Looking at 2 engine mods. Whats your opinion?

[biomedtechguy]

don't count on it....those magazine guys can get it but you and i can't.

Well, I am sure the quality build, including careful balancing and blue printing helped, but like I said, their results explain a lot about what a strong, consistent street performer my friend's 70 383 Roadrunner was.

 

[ir3333]

Well, I am sure the quality build, including careful balancing and blue printing helped, but like I said, their results explain a lot about what a strong, consistent street performer my friend's 70 383 Roadrunner was.

i remember the magazine build using a stock 340.Same deal, cam, headers, intake and carb and ended up over 400 hp.i know guys who duplicated the same build but only got about 360 hp give or take.They did use a big cam in that 383 build so you could expect a decent peak but it would not be very fast on the street.

 

[RobsRR]

don't count on it....those magazine guys can get it but you and i can't.

Yes I am skeptical of magazine numbers especially Dyno numbers.

 

[451Mopar]

Yes I am skeptical of magazine numbers especially Dyno numbers.

I'd like to see a comparison of Dyno numbers where the pulls start at 1,500 RPM

 

[biomedtechguy]

Those who are skeptical of the magazine article build featured, do you disagree with the route they took? Is that not a reasonable plan to find better performance? It was the route I took when I was a teenager and knew a lot less about adding performance to an engine. Headers, carb, intake, cam...Pretty straightforward, and far more beneficial than shaving heads to add 1/2 point of compression. JMO

 

[440rb]

I went from a dual plane intake, a .484/.284 purple hyd., a 750DP small tube hdrs on my street/strip 9.8:1 '71 340 with stock non ported 2.02 heads (220cfm@best), it made an honest 302fwhp on track. Went to a Holley strip Dominator intake+ 2" open spacer, an 850DP I modded, 1.3/4" race hdrs and a DC. .590" [email protected] SFT cam and made 367fwhp on track, with all ancillaries, had good bottom end for a 340, it use to pick the wheels and went from 13.3's@101>12.40@108.(race gears/converter) and was still ok on the street apart from highway cruising, all back in 1987.

Its not the hp that 383 made you need to take note of so much but what they did to it and what effect those parts/tune had on [email protected]:1CR. The op's .450" lift hyd cam with stealth heads and a 750VS is not going to do anything wonderful in his motor, raising CR even up .5 of a point won't help much either. Allowing the motor to breath Will.

 

[biomedtechguy]

raising CR even up .5 of a point won't help much either.

THIS!

 

[451Mopar]

Those who are skeptical of the magazine article build featured, do you disagree with the route they took? Is that not a reasonable plan to find better performance? It was the route I took when I was a teenager and knew a lot less about adding performance to an engine. Headers, carb, intake, cam...Pretty straightforward, and far more beneficial than shaving heads to add 1/2 point of compression. JMO

I'm fine with the article, Just curious how much power dropped off below 3,600 RPM with the larger cam.
If your driving with engine RPMs above 3,600 RPM then the larger cam is a good choice.
For a daily driver with a stock converter, maybe a bit too much cam?

 

[biomedtechguy]

Just curious how much power dropped off below 3,600

HORSEPOWER
RPM STK HDRS CARB INTKE CAM
3000 218.6 232.1 244.0 231.6 225.2
3200 236.5 247.7 257.5 250.3 243.7
3400 251.4 267.1 279.6 272.7 268.5
3600 270.5 281.9 297.3 292.1 295.8
TORQUE
RPM STK HDRS CARB INTKE CAM
3000 382.7 406.3 427.1 405.5 394.2
3200 388.1 406.6 422.6 410.9 400.0
3400 388.3 412.6 431.9 421.2 414.7
3600 394.6 411.2 433.7 426.1 431.5

 

[451Mopar]

HORSEPOWER
RPM STK HDRS CARB INTKE CAM
3000 218.6 232.1 244.0 231.6 225.2
3200 236.5 247.7 257.5 250.3 243.7
3400 251.4 267.1 279.6 272.7 268.5
3600 270.5 281.9 297.3 292.1 295.8
TORQUE
RPM STK HDRS CARB INTKE CAM
3000 382.7 406.3 427.1 405.5 394.2
3200 388.1 406.6 422.6 410.9 400.0
3400 388.3 412.6 431.9 421.2 414.7
3600 394.6 411.2 433.7 426.1 431.5

Yes, I read the article. What I am saying is the Dyno pull starts about at the RPM of the peak torque of the first cam, so you only see that the new cam is down around 11 ft/lbs at 3000-3200 and then the larger cam starts making more torque/power, but we have no idea if the smaller cam has a flat torque curve up to this point and if the larger cams torque drops only a small amount, or a lot more?
I think the larger cam could be down 50 ft/lbs at 2,000 RPM, and even more below 2,000 RPM? This is where compression ratio / dynamic compression ratio make a big difference.
I know for most of the Muscle car / race car people it is not a big deal, just throw a bunch of converter and gear into the drivetrain.
Just pointing out that there is more to consider than just a peak HP number.

