opinion on tunnel rams?

[special70gmc]

ok heres the storie my buddie just gave in to my nagging, hes hot a weiend tunnel ram and 2 450 holleys brand new hes been saving for no reason. ive wanted it for a while now as well as some more gettup/looks but will it have any adverse effects on my motor/power/drivability the motors an "oldschool'' LT-1 from a 70 vette 370hp stock with bowl ported heads 2.08/1.62 ss valves
10.2-1 compression comp cams xtreme 274H cam 490lift, eagle rods forged crank ect... will it do it good bad or no difference? i also do small amount of drag racing this motor frequently sees 6800 rpm .....thanks for you help -kyle


heres a pic and my engine as it is now.........enjoy

[rodnok1]

Sorry for the ramble...You can get good power, even more if tuned right from a tunnel ram, but they are mainly for racing. They can be hard to tune, I ran one for a while on a Camaro I had. Cold startup can be a bear sometimes, I use to prime the engine with some starter fuild to get things rolling. Tuning the carbs can be a real bear, too much carb really for a 350 street engine, but hey too much is better than not enough. The idle qualities are about the same, I always had plenty of vacuum once it got started. You just have to remember you have 2 of everything when tuning. I had a pretty bad off idle stumble and sometimes a backfire through the carb (lean) initially. It took quite a bit of tuning, had to change timing, idle mix, squiters and pump cams. It seemed to like having an automatic tranny behind it also...when I switched to manual it didn't run quite as good. I also ran the side mounted and the linkage looked cool but it made it hard to work on the back carb. Do yourself a favor and polish the manifold before you install it, they look alot better that way, I used clear engine paint to coat mine. One last thing if you run 6 cyl engine stands the clearance is very tight for air cleaner on that back carb.

[toddtheodd]

If that is an edelbrock air gap intake manifold on your motor already... and the price is right. I'll buy it from you. That way it won't just be sitting around collecting dust when you convert over to the tunnel ram.
Todd

[HeavyD]

For the street I think it would be overkill, but if u like the look of it, go for it. Advancements in dual planes (Edel RPM, etc..) have made the tunnel ram not nearly as popular as it used to be. Car Craft always used to test high tises against T-rams and the diference wasn't as much as you would think.

[crazy longhorn]

the tunnel rams setups are best suited to lite weight /high rpm combos(coupe or T bucket) . they look cool as hell......but no way do you need 900 cfm in carburation on a heavy truck! when it comes to carburation, more is NOT better.....on a street truck, that sees the strip from time to time, i would rather be a little small on the carb! it will run better through a bigger range that way! tunnel rams have a very narrow powerband, & the band is very high in the rpm range......if you were talking about a very large BB, the tunnel ram probably wont hurt the "street manners" too much(500+ cubes). you have a good combo on that truck.....IMO, i would leave it crazyL

[3 on the tree]

Some of the tunnel rams have top sections that can be swapped out for a single 4 barrel application. The last test I saw in Car Craft, a built 440 Mopar made more torque lower down than any other manifold tested, but this was a seriously hot motor. I like the looks of the tunnel ram also, and I would put up with a little more hassle to run one on the street.

[Brainchild]

I had a tunnel ram on my Nova,and it looks intimidating,and that was about it for me.Couldn't get it to run,idle or perform anywhere close to dependable enough.I swapped it out for a Victor JR,and a 750 double pumper and improved my times considerably.Plus it was very tame on the street compared to the tunnel ram.

I had a .030 over 350,11.1 compression,Comp solid lift cam .

But some people can tune them and love them,so floor it if ya like it

[tom hand]

Most likely you will wind up with less power than you have now....unless you are kicka$$ on carb tuneing......but if you dumped the carbs and converted in to EFI you can make it very streetable

[Randy70C-10]

I ran one for two years in my 67 Malibu (pic). It looked great but didn't do too much for my low-end torque.

[Palf70Step]

I ran one on the bored out LS6 Yenko 454 I had in my 58 Chevy. I don't remember the exact model, but it was one of the taller ones at the time. I had dual Holley 1150s on it, which as was stated was an overkill for the street, which I didn't really build it for, but used it anyways. It ran like heck but I had 4:88 gears with Doug Nash 5 speed. I spent every Saturday morning tweaking it for the Saturday night cruising (FAST Style). I am true backyard mechanic (in my words ...not very good), but my friend and dad helped me alot. That may have been the reason I had to tweak mine so much. The other thing I notice in my car was it made the right side of the car almost invisible. Couldn't see anything around that tunnel ram scoop used to coiver the setup.

[Randy70C-10]

Ahhhh yes, I should have mentioned that I was running 4:56 gears and my engine was a 454 as well, the carbs were only 450's though. I could have went to 600's, but anything more would have been over-kill.

[special70gmc]

so all of ya dont think i should put it on? i got a 3000 converter in it now do you think the less low end will help my severe wheelspin problem? bacicly i spin the rears if i keep in the throttle through 1st 2ed and just lay small strips in third gear with a 12'' wide street tire. i paid $500 so im kinda curious to throw it on there. on more question will those 450s really drown out my motor? or can i set em up right? i do know a fair amount about tuning but have never had the pleasure of workin on a car with duel carbs.

thanks alot -kyle

[Randy70C-10]

Looks like you have a stout engine, you should be ok. It's only an intake, you can always switch it back if you don't like it. I say go for it!

