Let's Talk Tunnel Rams (Yes again)

[railroad]

I have a set on the work bench and the tunnel ram also for a small block Ford. I am collecting parts for a 347 ci. I have not gotten far enough along to advise you on any issues, but I did see one set up that ran a balance tube between the vacuum secondary diaphrams. I think there will be enough tunability with the secondary springs and small primaries it will work OK. I bought both carbs used. Well one was previously owned and like new, never had gas in it. The other, someone has reduced the primary jets, I think 51's are stock. I think I had to change the PV also to get it back to stock. They both have electric chokes. I'll bet I can get by with just one set to function. I do not think the balance tube on the diaphrams is required, but it may make things work a lot smoother. I have been trying to think out the process if the opening of the sec is not sync. with no balance. It may happen OK at WOT, but if you flowed enough air to get a partial opening, would it delay the opening on the other carb? Might be easy for a passenger to see in T bucket. Just some thought. I don't think you will need progressive linkage with vacuum secondaries.

good luck,

 

[2old2fast]

I ran 390's w/vac sec w/ the balance tube for a couple years when I was running the 355, when I built the 388 stroker I switched to 450's w/ mech sec, both setup's are/were run w/progressive linkage. Both setups worked well ]w/ a little setup] but the 450's are a little snappier [but then again, the 388 is stronger overall]

dave

 

[Mike]

SM, those of us who have raced know the differences in the design characteristics of various parts. No matter what anyone thinks, every part out there is going to shine in a given RPM range and utterly fail in others. We didn't cut corners trying to run wee camshafts, because those cams were designed to work at low RPM ranges. Those wee cams were always cheaper than the 55 MM cores we used, but they simply were not designed to work in the RPM ranges we were running. We didn't run dual plane intake manifolds with vacuum secondary carbs, because that stuff was all designed to work in a lower RPM range. There was no sense in running parts designed to work from 1500 - 5000 RPM, when we were shifting the car well in excess of 9000.

But for some reason, people want to build a motor for a street rod that will likely never see the north side of 4500 RPM and they want to use all of those race components to do it. And that completely bamboozles me. When we sit down with a clean sheet of paper for a new motor, we start looking at what we're wanting to do with the motor and then we start selecting parts for it. If a motor is going to be run from idle to 4000, why in the world would we ever want to use a cam with duration numbers in the 290's at .050, with 1.125" of lift and separation angles in the 118° range? I spent enough years doing this stuff that I can tell you why - people want that drive-in idle quality, that's why. Never mind the motor won't make enough power off idle to pull a sick whore off a toilet stool, they want that rough idle. People forget their motor is going to spend the majority of its life running <2500 RPM, they just want that killer idle. But then they pitch a fit, because they don't want to spend upwards of $400/set for valve springs, because they are suddenly ready to admit they never plan to rev the motor over 4500. Then they pitch a fit when they learn the open pressures on those springs are going to kill standard cam bearings and their blocks are going to have to have the tunnel bored for 55 MM roller bearings. They weren't planning on spending that much on their entire "rebuild", so they suddenly start backing down on cam designs.

When a guy would walk in the door wanting the "biggest cam I can run with a stock converter and stock valve springs," I knew we were dealing with a real engine-building genius.

We did a motor for the boss' '32. 355 CID, a steel crank, a set of ARP bolts in some carefully selected stock rod cores we polished the side beams on, a set of flat top pistons that netted us 9:1 CR, a 278° Cam Dynamics Energizer cam, a set of our drop-in replacement springs, stock pushrods, a set of stamped steel 1.5 rockers, a vacuum secondary 600 Holley on a Performer intake, with a 6 quart Corvette oil pan and a standard oil pump. Dave Coan built a converter that was about 500 RPM loose and there was a bone-stock T-350 in the car. The motor dynoed (a Superflow 901T with the big brake) at about 330 HP and 310 ft/lbs. of torque. It had a noticeable idle, but was still very friendly off idle. Actually, it would rip your head off, if you could make it get hold of the ground. Parts the average street rodder would sneer at, but the car would dance circles around anything sitting in the other lane at a stoplight. You could stand on it at 30 - 35 MPH and the car would get sideways in tire smoke. With the air conditioner running, BTW. Now, tell me, why would anyone want to give up that much fun by trying to run race parts on a street motor? The car would idle at a stop light forever, rip your head off when the light turned green and it never balked at running pump gas.

