carb size for 512 stroker?

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JamesRR

JamesRR

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trying to max out my big block stroker. right now there is a 750 carb on it. Should I go bigger? I dont have the carb specs in front of me but I will find them. Cam is fairly large. Stealth aluminum heads. Is it worth getting different heads? working the ones I currently have? 2" headers. 3,200 stall, 3.55 gears but soon to be 4.10s. Dont drive it much but want to make it as wild as possible with few mods. How big of exhaust should be run? What timing are you guys running with a motor like this? Thanks

James
 
With as little details as you've provided, you may as well have asked "How do I make my car faster, it's blue?"
 
Since Pro Stockers are 500 cu inches...and you got 512 ...I would go with a tunnel ram with two 1050 dominators....since you got 12 inches more then a Pro Stocker...
 
RustyRatRod said:
With as little details as you've provided, you may as well have asked "How do I make my car faster, it's blue?"
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400 low deck block. 512 stroker kit from 440 source. 9.5:1 compression. Hydraulic Roller cam somewhere around .630 lift. Will post duration when I find the cam card. Holly 750 with edelbrock air gap intake. Heads are the stealth heads from 440 source. MSD everything. tti 2" headers. timing set at 15 initial 35 all in by 2500. 3.55 hears soon to be swapped for 4.10s. 3500 stall. Engine is painted light blue.
 
Heads ported or as cast? If they are as cast, why? That was nuttier than a sour fruitcake.
 
RustyRatRod said:
Heads ported or as cast? If they are as cast, why? That was nuttier than a sour fruitcake.
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as they are. I did not build the motor. I did manage to wipe a lobe off the cam though! This is what is in there now....
 

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Dont know why it posted that sideways...
 

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My motor is quite similar, although you have more cam. I run a 750, and it runs best with 34 degrees timing. Your best bet would be to have those heads cnc ported, since I think those are your weak link right now, more than the carb.
 
Have the heads ported, they should work fine, single plane intake like an m1 or victor, that thing could deffinately use more carb, i hear the hp holleys work nice or skip straight to the dominator. Mill the heads maybe a thinner head gasket to try to up the compression as much as possible atleast try to get 10.5:1, as for cam, more lift or go with 1.6 rockers, and im sure it would like more gear and more converter. 3800 or 4000 stall from a good company. Dynamic, ati, ptc to name a few and put those 4.10s in
 
That thing needs a 650 plus solid roller, blowed out ported heads and one really big carburetor, or two pretty big ones.
 
It's undercarbureted with the 750. Step up to an HP950 for a better and still streetable setup. IMO you cannot overcarb a 512 but the heads are a hinderance if they are not ported. The 950's a good compromise.
And it should be orange or black. It'll be fastest orange ;)
 
Okay, tonight......I'll stay up until midnight if I have to. We have a 505 on the dyno with a very similar cam and 750 cfm Holley. Good news and bad news, bad if you are running a hydraulic roller and you are thinking about racing it.
 
JamesRR said:
trying to max out my big block stroker. right now there is a 750 carb on it. Should I go bigger? I dont have the carb specs in front of me but I will find them. Cam is fairly large. Stealth aluminum heads. Is it worth getting different heads? working the ones I currently have? 2" headers. 3,200 stall, 3.55 gears but soon to be 4.10s. Dont drive it much but want to make it as wild as possible with few mods. How big of exhaust should be run? What timing are you guys running with a motor like this? Thanks

James
Click to expand...

I think that your combo is about maxed out as it's going to get or keep the headers, stall, block and rotating assembly and toss all the rest out.
 
if you have 1.5 rockers that's a .548 intake/exhaust cam

with 512c.i. i'd say 850HP holley, no choke. mech secondaires.
you dont need 900 950 1000 dominiators etc.

performer rpm intake would be better.

you definitely need big mama headers. not the little 1 5/8". your 2" should be fine

at 9.5:1 you will be perfectly fine on street gas. a bigger cam is a waste unless you can get the comp ratio to 11:1

if you are looking for et's then you are better off putting $$$ into chassis
 
moparlover said:
if you have 1.5 rockers that's a .548 intake/exhaust cam

with 512c.i. i'd say 850HP holley, no choke. mech secondaires.
you dont need 900 950 1000 dominiators etc.

performer rpm intake would be better.

you definitely need big mama headers. not the little 1 5/8". your 2" should be fine

at 9.5:1 you will be perfectly fine on street gas. a bigger cam is a waste unless you can get the comp ratio to 11:1

if you are looking for et's then you are better off putting $$$ into chassis
Click to expand...

I disagree..... More valve lift = More air in the engine = More Fuel = More Power. No way getting around it.

His lift on that cam at the valve is probably real close to .500 after geometry Loss. If it were me I would be lifting that valve way into the .650 range after Geometry Loss.

Big engine with a small camshaft..... WHY Bother? May as well left it a 400 CI engine. The 400 CI engine would be better off with the Wimpy Stick.

Example: I have a 410 Small Block Stroker. Heads flow about 270 CFM @.600 Lift, Iron Heads, 9:1 Compression , Lift at my valve is .634 to suck in that air at that lift. Duration is smaller at .242 ....... His .500 lift at the valve is a big part of why it will never run like a raped ape. Change the cam it will be a whole different car.

Call Bullet Cams and order up a custom grind.
 
well he could go with a 950HP if he went to a .650 cam, if he could get the compression up.

if it's for street he cant. if it's racin gas in there he could get the heads done and swap in some pistons with a slight dome.

i dunno. if he just puts the huge cam and a 950 i dont think the results will be all that. especially if his chassis is not up to snuff. and converter. and 2" headers.
 
