650 or 750?

[bluevenom867]

My 351 has a 750 Speed Demon(Barry Grant) on it now.
I'm thinking it might be too much because the car doesn't have low-end punch I though it would.
Here's the specs:
74' 351W
Stock Crank (might be forged,it's out of a truck,can someone confrim this?)
Stock rods resized and fitted with ARP bolts (190,000psi)
KB Hyperutectic Pistons
Hasting file fit rings
(the short block was completely balanced)
Crane cam (identical to TFS Stage 2)
TFS Track Heat heads with minor port/polish
Scropion 1.6 rocker arms
Manly push rods
Edelbrock Vic. Jr. intake
BG Speed Demon 750
It has close to 11:1 comp ratio with the heads and pistons.
The thing is,the power doesn't really come on until 3500rpm.
Maybe this is bacause of the Vic. Jr. manifold but I'm gonna juice it so it like the single plane intake.I also know the BG carbs flow more than there rated,so my 750 is more like a 800.I'm thinking of selling this and geting a BG Mighty Demon 650.I think this would help my low-end but I still want my massive top-end power.
The motor easly revvs to 6500rpm's and pulls extremly hard from 3500-6500rpm's.I know it's got torque because it breaks the tires loose at 2000rpm's when I power brake it.It just that 2000 up to 3500 is a little more sluggish than I like.I think the 750 is just to much for the motor at low rpm's.
What do you think?

 

[408stroker5.0]

You cant have the best of both world's man..... with that intake power will suffer a bit on the low end no matter what you do. I'd stick with the 750 especially if your thinking of Nitrous (Be Carefull.... Hyperutetic Piston's Aren't the Greatest For a Nitrous Engine) Have you considered an Edelbrock Performer RPM Air Gap Intake? An intake like this will still be alright if you want to use Nitrous and will definetly perform better at low RPM's but will still perform great at high RPM's. These intake's are great and infact MM&FF did a dyno comparison a while back on a 480HP 393 Stroker between the Air Gap & Victor Jr. Well belive it or not the Air Gap was only about 3-5HP off the Victor Jr. at high and mid range RPM's all the way up to 6500. The Air Gap was ahead (I cant remember the exact Numbers) at lower RPM's of course. I'd switch intake's especially since your engine will never be going above 6500RPM. As for Nitrous, yes a Single Plane intake will perform a bit better then a dual plane with nitrous, but with Hyperutectic Piston's in there I woudn't be giving here to much of shot anyhow. To play it safe I woudn't go higher then a 100HP shot. One screw up and those piston's will shatter like glass, and the chance's of detonation or nitrous back fire are pretty high with 11:1 Compression. Overall man I'd say switch over to an RPM Air Gap and keep the 750.... I think you would be pretty happy with the result's. Good Luck and let me know what you think.
Oh Yeah.... Even though your crank is out of a truck it's still a Cast Crank.

 

[mustangman33]

Man you got the kinda setup that I want, except for the cast crank and hypertecic pistions, but 351w have lots of hi end torq, I dont feel lots of low end torq but I consider it a good thing because when I want the power, I can get the power, not all over the road and stuff, but with that compression, you should go with an 850, a performer intake is also good if you can clear your hood, and if you wanna get rid of that bg 750, pm me, i heard that theyre pretty good, also, how much hp do you think you have.

 

[408stroker5.0]

DO NOT PUT an 850 on her..... Trust me, the setup I recomended above would work perfect. Whether it's a Holley or especially a Speed Demon, an 850 would be too much carb for a 351W, even with your combo.

 

[mustangman33]

Another 351w guy, I thought a 750 would have not been enough for that hi of a compression, could be wrong thou, but I thought with all of the power he should produce the air and fuel wasnt going to be there, the only reason I said it wasnt enough because the guys building my motor said that I needed a bigger carb when I changed my compression. And where in the hell are you guys finding these old blocks, searched for 2 years and came up empty. Hey 408stroker, how much hp are you running, they told me that if I went to 11.1 compression, Ill be around 512hp, I thought it should be more.

 

[408stroker5.0]

Not To Discourage you or disapoint you Mustangman33, that is a nice setup you got there for sure but 512HP will be pretty hard to hit unless you throw some even better head's on her, a pretty decent cam, and of course more compression like you said. Stroking it would be the ultimate way to breach 500HP, but your setup would need to be a bit more radical to get 500+ out of a stock stroke 351W. What's Your Cam Spec's??

As for my setup I havn't even been to the dyno yet as this current set up I have listed in my sig is about 3000KM old only. Going to the track and chassis dyno soon..... Estimated Flywheel HP is around 550+HP.
See's more street time then strip.

 

[battyice]

A old trick to see if your carb is large enough is if your engine pulls any vaccum through an intake port at WOT. In theory, with the throttle blades wide open there should be no vaccum in your intake manifold...if there is your carb is a restriction.

-By intake port I mean vaccum port below the carb's throttle blades. Also, I'm sure a certain amount of vaccum is acceptable, but I'll have to dig into my reference books to see exactly what an ideal level would be.

 

[bluevenom867]

No I don't want to change to a Performer RPM because last night,It was wet out and I lost traction and the car hit almost 7000rpm's with in a second.Plus I might stroke it still.I think it has around 450 flywheel hp,I hope.

