Warmed over 383 intake and carb questions

I have a 383 that I recently built and had a couple of questions regarding the intake and carb that I think some of you will be able to help me with.

Car:
67 Belvedere II
833 4 speed
3.91 Suregrip

Engine:
.030 over 383
12.4 : 1 compression
Comp Cams solid flat tappet , 247 / 255 @ .050, .600 / .624 lift, 109 LSA, 103.5 ICL
Trick Flow 240 heads
Trick Flow intake

My two questions are:

1) The ports on the Trick Flow intake are noticeably smaller than the ports in the heads. Would there be any gains to be had from some intake work done, perhaps such as a deep port match like Hughes offers? Trick Flow must have sized the ports like they did for a reason, but not knowing why, I had to ask.

2) What size carb would you guys recommend ?

This is a mainly street car, but I would still like it to perform as well as possible. Let me know if there is any other info I can provide. Thank you for any and all help, it is greatly appreciated.

I'm not sure about the intake porting results but I would use a 700 to 800 CFM carb like a Holley 750 double pumper or a comparable carb from another brand.
Thats a lot of compression for a street car unless your going to run it on E85 or race gas

Thanks for the advice Cab I appreciate it, and yes I forgot to mention I am running a blend of 2 parts 110 octane, 1 part 93 octane pump swill.

I don't know about the Trick flow intake but that's not a very big cam , I used to run a home ported Holley Street dominator on a 383 that made lots of torque and pulled up to 7000 on a 383.

I did the same mods to a few 440 SDs my buddy Mark 'GY3' still runs real low 11-oh's on his street driven 493.

I'm almost thinking a big single plane like the TF might be borderline "too much of a good thing" cross-sectionally for your combo. But to answer whether the ports are too small? Maybe/probably not, they probably make it that way deliberately.....because not everybody buying that intake is building a 511 Stroker low deck, there's probably a higher degree of taper (the runners are bigger at the plenum than they are to the head port.)

So not in your case, but a 383 with your combo basic combo but with only say 9.5-10:1 probably wouldn't fall out of a tree with that manifold. Your compression is the key to why your combo works as well as it does.

It's just a guess but I would think you would need at least more cam lift (to really use more of the sweet spot of those heads) before you would overtax the intake.

The carb depends more on the launch speed, if you're launching off the back squirter (assuming you have a double pumper) you could probably run at least an 850.

Ok it sounds like I may have to experiment with some different intake manifolds. As far as the cam I relied on the builder who did the work on the short block for me as I was not qualified to make that decision. I have not spun it past 7200, but it pulls pretty hard in the upper rpm range. I'm not dissatisfied with the way it performs, but just wondered if I left anything on the table performance wise when it came to the carb. Thank you for the advice !

I like to shift my motors, all race motors that I have driven, when they quit pulling hard, not predetermine by someone else
If you can take the car to a decent drag strip you can test different shift points (500 RPM increments to start with) to see what makes your car the best in the 330 and 1/8 mile times

Thats a good idea, and I will probably try to do that once I get a few more things sorted out. What prompted this post was that I noticed the difference in power from when I was driving it with open headers to once I was running a full exhaust and was wondering if some intake or carb changes might gain some of it back. The engine seems to like more timing. I started out with 34 degrees (16 initial and 18 mechanical), and now I am up to 38 degrees (25 initial and 13 mechanical) and it is running a lot better.

Your combo is close to my old combo and real close to my new.

My old combo was .030 over 383, 9.4:1, solid flat 250@.050 .580 lift, 1.6 ratio, ported 906, 2" headers, 5800 stall. This combo was modeled after the 500HP 383 Dwayne (Fast69Plymouth) did that is detailed in the tech archives. http://www.moparts.org/Tech/Archive/bb/25.html
If you have a 383 there is a lot of really good information in those two threads, definitely worth the read.

