Carb size

[Calgary351GT]

For anyone who remembers carburators...


I'm currently using a 650 dbl pumper on my 351W in my 90' GT (3300lbs w/driver)
I'm wondering if its big enough.

My engine:
-10.5:1 comp.
-Comp Cams 280H cam. 0.512 gross lift, 280 dur.
-AFR 185cc heads. 2.02 int.,1.60 ex., factory CNC porting.
-Torker II single plane intake, match ported.
-MAC shorties,X-pipe, Flowmaster 2.5" catbacks.

I'm running a stock t-5 with 4.10 gears. I shift out at btn 6300 and 6500 rpm.

Does anyone run a similar combination with a larger carb????
I've done the online carb calculations by which I shouldn't be too far off with 650 cfm, but I've also seen crate engines with 750's on them.

 

[Shamus O'toole]

IMO go with the 750, lose the Torker II and go with a Victor JR. If you want to keep the Torker at least put a spacer on it.

 

[Calgary351GT]

IMO go with the 750, lose the Torker II and go with a Victor JR. If you want to keep the Torker at least put a spacer on it.

Really, is the Torker such a bad match??? It's already been match ported to the heads, and I have no more clearance under my stock hood.

Besides, the Vic Jr. is rated for 3500-7500 rpm. Seems a little off my range.

 

[1987LXragtop]

Kinda curious about the set up you have...assuming emissions standards are similar in the Great White North ...do you have any issues with them? Considering a carb set up on my 87.

 

[battyice]

That 650DP is probably pretty close with a single plane intake manifold. If you think it is restrictive, try running a manifold vacuum hose into the cabin and connect a vacuum guage. At wide open throttle, you should have very little vacuum.

I have a Weiand Team G single plane intake on the 355 in my Camaro (I know it is a chevy but the displacement is close to yours so bear with me) with a 750 DP holley. I used to run a 650DP holley but upgraded to the 750 in search of more power. I had a heck of a time getting the accelerator pump cams and nozzles dialed in, and it still isn't as "crispy" down low as the 650DP. In the end I did gain trap speed, but lost some 60" and ended up with the same E.T. I am considering some mods to improve the airflow on my 650DP and putting that back on.

Does your car seem to lay down at the top end? I would expect a little more trap speed out of your combination.

 

[Calgary351GT]

Sorry for late response. I lost track of the thread.

I ran at the track last Fri night with my brother's 750 Vac and increased my best et by over 4/10th of a sec. My mph went up by over 2.
Ended up a best 12.787@108mph with a 1.8, 60 foot. The 60 foot was my best too.
So I guess I answered my own carb question...

My 108 mph trap does seem a bit low. I raced a 66' coupe with a similar setup as me. I creamed him of the line and up to half track, but he told me he was reeling me in towards the end.

 

[85_SS_302_Coupe]

For your combo, especially with those heads, that does seem a bit slow considering i'm running almost the same times with a 1.9 '60 on 40 year old ported heads and with a stock suspension. Is it an automatic? Any idea of the weight? I would have to think the Vic Jr would be better than the Torker II as well, just because it's probably the best single plane out there aside from the Victor Sr and those Parker Funnel Webs but those are for serious high RPM race engines. Personally i'd just stick with a Wieand Stealth because they'll breath up to 6500RPM and will make more bottom end than a single plane.

 

[86bluecobra]

I just swapped out my wiend stealth for a vic jr. What a difference. I picked up close to 2 tenths in the 1/8 mile. I also picked up mph which was very nice. I was also racing into a head wind. I know we have talk calgary351gt but congrats again BTW.

 

[Fast63]

Your carb is definitely too small. 750 it!

Junk the online calculators. A stock 302 with no mods and 200hp will show you 600cfm, while a 450hp monster 302 will show like 650, it's ridiculous.

 

[Sgt.5point0]

All the formulas say I'm about 120CFM too big also but my 830 DP seems to be working out fine. 750CFM sounds right for a modded 351.

 

[joel5.0]

Your carb is definitely too small. 750 it!

Junk the online calculators. A stock 302 with no mods and 200hp will show you 600cfm, while a 450hp monster 302 will show like 650, it's ridiculous.

..... back in the day, I had a little 289 that performed better, was driveable, and took care of some SBC', SBM and a few BBC's with an 850 cfm DP.

This was the time when Shelby's 715's, 735's and Boss 780's Holley carburetors were sought as upgrades for our little 289/302 engines. Is bigger better?..... nope, but in my case, it provided the goods.

 

[86bluecobra]

usally even when over carb'd you do not hurt the engines performance at WOT. You can effect drivability day in day out. A 750 dp works quite nicely on my 351w.

 

[Calgary351GT]

My brother's 750vac worked so much better than my 650dp. so I guess I'm gonna pick up a HP750dp.
As for the Vic jr. talk....
My cam (Comp Cams 280H) is rated from 2000 to 6000rpm.
The trorker II is rated from 2500 to 6500
The Vic jr. 3500 to 7500.

On paper, the torker seems a better match. Is this a load of bull???
With my gears and a 5-spd, my car will never see less than 4000 rpm on the track so I couldn't give a hoot about bottom end.
I do shift between 6000 and 6200, and the car does lag a bit at the higher rpm.
Maybe it is the intake crappin' out. The AFR 185' heads shouldn't be a problem.

Let me know. The Vic upgrade is cheap enough.($275). But I don't want to waste my time match porting and swapping another intake for nothing.