340 cam change, carb rejet suggestions.

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340fourspeedDuster

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I am running an 800 cfm Thermoquad model 9292 with the following jetting:
primary well jets 4099 (.099") diameter
metering rods 2024 which are a tapered rod going from .062" to .050" diameter
secondary metering rods 5137 (.137") diameter

Engine is a 340 +.040"
flat top pistons 9:1
iron X heads 2.02" intake 1.60" exhaust
aluminum Weiand 8007
Hooker ceramic headers with 2.25" exhaust Dynomax turbo mufflers.
Mopar electronic ignition 11° initial timing, 34° total timing
3.91 gears
4 speed 833
26" tall tires
Previous camshaft was a very mild Racer Brown tZSAXZz
Changed camshaft to a Lunati Voodoo 268°intake, 276° exhaust
  • Advertised Duration (Int/Exh): 268/276
  • Duration @ .050 (Int/Exh): 226/234
  • Gross Valve Lift (Int/Exh): .494/.513
  • LSA/ICL: 110/106
  • Valve Lash (Int/Exh): Hyd/Hyd
  • RPM Range: 1800-6200
Vacuum runs 7-8" at an idle of 700 rpm
Vehicle used at 1200 ft elevation
The car ran well with the previous camshaft, seems to run decent with this cam and no changes. Anyone with extensive experience with a similar setup please chime in.
Thanks in advance
 
Thats an excellent cam ran it in my 416 when I first put it together..as for the "thermo-bog" there as far better carbs. out there to use..
 
Thanks for your opinion on the carb. Proper adjustment of the air door over the secondaries on a Carter Thermoquad is the key to a smooth transition. I have had my "fun" with other brands of carbs. One back fire and the power valve is shot. Leaks, etc. Out here in Arizona, the phenolic float bowl keeps the gas cooler and less percolation. Summer temps are 115°F before you start the car.
Once again, Anyone with extensive experience with a similar setup please chime in.
 
I don't think your going to find someone with your exact set up. Or extensive knowledge of the set up.

Actual cam specs for the Racer Brown. Am would be very helpful.
 
Back in the early 2000s, I ran a similar cam in a 360 with aluminum heads. It wanted 14*minimum initial timing to bring the vacuum up. I ran an old 71 TQ on it, with factory jetting. It ran great like that at 950 ft. But we only see 100* at the highest here, mid 80s mostly.
I ran it with 1.6 arms,Hughes 1110 springs and their hi-perf lifters (circa 2000). With oiling mods that cam was still pulling deep into the 6000. I used to shift it at 7000/7200. just because I could. It also is a 4-speed, and I ran 3.55s,mostly.
Great cam choice with supporting Dcr.I ran mine at 10.9/8.8, with about 180 psi cylinder pressure. I squeezed some great fuel mileage numbers out of her too.
Sorry I can't help you with exact numbers but that carb went onto my winter motor, a 318, and I changed everything inside her to make that little 318 haul.
 
I am going to use 292/508 mopar cam. Will put in advanced 4°advanced to get better low end. This cam will have a pretty choppy idle but should get me nice power. Thermoquad i run with .101 primary jets, .145 rear jets and 1966 metering rods. For intake i will be using the holley strip dominator single plane. Rear gear will be 3.91's. Not set up this way yet but plan to do so in the near future. Now have a 280/474 cam & 3.55s but not too impressed. So will experiment with new set up. Just thought I would share.
 
Oh my ride is a 1974 dart sport. Around 3400 to 3600 lbs. Converter also plays an important role how vehicle will perform on the street or track. I have a 9.5" FTI 3400-3600 stall converter in a 727 transmission.
 
Your carb seems ok for jetting. May give 1966 metering rods a try. It just depends on what cam you go to.
 
I am going to use 292/508 mopar cam. Will put in advanced 4°advanced to get better low end. This cam will have a pretty choppy idle but should get me nice power. Thermoquad i run with .101 primary jets, .145 rear jets and 1966 metering rods. For intake i will be using the holley strip dominator single plane. Rear gear will be 3.91's. Not set up this way yet but plan to do so in the near future. Now have a 280/474 cam & 3.55s but not too impressed. So will experiment with new set up. Just thought I would share.

