421 sbc,11.6 comp,super vic,pro-systems 1000,M2 ported 227 Track 1's,powerglide,3.73,28x10.5w,and the car weighs 2700 with driver. Right now i have a comp solid roller 258-268@.050 .631-.631 on a 112 for a 300 shot. I find the motor don't want to pull past 7000 rpm is it because the cam maybe too small? I do drive the car about 25 miles a month if this matters also i cross at 6600 on motor. Thanks

94Guy,

First of all, tell me about your fuel system,--ie, type of pump, what size fuel lines, etc. Also what stall speed are you running?
What CC cam grind is that? The CS 294-5/304-5?
I have a cam that we use in a lot of 421 Late Models, and they'll go 25 miles in about 30 minutes, and one set of valve springs will last the season.....
This cam is 287/299 at .020, 257/269 at .050, 180/190 at .200, 112 LSA, in about 106° to 108° ATDC ICL, and .645/.645 valve lift, .020/.020 valve lash. It will pull up to 8100, although a 421 will probably want to stay at 7500 or so. The 421 LMs run a 287/295R7, I have put a little bigger exhaust on there for the 300 HP extra....
Please note: The 287/299 is 5° bigger at .200 than the CC 294-5 on the intake, and 6° bigger at .200 on the exhaust than the CC304-5. Shorter at the seat gives you a lot more bottom-end, larger in high-lift area gives you a lot more top-end. It will require a good fuel system, though.
If you have any more questions, I'll be around tomorrow night....
Thanks,

UDHarold

stall speed is 4500 N/A and 5800 on the spray. The fuel system is #8 from the cell to a holley reg. and #6 from reg. to carb pushed by a blue pump. Yes you are right about the cam#'s they are CS4013S/4024S R 112. I'm looking for more power on the top side. I think the cam is to small. I spoke with Cam Motion and the said i need something in the 270's-280's.

First, the fuel system. You said you had a Holley Blue pump. Do you have 2, one for the carb and 1 for the NO2? If you do, you need a 3rd Holley Blue. You put 2 of them in parallel (side-by-side) into a Y-Block, then have a #8 1/2" line go up to the front, where you have another Y-Block. Put the 2 regulators on the exits of the Y-Block, and run #8 line to the float bowls, one regulator per float bowl. The pump for the NO2 should be hooked up the way they suggest.
If you have only ONE Holley Blue, then buy yourself a good 250-gph pump for the cam/carb, and use the Holley Blue just for the NO2.
Second, about the cam. I have no trouble as far as your engine is concerned running a 310/318, 279/287 at .050, .640/.640 valve lift. However, you have that 3.73 rear, I'm sure because of the NO2. The bigger cams don't have a lot below 4000, whereas the one I recommended will pull from 3000 in your engine. How much N/A racing do you do? If the NO2 is only an occassional thing, you should cam more for N/A, if you shoot it all the time, then a wide LSA, big duration cam works.
Just let me kknow how you use the car....

UDHarold

You're saying that a 421 sbc needs a 250gph fuel pump :rolleyes: An 1100+ cubic inch diesel can't even burn that much fuel,and whats the point of 1/2 fuel line going into the carb when the needle valves arent even that big :confused: A mallory comp 140 won't feed that engine???

How fast is it?60ft. mph and et?

Bob,

Oddly enough, for the past 25 years, from 1978 through 2003, engines using my cams have picked up when the fuel supply was increased, IF the engine has been exhibiting signs of lack of fuel on the top end. This man's COMP CAM was exhibiting a lack of fuel on the top-end, and as mine flow more air on the top-end, they need more fuel.
Why are you continually arguing this point? If you don't believe me, then don't do it. However, people who run my roller and solid lifter cams that experience a flattening out at high RPM ARE running out of fuel, and increasing the fuel supply CURES the problem.
It has for 25 years, with tens of thousands of engines, whether or not you believe it.
Other cam companies cams MAY NOT show this, as it depends entirely on how reversion is controlled on the top-end. A lot of reversion lets you get away with a single Holley 110 or Mallory 140. Carbs richening up on the top-end are showing the effects of reversion. They're flowing less air, and need less fuel..... All my cam designs, including those I made for Comp Cams and that they still use, demonstrate this flattening out on the top-end. My hydraulics, solids, hydraulic rollers, and solid rollers are all designed similarly, and the higher(450 + BHP) engines will show this.
Want to prove me wrong? Call me up, give me your combo, i'll SELL you a cam. Run it the way you want as far as fuel system goes. If it gets flat and lazy on the top-end, you may, or may not, change the fuel system. If you do change it, and nothing happens, you can tell everyone. If it picks up, I expect you to tell us that, too......