 

[thumper460]

aint the carb.... If you have a barry grant carb... call HIM!! He is way cool and will help!! the cam is the same as a TFS2 what is it set in at?? the ICL?? you will get some snap back in the low end with the ICL in at 104-106* esp on a carb engine!! also the ign timing is WAY important... you can have the dist spun in so you have MAX ( Total) advance in at 1800-2000 rpm, start with a 10* initial and a total of 38* @ 1800-2000 and that will also wake up the low end!! manifold.... Hmmmmm, it is a mid to top end manifold!! The Weiand Stealth is an awesome intake from 0 to 7500 and will smake the doors off a Vic Jr at low speeds and almost pull with it on mid to top!!

You have BIG things... ( not those...lol) the reason the engine is a wimp on the low end is there a lack of velocity!! the carb isnt the problem... HEADS... Cam... Intake... THOSE are the problem!! SO fix it!! The cam ICL will help!! Ign timing at 1800-2000 will also help... Intake will also help!! Gotta remember.. Hell yeah, its a riot to scream sideways at 4500 RPM and scare the dog mess out of the girl next to you... but it also TOTALlY SUX having to catch up on a car, 5 cars in front cause he has a better combo TUNED right!! cool??

Just me.......................

Thumper

 

[dude5l]

Also, what gears are you running?

 

[bluevenom867]

3.73

 

[bluevenom867]

Oh I forgot it a built C4 I'm running

 

[bluevenom867]

Also,Thumper460,why would I need to change the h/c/i?
I'm also running 34 degrees total timing at 3000rpm's.
I'll run more with better gas.
It doesn't have "no power at low rpm."
It just doesn't have the same power at low rpm as it does in the 4500-6500rpm range.
You mentioned velocity,how about a velocity stack and a 1 inch open spacer?
Would that help?
Isn't the Weiand Stealth a low-rise dual plane?
I still want max power with the nitrous.
Witch would mean a single plane,right?
One more thing,how much power do you think I have and what 1/8 mile time would I run.(the chassie,suspension and drivetrain is all set-up)

 

[408stroker5.0]

The Performer RPM AIR GAP would still get you great performance with the Nitrous. Of course yes the Victor would be better. I woudn't be running to much Nitrous with those Hyper Pistons either.... you'll regret it. I'd concentrate on making the most out of your N/A combo.

 

[bluevenom867]

Hey,408stroker5.0,why arn't you runnig a Performer RPM?

 

[bluevenom867]

Also,408stroker5.0,on a shot 150 will I keep up to your N/A combo?

 

[408stroker5.0]

Not Perfomer RPM... Performer RPM AIR GAP. They Are Two Different Intake's.
I run a Victor Jr, because of my cam/head combo would benefit more from an intake like the Victor as 3000+ is were the power really start's to come in. She actually makes pretty decent low end power at lower RPM's as well though. If I wanted to I could run an Air Gap, but I would most likely lose a bit of top end power and have too much torque off the line causing launching/traction problem's. If I had AFR 185's then the Air Gap would be an excellent choice but the 205's I'm using really need an intake like the Victor to get the true potential out of the head's.

It's hard too say if your combo with a 150 shot would beat mine, as I don't know your suspension set up, weight, tire's etc etc. etc. HP whise, I'd probably be a little bit ahead even with your 150 shot.... It's hard to say though as a proparly tuned Nitrous set up,set for a 150 shot could produce an even higher HP gain (175+)

 

[bluevenom867]

ground pounder caster/camber plates,d&d K-member,a-arms,coil-overs,MAC uper control arms,SSC lift bars,MAC lowered sport springs,sub frame con.,koni skocks/struts,8.8 w/ moser axles,eaton locker,3.37 gear,c-clip elims.,full manul revers patern C4 w/trans brake,10.5x26in.slicks.
What about with that?

 

[408stroker5.0]

Why does it even matter, if you can beat me or not??? I really don't care.... Maybe if you lived in my area I'd say hell.... come too the track this weekend and we'll find out, but that dosn't matter anyhow. I'm just trying to point you in the right direction as too a better set up for your engine. Finding out who is faster is childish (Ricerish) and wont really help you out with your problem.

Anyhow Good Luck with your project and let me know what you decide to do.

 

[EMW150]

aint the carb.... If you have a barry grant carb... call HIM!! He is way cool and will help!! the cam is the same as a TFS2 what is it set in at?? the ICL?? you will get some snap back in the low end with the ICL in at 104-106* esp on a carb engine!! also the ign timing is WAY important... you can have the dist spun in so you have MAX ( Total) advance in at 1800-2000 rpm, start with a 10* initial and a total of 38* @ 1800-2000 and that will also wake up the low end!! manifold.... Hmmmmm, it is a mid to top end manifold!! The Weiand Stealth is an awesome intake from 0 to 7500 and will smake the doors off a Vic Jr at low speeds and almost pull with it on mid to top!!

You have BIG things... ( not those...lol) the reason the engine is a wimp on the low end is there a lack of velocity!! the carb isnt the problem... HEADS... Cam... Intake... THOSE are the problem!! SO fix it!! The cam ICL will help!! Ign timing at 1800-2000 will also help... Intake will also help!!

Thumper

I agree. It's all trade-offs. If you ditch the Vic Jr manifold you're not going to be as happy with the upper range. Same thing with the cam timing. If it wasn't for the nitrous I'd say put 4:30s in the rear but if you spray it you'll be out of gear quick. The only other thing I'd recommend is rent some dyno time and see exactly what the thing wants. I definately agree with the full timing by 1800-2000. That can make a huge difference down low. I run mine locked out with a start retard and it's very streetable. If you want to make a curve, I'd give it as much initial as you can with a shorter curve. Start at about 18 initial and give it full by 2000 or so. May see quite a difference there. It's definately not too big a carb. The carb on mine is a custom 750 ported/polished/calibrated that flows around 850 on the bench and you have more cubic inches than me.