 

[Curiousyellow71]

Yes, I read the article. What I am saying is the Dyno pull starts about at the RPM of the peak torque of the first cam, so you only see that the new cam is down around 11 ft/lbs at 3000-3200 and then the larger cam starts making more torque/power, but we have no idea if the smaller cam has a flat torque curve up to this point and if the larger cams torque drops only a small amount, or a lot more?
I think the larger cam could be down 50 ft/lbs at 2,000 RPM, and even more below 2,000 RPM? This is where compression ratio / dynamic compression ratio make a big difference.
I know for most of the Muscle car / race car people it is not a big deal, just throw a bunch of converter and gear into the drivetrain.
Just pointing out that there is more to consider than just a peak HP number.

I agree,
If the OP has a 3800 stall and its working properly, below that it shouldn't really matter much other then bad gas mileage.
But if he is looking for bottom end...I usually call that maybe 1000-3000, which makes no sense with a 3800 converter, so my guess the op is looking for some midrange power maybe 3800+
...The term bottom end is subjective I guess.

 

[Cranky]

It's the heads man, it's the heads! Just doing a good valve pocket job on a set of stock heads will do a lot. Never had a set of Stealth heads in my hands but if they are anything like the Eddy RPM's they are probably pretty decent already but can still use some work. And to me, mid range for a street motor is 2800 to 4200 or there abouts. And no mention of how much the 71 weighs? I'm guessing it's still pretty close to original except for the aluminum parts on the engine so the car is probably on the heavy side of 3700.....?

 

[fratzog lover]

What springs do you have? Are they matched to the cam or just 440 Source springs?

 

[RobsRR]

Wow a lot of ideas here. So I posted originally just to get opinions on whether to mill the heads at the same time when adding the rpm intake. The goal to bring up the compression 1 point to 10.4. I was wondering if I would notice the difference of 1compression point. I have to mill the intake regardless to make it fit. So I am thinking do them at the same time. My thinking doing both, everything will work better as a whole. I know my build is not perfect but that is how you learn. I will make other changes down the line and appreciate all the suggestions. I want to tackle this one first. As I said earlier the new intake needs to get off the shelf. I bought it about 4 years ago. I am not racing it and just wanted to try some other combo. Just playing not really unhappy with things the way they are. I guess that's why I haven't made any changes sooner. Car is dependable and looks good. Thanks everyone!!

 

[GTX MATT]

Did you measure the compression?
How is the distributor set up? Initial? Total? Vacuum advance?
What secondary spring is in the carb?

 

[RobsRR]

Did you measure the compression?
How is the distributor set up? Initial? Total? Vacuum advance?
What secondary spring is in the carb?

I measured compression when I built the motor. I sent the distributor out and had it set up. Using Using full manifold vacuum and vacuum advance and never messed with the secondary spring on the carb.

 

[GTX MATT]

I'm assuming you sent it to FBO - did he tell you how he set it up?

That secondary spring can make a huge difference.

 

[Cranky]

Do a mock up with the intake to make sure how it fits before cutting it. The factory specs are all over the place and aftermarket parts do not always conform to the factory stuff either. One time I had a Torker intake fit dang nice after cutting the heads .100"!!! All the intake needed was the bolt holes elongated. Thought that was kinda nuts....

 

[Budnicks]

I think the gear change like @Cranky suggested
would be one of the best bangs for the $$$
your converter may be more useful that way too
get the car moving quicker, far better seat of the pants feel
a better wider & taller performance tire, could help too

the head shaving really isn't worth
the work vs power levels & possible problems/hassles
not from the description I saw here, by the OP

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performance 101
more lift or even just more rocker ratio in some cases

more air in & out, the engine is just a big air pump
high flow low restriction air cleaner/intake path & exhaust path

heads cleaned up pocket ported (big choke point on BB MoPars)
Stealth's are only like 260cfm flow @ 0.600" gross lift out of the box
your current cam if far less than that
Even a RPM or Street Eddy head (can get them in 84cc & 75cc)
will flow better out of the box than many lightly ported std port (Chinese) Stealth's,
but that's not a cheap deal to change

better intake & properly sized & style of Carb for it's intended usage
or EFI/Tank etc., properly tunes/fitted

hotter ignition, coil etc., to burn the extra fuel

better low ohm resistance sparkplug wires,
proper heat range plugs

the combo that works together
instead of just a mix-matched assemblages of parts
the rest is pie in the sky type stuff

or a street car that thinks it's a racecar, won't be happy either way

 

[RobsRR]

Do a mock up with the intake to make sure how it fits before cutting it. The factory specs are all over the place and aftermarket parts do not always conform to the factory stuff either. One time I had a Torker intake fit dang nice after cutting the heads .100"!!! All the intake needed was the bolt holes elongated. Thought that was kinda nuts....

Yes will do. I took the intake and heads off. Waiting for a chance to get to the machine shop. I will mock up.