496ci Tunnel ram

[BattlestarGalactic]

First, always easy to armchair, and we aren't writing your checks LOL.  Always need to remember that these are the days...when could you bolt together mostly off the shelf parts for 650 HP in an FE.  It's a cool engine and I am not throwing stones in any way

However, I would like to clarify a couple after your response

1 - My comments are only to throw out ideas because you mentioned you would have liked to see 700 HP, nothing else

2 -  I have never seen 660s not make HP over 1850s, even on smaller engines  So my thought goes to two things, either bad 660s, or the ignition.  Not a curve issue, but maybe a bit of a ignition problem that wouldn't let more cyl fill do it's thing.  Just a thought, too bad the 750s couldn't make it on their, I think it would have liked it.   Something to look at would be a close look at the curve/numbers to see if it was getting funky up top.  Could even be a valve bounce or float that is acting like a governor.  Just a thought without seeing the sheets

3 - The cam discussion wouldn't have revved it higher (unless you wanted that).  TFS behave differently than other heads.  The intake port is real good for it's size.  However, a second part of it being good is it's small and reacts quickly, it doesn't need or want a ton of overlap to pull it along using the exhaust pulse.  So you can spread the centers and they are happier (wider LSA) .  The exhaust on an TFS though is good, but not as good as the intake, so they tend to like more duration to empty the cylinder.  So lets say you used the exhaust same intake lobe, but more exhaust lobe and spread them, you'd likely make more power everywhere, not really an RPM increase. 

Would those changes reach 700 hp?  I think so but, it really depends on the intake too, it may need some rubbing.  However, I am not a tunnel ram guy, but I do like playing with runner length math and what you are seeing makes sense...more torque for a given flow.  That being said, I think there is more in that bad boy

Again, no negatives, as I said, when you can run gallons of fuel through the dyno, not break and then go racing with over 650 HP, that's a good one.  Just bench racing based on your 700 HP comment

Ross, we're good.  It's all good discussion material.  I still cringed every pull, but it all ended well.  Heck we tend to put a bunch of pulls on them.  Can't recall if it was the original 496 or the previous build that we put 34 pulls on it!!  Then raced it carefree.  Good builder, good parts and some good luck thrown in.

I've had the dream of putting a TR on the car for a few years.   Jay made it possible.  After reading his book and the slight chance of an increase in power added to the "want to buy" thought. 

When it all fell together this winter I went for it.  Here it is, dynoed, and are my dreams fulfilled?   Ya, mostly.  Did I want to see a 20+ HP increase?  Sure.  Did I see it?  Sorta, only through the middle but not like I imagined it.  Jays book was WRONG!!!!!...........................LOL!!! ( Sorry, just had to throw that out there.  No blame at anyone!!).

I thought the motor made 675 before, but it was 665, so it was going to take 30+ to get that 700 mark.  My mistake(should have dug out the dyno sheet sooner).  Like I mentioned Jay's motor did crack the 700 mark and was "sorta similar" to what I have.  He did run 660's and then 860 center squirters and I think the big ones topped the 700 but he said it was kinda ratty down low.  So, that is where my dream of 700 came from.  I know it was a stretch.  When the peak was down I was really bummed, but after looking at the curve and seeing the substantial increases I was a bit more relieved after throwing all this money and time at it.

I too would have assumed the 660s would make an improvement.  Maybe they could have if we spent more time on them.  There again, we were kinda limited due to scheduling and I went into with that in mind and it was well known to everyone.  Run any carbs I can get rounded up, but then time became an issue and if we wanted to get it done with the 8 gals of fuel, we had to narrow our field of vision.  My nasty old 1850s have served me well for decades, so I choose to stick with them.

As for power curve, there was a little dippty doo after it peaked.  With adjustments we gotten it to flatten out, but not raise overall power.  Was not an issue with tunnelwedge using same distributor and shops MSD box.   Not saying it couldn't be ignition, but the parts used had no issues previously.

Cam:  Like mentioned, this motor was not built to run the TR.  Improvements can be found, someday.

People are often shocked when I tell them they need to go smaller on the camshaft but a lot of guys over-cam with modern heads.   I bet the overlap on that cam with the .050" durations being as high as they are, coupled with a 107 lobe center, is probably at 100° or more. 

If you decide you want to tinker at the end of this season, get in touch with me.  Catch me in a good mood and I may even float you a cam to try....