SM, I'm guessing something between 80% and 90% of everyone else has already quit reading by now. But we both know a short block is nothing more than the foundation of an air pump, whereas the cam, cylinder heads, intake, carb and headers are only going to determine the RPM range where that air pump will be the most efficient. And yes, it only makes common sense to carefully select those components so they will not only work well with one another, but will also sing harmony at the RPM range I am planning to run my motor in.

But since I have this old 327 sitting here, I think I'll run a DMPE M5 18-71 high-helix with a C.G. three hole composite hat and a Waterman Mega Bertha pump on it. Because, you know, it looks so cool. It's got stock, cast pistons in it, so I can still run pump gas, but I want to build about 50 PSI with it, so it will make really good power and produce that blower scream. Do you think I will be able to get it to idle smoothly at 500 RPM, so I can run a stock converter? And since I'm only driving this thing on the street, I won't need those big valve springs and 0.500" pushrods, will I? I can't afford to have the spring pockets opened up, so I'm hoping the stock springs will work.

 

[sstock]

Mike this all makes too much sense about parts working together for a particular combo, but you have to understand people, including myself think nothing looks better than a T Bucket with a dual carbs sitting on top of a tunnel ram. We gotta have it, thus the comprimises that we must live with begin. Frustration for the professional engine builder for sure.

 

[blyndgesser]

I am a functionalist, so I tend to agree with Mike and ScreamingMetal. I'm not crazy about dummy carbs or fake blowers or things like that, but they are probably preferable to having the real thing if the real thing doesn't result in an enjoyable, drivable car.

When I build mine (eventually), I'll probably have fuel injection and an ECM under the driver's seat. Or it'll have a Cummins diesel. Or a Mercruiser 181 with a pair of Webers. Or some other bizarro combo. Whatever I do, it wouldn't satisfy a lot of folks, because it's not "pure enough" or whatever.

Bottom line: it's your car, and you have the right to spend whatever you want on it, and make it into whatever you want it to me. And if it doesn't work the way you want it to, you have the right to ask for assistance. And you can probably expect to be flamed along the way, for whatever choices you might make, just as I expect to be flamed for mine.

 

[Fort Fun]

Tunnel ram on the street, no compromises: http://www.tbucketeers.com/threads/engine-tuning-issues.13072/page-3
Ask Mr. Fixit

 

[Fort Fun]

Tunnel ram on the street, no compromises: http://www.tbucketeers.com/threads/engine-tuning-issues.13072/page-3
Ask Mr. Fixit

http://www.tbucketeers.com/threads/engine-tuning-issues.13072/page-4 - this page starts with the results

 

[Screaming Metal]

But since I have this old 327 sitting here, I think I'll run a DMPE M5 18-71 high-helix with a C.G. three hole composite hat and a Waterman Mega Bertha pump on it. Because, you know, it looks so cool. It's got stock, cast pistons in it, so I can still run pump gas, but I want to build about 50 PSI with it, so it will make really good power and produce that blower scream. Do you think I will be able to get it to idle smoothly at 500 RPM, so I can run a stock converter? And since I'm only driving this thing on the street, I won't need those big valve springs and 0.500" pushrods, will I? I can't afford to have the spring pockets opened up, so I'm hoping the stock springs will work.


Hahaha....yea Mike....I know the feeling......hahaha. And the HyVol chain needed to spin that 18-71, yada, yada, yada.....

 

[Mike]

We gotta have it, thus the comprimises that we must live with begin. Frustration for the professional engine builder for sure.

