dr_hunt
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Posts posted by dr_hunt
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The biggest problem with using the volume calculations, like was shown in an earlier post, to determine airflow capacity in relation to carb sizing is that it is not apples to apples. Manifold vacuum is at zero if the carb is sufficiently sized and above zero if it is not, it is a simple airflow dynamic situation easily calculated by standard engineering principals. Carb flow ratings are based on 4.5 inches vacuum. So, it's not apples to apples. At zero vacuum carbs, especially holley carbs flow significantly less and it has been proven time and time again. A 750 only flows about 690 cfm at zero vacuum, but flows 750 at 4.5 inches of vacuum, which is why most people run a 750 carb on a 350. I run a 900 cfm C&S aerosol billet carb on my 406.
You can overcarb an engine, but considering that GM routinely installed 750 cfm carbs on stock 350 engines, you'd be hard pressed to go wrong with that selection.
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Kind of what I figured, a couple guides were tight. LMAO. Mine work great, I spent quite a bit of time porting the bowl areas on both the intake and exhaust sides and they work great. Mine had 2.055 valves but the seats were only cut for 2.02 valves. I had the seats cut for 2.055's. Overall I'm pretty happy with them except for the fact that I have almost as much in them as a set of AFR's. LOL
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BTW... clevis plates and gussets should be welded on one side of the joint only. This is per FAA spec for CroMo welding and the book "Construction of Tubuklar Steel Fuselages."
I was wondering when someone was going to mention that.
Some of the welding was obviously tig and the rest mig. None of those welds would likely pass inspection or testing for various reasons. If your serious about running those without worry then I'd have them sent to a lab for non-destructive testing. Weld defects that I can visibly see in the pictures effect the quality and hardness of the metal. There is lack of root fusion, lots of weld splatter and the welds are very undimensional throughout, meaning not the same width along the weld. Overall they are extremely poor welds IMO and look to be the work of a novice at best.
Paint covers alot of defects, I call it a DuPont overhaul myself. If you remove the paint with some paint remover and use dye, you can detect porosity yourself. You can also magnaflux it cheaply at a auto machine shop and maybe see some signs of lack of root fusion since the weld never melted with the base metal. Ultrasonic testing would be a good idea also. x ray is kind of expensive.
And yes, they may work, but if they fail while driving the results could be a disaster. I would think it would be prudent to at least inquire about getting a quote for some testing by a qualified lab before you run those. Obviously the decision lies with the owner of the pieces and this is just my observations from the pictures provided and nothing more.
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I'll work on the pantera pictures, nice car, but not show quality, this one is a driver. Interesting car though.
Red z is still sitting, so is the '55, although the motor, trans and trans crossmember are now in the '55. Rad showed up the other day for '55, need to install a wiring harness in '55, not looking forward to that.
Jeep is hauling A$$ as usual but the snow and lack of doors on the jeep keep it from being driven. I'm really pleased with the heads so far on that motor.
The z is the next thing on my list, after roundy round racing that is.
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Off this next weekend to go race southern sport mod IMCA in Abilene TX. I built a motor for a guy in that class and he is letting me race his car in that series when I can.
Also building a 408 cubic inch cleveland stroker for a Pantera, should be a nice build for you ford boys.
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Poor bastard! You have the worst luck! You'd be better off if you'd have gotten kicked in the nuts!
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Something a little more proven. About 600HP in street trim.
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Out of box Holleys are safely designed for sea level applications. They're typically pig rich since fouled plugs are a lesser liability than melted pistons. Unfortunately the compromise is driveability and optimum performance levels. Best bet is to go wide band. I have 383, AEM wideband, HP 750 244@ .050, ..613/585 ISKY, Vic Jr, Mallory 140 and return style reg like G-Vette's 1st pic above. T56 (.62 6th) w/ 3.7 rear and get easy mid 20's mpg cruising 75-80.
Diddling with the jets and powervalve restrictions is just the tip of the tuning berg.
I got tired of all the compromises I was dealing with my HP carb and started researching, eventually drilling and tapping out my $600+ carb and making my own bleeds, and tuning myself. I'd post my specs for my 750, but its absolutely pointless since I'm at high altitude and every engine combo will be different. Not that you will have to, but as a hint I'm a mile from any Holley rule of thumb spec and have changed every emulsion hole, air bleed and jet. The result has been a carb that performs like FI, no stumbles hiccups, or misses, flat cruise and wot AFR and for the first time my plugs stay clean.
Not for the fainthearted as you can turn your carb or your engine into a pile of junk as well.