1)That 280 cam wants about 10.4Scr with iron heads, and 11.4 with aluminum. And you're right about 3.55s; that cam is way past 3.55s. Try 4.30s; those will wake her up. With an automatic, she'll want some serious stall just to get moving.
A well-engineered 280*cammed 360, should spin street 275s to well past 60mph, in an A-body, with street suspension. BTW, 6800 at the top of first should be close to 60 mph.
With 3.55s that's a bit of a problem if you short-shift her. When you hit second with an automatic; if you don't stretch out first gear,the Rs fall too far. You're gonna have to get into second at around 4000/4500. That means yer gonna have to wind her up to about 6800 in first. If yer shifting at 6200, yer choking it, and bringing second in at 3700ish, and nobody is home down there. The ponies are sleeping. So you have to wait for the alarm to go off up around 4000; then they start rubbing the sleep outta their eyes.And they don't really wake up until maybe 4800. Now 900 rpm doesn't sound like much, but with 3.55s in second gear, this is from 55mph to 71mph, and that poor engine is starting to feel the wind. So yeah, you gotta wind em up in first,with an automatic. This is also why an automatic doesn't really like a tight 108LSA. When it falls off the curve, it falls harder than when it falls off a 114LSA. Doesn't sound like a big deal, but you'll feel the 108 fall right away. Actually you'll feel it more on the approach side as the 108 cam has a decided two-stroke power band; there's; nothing....nothing... I think it's coming..... and then KAPOW! it's here and then it pulls really hard for about 1500 rpm and then KAPOW!,it falls off the other side of the curve.This is why this cam is not well-suited to an automatic; and it only gets worse with the 292* cam
2) If you're gonna spend more than a little time in the 6000s, then you need to prep your oiling system to survive it.It's not hard, but the engine has to be torn down,completely.
If you put the 292 in you're gonna see that it wants to be shifted at past 6800, so the engine won't survive that very many times and then the rod bearings are gonna spin; unless you do the oil-system mods. If you also short shift this cam, then it would have been far better that you had a 268 cam, cuz if you line up with the guy that does, he might clean your clock.

3) The 292 needs 10.7 Scr with iron heads,and about 11.7 with aluminum.With iron heads the bottom will be soft;not may be soft , but, will be soft. How soft? Like a factory 360 with a 2bbl cam, and the compression pumped up to 8.6. This effect diminishes with rpm and by 3000/3500 the 292 will be picking up, but it's not really awake til it gets up in the high 4000s. So your 3400/3600 will really help you get past the low-rpm doldrums.
If you run the 292, I'm assuming your car is a race car, so my comments don't apply; but I can't see a 292,a360,and 3.55s in a racecar.
I highly recommend not to run the 292 with an automatic,as a streeter.
Your results may vary.

4) My experience;
The 292 makes lotsa power from 5000 to 7000, at or near sea level.
In my street-367; it had nothing below 2000,and from 2000 to 4000,a good stock 360 I think was better. I ran it at 11.3 Scr in a 367 with OOTB Eddies
When I had that combo, I ran a regular A833 and with 3.55s, I couldn't wait until 5000rpm/42mph for the power to show up. Like you say; "I was not too impressed". I swapped in 4.30s which were nice, but they sucked on the hiway,lol. Finally I conceded that the 292/108 was not for me, and I pulled that lazy-azz 292 out before the end of the summer..

5) After that I installed a 270* cam, which I liked a lot. But 4 years later it dropped some lobes and I had to kiss her goodbye.
I currently run a 276/286/110 in my now10.9Scr, aluminum headed, 367, with a starter gear of 11/1.. This is still pretty tame in a streeter, but she's a wild ride. I run it with 3.55s but I have the A833 with the 3.09 low gear, and I have a gear-splitter. If I was stuck with a regular A833, there is no way I would run it with 3.55s. No way.And it's only a 276*, and it has an adjustable "stall",lol.

6) IMO, if/then
IMO, if you need more power in a street-360,than the 280 can muster,and if your compression is up where it needs to be,then; IMO; you need more head or a bigger engine...........................or you need to supercharger it.

7) If you're really gonna do it, remember the power doesn't start 'til she's really singing, and the rest of the time, without compression, you'll be disappointed, again. But if you install 4.30s and with your 3400/3600TC, then once she hits 4800, yer gonna .....giggle like a schoolgirl.
 
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I am going to use 292/508 mopar cam. Will put in advanced 4°advanced to get better low end. This cam will have a pretty choppy idle but should get me nice power. Thermoquad i run with .101 primary jets, .145 rear jets and 1966 metering rods. For intake i will be using the holley strip dominator single plane. Rear gear will be 3.91's. Not set up this way yet but plan to do so in the near future. Now have a 280/474 cam & 3.55s but not too impressed. So will experiment with new set up. Just thought I would share.
You will probably not like the springs on the rod tree with the little vacuum generated by the cam. Remove the springs and allow the cam in the carb base to enrich the mix.

I would rather see 4.30 gears and a 27 inch tire. Something like a 275/60/15 would do.

If this were a drag car, I was say more converter. The car is heavy by 400lbs. @ a min. I’d rather see this at 3200lbs. MAX!

Use AFB rods bent 3/4 of an inch shorter, clip the ends to use for tuning.
I’d also suggest a carb spacer on top of a RPM intake over the single plane. Even more so with gears of 4.10 or less.
 
Good advise thanks!!:) i have no experience with said cam. So any advise is golden to me! 3.91's is the max for me. Car will still be street driven. Good thing i can put up with noise & racket.
 
More initial timing and recurve the distributor. My guess it's going to want in the 20 range for initial.
 
Distributor is from FBO already has timing plate in it. Not sure where its set @ though. Came with a sheet that shows initial setting for timing. Also has fbo springs. It is a distributor he used to sell for street strip. Used to run the mopar performance distributor but would ping with it. Think springs were too soft and internal weights were tiny compared to the original style mopar distributor!:eek:
 
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