Was wondering if any one had tips/trick for cross ram tuning. Have a Edelbrock XF-C8 on a 301 w/ 2 AFBs on a hot 301. One bank looks to be quite a bit fuel heavy, carbs are synced via vacuum gauge and I just noticed today one of the metering rods has an o-shit on the tip. Going to pickup a spring kit and new metering rods tomorrow but was wondering if there was anything to keep in mind when tuning w/ these intakes.
Years ago, either Popular Hot Rodding or Hot Rod did a manifold shoot-out. What they discovered with the crossram was it had a reversion problem. When the engine was idling, you could see a vapor cloud mist over the carbs. They tried making reversion dams using epoxy and sheet metal, which helped a little. The interesting thing was, the Street Tunnelram and the Strip Dominator did the best for torque and HP. A friend of mine ran the crossram on his BBC but even with reversion plates, he could never get it to tune properly. Now he runs dual quads and will soon switch to electronic converted Hilbourn injection.
I was literally just talking to a buddy today that had a hot 350 Chevy he used to street race with one of the factory crossrams & dual Holley's on it back in the 80's. He was telling me that he couldn't get it to run right with the cross ram and that the passenger side header would glow cherry red sometimes. So his dad drove him to upstate NY (Monticello I think) to see a guy who worked out of a barn on mostly Holley 2 barrels for the circle track guys. The guy told him $700 to work both carbs. A lot of cake in the 80's. He didn't know exactly what the guy did to the carbs but he said it ran fantastic from then on. He also mentioned the guy had some kind of flow bench too. Maybe you can find one of these circle track carb guys locally to straighten it out.
I'm interested too, i'm gunna be running 450 holleys on my 301, i was figuring a pair of bigger accelerator pumps to make sure the gas gets all the way on acceleration
If I come across anything I will keep this thread alive... Curious to see what happens...I bought another cross ram for the small ford in my galaxie about 8 years ago that I'd still like to install.
Don't know much about setting up AFBs for a crossram but I know a bit about setting up Holleys. Around 1975-76, I used a '60's vintage Offy cross ram on a built 350 SBC in my '64 Chevelle. I used a pair of List 1850 600 cfm Holley carbs, jetted about 3 steps richer all around and I experimented with several different lower number power valves until I found the right ones (I think I used #3.5 or 4's) to keep it from loading up and surging at idle. Other than that - and connecting the secondary vacuum diaphragms together with a vacuum tube, to balance and equalize the secondaries, it worked great. It was a bit cold blooded (no heat passages in the manifold) and had to be thoroughly warmed up before you got on it hard. I'm sure it killed off some low end torque, but it was no worse on the street than any of the tunnel rams of the day that some other guys were running and once the revs were up over 3000 rpm - where both the cam and the manifold started coming on and really started working together too, it pulled really, really hard, right through to about 6500 rpm. For a lightweight rod or a hot street 'nostalga' street car, I'd run one again in a hearbeat!
I ran a "DZ" copy on a 327 back in the 80's. At first it was miserable. However after tinkering around I finally had it running good! I was EXTREMELY broke so alot of what I had was out of necessity (what I found cheap at a swap meet) rather than being able to just go get what would have been ideal. I ran pieced together vac sec. Holley's. 600 bases & metering blocks with 450 centers. IIRC I struggled with the idle and ended up drilling holes in the butterflies to get the correct idle slot exposure I also restricted the idle circuits in the metering blocks. REO acclerator pumps and bigger discharge nozzles - and as been mentioned I went with pretty small Power Valves. The BIGGEST improvement I made during this entire firedrill was the addition of an MSD ignition. The problem with a lesser ignition was that during the learning curve (when things were way OFF) the plugs would foul. With the MSD it would fire the worst plugs allowing me to evaluate the changes and keep making improvements in the right direction. YMMV
Run a large vacuum hose between the two carbs. The back of the base plate usually either has pipe plugs in it or a big nipple. Hook a hose between them and it will help a lot. Also make sure the secondary throttle blades are set the same. Most guys overlook that. If one has the secondarys cracked more than the other, you can't get them syncronized. Attention to detail is making them really even and giving the carbs a common plenum (vacuum hose) has worked best for me.
Can you imagine using 2 Holleys 600 DP's with 4-corner idle mixture adjustments mounted on a crossram??? That be fun tuning them...
Here's a pic of the GM version setup with the 600 cfm Holley DP's.... Brand new systems complete with the air cleaner and inline 6 thottle cable are fetching around 8000.00 bucks!....... Yikes!
This isn't much help, but I remember seeing an article in an old magazine about a kit that Edelbrock made to install in Holley 4 bbls (don't even remember the size) to use on their STR crossram intakes. Larry T
Just won the bid on a x c8... Can't wait to pull my hair out.. What do you guys think , instead of connecting the two plenums to correct the vacuum issue caused by cylinder 4&8 , and 5&7 firing consecutive, what about a 4 7 swap cam?