Last year I tried lots of intakes and carb on my old combo. I have an RPM, TM6, Victor 383, M1 4500, Holley SD, Torker, and tunnel ram. For carburetors I have run everything from a Demon 750 all the way to a 1050 Dominator. My TM6 has had the dimples welded up and the top blended into the runners and it has proven to be the fastest on my car (3400lbs Duster). I did also use a phenolic 2" merge spacer and would say that with all the intakes a spacer most always helped, especially on the RPM. A 2" merge spacer on the RPM was a noticable difference (picked up the front wheels). My best carb has been an 4150 QF 950 Annular booster (v1.450/tb1.750), so don't be afraid to carb up, especially since you have some decent compression. The only thing I noticed with a larger carb is it requires more tuning. The 4500 2 circuit on the RPM was also a good combo using a HVC 2" adapter. On my car, I lost 2 mph when I put some exhaust on it from open headers. What I have described above is with a 3.5" exhaust (race muffler and extension to rear tires). I kept adding timing and it kept getting faster, I finally quit at 40 degrees. In the summer I will dial it back to 38 ( dist is locked out). I shifted at 6000 1-2, 6500 2-3, 6800 through the traps.

If are over 3500lbs and have room for a spacer, I would likely suggest the RPM with a 2" merge spacer with an 850 or larger annular booster carb. The dual plane seems to like the annular booster and an annular booster tends to do better with a larger venturi (+1.450). You will need a fairly high stall converter and a decent gear to really make it work.

Thanks Clovis, I will definitely check out that thread. I have an 850 street HP Holley on the car now. The guy who did my machine work and put the short block together recommended a 950, but I was just looking for another opinion or two before I spent the money on another carb since most of what he builds are big cube strokers. From what you're saying though the 950 might be worth a try. For exhaust I have TTI 1 7/8" headers and full 3" exhaust but I figure the Dynomax Super Turbos are probably what's robbing the most power. I don't have room under the hood to experiment with spacers, at least with the Trick Flow intake. As it was I needed to make a "low profile" wingnut in order for my air cleaner to clear the hood. I could probably use a little more gear than the 3.91's, but the rearend is less than a year old and probably doesn't even have 1k miles on it so I hate to tear it apart again just yet. It also helps keep the rpm's down a little for highway cruising. Thank you for sharing all of the information for your combo with me I greatly appreciate it.

I didn't look it up but a 850 is typically 1.56/1.75 So that particular 950 1.45/1.75 would be smaller. Might still be better but just pointing this out.

Yep, a 1.45" venturi with an annular booster is nowhere near a legit "950"... that's just an advertising game. It's really all about venturi size / throttle bore size / booster config. From what I've seen, a 1.50" v / 1.75" t / downleg flows pretty close to a 1.56" / 1.75" / annular, although the atomization characteristics are going to be different.

Heavy street car with manual trans and not tons of rear gear, generously sized heads with big intake valves for the displacement.........

I’d run an RPM with some sort of “HP” 750 on it.

Thanks for pointing that out. So I looked up the specs on the 850 I have and it is listed at 1.56/1.69, and the 950 version is listed at 1.56/1.75. Fast68Plymouth, I'm sure I could round up a 750 and possibly an RPM intake to try if you think that may be a better route to go. This will all give me some guidance on different things to try instead of just guessing. Thanks again everyone.

Like what Fast says, I think of a street combo in terms of leverage:
Heavy/tall gear/tight converter vs engine output, admittedly a gross simplification, but logical to me.
In a way, it distills to Velocity vs. Volume, though the curve for either needs to be considered & dealt with.
Examples: big ports & cam like say a '69 Boss302 were a bit clumsy, and my Hemi 4-speed RR really liked more gear (4.10 vs 3.54).
My little 292" SB 4-speed '57 Chevy from WAY back in the day flat left on everybody, every time, on the street. Big motors were a challenge near the top end.
Though today we'd laugh at how small everything was on/in that motor, it had port velocity.

I thought the not-really-a-950 deal had been addressed by Holley - should be 2 different part #s, I think.
The annular AVS on one of my RRs is cleaner & more responsive than its original AVS, though I suspect the original needs fettling.

.

The 1.56/1.69 is a configuration I don’t care for.
The “original” 850 was 1.56/1.75
The old 830 race carb was 1.56/1.69, along with the “Street HP” 850
The QFT/Brawler 850 is 1.39/1.75(chokeless)
The QFT/Brawler 950 is 1.45/1.75(chokeless)

The original Holley HP 950(80496) is 1.37/1.75
A Holley “Street HP” 750 is 1.37/1.69- this is the configuration I’d be using......pic your favorite brand.