[Brainchild]

It's worth the price of gaskets just to cruise town and intimidate people for a weekend

Toss it on there.

[RON WOODGEARD]

I have ran Tunnel Rams since the early 70's, Big Blocks and Small Block. The Old "Shoebox" and the Offy "Turbothrust" are dynamite street tunnel rams when carbed within reason.. Ya you're going to loose on the bottom end unless you find a Offy Turbothrust, it's RPM range is 1500 Up... But you MUST have LOW GEARS, so when you just get going you're close to the bottom end of the curve.!!

I have a new Turbothrust sitting on the shelf with 2 Holley 390 CFM carbs ready to go on my truck now, I want to get some of the other stuff out of the way before I put the Stall Convertor in and spend time tuning carbs together..

Tom Hand is right on with the EFI instead of Carbs,, That's crossed my mind also..

The engine, combo you have is Ideal for a Tunnel Ram !!!! what about your gears??

And I would play with those carbs, That's 900 CFM when needed !!

Tune the Primary jets down as far as you can, Then jump the Secondaries up to make up for what you've taken away..

Or even better yet, get a fuel/air ratio meter and set them up with it..

[special70gmc]

my gear ratio is 4:10 in a dana 60 i just blew it up about 2 months ago and put a powerlok in it really sucks i only have a 27inch tire on her so highway driving is kinda hard Ron do you think the twin 450s are too much carb? also should i buy some spare jets? if so what range of jets (sizes) should i purchase? thanks -kyle

[RON WOODGEARD]

I ran a Shoebox ( remember the ones that had the Big Square tops, IE: the name Shoebox) On your almost exact motor in a 70 Z-28, It had a Factory Rockcrusher and 4:10 rear.. I ran it with Holley 600's We didn't have 450's Back then..

I really believe the 450's are going to give you all you need for street/strip.

As far as a starting point, That's hard to say without being there Hands On.. BUT...

Start with what you have, Check the Jetting that's in the carbs now and be sure whatever they are they're the same size both in the Primaries and secondaries. Side Mount carbs are hands down the easiest to work on, But I have always been partial to inline.. ( old school for an old guy I guess) When you want to make a jet change on the "Side mounts" you don't have to take one or both of the carbs off, and better yet is the new ( to me) blocks that you can change the jets without removing the bowls.. talk about making a pain in the ___ job easy, or at least much easier...But you'll pay for the convenience in the pocket book too.

Set up each carb seperately on the manifold you have on the engine now, DO "Everything" on a single manifold, When you're satisfied with its "Smoothness" go to the next one. Now remember you're going to have two of these so you're not looking for performance out of one, you want smooth acceleration, smooth running with get ya down the road performance without sputtering and hickupping, But Not rich!!! if you're rich with one, it'll double of course with two. The pickier you get with setting up each carb. independently, the easier your adjustments will be when it comes to syncronizing them together.

I Highly doubt though with your Engine and a 450 Holley it'll be rich on the primary side. But on the Primary sides with 2 450's you will probably be rich at idle and just off throttle.

A fuel ratio meter is a GREAT help when setting up any Carb., Single or Dual..It's on my to get list, 2 meters, one for each side of the exhaust. But they have Hand Held ones that go in the end of the exhaust for tuning purposes. The other tuning aid that's great is a Vacuum Gauge..

you do the regular turning of the Air needle adjusters just like you do with one carb.

And you can never have enough Jets in your jet holder,, someday, sometime you'll use each and everyone of them..Especially #58s to #80s ..

One other note, With the depletion of Vacuum at an idle that happens with a Tunnel Ram, You MAY or May NOT have to buy a vacuum canister that's made for just this reason.. I have been lucky, I have never had to go to one, ( maybe that's because I didn't buy 2 780's to bolt on top either) But I have set up other guys ( and one girl's) setups that we had to get one.. It's to keep the vacuum up for the use of Power Brakes.

[RON WOODGEARD]

heres what your engine is turning @ 60 MPH..

60 MPH X 1.0 tranny final gearing X 4.10 rear end gears x 336 I don't know what to call this number, it's a calculating # This total sum is then Divided by 27 tire size in inches = 3061 RPM

This formula is one that many of you may have.. Miles Per Hour X tranny output X rear end gears X 336 = ???? # then divide that answer by tire size this equals your RPM @ the speed you started with..

My point being that your rpm is always in the high range in the lower gears where a Tunnel Rams general output is.. Especially when you're "In It".

If you want to get technical,, You could take the gearing of your tranny in low (2nd & 3rd) gear and input that along with a slower speed to see what your RPM is when you shift into the different gears..

[special70gmc]

thanks ron so i think itll work out after all im gonna go ahead and put it on in a couple weeks and then ill take some pics for everybody. im sure ill have alot more questions for you in the future thanks alto -kyle