Tuning info from the factory cross-rams or Edelbrock STR series, or the later offy cross-rams, or the factory Hemi or Max-Wedge intakes for that matter, is not applicable in any way shape or form to an XC-8 or Edelbrock X-1, as the two types of intakes are completely different. The factory and STR type intakes are true cross rams, in that both carbs feed a common plenum. The XC-8, X-1 and others are not cross-rams, they are ram-logs. The runners from one bank are fed by their own individual plenum, which is completely seperate from the other. The only thing the two different styles of intakes have in common is that the carbs are side by side, rather than in-line.
No, it wasn't. The plenum was interconnected. In fact, if you go through the old Direct Connection performance bulletins, bulletin #34 actually deals with increasing the size of the interconnection to a 10 sq. inch cross-section, and spells out how to re-calibrate the carbs for said modification.
I ran the Offenhouser cross ram on my 30 with 2 390 cfm Holleys car ran great on the street. If anyone can tell me how to post pics from this damn iPad I'd be happy to post pics of the truck.
Doesn't seem like anyone on here has tried that. It may help but I don't know how much. The problem to me with that manifold is that you are basically inducting two separate 4 cylinder engines with a common camshaft/crankshaft. Without linking them via some sort of common plenum, you will play hell trying to get it to drive decent. Especially idle and off-idle. Been there done that. You can band-aid it some by connecting them but there is a reason the later tunnel rams and factory stuff used a common plenum. It is needed. Connecting the carbs externally like I mentioned helps, but it is really a band-aid.
If you plan on running vacuum secondary Holley carbs, make sure you buy the ported "quick change" secondary spring covers... And hook up a vacuum line connecting both ports... I think that was mentioned above..^^^ Ford did it with the 2x4 FE motors (one of Ford's better ideas..) and it worked out beautiful! I did it for my tunnel ram setup... Still waiting to try it out...
OK, whatever... There are multiple posts here on cross rams and tunnel rams which will help you. Do a search and read all you can read. Pay attention to those that say it can be done with tuning, because it can. I ran a tunnel ram / dual 4 barrel intake back in high school YEAR ROUND in my daily driver for several years (in midwest winters). Yeah, it took some tuning. But doesn't everything (if you really want it right)? My current car runs an Offy divided log type cross ram (very similar to the XC-8 Edelbrock) with two 500 cfm Edelbrock carbs and has been relatively easy to tune. However, it does take running an appropriate hot ignition, more ignition advance (I run 18-20 at idle and 38-40 full in on a sbc, good fuel and 10:1 compression). You will need a camshaft that will work well from about 2500-6500 or maybe 3000-7000 and a 4 speed (or serious stall converter) and some good rear gears (I run 4.88). Mine has been together and running well for almost 8 years. I bump it off the rev limiter at 7,500 rpm frequently. It idles decent (for a big solid lift cam) and I drive it around town at 35 mph and less all the time. It runs well. But it runs like you would expect it to run if you build an engine like this. Don't bolt it on a stock engine with 3.23 rear gears and expect it to work... Because it won't. Here is an old video of it getting along just fine... http://www.youtube.com/watch?v=GslLKzhPth8&list=UUxAzQtMyUly9rSIkTWIHjlw&index=14&feature=plcp
Might be worth a shot, but I suspect it would be subtle, and you would probably need dyno time to find any real gain. Probably going to be sorry I said this (been going back and forth with posting this since the thread started), but I would look at down-leg boosters, 1" open spacers with shear plates on top, and lots of pump shot to cover the hole in the fuel curve until it comes on the mains. A few pretty smart people think that most of the fuel stand-off with ram logs is caused by the shallow plenums with flat floors. Think about it, and if you understand how carbs work, you will see where this is going. The comments on running an MSD are right on the money, it will make it alot easier to sort out.
Don't know anything about your manifold...but I ran the Offy version of the GM 1968/1969, 302 engines manifold way back on a 350 in my 56, 210. Other than filling in the plenum a bit, I ran it for about 2 years. My only car..! After filling in some of the plenum volume, it ran pretty good. My major difference..out of three different tops...I ran the single 4 barrel top. It seemed to like the 830cfm Holley the best out of several tested. So it can be done...just takes the right combination. Mike
There seems to be a lot of confusion here regarding cross ram intakes. As already stated by others, there are single plenum intakes (like the early z28 and the previous poster), and there are intakes that are log style totally individual runners per side. They are completely different with absolutely different characteristics.
I don't see any advantage to changing firing order or being concerned with vacuum issues. These log type intakes are running like two separate 4 cylinder engines. The left bank intake feeds the right side of the engine 100% and the right feeds the left. If you have the linkage set up correctly, you can spin one of the rods back and forth so that you can sense the highest clean smooth idle and then lock it in place. It is not a lot different than turning your idle screws in individually seeking max vacuum.
I have a old 60's m/t cross ram on my little gasser and am just now trying to work out the bugs. Seems the vacumn on one side is higher then the other while adjusting carbs. Do you think drilling and tapping holes to connect the sides will help/ thanks
My neighbor had a lot of trouble tuning his offy cross ram. he did a little research and decided to link the two plenums. There are some nice pictures of how he did it about half way down the page. http://www.jalopyjournal.com/forum/showthread.php?t=442688&page=4
I was going to suggest this as well. I have done this and it hepls a ton. Nothing that I figured out on my own someone else that knew or knows more about it than I do suggested it when I was wrestling with one.
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