Tunnel Ram and 660 Holleys

[larrycoyle]

Just goes to show there is nothing like keeping good records of all of your data. Never know when it will be useful. Even better is to know where that data is after all of these years...

[Troy Patterson]

I like the 660's as a concept, but as a carburetor guy, I am aware there is potential way beyond them in throttle response, driveability, torque and horsepower.

I have never seen a custom built carb that was "bench" tuned which was on the money. If you don't have the money or don't have access to a sharp tuner or aren't one yourself, and your engine runs pretty good, even better than the last set-up, the average guy assumes it great.

A winner wants to know for sure.

TMPCarbs.net

[SBC]

Looks like a port matched TR1YX is "around" 6.6 long.

[SandRacer]

What kind of porting will I need to do to the pro-ram II to make it run well on my 406? I normally shift at 7200 with the Dominator, but it turns way past this with ease. What kind of RPM will I need with the tunnel ram and 660's? If I have to cut this apart to port, where do you recommend cutting?

thanks,

Tom

[toddcalo]

larry I noticed you were running as much as 47 to 51 degrees ig advance do you feel that same amount of advance could be used with more modern heads like the cast iron iron eagle dart heads? why do you think the motor responded to so much advance?

[toddcalo]

Just thought maybe Larry would see this and respond to my last post. Thanks Larry

[maxracesoftware]

larry I noticed you were running as much as 47 to 51 degrees ig advance do you feel that same amount of advance could be used with more modern heads like the cast iron iron eagle dart heads? why do you think the motor responded to so much advance?

both the 293cid and the 296cid wanted between 51 to 53 deg BTDC
ignition timing .

its the 323-324cid that liked 47 BTDC

you have to remember this was 20+ years ago
with old #292 Turbo 23 deg Heads

a 293cid w/2.870" stroke = 4401 fpm piston speed at 9200 rpm
a 296cid w2.900" stroke = 4447 fpm @ 9200

back then...everyone was running 50-53 BTDC on those Engines,
it was first built by David Nickens and Brown
and had 53 deg BTDC..running 9.0's to 8.90's i think was fastest
around 149 mph was also the fastest ?

i re-Ported the Heads + Intake Manifold Mods + rebuilt entire Engine
and had it running faster at 8.60's and 154+ mph
but it still wanted 51-53 BTDC

i think it was a combination
of a lot of Dome height + low Piston Speed + too high Octane ?
ran C-14 Gas from what i remember.
..those Heads had a bunch of Swirl..so it wasn't that ?


years later, i had an IMSA Racer with a Buick V6 hi-CR engine
that was using VP C-14 Race Gas and had about 4-5 new Drums left,
he switched over to 9-9.5 CR low comp V8 SBC Buick Head engine
legal for that IMSA Class also...since they had 4-5 new unopened
drums left of C-14 Gas ..he wanted to try to use that on the new
9:1 CR V8 SBC engine on my Dyno.

we started of at 32 deg BTDC
and tried 2 deg incrementals
it made the best TQ + HP Curve combination with 48 deg BTDC
... i talked them into trying Exxon 93 prem gas,
and started all over back down at 32 deg btdc,
it made the best Curve at 36 deg BTDC on Exxon.

it was a solid +19 HP better w/Exxon + 36 deg
than VP C-14 with 48 deg

that's the most difference i ever saw on my Dyno tests ,
and never have seen those kinds of Power differences again yet
since that Day.

They went Race a few weeks later and got the Pole-position
with that V8 engine...and finished 5th in IMSA Race,
thats the very best the Guy ever did,
and i've lost touch with them over the years,
i'm pretty sure he's retired or has quit racing years ago ?

Darin or others probably have more insight or dyno experience
with these 287 to 296 cid Comp Engines back then
they could share what ignition timing they required ?

[maxracesoftware]

it was a solid +19 HP better w/Exxon + 36 deg
than VP C-14 with 48 deg

corrected previous Post ....found old Dyno Sheets ...
it was 522 HP C-14 + 48BTDC -vs- 541 hp with Exxon 93 + 36 BTDC

19 HP difference at most

[toddcalo]

Thats very interesting, I have a iron eagle 235 head on the motor I currentley have in my drag car, angle milled to 47cc with about a .400 dome its a 355 around 16 to 1 comp do you think its possible this motor might like more than 40 degrees? I burn sunnoco maximal 116 I turn 8500 to 9000 rpm . Also was wondering if fire slots in the piston domes would help any? Thanks Larry For all the time you take out to answer all these questions.