Some guys recognize they are heading down a path of frustration and know how to tune their ways back out of it. And that's OK, because if someone uses their noggin for more than a hat rack, most self-created problems can crutched away.

I'll not name any names, but when one of our members was having some tuning issues, he asked for my phone number and he called me a few times, to discuss what he was fighting. All he needed was a bit of insight from someone who was standing far enough way to see what was really happening. And even though he subsequently contacted me to thank me for helping him out, he really didn't have to do it. It's like I told him, seeing a guy sort out a problem and start enjoying the car that was a hated monster the day before is all the thanks I need. If I can turn a guy around and point him in the right direction, I'm always willing to do it.

It's the guy that stubbornly refuses to accept wise counsel that wears me out. Or the guy that refuses to provide details about his problem. If I tell you my truck won't start, can you tell me what's wrong with it, without me supplying any more details? Heavens no, but there are those people that do. Don't believe me? Let me show you a whole list of e-mails I get from people who write me to tell me my "forum is broken", because they can't log in and they need me to help. Gee, Mike, does your truck turn over, when you hit the key? Does it have gas in it? Can you check to see if you have secondary spark? Like I said, I like helping a guy get his car running better, but when I have to milk every last detail out of them, I get frustrated pretty quickly. Or when they refuse to check something and then report back.

And blyndgesser, I'll never flame anyone for trying to be unique. I'm the one who raced Chevy inline 6's and 90° V-6's in a gas dragster, mind. I love unique and different. But if one is stepping off into the unknown, one has to first accept the direction he's heading. I was just talking with the owner of the race car, a couple hours ago. We were talking about a race where we had to run a guy who was a bit of a hero in the semi-finals. I apologetically explained to him that it would take us a few minutes to get our car jockeyed into the water box and he laughed and told me to not worry about it, because he was fully aware he had nothing for us anyway. When you go from Z-cutting SBC intakes, to make a tunnel ram for a 90° V-6, to suddenly having giant-killers admit they can't run with you, that is a load of satisfaction you cannot imagine. But I also remember what it took to get there. And that's why I'll never flame a guy for trying something off-the-wall. And when you do the 181 with the Webers, mind I'm going to be wanting to see pictures, because that's the kind of stuff I love to see.

 

[Screaming Metal]

I gotta get ready for the 1 month long Motor Building Seminar.....(one thing I love is the food).....and for the folks in the know, we're gonna argue the fine merits of porting and polishing....wall surface finish VS flow @ the flowbench.
A really nice 15 micron finish VS 40????? We've already hashed out the finishes inside where it counts, on the decks and in the bores....NOW, all we gotta agree on is to get everything within each cylinder within .000005 of everything else, flat parallel and perpendicular.
Hey Mike, we love Ya dude! I love to see ya on the Jazz!
And we have one of the best group of guys here....even if some of us are crazy....myself included...
I'll see ya'll in about a month, till we pack up and go for another seminar.....

Then WE can get that 18-71 blower @ 50 PSI on NITROMETHANE, and possibly get 10,000 Horses.
Hey Mike! Wanna Drive?????

 

[Nevadavic]

Hey Mike, Thank you soooo much for your expert input! But I'm with member "sstock; ".......but you have to understand people, including myself, think nothing looks better than a T Bucket with dual carbs sitting on top of a tunnel ram. We gotta have it, thus the compromises that we must live with begin. Frustration for the professional engine builder for sure."

Yes, there's a stumble when the pedal is pushed too hard, but again I like the "the look" and will deal with it. The engine is a Corvette 327, Camel double hump heads, a mild cam (summit k1102), initial timing at 12 degrees, Edelbrock 1406 carb in the front, back carb blocked off, as per Ted Brown, Powerfire electronic ignition. It idles around 750: smooth once the intake warms up. Vacuum is 14-15 Hg at idle with can hooked up to manifold vacuum port. It all works for good me.