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Hey guys! So this is my motor out of my 71 Nova... This supposedly was built by Pro Machine in Salt Lake City Utah... this motor has never ran right... I’m not sure what I am missing... but it hiccups spits and sputters when ya put it down to the floor boards... if your slow on the throttle then it’s ok it slowly climbs RPMs but if floored it will bog down...

Those are two Holley 450cfm carbs...
Now it smells like it’s almost getting too much fuel (equipt with electric fuel pump) but things I read say they need bigger carbs than 450s?
Also what would be a good head combo with this intake? Looking to add aluminum heads to this setup..
 

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Specs on the engine ? The old large plenum TR's are pretty tough to get right on the street . When you shove the pedal down , the fuel falls out of suspension leaving a huge void in mixture going into the cylinders .That's why they're hard to get to run on the street you cash bandaid the problem with a big accelerator pump shot , but that adds to the ( usually) over rich condition you already have .
 

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Discussion Starter · #3 ·
Specs on the engine ? The old large plenum TR's are pretty tough to get right on the street . When you shove the pedal down , the fuel falls out of suspension leaving a huge void in mixture going into the cylinders .That's why they're hard to get to run on the street you cash bandaid the problem with a big accelerator pump shot , but that adds to the ( usually) over rich condition you already have .
This is a 350 bored 40 over... i took the cam out and found a worn lobe in the number 7 cylinder intake...
also the valves in the back 4 cylinders were white ( running hot?) while the front four were black... I’m tearing this down to make a stroker but I’d like to keep the tunnel ram as my hood is cut for it already... just needs to run right
 

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I had a TR1X on my 65 Chevelle back in high school, been a long time since i've seen one. Word of advice, don't drop an allen wrench down a runner while tightening the bolts inside the plenum, especially if that valve happens to be open. That knowledge cost me head & intake gaskets, intake valve, and touching up that valve seat.

Grant
 

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Those crummy 450 CFM single accelerator pump mechanical secondary carbs are not doing you any favors. Complete crap when put on a tunnel ram unless you are just a show cruiser.

Put a pair of 600cfm vacuum secondarys reworked for tunnel ram use, or hunt down a pair of now discontinued 660 cfm Center Squirters and it will be a whole different animal.
Even a pair of regular 600 or 650 cfm Double Pumpers would be a better place to start than those fosdick 450's.
Double pumpers will require sideways mounting them and new linkage though, because they are longer and won't fit inline.

It's not the 450's size that is the problem, it is the calibration and mechanical secondary with no rear accelerator pump that is the problem.....those carbs were originally designed for single carb use on big 4 cylinder and small V-6 engine use....2 used together on one engine cuts airflow signal in half, now signal and airflow moves too slow when you stand on it with no rear accelerator pump to make up for it and you get a lean bog-o-rama.

Giving a recommendation on heads is going to depend on stroker engine internals like cubic inch, compression ratio, and cam choice, your budget, and what you expect from the engine HP-wise and how you plan to use it (cruiser, street/strip, just mostly drags, etc?)
 

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Mine is admittedly a street cruiser ,but I really like my 2x 450's . I tried 2-8007 vs ,& 2-1850 vs . experimented with jetting , power valves , shooters & diaphragm springs . In the end , the 9776 450's gave the best overall responsiveness & driveability . JME.
 

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Specs on the engine ? The old large plenum TR's are pretty tough to get right on the street . When you shove the pedal down , the fuel falls out of suspension leaving a huge void in mixture going into the cylinders .That's why they're hard to get to run on the street you cash bandaid the problem with a big accelerator pump shot , but that adds to the ( usually) over rich condition you already have .
Yeah, I would love to try taking a old ram like that and making an entirely new welded sheetmetal top for it, about 1/3 the height of what is there and roughly 1/2 the plenum volume.

I just had no positive results at all with the 450's on 12 second or faster street/strip type stuff, even with 3000 stall and 3.73 or better gears...tried it once on a 327, then again on a 383. Just could not seem to get a rich enough initial stomp, so it was "whoooo....wha.....whaaa....whaaa....whaaaaaa" struggle for what seemed like a full 1 second and then finally run clean up the rpm scale.
TR1Y iirc, not quite as big a plenum as the one in this thread. Might have been TR1X?
?????
A HP body 750 Vacuum Holley on a Pro Products Hurricane single plane was 3 tenths faster on the 383.
 

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That's a major difference that I omitted , I'm running a edelbrock Street tunnel ram. Much smaller plenum . also ,I run a manual trans so that helps as well . I had a 70 chevelle 450 horse 454 ( factory qjet , th400 trans) in another life , the amount of bog/ lag that if had is pretty equal to my TR setup .
 

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Discussion Starter · #12 ·
I’ll have to finish taking the motor apart to figure out the specs your asking I have no idea... but all that will change once it’s made to a 383 stroker... which will be awhile haven’t taken jt to the engine guy to get hot tanked yet obviously... y’all think the 450s are ok? Or is that the issue? What if a guy went with sniper efi? Would that be worse or better?
 

