496ci Tunnel ram

[BattlestarGalactic]

Ok, here's a little update from my intake changeover this winter.

496ci, 12.5/1 comp, stock TFS heads, Comp roller 274/280 .683 lift, 107 CL(installed at 104), tunnel wedge, 1850 holleys
Made 665 hp at 6600, 621 ft/lb at 4400.

Installed adapter and Weiand tunnel ram.

Made 655 hp at 5800, 636 ft/lb at 4300 with 1850 Holleys.

It picked up torque down low and carried that torque up through the mid range, unlike the tunnelwedge which fell off as rpm increased.  In the big part of the curve it was up 30 ft/lbs over the tunnelwedge until about 6000 rpm where it then started to match the tunnelwedge numbers.  HP was up 15+ through that same part of the curve, but fell off over 6000 rpm to be -10 hp over the tunnelwedge at 6600 rpm.

It took quite a bit of tuning on the carbs to get them set up to run side saddle over backwards.  The side to side A/F was way out in left field.  After 6 gals of 112 and 5 hours of attempting to strip the bowl screws out of those 1850 we have it dialed in darn near perfect.  I think we had 18 pulls on it total.   The first pull was with the 1850's, did a quick jet change to fatten it up a touch and the power dropped off.  We threw the 660's on it to just see what would happen,  They were worse overall so we put the 1850's back on and continued to dial them in.  My friend had a new pair of 750 HPs but never tried them due to trying to get fuel lines set up in a reasonable time frame.  He didn't have fuel block for them yet(his build is still in pieces) so getting it all set up was going to take time that we really didn't have.  This was a one day dyno thrash of sorts, so we just moved on.  We played with timing, from 36-40* and it didn't care.  We also played with valve lash from .016 to .022 and again not much change to speak of.  The velocity stacks made negligible difference in power.  It leaned it ever so slightly.

I think the biggest problem with it was the fact when I originally built this motor 2 yrs ago I was really concerned with transmission longevity(mainly first gear) and so I had the shop really hold back on overall power and RPM range.  Since installing the Liberty Equalizer last winter I have NO qualms about making as much HP as I want.  The tunnel ram now is conflicting slightly with the camshaft choice and not allowing it to pull up through like the tunnelwedge did.  I'm not going to do anything about it currently.

I brought the motor home this evening.   A few weeks ago I dropped my pressure ring off for a new heat shield install.  I have that back and I put the clutch back together Saturday evening so it's all ready to put back in the car.  It will run whatever it runs.  I can see an 1/8 mile improvement with the increase in torque and HP but I'll be curious to see if it carries it through the 1/4 mile.

Overall I'm happy.  Like anyone else I had high hopes to see a big "700" number but that will have to wait for another day and other changes.  My friend is going to make me an aluminum "mailbox" style scoop to try out this year.  If the velocity stacks don't work out well, I can try the scoop and see if the ram air effect will pick it up some.  It went 10.28 first weekend out last year.  In the heat it was in the 10.4 range.  If diesel prices stay sane enough to be able to afford to go anyplace this year, I'll see what she will run.

Dyno video from FB:
https://fb.watch/bCwYlZNVxC/

[6667fan]

I thought just the opposite was gonna happen, as in more hp and less torque than the TW.  Good thing there wasn’t another contest.

[1968galaxie]

Was the tunnel ram ported?
Reverse taper in them without porting - and may need to be welded up at the top to enlarge the plenum opening.
Almost need to find an old 351C pro stock ported tunnel ram.

[JC-427Stroker]

Looks great. 

Those extra 145 cu inches  are using up that TR.

[blykins]

I think the tunnel ram may have been a cork for that big of an engine.  When you see the peak hp rpm go down that much with a change, something is choking it out.  That's in combination with the camshaft just having way too much overlap.  As a general rule, you really shouldn't ever see a 496ci engine with a 107 LSA and that much duration.   More efficient heads need less overlap, especially with the runners that a tunnel ram has.

[BattlestarGalactic]

Brent, I totally agree.  Like I mentioned, this motor was originally designed to be very mild due to other issues.  The TR was not even in the thought process for down the road.  Once I spent the money on the transmission it has opened up the world to anything I want to do.  I took the plunge and bought the adapter and TR and going by Jay's information it "should" have picked up overall HP.  Not huge, but some.  I was surprised when it fell just short at upper RPM.  Jay's dyno mule was very similar to what my motor is(likely mine has less cam) but similar CI, heads, his has a touch more compression.  Nothing is apples to apples, but I was using it as something to compare to.