Something to think about.  Thank you for the offer.  Time will tell this year. 
My only hope(to save money LOL) is I could reuse my existing springs if they are up to the task.  If not, I guess at that time the heads would have to come off and I would then port the adapter to the heads and the TR to the adapter.

Not sure if a lot of people on here watch the engine masters program, I subscribe to the Motor Trend deal just so I can see those episodes. They have a recent episode where Frieburger puts a tunnel ram on his big block chevy for aesthetic purposes. The results were almost exactly as you describe above. Fatter torque curve and power down low, loss of power at the very peak. Might be interesting for you to watch if you haven't seen it yet.

The crusher camaro?  I think I saw that?  I've watch a lot of those Engine master videos(though not a member).  Always very good, solid information, not BS or sales pitches.

The thing is, at least from what I remember growing up, a TR was all about high rpm power.  It seems backwards to see it make power down low.  But remember the Mopar cross ram with 3 ft long runners in a regular car.  So going by that, you would know that it was not really a high rpm intake.  More about torque. 

[JC-427Stroker]

Not sure if a lot of people on here watch the engine masters program, I subscribe to the Motor Trend deal just so I can see those episodes. They have a recent episode where Frieburger puts a tunnel ram on his big block chevy for aesthetic purposes. The results were almost exactly as you describe above. Fatter torque curve and power down low, loss of power at the very peak. Might be interesting for you to watch if you haven't seen it yet.

I'd venture to say that on this application the runner lengths and volume  had much to do with the results.  It would be instructive to have seen a vac reading under the carbs.

Here's my 565 (Ford Motorsport A-460 heads)   Single 1,200 vs TR with two 1,050's. The single 1,200 was pulling 1.3" vac from 6,000 - 7,200.   The two lines on the bottom are the fuel curve. The 1,200 was running a bit "fat" and we didn't worry about re-jetting it to get closer to 13:1 AF because I wasn't there to get the max out of the single 1,200.  There was probably another 10 hp in jetting.  So it would have peaked at 950 vs the 940.

The Tunnel ram by itself is worth about 30 hp over the single.  The other 30 hp on the graph is the GZ vac pump pulling 9.5" of crankcase vac.

This is a short runner tunnel ram with 6" runners. The TR want's to rev to 7,800 -8,500 and I want it to make peak power at 7,200.  ( It runs in a jet boat)  I'll be going back to the dyno with plenum spacer inserts to add approx 1" to the runner length and see what happens. 

[JC-427Stroker]

People are often shocked when I tell them they need to go smaller on the camshaft but a lot of guys over-cam with modern heads.   I bet the overlap on that cam with the .050" durations being as high as they are, coupled with a 107 lobe center, is probably at 100° or more. 

If you decide you want to tinker at the end of this season, get in touch with me.  Catch me in a good mood and I may even float you a cam to try....

The cam in the 565 above is 275/277 @ .050 with .455-.421 lobe lift with 1.8 rockers 113 lobe sep.  It's the baseline cam. The two new cams for comparison are ....  271/278 .46X -.43X -111 lobe sep  and 278/284 .46X - .45X  112 lobe sep.

It should be a couple fun days on the dyno.

As a comparison .. The 275/277 cam replaced a cam ground nearly 20 yrs before that was 281/286 .436-.438 on a 113. the engine made 954 hp with that cam with the single carb.  Bigger isn't always better.

After this project it will be time to start working on the 427MR stroker motor.

[JC-427Stroker]

The thing is, at least from what I remember growing up, a TR was all about high rpm power.  It seems backwards to see it make power down low.  But remember the Mopar cross ram with 3 ft long runners in a regular car.  So going by that, you would know that it was not really a high rpm intake.  More about torque.

That Chrysler Cross Ram is an entirely different animal than your tunnel ram, but that being said, a properly sized TR will pick up power everywhere over a single 4.  Much to do with better design and more even runner lengths cly to cly and air fuel distribution.

Assuming a 351c TR was designed for 351" at 8,000- that's an airflow requirement of 812 cfm at 100% VE.

496" at 6,000 is an airflow requirement of 861 cfm with 100% VE.

A TR designed for a 500" engine operating at 6,500 would have entirely different results than you experienced.  Runner length, cross-section area , taper and plenum volume all work together.  As blykins stated,  a cam with different timing events to fit the TR application would be beneficial to this application.    It would be interesting to see what the results would be on your engine with a fabricated plenum of 475-550 cubic inches.