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View attachment 525181 View attachment 525182 Hey guys! So this is my motor out of my 71 Nova... This supposedly was built by Pro Machine in Salt Lake City Utah... this motor has never ran right... I’m not sure what I am missing... but it hiccups spits and sputters when ya put it down to the floor boards... if your slow on the throttle then it’s ok it slowly climbs RPMs but if floored it will bog down...

Those are two Holley 450cfm carbs...
Now it smells like it’s almost getting too much fuel (equipt with electric fuel pump) but things I read say they need bigger carbs than 450s?
Also what would be a good head combo with this intake? Looking to add aluminum heads to this setup..
Hulk, I had a 350sbc, with a tunnel ram for 20 years in my Chevelle. I had never had any issues. The TR was a edelbrock TR1X with a pair of 390 cfm Holley list 8007 carb. I smoked my tires with no problem. :cool: It ran from idle to 6500 RPM. With 410 gears and TH350 with 3000 stall converter and shift kit, it takes off like wild beast!
Get rid of the 450 Holley. They are crap, and get a pair of 390 Holley. BTW run a vacuum hose between the two vacuum pod for uniform secondary operation.
 

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Discussion Starter · #14 ·
Hulk, I had a 350sbc, with a tunnel ram for 20 years in my Chevelle. I had never had any issues. The TR was a edelbrock TR1X with a pair of 390 cfm Holley list 8007 carb. I smoked my tires with no problem. :cool: It ran from idle to 6500 RPM. With 410 gears and TH350 with 3000 stall converter and shift kit, it takes off like wild beast!
Get rid of the 450 Holley. They are crap, and get a pair of 390 Holley. BTW run a vacuum hose between the two vacuum pod for uniform secondary operation.
I’ll look into that! I also have 4:10s and a turbo 350 trans with a 3000 stall shift kit... I was debating on throwing in a souped up 700r4 tho idk if that would change a lot... I just hate it screaming for help like driving highway
 

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I’ll have to finish taking the motor apart to figure out the specs your asking I have no idea... but all that will change once it’s made to a 383 stroker... which will be awhile haven’t taken jt to the engine guy to get hot tanked yet obviously... y’all think the 450s are ok? Or is that the issue? What if a guy went with sniper efi? Would that be worse or better?
Dual Sniper TBI's on a tunnel ram would certianly make tuning changes a snap and clean up a lot of issues with driveability.

You can make the 450's better, and maybe make them just fine for your application...but it will probably take $150 or more in tuning parts...jets, air bleeds, pump nozzles and pump cams, feed orifices, maybe even emulsion bleed rework in the metering blocks. They will still never be strong in a power competition.
 

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One thing to always consider is that mixtures left to their own devices hardly ever flow well in an evenness sense with open plenum intakes. It takes a fair amount of work to level out cylinder to cylinder mixtures with carburetors or TBI both of which no matter how precise at the venturi or in the throttle bore where fuel is entered to the airstream a lot of mayhem occurs in the plenum. I think the best solution for your induction system is a throttle body supplying air only with fuel being port injected. This takes fuel air separations, distances to an open throttle at idle and cruise affecting mixture ratio distribution, and removes fuel pooling. With simply moving air the plenum to runner problem is a lot simpler and more balanced cylinder to cylinder. Then the fuel is added at the runner to port junction. The latter situation is better served with modern chambered heads and attention to the squish/quench clearance since all air and fuel mixing is done in the combustion chambers, so chambers modern heart shaped chambers are the only way to go. The common L31 Vortec is often sighted as the base configuration you should be looking for. But the piston comes into play and you need the heads off to see what is in there. A flat top will want 74 cc chamber head to keep the compression in check with pump fuel, a dish piston will need a 64 cc chamber since some of the compression volume is in the crown shape. Without decking the block and assuming it hasn’t been then a cast iron head with a Ricardo (L31 style chamber) is a better solution as aluminum heads like a thicker gasket which pretty much makes zero decking mandatory to get the squish/quench clearance into the .035 to .045 inch range. With iron and a factory deck height of .025 inch you can get into the ‘hood with .015 inch shim gasket which can be put with aluminum heads but can become a wear problem since those heads will move more compared to iron so they scrub on the gasket with an iron block.

Bogie
 

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1967 Chevrolet Biscayne 10-71 blown 433 Big Block Chevy, T400 & 12 bolt 3.73 rearend
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Hulk6474, I have run a tunnel ram on my street hot rods since the early 80's and have run carbs from 450 thru 1050 cfm on engines from 327 to 433 cu.in. and will tell you that anything can be made to work with enough time, testing and tuning. Many factors come into play when building and tuning an engine to run a tunnel ram especially on the street. The 9776 carbs are a good choice for a street application, but the manifold that you have is far from optimal and those carbs would require considerable tuning to work acceptably with that manifold. The small cfm provides good throttle response once you overcome low booster signal the manifold provides. If you want to run a tunnel ram on the street my advice is to obtain a different manifold as a start.
There is more to successfully running a tunnel ram set up on the street that just the carbs and manifold. Cam timing, compression ratio, vacuum signal and ignition timing all come into play. It should be put together as a complete package.
BTW, for those that say it can't be done, here is a picture of the 433 inch Big Block Chevy that I ran on the street for 18 years before switching to my current combination.
525548
 
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