is a official rebuilder for edelbrock, I wanted 1901's which are manual choked and 4 steps leaner on the secondaries but she was out so I bought the 1904's. I will have to drop the the secondary jet sizes but I'm ok with that. They cost me 315.00 each (discount when you buy2) and both look like the just come out of the factory boxes. 1 looks like it's never been installed and the second one looks like maybe it might have been installed but can't prove it. She goes completely thru them and rebuilds them. Double checks all parts, specs and only uses edelbrock official parts on them. I would check her out, her and her dad also run and tune them for people in their shop once installed. I'd buy from her again any day... ...
I have a 409 with the M/T cross ram project in the mix. I picked up a pair of 450 quickfuel vacuum secondary carburetors. At the stage of trying to figure out the linkage with the carburetors mounted sideways.
I have a friend with OT Z28 OEM crossram two Holley carbs . He is not mechanical . Forget slow speed cruising in this thing . It looks bad *** and runs great at what RPM it was designed to run at WOT , not going to a cruise in
@saltflats Tie both carbs together Pull & pusher then bell on second carb with another bell & ****erfly then to fire wall ? Kinsler has big selection of. For Op 383 I still think 2 Two barrels carb's . If that 383 is going to see 7k plus R's will need good parts Crank Rods Piston Val train
Gimpy - THANK YOU for the comment about the camshaft profile! I have never had really great success in trying to get any low end out of cross rams, although they pull HARD in the mid-range up. Definitely not my favorite street set-up. As far as carb size, two 500's (at least if they are AFB's) is certainly not too much for a 383 on a good inline 2x4 intake. I personally run a pair of genuine Carter 625's and straight linkage on a 390. They are smooth and powerful from 550 (idle) to WOT. Jon
The LSA change makes so much sense! wish i had thought of that years ago, I loved the way it looked but it was too much pain in the *** for a daily driver.
Call me Mr Lucky but I drove this Austin as my daily driver for a full summer in the ‘70s. It was a 283 +0.030, C&O Hydro, an Engle solid lifter cam of unknown specs, two Holleys and a cross ram (Edelbrock?). I was young and dumb. I bought the car unfinished and just ***embled it with the parts that came with it. Custom headers/exhaust and 10” M&H slicks were my contributions. From day one it started and ran fine. I do remember that it had a fast, lumpy idle and could have used more stall in the torus wheels but it took me everywhere, including dates, until the rainy season started. I have no idea what those Holleys were or what the cam specs were but it ran fine. I do remember my Dad finding the carb linkage out of adjustment causing it not to idle down. I had no idea that cross rams were difficult until I read about it on the HAMB. Just dumb luck I guess….
Hi all. Thank you for your thorough and very helpful responses. Not knowing my cam specs, this looks like this will be a gamble! I tried to order 2 1904 Edelbrock carbs from Riley’s yesterday, but learned that they have none available, or in their pipeline to rebuild and sell. Will have to keep my eye out for a pair. If any of you have one or 2 used ones for sale, or know someone who does, I would sure appreciate it if you would let me know. Again, thank you all for your help. I appreciate it! Joe
Put a conventional cable bracket on the driver side one, and attach the cable in the conventional fashion. In an adjacent hole to where you attached the throttle cable, attach a linkage, and run it to the kickdown hole on the other carburetor. If necessary, drill holes in either or both bellcranks to get them to be the same distance from the center of the primary throttle shaft, so the movement is identical.
Hi all. Am happy to report that I located and purchased a pair of rebuilt 500 CFM Edelbrock AVS 2 carbs. I got them from The Carburetor Shop in Forest Lake, MN. The guy I ordered them from this past Wednesday could not have been kinder or more helpful. They arrived yesterday afternoon. They look like brand new! The price for the pair? $435, shipped to my front door!!! Jason’s suggestion of using a balance tube between the carbs sounds like a really great idea. Jason, did you use 2 crossover tubes? Aluminum or phenolic spacers? Thanks again!
On my M/T intake it has a built in crossover but I plan on running a 4 hole spacer under the carbs to try and boost the signal strength. Hopefully it will help not let the fuel just lay on the intake floor but instead send the better atomized fuel down the runner. Plus my intake is already 4 hole, the later intakes had an open square hole, not sure what they found to warrant that. I do wonder if I rounded the bottom edge of the hole if it would help direct the fuel down the runner better.
The M/T manifold is one of, if not the best, configurations to attempt to get enough lower rpm manners. Still a challenge, but the starting point is ahead of just about all of the others. Mentioned many times, but these were designed for all out road racing.
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