[maxracesoftware]

Thats very interesting, I have a iron eagle 235 head on the motor I currentley have in my drag car, angle milled to 47cc with about a .400 dome its a 355 around 16 to 1 comp do you think its possible this motor might like more than 40 degrees? I burn sunnoco maximal 116 I turn 8500 to 9000 rpm . Also was wondering if fire slots in the piston domes would help any? Thanks Larry For all the time you take out to answer all these questions.

i also had/have an old 23deg Pontiac/Brodix "aluminum" Head
Chambers unshrouded + anglemilled back to 56 cc's 13.7 CR 12 cc Dome
4.033x3.480=355 cid ..it was an experiment in trying to determine
how much TAPER i could run or the effects of Intake Port/Runner Taper.
it made 720 HP between 8500-8700 and Peak TQ 483 @ 6800-7000
it liked 48 btdc with VP C-16 on the Dyno @ 600 rpm/sec

on the DragStrip, it wanted 45 deg BTDC and ran about 2 MPH
faster than it should have. It accelerated the 1st half of DragStrip
like it should have..but the last half was faster with more TAPER
than the Dyno showed and wanted less timing than the Dyno
7.50's ET at 181.459 mph was best , 1.079 60 ft.
it appears the large Taper along with hi mph Ram-Air helped 1320 MPH,
before the Taper mod increase..it ran 179's at almost the same ET 7.619
and liked 46 btdc on Dyno and 46 deg on DragStrip


back to those old 293-296 SBC engines,
on 1 of the 296cid engines , i tried radiusing + rounding off lowering
the Dome..that lowered CR to just about exactly 12.00:1 CR,
the net effect was the RaceCar ran the same as before (8.62 ET)
and still wanted 51-53 BTDC as before ...but that was also in
good air....so it didn't really change anything on that Engine.

2nd hand info from David Nickens...."Leave the Domes sharp !,
don't round them off, all you'll do is lower the CR and run slower"

..basically David was correct ..as with sharp edged Domes and 12.7+CR
the Engines ran more consistently faster under varying weather
especially in the Heat . ..so i left the Domes alone and kept CR as high
as i could no matter what and concentrated on Heads + Intake Manifold, etc...from that point on ...never went back and re-tried Dome mods
on those Engines.

in contrast the SS 350 engines will like 34-36 deg BTDC w/C-12 gas
with flat-top pistons and 11.46:1 CR..at 7200-7300 rpm
with 4191 fpm

On your Engine ..you just have to experiment on the Dyno
to see if its likes more or less than your 40 BTDC ??
Always try 1 or 2 degrees less or more than the Dyno
at DragStrip and see if it likes it ?
there are a few times when an Engine wanted slightly different
BTDC than the Dyno.

when trying Timing changes on the Dyno,
always watch the first few TQ + HP Numbers at the start of the Pull,
even though the Peak TQ + Peak HP may have slightly increased
with more BTDC timing..if the first few Numbers are hurt or lowered,
i'd back down the BTDC at least 1 or 2 degrees to be safer .

your Piston Speed with 355 is probably between 4930-5220

sometimes a 468 BBC with a 50-53 cc dome likes between 46-48 BTDC
at around 5000 fpm..its hard to get more than 12.5 CR
with a large Cam in a 468BBC with 26 deg Heads

[ZEROMAN91]

Rather than put wire into the feed hole could I buy the blank brass orifices somewhere and drill them out 017 smaller than stock? Who would sell the brass? I've never seen them listed as a part #!

[mallow415]

I was checking out the search post and like sandracer I am running in the sand also and running something similar but it is 306 chev 4.03x3.00 with iron eagle 230 heads and 2970 edelbrock in. plus shooting nos. Was looking at using a t/r and making a sheetmetal top for a single carb (1050 dom). The rules penalize heavy for using a sheetmetal in and or two fours with cast t/r. Using a cast t/r with a single carb would be the same as a standard intake. The motor is turning 8800. Can this be a benifit or will it cause a lot of disturbution problems. Thanks this is one great site!

[Troy Patterson]

The 660's are neat carbs. One of the reasons people like them so much is the 1:1 throttle linkage coupled with the relatively conservative carburetor size. It feels awesome and works great if your carb / calibration allows you to stick your foot in it and have it respond. Engines love that.

The down side; There has been several decades worth of carburetor development and technology since the inception of the 660's, that 660's are not taking advantage of. The power capability of the 660's have been greatly surpassed. But, if that's what you've got, by all means run'em and add the secondary metering blocks.