Something else to consider ... TR's are nearly impossible to properly jet without 8 -02's on the dyno.
Bank to Bank A/F are mostly meaningless in that situation unless you have an expert plug reader with you while on the dyno.  There's power to be found in balancing the jetting cly to cly.

I love the way it looks and I hope you get some added performance at the track with it.  Just curious ... what were the HP numbers at 6,400 - 6,500 ?

[BattlestarGalactic]

I realize the cross rams were not in the same ballpark as what this tunnel ram is.  Those had long, small runners meant for torque.

I had thought about checking vacuum, it had a port already and could have just plugged it in, but forgot about it in the thrash of working on it.  I think I might throw a vacuum gauge in the car and see what it does on the track.  That will at least confirm the carbs are too small.  I could add a channel to my data logger if I buy the sending unit.  I wanted to add an A/F meter to it also.

I do know the secondaries were pulled full open at 4500 rpm as the dyno loaded the motor.   That was first on the list to confirm as we saw fuel numbers kinda whacky.

It was down 10 hp at 6400 rpm, nothing horrible.  That was the little wiggle in the HP curve after 6100 rpm.  It dropped another 5 hp by 6800 rpm where we shut it down.  The old tunnelwedge held a straight line to 6800 rpm.

[Barry_R]

Cool has to count for something - and a tunnel ram and velocity stacks are about as cool as things get.

I will sign on and agree with the cam comments - not as concerned about the "big" @.050 numbers (you have some compression and cubic inches) as with the short LSA and assumed valve events.  For past EMC efforts I have intentionally tightened up LSA/events to chase the results you are seeing - more torque through the middle while giving up peak power at high RPM. 

The intake thoughts are also on the right track.  That tunnel ram was originally designed with 351 cubic inches and a bazillion RPM in mind.  And port work was likely considered inevitable.  Clipping it onto a nearly 500 inch engine is always going to be a bit of an experiment.  I suspect that if you handed that adapter to Marcella or Hogans with instructions to build a tunnel ram for this application you would get something back with very, very different runner lengths, taper, cross section, and plenum volume.

I also think that a pair of 750s would pick it up.  Them small carbs were stock sizes for 427/428 inch engines in street applications.  Using them in a high demand application is going to give you some goofy fuel curves until you get a grip on the tune or modify them.

And none of this matters once the car hits the track.  Then the truth is revealed.

[TomP]

I would agree. A couple 750-780 vaccums would help. I would also cut down the top, get rid of plenum volume and be able to fit under the teardrop hood. Only Fairlane the manifold I made is pretty much like that TunnelRam missing it's top half with some of the webbing cut out between the runners. Instead of a four quart plenum volume it's more like one quart.

[JC-427Stroker]

I realize the cross rams were not in the same ballpark as what this tunnel ram is.  Those had long, small runners meant for torque.

I had thought about checking vacuum, it had a port already and could have just plugged it in, but forgot about it in the thrash of working on it.  I think I might throw a vacuum gauge in the car and see what it does on the track.  That will at least confirm the carbs are too small.  I could add a channel to my data logger if I buy the sending unit.  I wanted to add an A/F meter to it also.

I do know the secondaries were pulled full open at 4500 rpm as the dyno loaded the motor.   That was first on the list to confirm as we saw fuel numbers kinda whacky.

It was down 10 hp at 6400 rpm, nothing horrible.  That was the little wiggle in the HP curve after 6100 rpm.  It dropped another 5 hp by 6800 rpm where we shut it down.  The old tunnelwedge held a straight line to 6800 rpm.

If it holds on that well you should see some benefit from it.  GREAT.

I can't tell you how many times I've been on the dyno with an engine and forgot to do something I was thinking of doing when it was getting bolted on.   I now try to make a Check List the day before.    It helps.

Good luck with it.

[frnkeore]

There is a lot that can be done with the adapter and the Weiand TR. I had hoped that Jay might try a set of 850's on his 504, just to see if there was any improvement, at all, in out put.

I think that something that should be tried, with this TR, for large ci engines (450+), is back to back test with 660's, 4779 type 750's and 4781 type 850's. I don't think mixing venturi sizes together is best.

Curiously, the bolt pattern on the lower manifold is the same as the Dominator but, you would need a transition base, to make it IR or a transition and a open spacer to make a plenum under the carb. Interesting but a little spendy.