Obviously, you can just start with what you have and see how it works out.
The main difference I’d expect between your carb and a true 750 would be in throttle response at lower operating speeds and fuel efficiency.

Thank you for all of that information. The only other carb I have on hand is a race 830 off a Penske R5 cup engine and from what you're saying it is similar (at least out of the box) to the street HP 850 I am running now and the "original" 850 you reference is the same 1.56/1.75 configuration of the current 950 street HP Holley.

To clarify, I don’t think a different carb/intake will make “more power” at WOT than what you already have.

My suggestion was based on improving the street manners, but if you’re happy with that aspect of how it runs, then save your money.

It’s not like there’s a magic 30hp hiding in a carb swap(unless there’s something way off with the current carb).

I understand, thanks for adding that. I'm happy with the way it runs, but was mainly just wondering if there was a little extra power hiding somewhere. I'll likely just keep driving it as it is, and when I stumble across some of the parts you mentioned (without having to buy them new) I might do that and experiment a little.

.030 over 11.5 TRW pistons Torker intake 3310 Holly 509 cam, according to Wallace calc made 400 hp. Went 11.60s @ 118, in 1980
Street Hemi converter, 4.88 gears 29/10,5 tire

With a 3.91 gear, I'd guess that that motor won't see 6K rpms often. You want the smaller size intake manifold runner to keep up the air speed. Try a vintage Edelbrock DP4B, dual plane or something similar. You probably want good street performance and avoid 3" exhaust.

Wow that was an impressive timeslip for 400 hp ! I could try a dual plane too, Fast68Plymouth also recommended that (RPM). I live in somewhat of a rural area so it does see well over 6K regularly though :-)

I probably went through 10 carburetors last year. I actually wound up buying a Barry Grant Gold Claw and gathered up all the venturi sleeves, throttle plates and boosters, so I can go from a 750 to 1050 and alter between down leg and annular boosters. I got a lot of information for that setup from reading Brad’s post here and over on Speed Talk, again a lot of good info. I do agree with the statement that you really can’t go by the ratings (750,850, etc) it is venturi, throttle plate and booster. I will say also that an AFR gauge is a really nice tuning aid. I am probably going to bail off and get a second one for the other side on mine. Between time slips, AFR readings and plugs you can get a pretty good handle on what’s going on but to Dwayne’s point, is there 30 hp hiding probably not. For me I do want to get the most of out what I have to a point, but in reality if you are racing, consistency and maintenance are more important.

I'm generally in agreement here, I think that manifold is hurting your torque without a significant HP payback up top.

A performer RPM will certainly help your upper bottom and probably work the converter harder throughout the middle, I just don't know if I would prefer it over a mildly ported Street Dominator on your 383 which I think will be just as strong through the middle and (at least from my personal experience) a bit better up top.

The Best thing about a BB Mopar is it's so easy to swap the intakes and compare them literally back to back at the track.

Clovis has a good idea regarding the AFR gauge. That is something else I can do over the winter. In a perfect world I will be able to line up an RPM intake and maybe another carb over the winter and try some things out in the spring. Thanks guys!

A vaccuum gauge you can observe going through the traps would help a lot too, I suspect an RPM might be more restrictive up top than a street dominator.

i used a DP4B intake, 850 Thermo-Quad, SSH-25 cam on an otherwise stock 383.
2500 converter and 3.91's in my charger.
that combo worked pretty good for what it was.
best et was 13.56 [i can't remember the mph] but usually ran 13.79-13.90, without getting into the distributor to get a good curve.

Other than it being over 12:1 compression it sounds like a good combo. Being from Michigan maybe I'll see you around? Like some have mentioned, I'd just tweek the carb you have. I'm sure a rear gear would make it feel like you found some power.

I think you're right, I should have went with a little more gear. I am in SW Michigan near Kalamazoo. It looks like you may be on the east side of the state? I have really only met a couple of people from Moparts in person but it sure would be nice to run into more !