When I bought my 78' the owner had rebuilt a 71' 400 small block bored 30 over and put a 750 Street Demon Carb on it. He said that the carburetor was not tuned because "it ran pretty good when I put it on out of box" So I am getting the carb tuned. I am going to a place near me called "dirty dirty racing". The guy told me to order a carb tuning kit from SummitRacing and they would put it on the dyno and tune it. My question is, do y'all think that is excessive? Should I just take it somewhere to get it tuned and not dyno'd? I really am new to this so I don't know much and I don't want to get ripped off. He quoted me $450 to put it on the dyno and it sounded like that was the only option. Which I'm sure the the car will run perfect after that, I just don't know if I need to do it. Thanks for y'alls input.
Also the carb kit cost me $75 dollars so $525 total.
(also I chose this place because they were Holley Certified, according to Holley's website)

 

They dont even know what if it needs, if it does at all...they should have these parts in stock if they deal with carbs on a regular basis. Bet the last guy brought them a $75 kit laying on their shelf just for you.

 

Dyno tuning is valuable as long as the dyno operator knows what they're doing.

You can get get most of the way there tuning on the street, but you'll need the right tools to do it, like a wideband AFR meter. This will cost you about as much as it would cost to get the dyno tuning done, but you can keep everything at the end and tune a second car.

What the dyno enables that is much harder to do on the street is tuning for performance - they can play with the air fuel curves to find out what your motor likes best. Odds are if you're averaging 12.0-13.0 across repeated WOT runs on the street, you're about as good as you're going to get. But you still won't be able to tune for things like maximum timing for power.

A good dyno tune at $525 is a good value, especially since that includes parts. Make sure you get that kit back at the end, because it'll include parts you may use for future tuning sessions, and if you need the parts that were "used up" in the tuning session, you can replace them for fractional prices.

*edit* I also agree with cv67, I'm a little surprised they don't have these parts on hand.

 

here is what I did....

1) I bought a bolt on O2 sensor kit and installed...

https://www.speedwaymotors.com/FiTec...BoCQo4QAvD_BwE

2) Inserted a used single wire O2 I had laying around.

3) hooked old analog volt meter I had to O2 output.(digital meters jumped around too much for me to get a steady reading, If you can mentally smooth a common digital may work for you)

4) drove around and changed jets until I got 14.7:1 ratio for part throttle, and 12:1 for WOT. I don't recall the voltages offhand (google) but was something like .75v for 14.7:1 and .9 volt for 12:1. I ended up going down a jet size on the primary, up several sizes for the secondary, and changed the power valve to a weaker one. I also upped the squirter size one to remove some secondary transition bog. Took about half a day total.

 

You can really use this.., and it has alot of extra engine tuning tips also. Well worth the price.
(plus the off the shelf setup of each of their carbs)

 

You CANNOT tune the carb until the ignition timing is spot on. Take your car somewhere else as they did not even mention that to you.
The chassis dyno is a great tool but these days....all the operators know how to work on is EFI stuff.....
You need a person who is fluent in carbs and distributors.......
You can do the timing yourself with tech papers from Lars, a tech contributor here. E-mail him at V8fastcars@msn.com. He also has carb tuning papers and other interesting reads.
You can tune the carb yourself with an A/F meter........it is fun and rewarding.
As far as the shop having the parts in stock, I doubt very highly that anyone stocks this kit in their defense:
https://www.holley.com/products/fuel...its/parts/1921

Not sure what "Holley Certified" means and to me it seems like it means about squat.......try calling them sometime, you will catch my drift.

Jebby

 

So took it to the guy for the tuning of the carb today. It was a pretty fun experience. Super nice guy that ran the place out of his garage, so I just got to walk around the car and talk to him as he did stuff. He walked me through everything he was doing and why he did it, so I had a good experience. Told him everything the car was doing and the first thing he did was check the timing, turns out that was off and the carb was adjusted to "compensate" for that at idle...didn't totally understand it but the guy explained it all twice lol. So he got the timing down, then adjusted the A/F ratio on the carb. He had the exhaust hooked up to some computer that was spitting out the A/F. He made a few adjustments on the carb and timing once he ran it on the dyno as well. He ended up not needing the carb kit that I bought so I offered to sell it to him and he knocked the price of the job down to $390 from $450. (I bought it for $75 and this was easier than selling/returning). Overall really fun experience, he did say that I should replace the fuel pump because he didn't think the pump was performing well due to the HP fall off at WOT, (I think that is what he said).

Thanks for y'alls advice, what do you think about the numbers I got from the dyno?
Max Power = 276.1(HP)@4500(RPM), Max Torque = 357.8(lb ft)@2800(RPM)

 

I would say that is a fairly mild build......although the fuel pump may be holding you back as stated. Max power at 4500 rpm says it is a small cam......stockish heads. Those number equate to about 325 horsepower and 430 ft/lbs. torque......but I will say your dyno guy did what he was supposed to.

Jebby

 

Does it run better? How much difference did you see? What were the starting numbers? Are you happy with it? Then it is money well spent.

I am surprised at the big RPM spread between max tq and hp. Is that normal?

 

Ya it’s runs much better, it no longer diesels and the idle is very smooth along with better throttle response. Before if I hit the gas quick, the engine would bogg down and die. I would have to feather the throttle before revving it up, which made inclines from a stop suck.

As far as the engine the previous owner put a “pro comp cam” (I think) but that’s all I know about that. I really am just starting to learn about all this so I don’t have all the answers. I know the intake is an aluminum Edelbrock though.

Edit: previous owner wrote down the cam info, I went and found it. What does this mean?
”comp Hyd. cam 284-550”

 

That would imply that he has a CompCams cam with advertised duration 284 and .550 lift. This is highly unlikely... The only CompCams hydraulic cam with 284 duration is the XE284, and it only has .507 lift. Comp also makes a 284 solid-lifter cam with .550 lift that is usually used in oval track racing. A 284 duration cam would not have anything resembling a "smooth idle", and would not work well with stock heads and other stock components. Not likely that you have a 284/550 cam in a smooth-idling engine producing just over 300 hp net at the crank.


Lars

 

Sounds like the guy knew what he was doing.

 

Here is the engine at idle, I called it smooth but maybe it isn't. What would you describe the idle as?


Based off how it sounds, do you think it could have the solid lifter cam, 284-550?

 

Cant hear any solid cam type noise, course the exhaust is a little loud
Could very well be the Comp 284;not bad in a 400 horrible in a 350

 

Ah yes the glorious harbor freight carport, my mom wanted to kill me after she saw it in our yard. Completely off-topic but I couldn't help but notice.

 

haha I was waiting for someone to call it out. How long have you had yours/is it holing up? I’m curious how much it will hold up, I got the 2 year warranty but we are moving in about 6 months so I’ll have a real garage at that point.

 

Just set it up two weeks ago. Much better than the car cover I had, too much humidity built up under it and left some nasty-looking rust bubbles on the headlights.

 

I doubt that is a XE284 camshaft as well......240/246 @ .050 .507/.510 lift on a 110. It would sound a lot more radical.
What cylinder heads/intake are you running?

Jebby

 

I'm not sure about the heads, is there any way to check by looking at the engine?
Intake is, Edelbrock RPM Air-Gap, aluminum.

 

Either side of the cylinder head should have some manufacturer info on it, the section where the alternator and A/C brackets would bolt too. These are symmetrical, so maybe you could see the back side if the fronts are covered.