I build a replacement for the 660's incorporating advancements in carburetor technology since the 660's were designed so long ago. And although, I can do a pretty good job of bench calibrating, I have earned a good deal of money recalibrating "bench calibrated" carbs. Every engine / application is different, no matter what, so I will not pressume to be telepathic or whatever, but I can get you in the ball park. Best performance, in every case comes from in car / truck / tractor / little red wagon / lego-mobile tuning.

Troy Patterosn TMPCarbs.net TMP Carbs

[bigjoe1]

I have an old pair of 660 carbs that I keep around just to see if any of this NEW stuff is any better. These have been reworked my myself, and flowed on a flow bench and soforth. I have NEVER seen any more than 2 or 3 HP differance from any purpose built tunnelram carbs.The only thing I see, If the engine will rev up past 9000 RPM, they tend to go rich. These 660 carbs flow 805 CFM on my carb test fixture, up from about 730 in stock form.They are very good from 6000 to 8500 RPM.
JOE SHERMAN RACING

[Troy Patterson]

Big Joe, remember 2002 Engine Masters? Granted you won.

But, one of those contenders, the Nelson Racing entry specifically, ran one of those new fangled modern set up carbs. If you recall, we placed 7th. Now, had Tom not left the air correctors in the dyno control room at Westec, we'd taken 6th with our best "tune-up."

Now, not to sound like one of those "coulda, shoulda, woulda" kind of guys, the fact remains our TWO days (that's only 2 days) of dyno testing / experimentation / evaluation prior to our day at Westec, netted us 7th, not far behind your heals.

And I haven't said anything of the crank grinder screwing up the custom crank they were grinding for us, forcing us to go to a GM forged unit at the last minute - costing us 7 cubic inches. And, I haven't said anything of the two points reduced compression ratio this forced us to run. And, we were forced to run heavier pistons and wider ring package. And, as a result of the undelivered crank as promised, we were forced to literally throw the motor together during a couple of all-nighters just before the competition.

I don't want to give myself more credit here than I deserve. It was Nelson's baby - that I contributed in brain power and time, not to mention the carburetor. I will say I would have done a number of things differently had it been up to me.

So, back to the carburetor. Our 286 cc intake ports, Super Victor (I cleaned up / mildly ported) together with my new fangled modern set up carb and spacer allowed us to produce 426 lb.s torque with that throw together of an engine @ 2500 rpm during our 20 minute tune session.

We spent a little time at Bill Marapolus' (sp?) shop the day before on his SuperFlow, during which time he presented us with his "best ever" Winston Cup carb. Bill said he'd dyno'd it on hundreds of engines, comparing it to other carbs. Bill said no other carb out performed it. He acknowledged some had performed better here or there, but never over all better - until mine. The carb I built for our 2500 - 6500 rpm motor (a 1075-1100 cfm) outed his best ever carb by 7 horsepower across the rpm range - with room for improvement.

More specifically, I know how his "Cup" carb is built and calibrated, and I have driven them. Hands down, my carb would be worth a few tenths in the quarter (for example), if not more.

Back to the Engine Masters motor. If you calculate the hp & tq we made per cubic inch, then add back the 7 cubic inches and the 1.5 to 2 points of compression we didn't have as a result of the crank debacle, we'd been in second or third place. Two more days of dyno time and we'd taken home the money, and I haven't factored Tom leaving our best jetting on the counter in the dyno control room. Those little jets cost us like 15 horsepower, and 6th place on that 359 cid / ~10.5:1 motor.

Nelson had modified a Smokey Ram which never had a chance to get worked out, nor a highly modified Victor 4x4 I had prep'd. I have no doubt, my modified Victor 4X4 would have been worth another 20-30 lb.s torque and as much horsepower, but Nelson was chicken and we ran out time.

Furthermore, I'll point out the carb ran full 1:1 primary to secondary throttle actuation. Contrary to David Freiburger's account that the adjustable 1:1 throttle linkage was there to retard the opening of the secondaries, it WAS THERE to allow me to open all four at exactly the same time! No progression whatsoever, W.O.T. at less than 2500 rpm (to allow the dyno to begin recording cleanly at 2500 rpm). The motor purred like a kitten! It almost sounded as though the dyno wasn't going to pull it down.

How many days/months did you spend on your winning motor? I don't mean to sound sarcastic - just competitive.

All that said, I do have respect for what you have accomplished and your knowledge.

Troy Patterson TMPCarbs.net TMP Carbs