I have 660's with mine but, I'm going to try a IR, MFI on mine, tapping the adapter for Hilborn type nozzles. It's a ways down the road, I'm collecting components for that now.

Other thoughts that I have on this engine, is I think those 660's need work and the cam needs tweaked. If you only picked up 3 hp, you's be right with Jay's 504. He only picked up 3 hp over the 660, Dove TW but, 50 lb/ft of Tq.

 Since these head back up after .600, I'd try to keep the lift at no more than .700 net and get as much .200 lobe duration as possible at that .700 lift and Spread the LSA to 110.

[blykins]

A couple of notes there...

The TFS heads do back up starting at about .625-.650" lift, but obviously they don't know it.  The heads work well at lifts up to .750" so far and I do not restrict lift with them now. 

A maximum amount of .200" duration is probably not something that Larry would want.   Adding a lot of .200" duration can have a tendency to make a camshaft a "spring eater" and a "seat beater".   There's a lot of room for discussion there and a lot of relativity in specs, but maximizing .200" durations increases the rate at which the valve opens and the rate at which the valve closes.  Not always a good scenario and sometimes those situations are best for extreme competition cases. 

You will also find that big inch motors like this with efficient heads can often take advantages of really long LSA's.  In Larry's case, with .050" durations in the upper 270's on a roller cam, I wouldn't be surprised if I needed to grind a cam with a LSA of 112-114 for it to work.   I've done some big inch, high rpm BBF pulling engines that ended up with LSA's at 119-120.  Remember, the LSA is just a byproduct of how you control overlap. 

[frnkeore]

A couple of notes there...

The TFS heads do back up starting at about .625-.650" lift, but obviously they don't know it.  The heads work well at lifts up to .750" so far and I do not restrict lift with them now. 

A maximum amount of .200" duration is probably not something that Larry would want.   Adding a lot of .200" duration can have a tendency to make a camshaft a "spring eater" and a "seat beater".   There's a lot of room for discussion there and a lot of relativity in specs, but maximizing .200" durations increases the rate at which the valve opens and the rate at which the valve closes.  Not always a good scenario and sometimes those situations are best for extreme competition cases. 

You will also find that big inch motors like this with efficient heads can often take advantages of really long LSA's.  In Larry's case, with .050" durations in the upper 270's on a roller cam, I wouldn't be surprised if I needed to grind a cam with a LSA of 112-114 for it to work.   I've done some big inch, high rpm BBF pulling engines that ended up with LSA's at 119-120.  Remember, the LSA is just a byproduct of how you control overlap.

The heads know that they are loosing flow and so do the cylinders, it's just a question of how much they are loosing and how turbulent they get. If they stay at the same cfm or increase at a lesser rate, that's one thing but, when they back up, something is wrong and they are probably getting turbulent, while they are doing that, disrupting the flow pattern, into the cylinder.

Are you trying to tell me, that a head that doesn't loose flow in it's higher lift range, will produce the same hp as one that does loose flow?

Regarding the .200 duration, the both the In & the Ex ramps can be made to smooth the spring acceleration and deceleration out.

I don't doubt that a 112 LSA would be good maybe better but, I don't like to take to big of jumps at one time (on anything) and 110, has worked on this size engine.

[blykins]

A couple of notes there...

The TFS heads do back up starting at about .625-.650" lift, but obviously they don't know it.  The heads work well at lifts up to .750" so far and I do not restrict lift with them now. 

A maximum amount of .200" duration is probably not something that Larry would want.   Adding a lot of .200" duration can have a tendency to make a camshaft a "spring eater" and a "seat beater".   There's a lot of room for discussion there and a lot of relativity in specs, but maximizing .200" durations increases the rate at which the valve opens and the rate at which the valve closes.  Not always a good scenario and sometimes those situations are best for extreme competition cases. 

You will also find that big inch motors like this with efficient heads can often take advantages of really long LSA's.  In Larry's case, with .050" durations in the upper 270's on a roller cam, I wouldn't be surprised if I needed to grind a cam with a LSA of 112-114 for it to work.   I've done some big inch, high rpm BBF pulling engines that ended up with LSA's at 119-120.  Remember, the LSA is just a byproduct of how you control overlap.