Here's endless reading from here, some good advice, some just big egos,...good luck!:
LOL, so true, which is why advice on changing your boosters is such misleading information. They all go together, it's not as simple as most people think. Buy a carb with downleg boosters for the best signal and tune from there. Heck, buy the holley carb tuning book, written by the Pro's that built your carb and soon you'll have it all dialed in. My book is sitting on by bookshelf in my office.
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Simply not true. There is play in the gears which is required to run properly, that play is the reason why they will not transmit harmonics of the crank.
This is a quote from Pete Jackson Gear drives Q&A section.
Fiction mixed with fact : Gear drives create harmonics
Fact : Every rotating part that contacts another, or part that is
stressed under load in an engine ( crank, cam, valve train,
gears, chains etc. ) creates a harmonic ( frequency ) . Some
frequency are harmless, a simple matter of unavoidable
friction , while other are percussive & concussive, and are
capable of creating damage in very short periods of time .
Gear drives, chains ( yes chains ) and most valve train
components create frequencies which are a simple matter
of friction and rendered harmless by simple lubricants (oil).
An unbalanced or improperly balanced crank , ( especially
if the harmonic balancer is removed ) create the percussive
and/or concussive types which can over a period of time
( if severe very short ) cause damage , above and beyond
anything considered normal wear . Gear drives absolutely
do not create these types of harmonics .
I never said they cause harmonics nor did I question there reliability. All I said is a belt drive may do the job with out the harmonics (transmited) by a gear drive.
Belt drives don't have the durability that chains or gear drives have. Simply to say, they are without a doubt the most inferior of the three. If the belt drive is so good at removing harmonics then it also is the least accurate of the three also as the belt is stretching. Belt drives come in wet and dry versions. never run a dry belt on a street car or you run the probable chance of shredding it by debris entering between the belt and gears. Wet belts you can't see and you have to disassemble the engine to inspect unless your running a cloyes 2 piece or similar cover. For logetivity accuracy and durability, your better off with a billet roller chain or gear drive.
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I didn't say it caused them, just transmited them.
Simply not true. There is play in the gears which is required to run properly, that play is the reason why they will not transmit harmonics of the crank.
Also there is nothing more durable than a gear drive, just ask CAT, Cummins and Detroit! Anyone who thinks otherwise is absolutley positively wrong! Chains do break and any HD application especially industrial, uses gear drive for simplicity and durabiltity. I know of several Reher-Morrison BBC's that had tchain and gears and the chains gave up, destroying the engines.
I have run them in several of my personal street engines with over 100K miles logged and zero problems. The sound may delay your detection of engine sounds will in no uncertain terms prevent you from finding it.
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IMO there is nothing better. The sound you speak of is really minimal compared to most exhaust notes of today's mufflers. I doubt you'd even notice it.
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Here is how you work on getting it right. Play with jets and once you have the main jets set, it is time to play with power valves. Install a vacuum guage, you can get a cheap hand held one from any parts store like autozone. You can put it face down to the windshield under a wiper, just make sure the hood doesn't pinch the line. Watch when your driving, like going up a slight incline at highway speeds, or accelerating slowly at highway speeds, you will notice the vacuum reading falling. As it falls, it will come to the opening point of your power valve, then pick up a little. If you have a wideband you can tell when the power valve opens because the meter will go lean for a while, then the valve opens, and the meter begins to show rich. You'll probably notice the power increase right when the power valve opens, but maybe not. It's hard to tell with a higher hp motor than with a stocker, like a 6 or 4 banger.
If your PVCR's are too small, the meter won't go up high enough, and power will suffer because the engine is still too lean. You can drill out the PVCR's with a small drill bit in a fingertip drill bit holder. If the PVCR's are too big, you will see a big jump in the meter readings, and maybe a puff of black smoke when accelerating. You see that alot in turbo cars that are blowthrough.
Now that you have the power valve mixture correct, try some different power valves to see what drives the best with your combination.
You should use a power valve that is about 2 inches of mercury below the LOWEST manifold vacuum reading you get on cruise and idle (in gear for automatics). If the power valve flutters open at idle, it can act as a pump, and push extra fuel into the main well, causing a drip from the booster venturis. If the power valve opens a lot while you're driving down the road, your gas mileage will suffer.
Hope that this helps you get it tuned right. I'd bet you have several things going on, all of which are covered.
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If you will do what I have outlined above it will give you all the mpg's your going to get out of that carb. PERIOD! If people really don't have a clue about how to answer a question then don't answer it. I have a pet peeve about ridiculous answers that are completely wrong and lead people down the wrong path which directs them to spend money needlessly.
You can't change boosters without special tools and knowhow, besides, you'll screw up the fuel metering circuit anyway, which are balanced by holley engineers. Why anyone would attempt to do that is a real
Squirters have absolutely zero effect on cruise mpg and so do secondary springs. And don't waste your time on any fuel pressure regulator and return fuel line as it's fixable for probably less than $20 and about an hour's time pulling the bowls, jetting and following the procedure above.