UDHarold

Originally posted by Rapid Robert:
You're saying that a 421 sbc needs a 250gph fuel pump :rolleyes: An 1100+ cubic inch diesel can't even burn that much fuel,and whats the point of 1/2 fuel line going into the carb when the needle valves arent even that big :confused: A mallory comp 140 won't feed that engine??? Robert,
I probably shouldn't even bother but,,,,,oh well :D

Harold has been doing this stuff for a few years & he talks with just a few racers daily & get input as well as giving freely of his expertise.
Instead of questioning his fuel system every time he posts about it why not give him the benifit of the doubt that he just might know what he is talking about.
Even if on the off chance that it isn't needed, what possible harm is going to come from knowing your fuel system is adequate or even more than adequate??
Not trying to be a pain here, it's just I know Harold & have spoken with him more than a few times & feel he may actually know what he is talking about ;)

Hi Harold ;)
Was busy typing & didn't know you had posted

Happy Holidays

I like reading Harold's stuff. We are fortunate to have him post. smile.gif

I just don't understand that while Harolds cams are proven time and time again with upgrades to the fuel system....... that people want to argue the point.

You want a Harold cam = You want to go faster
Faster = More air into the engine
More AIR = MORE FUEL?!

C'mon people.
:rolleyes:

Hey Bob, I think Harolds calling you out!!!

I personally feel that "Rapid Robert" is in denial, and completely afraid to go faster that 114.59 mph. graemlins/clonk.gif What other reason would he have for being so argumentative? I took Harold's advice and installed a Magna Flow 500 on my wagon, that's enough for a Pro Stock car. I not only picked up ET and MPH over the old Holley Black, but I'll never have to upgrade again.

It seems to me that Bob just likes to argue and rattle the cages.

Thanks Harold for all the advice and I will definitely be installing that 1/2" fuel line from front to back as you suggested for my 454. graemlins/thumbsup.gif

I myself am also uncertain on which side of this disuccion to take. I used to run 2 -8 lines from tank to filter( russel 2 in 2 out ) to two Holley Blue Pumps then -8 from there to two holley regs. then -6 to the float bowls, car ran decently but not great ( 11.20's )Later on I went to something similar to what UDH said about the Y Block .. and the idea just didnt seem right .. if one pump is pushing more, it seems it would just over power the other. Freind has a 70 Vette all of 3600 lbs + runs one holley Blue pump -6 line to a holley reg then -6 to carb .. with an Ultradyne Cam ( bought it approx. 1998 )and he runs 10.30's .. he does have 22 cid on me, and better weight transfer. I redid my engine and fuel system back in 2000 went to -10 from tank to russel filter, -8 to one holley blue and 1 -8 up to a Holley reg with -6 going to carb.... car ran 10.80's Now I have a BG 280 and a MUCH bigger tire and it runs 10.60's ( 60 ' went from 1.6xx to 1.46 .47 ) There is alot of disagreement on this question from alot of people with extensive knowledge in this area.. personally.. go with what you can afford and/or what works best for Your specific combo.

Without naming anyone in particular :rolleyes: , some people that post here run off to other sites and bad mouth this site and Harold for no particular reason other than to impress ones they look up to with mind numbing blindness. graemlins/clonk.gif

Having very little to offer/advise based on their own experience, they choose to base their opinion based on what others think, now that`s just sorry I`ll say that much graemlins/sad.gif

well put big red. when i purchased my 288/296 solid from harold 5 yrs ago i talked to him then and he told me i needed 2 holley blues and i'd run 2to 3 tenths faster, i never tried it , but this season i'm going to go thru the extra trouble and try 2 pumps. why not give it a try?
whatever happens i'll report my results.ray

I don't notice any laying over, but I wonder if I'm at the low end of Harold 450BHP cut-off point.

Question, my car is NOT a race car but a toy, cruiser, and occasional racer. ( every category BUT show car I suppose). ITs hard for me to imagine it pulling any harder than the 118.75 mph it runs BUT, would a Holley Blue pushing through the stock 3/8s line, through the AC mech pump do any good at all?

I would rig it to run only when I want it to, not full time. Worth it? It was the only "upgrade" I was considering this year.

( ps. I'm still thinking the added bowl capacity of three side hung float bowls is saving my arse from fuel starvation).

Gene
do you think its possible that when you arent using the electric pump it could become a restriction to the mechanical pump???

Harold,

I would like to get an opinion on the Comp Cams XR292R solid roller I am running. Is it one of the cams you may have designed that would benefit on the top end from let's say a Mallory Comp 250 pump.

