Holley 4150(750 dbl pumper) with tunnel ram
- Thread starter DPI
- Start date
Coupefreak
New Member
What size engine?
what kinda modifications? I.E : heads, cam, timing, etc.
a 750 DP in MY opinion, is kinda big for a mild SBC.
but thats just MY opinion
Vance
what kinda modifications? I.E : heads, cam, timing, etc.
a 750 DP in MY opinion, is kinda big for a mild SBC.
but thats just MY opinion
Vance
Coupefreak
New Member
DPI said:
OK........it should work, you will probably hafta "fine tune" it with jets, power valve, etc.
Brucer
New Member
if its just a single carb on the tunnel ram,first thing i would do is get rid of the power valve and put a plug in its place, go approx. 4 jet sizes bigger on the primary side, that will be a good starting point....
a few years ago i had a 306 carbed engine (.030 over 302)in a 84 mustang, 10.5:1 comp, e303 cam,e7 truck heads with 2.02 and 1.6 valves, 750 cfm dbl pumper.. if i remember correct i pulled the power valve and plugged it and was running 74 jets on the primary side and 74jets on the secondary side..
and never had to mess with a power valve again
the 427 in my old truck has a 950 dbl pumper,i removed the power valve. i have like 80jets on primary and 82jets in the secondaries, its a little rich on the primary side and i havent had a chance to run it on the top end with the new rearend and stuff in it..
nothing worse than being out cruising, and blow a power valve...
a few years ago i had a 306 carbed engine (.030 over 302)in a 84 mustang, 10.5:1 comp, e303 cam,e7 truck heads with 2.02 and 1.6 valves, 750 cfm dbl pumper.. if i remember correct i pulled the power valve and plugged it and was running 74 jets on the primary side and 74jets on the secondary side..
and never had to mess with a power valve again
the 427 in my old truck has a 950 dbl pumper,i removed the power valve. i have like 80jets on primary and 82jets in the secondaries, its a little rich on the primary side and i havent had a chance to run it on the top end with the new rearend and stuff in it..
nothing worse than being out cruising, and blow a power valve...
Mike
Well-Known Member
A 300 cubic inch engine can only pull 738 CFM, and that is clear up at 8500 RPM.Coupefreak said:
It will work a lot smoother to tune the power valve to the application and leave the jetting where it is. Otherwise, it will be slobbering when it doesn't need the additional fuel. Removing the power valves ~can~ (not always) work on a drag car, but for most other applications, they are pretty useful.Brucer said:
We've been modifying the base plates with check valves for 10-12 years, which eliminates the majority of the ruptures. Holley has even begun adding check valves, themselves.
Mike
Well-Known Member
Which supports what I said earlier, that ~some~ drag applications can benefit from not using a power valve. In a drag application, we use other tricks to introduce as much WOT fuel as we can, so we're doing things like modifying accelerator pump check valve weights, etc. ~Most~ drag cars leave at RPM levels that are high enough a power valve circuit is unnecessary anyway, as air flow is already well established and the venturi is flowing the main jet.Brucer said:
For applications that can see a lot of lower RPM, the power valve can be invaluable to covering up a stumble. An oval track car on a caution lap needs to keep the plugs clean, but it also needs richening when the green flag drops, until it is back to flowing the main jet again.
If a fellow cannot properly adjust valves or use a timing light and a vacuum gauge, then he's likely going to want to be shy of anything using a power valve, as quickly as possible.
On the other hand, if he's willing to work with accelerator pump cams, pump cam positioning, nozzle sizes and power valves, then he can come up with a combination that can transition off idle smoothly, whether that be at part throttle or full throttle.
Adding jetting in order to remove a power valve is not curing a problem, it is merely covering it up with a Band-Aid. And quite often, it will create another problem in the form of a part-throttle, lean backfire. (At least it won't take out a power valve that way...)
Brucer
New Member
Mike said:
i guess i dont know what the hell i'm talking about.guess i cant tune an engine or carb to save my ass... sorry to the OP
i do not run a power valve in any holley carburetor i've owned and havent in any performance street vehicle i've owned in about the last 20 years... and if you cant make 400+hp at the crank out of a naturally aspirated 355 ci small block maybe you need to try something different. Automotive Performance and Machine might get you on the right combo
yes i know that THEY SAY a power valve plugged carb will run rich at part throttle, but YOU also know with all of the other carb tuning basics, a timing light, and valve adjustment and an ignition system and stall a calculator a vacuum cleaner and a hair drier
you can definetly get rid of it.. yes it takes time to tune it , sometimes alot of time to get it right. and to the OP (dont listen to me :lol:,evidently i dont know what i'm talking about) i give you a word of advice . buy holleys performance carb tuning book,i guess they still sell them, bought mine about 20 years ago.. the book will help you understand the break down of the different circuits in the carburetor, give you the run down on pump cams and accelerator pumps, air transfer slots,power valves,jets,metering blocks,discharge nozzles, vacuum secondary springs and just about anything else you'll need to know about a holley carb.