My intake is not ported, beyond matching the two halfs(there were horribly off along with the gasket).  The intake, adapter  and heads are fairly matched, but needs work to be right.  I was not pulling the heads and going through all that this winter.  I was just doing a "simple intake swap"  LOL!!!!   Oh, the can-o-worms I opened.   

It's all going back in the car as is.   There will be another time to make improvements.  At least it didn't fall off 50 hp!  The car will likely still pick up a touch with the power it did gain through the curve.  I need torque and I did get that.

[hwoods]

is there a top plate for that intake to fit Dominators?

[My427stang]

I think 4 things, even though mid 600s is a strong ride

1 - Too much overlap and potentially too much cam, latter depends on gearing, but regardless wide spread and more exhaust split for those heads, as much as 115 LSA in that lobe range for spread and 10 degrees split
2 - Not enough carb, dual 1850s are not enough IMO, I’d go 750s or dominators
3 - Any chance of ignition issues, Adding needed fuel and losing power may be an ignition issue
4 - Agree on the intake and porting but I’d look at top three which will then drive you to some rubbing

Thanks for sharing, any one that handles pull after pull is a good one!

[1968galaxie]

Regarding camshaft timing.
A cylinder head with great .300", .400" + flow the less advance is required. Instead of a 104 ICL, one can use 108 or even 110 ICL.
A larger displacement engine will typically require an earlier exhaust valve opening meaning 114 ECL or even 116 ECL.
The spreading camshaft centerline is a result of the later intake CL and earlier exhaust centerline.
Result -> larger lobe separation.
Overlap is the result of proper intake timing and exhaust timing.

[Stangman]

So you didn’t get exactly what you wanted but maybe the extra torque will get the big girl going a little earlier that the drop off in HP won’t even be noticeable. If you aren’t happy with the outcome then at least you know either a little rubbing on intake or a cam change shouldn’t be to bad.

[BattlestarGalactic]

is there a top plate for that intake to fit Dominators?

Yes.  I have a friend with one and was offered it but with no Dominators to try it was a moot point.

I think 4 things, even though mid 600s is a strong ride

1 - Too much overlap and potentially too much cam, latter depends on gearing, but regardless wide spread and more exhaust split for those heads, as much as 115 LSA in that lobe range for spread and 10 degrees split
2 - Not enough carb, dual 1850s are not enough IMO, I’d go 750s or dominators
3 - Any chance of ignition issues, Adding needed fuel and losing power may be an ignition issue
4 - Agree on the intake and porting but I’d look at top three which will then drive you to some rubbing

Thanks for sharing, any one that handles pull after pull is a good one!

I only turn it about 6500 at the traps.  When we built the motor originally that was one of my stipulations.  It made peak at 6600.
We tried the 660's, they were fatter then the 600's but power fell off.   I would have like to see what the 750's would do, but wasn't in the cards Saturday.  The whole dyno deal all came up real quick and I wasn't able to get all my ducks in a row like I thought.  Waiting for the next slot might have been awhile and I just decided do with what I have.  There again, buying $1700 worth of carbs is not really in the budget right now(what friend paid for his two).

Distributor is locked out.  We played with timing and it didn't really change much power wise.

So you didn’t get exactly what you wanted but maybe the extra torque will get the big girl going a little earlier that the drop off in HP won’t even be noticeable. If you aren’t happy with the outcome then at least you know either a little rubbing on intake or a cam change shouldn’t be to bad.

Yes.  Something to ponder for sometime down the road.  Whatever it runs, it runs.  I do think it will see a slight improvement, at least the 1/8 mile.

[mbrunson427]

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.

[My427stang]

I only turn it about 6500 at the traps.  When we built the motor originally that was one of my stipulations.  It made peak at 6600.
We tried the 660's, they were fatter then the 600's but power fell off.   I would have like to see what the 750's would do, but wasn't in the cards Saturday.  The whole dyno deal all came up real quick and I wasn't able to get all my ducks in a row like I thought.  Waiting for the next slot might have been awhile and I just decided do with what I have.  There again, buying $1700 worth of carbs is not really in the budget right now(what friend paid for his two).

Distributor is locked out.  We played with timing and it didn't really change much power wise.

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

[cjshaker]

Like everyone knows, basic rule is shorter runners favor higher RPM power, longer = better torque, so to me the numbers aren't that surprising. Like Brent and Larry said, optimizing everything would probably make a pretty noticeable difference, but like Larry said, it is what it is for now.

On the track, I would not be surprised to see an improvement. You'll be getting cooler air, and that is a big deal.

Either way, it's a winner in my book. The cool factor just went off the charts, so that alone is worth a full second..lol
I like it!

[blykins]

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....