My system consists of -10 line to a 12" long -10 in/out filter to the Carter 172 to a -8 in/out filter to a fuel log with -6 inlets to the "out of the box" 850 DP carb.

I already have a test planned for this spring that will compare pump-to-pump ET and MPH and I WILL report un-biased and objective results.

I have run 125.1 mph so far with the Carter.

I would think a big mech pump like the 172gph Carter would be all you`d need.
I agree with RatOnaStick, the idea of drawing fuel through an non functioning electric pump doesn`t sound good. Is that really how it`s set up??

BigRed,

Is your last response referring to my combo and the Carter?

I have run sustained highway speeds with the Carter 172 pulling through a Mallory Comp 250, but did not make a pass yet with the Mallory either hooked up separate or in-line with the Carter...That's this spring

Tom

You'll have no problems pulling fuel thru an electric, even with a pure stock mechanical.

I ran as fast a 8.9's at 150 in my back-halved 3000lb '70 Vette with a 505 (100 over, 1/4" arm +400 rod) on gas single 9375 1050 and one little Holly Blue in the rear. This was 15 years ago not sure about the quality of those pumps now. Never an issue on the long end. ;) BTW that was with a cheesy little box stock Crane 268 roller. Decent Brodix -2 ported by Champion, Davis step headers and a few other tricks. We always laughed at the Barry Grant stuff with Mega flow and Mega $$$$'s . If your combination is correct and properly tuned, you would be amazed at how little gas is needed.

Originally posted by mc71454:
BigRed,

Is your last response referring to my combo and the Carter? Tom Not at all, just typing at the same time. I was responding to 427L88`s situation. Sorry for the mix up.

Everyone,

Here's my reasoning, and I have maintained this argument for over 20 years.
Everyone has run other cams besides UltraDyne. Have you noticed that at high-RPM the carb goes rich, and you have to lean it down? Have you ever wondered WHY?
Because the exhaust opens first, a lot of it depends upon the exhaust, and how efficient it is. A very efficient exhaust will have less back-pressure than a less-efficient one. Remember, the piston is rising on the exhaust stroke, and pushing the burned exhaust gas out of the cylinder. This burned exhaust gas has both volume and pressure, and they are both decreasing as the piston approaches TDC(Differential Equations, 101...). At some point, the intake valve opens BTDC, and the existing pressure and volume of exhaust gas in the cylinder is the REVERSION. The intake is at a slight vacuum, the exhaust has a POSITIVE backpressure, and the exhaust/reversion flows into the intake runner, because the piston is still rising and pushing the exhaust out of the cylinder. If you had 2 cams from 2 different cam companies, but each used the same exhaust master(perhaps you had one company regrind the exhaust?), WHERE the intake valve opened will govern HOW that cylinder fills. This is assuming the valve opens fast enough to be where it needs to be ATDC. If it's just a slow opening intake, it won't work very well.
So we suppose we have 2 different intake lobes, say one opening at 42° BTDC, the other at 39° BTDC. They both have the same .200" duration. What happens? The cam opening at 39° BTDC put less reversion in the intake runner, so ATDC it started flowing SOONER than the one opening at 42° BTDC. At the .200" duration lift it is ahead in velocity, and will STAY ahead for the rest of the cycle. It will put more air into the cylinder at ALL RPMs.
Now back to that richening-up carb. The higher you go in RPM, the more disruptive reversion is. Any decreasing of reversion pays off in big increases in air-flow, particurlarly at high RPM.
My designs have, since 1977, shown a flattening-out somewhere over peak torque, if the fuel supply is inadequate---That's circular reasoning, too. If the fuel supply is adequate, the engine will not flatten-out. I feel many of those who run the cams straight-up do not flatten-out because reversion, caused by the delayed exhaust opening, richens up the carb.......

I hope this has been of interest to you all. Other cam companies have their own opinions and beliefs, but this is my firm belief since 1980....

Thanks,

UDHarold

Harold, what if i maintain 7 1/2lbs. of fuel pressure all the way through the 1/4 mile? Is that good enough? The reason i ask is because Patrick James @ Pro systems carbs has always asked if the fuel pressure stays steady when you tell him you gain in the 1/4 mile by jetting up the carb.

94Guy,

I was referring to VOLUME, not pressure. Pressure is measured right after the regulator, and I'm talking about a condition in the float bowls. Fuel is being pulled out the jets by the cam's design and resulting airflow. If it is being pulled out faster than it is getting into the float bowls, the engine will flatten out--- It needs more fuel. Almost always the fuel pressure gauge does not show a drop in pressure.
It is inadequate volume, not inadequate pressure, that causes the flattening-out.