Mike
Well-Known Member
No need to cop an attitude, OK?Brucer said:
You are of the opinion you can successfully set up a carb without a power valve. Good on you and the 20 years you've been doing it.
In the 35+ years I've been racing and building race motors, I've consistently found positive results on the race track and on the dyno by using all the systems Holley built into their carburetors - the idle system, the main jet system, the accelerator pump system and the power valve system. As well as the choke system on the street-driven applications.
400 HP out of a 355 is a piece of cake. With an out-of-the-box cylinder head, scant compression and a wee camshaft profile, it isn't going to happen. Sorry if that causes you a problem, but I make a living doing this stuff and I've got a pretty good idea of what it takes to make 400 HP out of a small-bore motor. But you must be right, all the track championships our motors have won are just figments of my imagination. None of those countless NHRA and IHRA national records that hang on the walls of the hallway outside the office are real. Those engine builder of the year plaques we've been presented by two sanctioning bodies are complete fakes. So yes, please, get me contact information on this shop you mentioned, so I can get on the right track as quickly as possible.
Ooops, you forgot to mention that he should rip the pages about the power valve circuit out of the book. Heaven forbid he should read any of that 'disinformation', right? (I'll not bother mentioning how much carb technology has advanced in the two decades since that book was published.)
I know some of the fellows at Bowling Green, maybe I should put you into contact with them and you can explain to them how ignorant they are for having put power valves in all the carbs they've built. And look at the silly gooses - they not only sell standard flow power valves, but they also sell high flow valves. Or maybe I can put you in contact with any number of aftermarket carburetor shops that offer power valve boost referencing for blower carb applications. What in the world are these people thinking? Just take the power valve out and throw it away, right?
I recently had a limited series 390 Holley apart for a customer. This particular carb had come from what I consider to be one of the premiere shops in the country and carries a breathtaking price tag. When I put it back together, I replaced the 4.5 inch power valves that the shop had used with fresh ones. Go figure, those idiots using power valves, eh?
Now you can swell up all you like, but I'm going to stand by what I said before. If a fellow can adjust valves correctly, adjust timing correctly and prevent vacuum leaks in the intake tract, the power valve is a very efficient means with which to tune. If that same fellow can't get all those things right, then he's going to have a motor that is likely to be sneezing through the carb and putting the power valve at risk. I'll leave you to sort where you fit into that scenario.
dustytrails
Member
ok since we are on the subject of tunnel rams I have one with 2 holly 450's on a 350 bored out 60 over with over size valves and a mild cam,msd ignition,I cant seem to get the stumble out of it ,normal accelearation no problem but under a quick take off it stumbles and just about dies but quickley catches up and blasts off ,does it at any speed 35 mph floor it and it stumbles,55 same thing,normal driveing no problem,set linkage up to only use 1 carb just for a check and made no difference still stumbled
Brucer
New Member
Mike said:
mike, i dont swell up.. in your first paragraph there you rounded up my asumption of a power valve.. with your statemment of, i REPLACED the 4.5 inch power valves that the shop had used with fresh ones.. go figure, those idiots using power valves,eh...
ok we established the first thing as of why i dont use power valves, if your not using power valves, your not replacing them, your not having to pull a float bowl off on a friday night in a parking lot with a flashlight, i'll stop and hold the light for you..should i go on? eh?? and if youve ran power valves that long on streetrods, you've probably done that, if you had the engine tuned, timed and running perfect youve still done it.. especially if a car sits dormant for around a month or so in a garage, and you go out to fire it up and poof, blown power valve.. or a hotrod thats sat all winter...
yea connect vacuum gage, check it, drop down roughly 4inches and you can get a high flow powervalve, those have the red dot on them dont they or am i wrong? been a while since i bought one..
and did i call anyone an idiot, i dont think so.. but i can, idiot would be too nice in my book.
coloradotbucket
New Member
I am setting up a tunnel ram with dual 600 Vac Secondary Carbs. Double pumpers are trouble in my opinion - secondary pump shot needs a tremendous amoung of RPM for it to be used. Holley Suggests a stickshift with a double pumper although some people with loose converters use them. Two would probably make it puff black smoke when throttled. For whatever its worth, I would think a vacuum second by its very nature would be a better carb for a tunnel ram, although there is probably somebody else on here who would disagree. I am still getting my pieces together for my set up. I wouldnt remove powervalve without expecting a sooty idle. Powervalve removal is for cars that don't need a strong transition circuit I am thinking.
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