IMO what separates he really good enigne builders from the rest are the ones that can tune their engines and those of others. Cause if you build it and it's tuned all wrong, your customer is not going to be satisfied and probably won't come back. But if you tune someone elses engine and get it working right, they will be at your door the next time they need a motor.
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Actually with Holley carbs, any pressure between 4 and 7psi is within spec. Having to run 5 or 5.5 psi is simply not true. Chevy ford and chrysler put holley carbs on sbc's in the 70's and absolutely none had fuel pressure regulators or return fuel systems. All they had was a simple mechanical stock pump and a 3/8's line.
A little bit about holley DP's is contained in the following. You'll have to jet down then open up PVCR's to make it get mpg. Anything else is a complete waste of money and time.
Double Pumpers and Gas Mileage (or lack thereof...)
Have you heard people complain about the gas mileage they get with performance-type double pumper carbs? There is a reason that the 0-4776 through 0-4781 double pumpers get bad gas mileage. It's the jets! Surprised? Holley sizes the jets and air bleeds on these carbs so that they run on the rich side at cruise speeds. They make more power this way, at the detriment of gas mileage. These are competition carbs, and they are supposed to work this way. Why don't we just put leaner jets in them to get mileage? Because the PVCR's are small, and under power conditions, the carb will supply an overall lean condition. What you can do is lean the jets out, then enlarge the PVCR's to compensate for power situations.
The way to do this scientifically is to measure the diameters of the openings of stock jets and PVCR's using drill bit diameters. Then calculate the total area of all the openings, and add them up.
A = 3.1415 x dia x dia / 4
Decrease the main jets for proper cruise mixture, and enlarge the PVCR's until you get back to the original area of all the openings. This way, your cruise mixture will give you good gas mileage, and under power, the engine will have proper mixture.
BTW PVCR's are power valve channel restrictions and are the two little holes under the power valve.
It really is just that simple!
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Nope, don't sell the z for the wrong reasons.
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IMO anyone using a manual trans and no scattershield with any type of modified engine is rolling the dice on not walking or being injured. It's a good idea and cheap insurance.
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Now that's cool!!!! Can't wait to see it in the flesh. What rear end you doing?
Hope you ditched the pj's for the race. Would of looked kinda gay otherwise.
JK! -
Next time have your fashion coordinator do something different with the PJ's!
Or were you just trying to make the car look better? -
I don't think it'll be all that bad. With the short tires, a 3.90 gear should be ok considering how light the car actually is.
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IMO if your serious about having it stay together then the EMCO 4 speed is about all that can handle big hp and tq, that's what they use in Nascar. The rest just don't hold up, otherwise you'd see them in Nascar. But no 5th gear. But you can tailor your gear ratios with 11 input gear ratios and like 29 shifting ratios.
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Well, I guess it's back to a plan. U going to get another manual or just go automatic?
I love shifting gears but haven't been able to find anything besides a lenco that will stand up to big TQ and HP, at least not for very long.
Probably time someone really developed a trans that could take the abuse, something like a dual countershaft design with small diameter gears.
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Yup, now that looks like alot of fun! I'd get one too and teach him how to drive. Then bring him down and we will let him take a spin in the mud pit in the '33 with the alky 509 slingin' some mud!
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I love twins, don't get me wrong I really do, double the fun, double your pleasure, etc, etc! But I gotta go mondo single turbo, intercooled, efi this time on a 10:1 motor and possibly alky injected! Oui! Now that's slow!!!!
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LMAO, your right!!! Sitting at the light with 5psi boost on the two step and t-brake, it launches so hard that it blew the slicks right away as the boost rockets to 12+ in the blink of an eye. I couldn't watch the gauge anymore since I was watching the track and trying to keep it straight while smoking tires. Short shifted to high which stopped the wheel spin and the tach was at like 4500 and it felt like I was on a rocket sled. Front end was light and it was dancing all over the track right and left but the monte is easy to drive and has PS. In a z I can only imagine what it's like and why on gods earth you'd want more turbo's is truly beyond me. Well, maybe you have the combination of tires and suspension dialed in and it's a breeze to drive. I can tell you that your crazy and really be right on in description. But I like you anyway.
As for the baddest z on the planet, he can claim whatever he wants and the two of you can duke it out.I am going to complete my single turbo project this year and just go SLOW.
Squirters have absolutely zero effect on cruise mpg and so do secondary springs. 
carburetor choice
in Gen I & II Chevy V8 Tech Board
Posted
LOL, I think a carb in the 650 cfm size would be perfect IMO
Listening and comprehending are two distinctly different subjects.