UDHarold

I kinda thought the motor stops pulling because the cam seems small for the motor. Do you believe that? Thanks

Originally posted by UDHarold:
94Guy,

Almost always the fuel pressure Gauge does not show a drop in pressure.
It is inadequate volume, not inadequate pressure, that causes the flattening-out.

UDHarold Hi Harold.
I don't get what your saying.... seems to fly in the face of some basic physics involved with carberators... If the pressure is maintained and the needle and seat opening adjusts to keep a constant bowel level, how could the flow be low with good pressure? :confused: The way I understand it, if the flow requirements increase, the float will drop, the needle and seat opens more and than if the fuel pressure keeps up... shazam you have more flow. If you jack the pressure up, you can force more gas into the same needle and seat opening until you loose level control in the bowels.... I have run a belt pump with a Carb and purposely run a higher pressure at the top-end just to overcome a basic flow problem with using a modified gas carb and can understand more pressure more flow.... but with a electric pump(s) and a mech regulator that is keeping up as indicated by no sag in pressure, I just don't see how you can say the flow is low??? I'm not addressing your suggested need for more fuel on the top end with your cam design, just how you get more flow with constant pressure at the fuel bowel. Maybe you can take the time to explain it to us, in more basic terms, or not. BTW With my Injected methanol set-up, when I lean it out (solenoid controlled bypass on rpm chip) at around 900' it's just liking hitting the NOS again... A little off subject, but interesting difference between gas and methonal... I have seen some variable speed pumps that can be used to regulate pressure as a function of rpm but it's not to common. Most folks that can are going with FI because of the way better control. graemlins/thumbsup.gif

I'll take a stab at pressure vs. flow.Take a tub of water with a hole in the bottom draining the water out,put two hoses in pumping water in, one is 1/4 inch id the other is 1 inch id both have the same line pressure of 6 pounds which one is going to keep the tub fuller?

Everyone,

I am NOT a fuel system expert, the people at Hilborn used to argue me down that a #6 3/8" braided steel line would carry enough fuel to feed a 468 FI BBC at 7500. They were right, for the EXACT correct bypass pill. The only problem was that if you were changing pill sizes 2 numbers at a time, you might hop right over the correct pill; There was NO indication you were approaching the correct pill size. However, with a #8 1/2" line, as you approached the correct pill size, the engine got better, power-wise.
In other words, the #8 line made it much easier to tune. I found this out in the mid-80s working with my Super Mod engine builders in Ohio and New York.
I only know what about 26 years of experience has shown me: If an engine USING my cam designs goes 'flat and lazy' on the top-end, it is running out of fuel. This only happens with the use of either stock or #6 3/8" fuel line, or a low-volume mech pump, or a Red or Blue Holley pump, or a 140 Mallory. Single pumps of over 220 gph using #8 line NEVER show this flattening out. Neither does the 172-gph Carter mech pump using #8 line.
My theory of high-RPM airflow and the disruptive effects of reversion, and the well-known phenomenon of carbs richening-up at high speed all indicate the probable lack of fuel caused by my cam designs' increased airflow at high RPMs.
BTW, if you turn off your engine when its' in that 'flat and lazy' mode, coast down, then pull your plugs, they are definitely lean. If you drive back to the pits before you pull them, they are not. Jetting's OK, just lean when 'flat and lazy'.
My thoughts----What works, WORKS!!!!

UDHarold

BTW, this only holds true for running the cam in a 4° to 6° advanced position; cams run straight-up generally accept whatever fuel system you have. They just don't make as much power as the ones that are advanced......

OK I'm going to try and stick up for Harold here. I run a UD cam 108 LSA installed at 102 ICL. The engine is a SBC 350 that makes 490 BHP at a low 6100 RPM 460 ft/lbs @ 4900 rpm. My fuel system is; stock tank with a competition engineering sump, aeromotive fuel pump, #8 line to the regulator, from the regulator 12 inches of #6 to each fuel bowel. When I ran it at the track it did exactly like Harold says, it becomes lazy at the end of the track 5600-5800 rpm. I had to increase my regulator to about 9 PSI. This increase did not solve the problem, but it made it a little better. Only now the crab floods out because too much pressure(so I had to decrease the pressure). I believe eliminating the #6 line in exchange for a #8 will alleviate the flat and lazy problem. If it dosen't I'll report back.

Originally posted by Aaron Kelley:
I run a UD cam 108 LSA installed at 102 ICL. The engine is a SBC 350 that makes 490 BHP at a low 6100 RPM 460 ft/lbs @ 4900 rpm. What UD cam do you have? Is it hydraulic, solid, or roller. Those are some pretty numbers