The heads know that they are loosing flow and so do the cylinders, it's just a question of how much they are loosing and how turbulent they get. If they stay at the same cfm or increase at a lesser rate, that's one thing but, when they back up, something is wrong and they are probably getting turbulent, while they are doing that, disrupting the flow pattern, into the cylinder.

Are you trying to tell me, that a head that doesn't loose flow in it's higher lift range, will produce the same hp as one that does loose flow?

Regarding the .200 duration, the both the In & the Ex ramps can be made to smooth the spring acceleration and deceleration out.

I don't doubt that a 112 LSA would be good maybe better but, I don't like to take to big of jumps at one time (on anything) and 110, has worked on this size engine.

I just looked back at some of my head flow data.  It's been a bit since I've had a set of non-ported heads on the bench, so I had to look back at some notes.  I remembered wrong, they did not back up between .600-.700" lift.  They didn't gain, but they didn't lose.  In other notes that I made, I noted that there was a "sound change" starting at .600" lift on the bench, but no backing up.  My flow data for these heads is listed on Stan Weiss' website. 

Regardless, the heads (and engine performance) don't seem to mind the higher lift camshafts at all.

By nature, when you increase the .200" duration, you have to accelerate and decelerate the valves at a higher rate.  That's just something you can't get away from, the valve just simply has to open quicker and has to shut quicker.  I agree that there are ways to possibly soften that, but any attempt to maximize .200" duration will generally result in a lobe that's pretty aggressive.  On a bracket engine, you don't want a camshaft that will accelerate wear on the parts, as the engines will generally last many seasons without a freshen-up.   

[BattlestarGalactic]

It's in.  Transmission is in.  Lots of little stuff to do yet.

[My427stang]

It's in.  Transmission is in.  Lots of little stuff to do yet.

Awesome, when does racing season start for you?

I don't doubt that a 112 LSA would be good maybe better but, I don't like to take to big of jumps at one time (on anything) and 110, has worked on this size engine.

Frank, LSA is a funny thing.  In and of itself it is a value that does no good to anyone.  110 LSA on a 320 adv hyd roller, a 310 degree solid roller with lash, and a 290 adv solid flat are all completely different cams. Its all about resulting overlap, actually all valve events. So I agree, big engines have done well on 110, but I'd bet a dollar this one had a ton of overlap.

However, also agree that experimenting with big changes can be risky, but low overlap big inch builds with good heads are pretty well proven, even on our own dyno page here. Not to mention, basic building from the 1960s still apply, the more efficient the head, the less overlap you want or need, been that way for a long time and applies here.

What sort of sounded like a lecture is over...back to bench racing, none of us can really say if this was too much overlap without the cam card, but my guess is somewhere around 306/312 to maybe as much as 310/316 advertised given the cam specs. 

That would be at least 95 degrees of overlap, that's proven to be a lot more than a good fast head on a big engine needs.   Assuming the intake lobe is at 306 and exhaust is at 312, I'd probably rock that back to 106 or 107, use the same intake lobe, use a similar lobe but 10 degrees greater than the intake, and 113 LSA for 85-ish degrees overlap, and even then, that's on the high side of overlap for me, I probably would even go wider and add a smidge more exhaust lobe

I also think that these heads "backing up" is a bit of a misrepresentation, and hard to tell how a calculated 28 inches of flow behaves in the engine with the negative exhaust pulse, water hammer effect (especially with the long TR) and standard atmospheric pressure, but in practice, they don't seem to be as affected at high lift as some have thought

Here's a funny comment, with all that preaching, I am likely freshening my 489 up after 16 years and adding a set of ported TFS and a ported Victor to replace a port matched Victor and ported Edelbrocks.  Guess what my cam is?  110 LSA ...however, it's 74 degrees overlap with a good bit of split, so it's likely staying, however, if I do decide to recam, I will likely go with even less overlap and a bit more intake and exhaust lobe

[cjshaker]

That just looks freakin' awesome.

When looking at the numbers and focusing on why peak wasn't higher than before, remember that Larry was running a tunnelwedge, and that is about as good an intake as there is for a racing FE. Just the fact that it made significant improvements throughout the midrange, over the TW, is a win in my book. It'll be easy to hook up a vacuum gauge on your first runs, just to see where the carbs sit on airflow. Borrow a GoPro to video it and check it out afterwards.

Edit: I swear the FE and the 351 Cleveland are the absolute best looking engines with a tunnel ram. They just look...."right".