Carburator is the last part of the equation. Cheapest way to get it to run like a rapped ape is to change out the cam and max out the potential of the head flow he already has on tap.

That change alone will be like going to bed with a sex crazed Nympho Chick. You better be holding on tight and ready for a ride!
 
Have a break between dyno runs.

Actual OOTB Stealth head flows as we tested them.

.100..........66 cfm
.200.........142
.300.........205
.400.........240
.500.........255
.600.........267
.700.........268

Best OOTB Stealth head I ever tested.

.100..........73
.200.........151
.300.........214
.400.........245
.500.........262
.600.........276
.700.........281

They generally run like the first set of flow numbers.

Should he get other heads? If your goals are no more than 750 HP or so, the Stealth heads can be made to go there with porting and bigger valves for less money than buying other heads and having them ported into that horsepower range. I say that because no OOTB aftermarket aluminum head can go 750 HP without them being ported also.

Back to work........
 
What can we do with a 750 cfm carb and a hydraulic roller?

So this 505 has been a pain in the pahtoot! It has a 750 cfm Holley and now a hydraulic roller about the same duration as the OP but is running .632 lift and the heads are flowing right around 310 cfm at that lift.

First to deal with........the hydraulic rollers. These are Crane rollers going for about $650 a set. Called Crane, "What do I use for pre-load on these solid gold lifters?"

So when we finish the dyno pull (6200 rpm), the lifters, that were silent at the start, are rattling their guts out.

"Hey Crane, what gives?"

Use more preload.

"And if that doesn't work?"

I don't know. We generally use more pre-load if they collapse.

"Okay" sez I, "thanks."

More pre-load goes in and they are rattling at the end of the run.

At what rpm will they not rattle? Well they still rattle at 5200 rpm and why have 505 ci that you can't wind more than a stock 383?

Hey son! We're going to put the solid rollers on this cam.

You see, the hydraulic lobes I have access to don't suit my purposes so I had the cam ground with solid roller lobes.

Here are the back-to-back pulls. First with hydraulic lifters and then the solid lifters.

RPM.............TQ/HP...............TQ/HP

3000..........517/296.............523/299
3200..........539/328.............548/334
3400..........583/377.............594/384
3600..........587/402.............598/410
3800..........587/425.............599/433
4000..........597/455.............600/457
4200..........589/471.............600/480
4400..........596/499.............600/503
4600..........609/533.............611/535
4800..........617/564.............613/561
5000..........611/582.............619/589
5200..........605/599.............614/607
5400..........594/610.............601/618
5600..........578/616.............591/630
5800..........556/614.............574/634
6000..........544/621.............560/639
6100..........533/619.............550/639

Now the customer provided an Edelbrock Torker II intake for his build. The above runs are with the Torker II. Next is what happened when all we did was change to an Edelbrock RPM Performer intake.

3200..........600/366
3400..........616/399
3600..........630/432
3800..........627/454
4000..........621/473
4200..........612/490
4400..........599/502
4600..........603/528
4800..........609/556
5000..........607/579
5200..........611/605
5400..........603/620
5600..........591/630
5800..........567/626
6000..........546/624
6100..........534/621

Yeah, 32 more lb-ft of torque at 3600 rpm.

What about a bigger carburetor? Maybe we'll see tomorrow morning.

SO........JamesRR, what is wild as possible?
 
"You see, the hydraulic lobes I have access to don't suit my purposes so I had the cam ground with solid roller lobes."

And you're inquiring with Crane about noise? You are tired...lol.
Can you toss a 1" spacer and a 950 on it with the RPM?
 
moper said:
"You see, the hydraulic lobes I have access to don't suit my purposes so I had the cam ground with solid roller lobes."

And you're inquiring with Crane about noise? You are tired...lol.
Can you toss a 1" spacer and a 950 on it with the RPM?
Click to expand...

Yeah, what gives with that kind of clown move huh? And no, I don't think you are picking on me, I see the humor!

Consulted with the cam grinder about using those lobes with hydraulic lifters, was told they work great in that application. This isn't willy-nilly guesswork, lot of research goes into these projects. Couldn't afford to try different hydraulic lifters. I would have liked to see what the Comp Cams Pro Magnum worked like with their short travel and the zero to .010" preload. There seems to be a real problem with oil bleeding by the short, stock, lifter bores unless they are bronze bushed and honed to tight tolerances. If you don't spend the $1000 to do that the high valve spring pressures collapse the hydraulics and the lifters rattle. We had to meet a budget on the 505 and it didn't include the lifter bores being bushed. I don't intend to build another hydraulic roller cammed engine.

In the past, the 2" spacer has done zip on the RPM and I don't own a 1". The RPM is back on the shelf and we must finish with the 505 before noon. The plan is to try a 950 on the customers Torker II and then add a 2" spacer to that just for the fun of it. We've got two pump gas street engines, a Victor headed 446/440 and a RPM headed 496/440 in the assembly room and they need to go out next week.
 
my experience with Hyd rollers in a big block mopar is there just fine long as you want to be all done by 5800. and yes i have run one. funny thing is everybody keeps telling me how great they work, i've yet to see any dyno pulls where they still make power over 6grand. by then the dyno numbers are all over the map because of the instability. what self respecting performance big mopar is done at 5800. and yes, the 750 is a little small for a 512.
 
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