17059272 modifications

[Marx3]

Hi, I am building a 17059272 for a friend of mine.
The carb is in good shape and untouched.
It goes in a freshly built 454 early 90's truck engine. CR is beefed up to 9.4 and it has a Weiand Action Plus intake.
cam is an Erson 120201
288 adv.
492 lift
112 lsa

454 sits in a Deathproof clone Nova with M22 and 4.11 gears.

Carb has 72 jets/ 52P rods with DH sec rods.
I can measure the rest. Opening distance will be 1.3" and the pull-off realeases stock in about 2.5 seconds.

Do you think I need to modify anything anywhere ?

[Marx3]

I measured things except the idletubes, they have clear passage, so I wont bother replacing them if the stock size is fine.
DCR: ~.045
Discharge: ~.025
lower idle:~.067
upper idle: ~.067
upper main: ~.070
lower main:~.040

jets: 72
rods: 52P
secondary rods: DH/.057
pull-off release time: ~2.5 seconds
open distance will be 1.3

I have a portable O2-sensor to measure AFR, but would like have it as close as possible as my friend lives far away, and I wont be dropping by to measure AFR's anytime soon.

[ejowrench]

I have no idea what the cam specs are, but the closer they are to 'stock', the less mods you will need to do to the carb. I like to see what the engines wants before I dive in with a drill. J

[ejowrench]

Go ahead and install the carb as is and get a feel as to what it wants. Make sure you can easily adjust the APT.  Make a lot of notes and use common sense.

My guess is that your main jets are a little lean, but try 'em any way.

[Marx3]

Do you know the stock cam specs for a 1992 454 cam?

The cam is pretty mild. engine made about 13-15" hg when I visited him a while back. It has to be mentioned that this was with a stock 750 Edelbrock and without vacuum advance hooked up. I am positive it will be better with a properly set up Qjet.

As far as I know this carb might be from a 301, if this is the case it will propably need changes everywhere to work good on the 454. I know it is not from a 301 turbo, since the secondary rods are not the paperthin DX's...
As I wrote, I dont exactly have the opportunity to take the carb for a testdrive. If I could do this I would build the carb from guesswork based on the many Qjets I have build over the years using Cliff's advise.

Also, adding by-pass air might be a good idea, I dont know :-)
I dont mean to be rude, but I hope someone else will chime in...

[ejowrench]

Marx 3,

Yeah, it's me again. Maybe someone out there has a better answer than me [no dought], just remember, there is no such thing as a 'pre jetted' carb. That's a marketing term to describe a carb that is too rich. I feel if you want your carb to run at it's best, you are going to have to get it running and spend some 'quality' time with it.

[Marx3]

Hi again ejowrench, how have you been :-)

I realize this. I know I need to spend some time finetuning the afr, but like I said, my friend with the car lives far away, so I want the carb to be as close as possible...

a 9.4:1 454 with a pretty mild cam should be pretty easy to pre-jet since, well, since its a mild 454. There must be many other cases :-)

Maybe I misunderstood your first post, but you said you didnt know about camspecs, and it sounded like you had not read the whole post. I have built many carbs, and tuned many cars using my LM-2 portabble O2-meter.
My friend currently runs a stock 750 Edelbrock and it runs very lean at cruise an pretty lean at wot. He dont know the difference, so I want him to be positively surprised when he receives the Qjet. This is why I need this carb to be as close as possible. Pre-jettet if you will :-)

[ejowrench]

Marx3: I re-read your original post. I'm not really sure what 288adv means. Is this the duration? If so, at what tappet lift is this measured at? There are many different ways to measure duration, but every cam manufacture has a spec for duration at .050'' tappet lift. That's what I look for. Advertised duration means absolutely nothing to me, it's just a number to reference a cam, sort of like a part #.

I'm just curious to know the cam specs at .050''. Maybe you still have the cam card?

[Marx3]

288 advertised duration, 214 at .050...
Sorry I didn't put the duration at .050, I read somewhere in here that dur. at .050 was more or less useless information. Cliff wrote it if I remember correct.

[Marx3]

btw, I came to wonder: if there is no such thing as a pre-jetted carb, what is Cliff's business all about then? :-) Again, dont mean to be rude or sassy :-)

[ejowrench]

Marx3, Thank you for the cam specs. This cam is very close to stock. [as you already know].

I believe Cliff said in his book, something like- if you install your a carb on a performance [modified] engine and you believe you will need to make changes for optimal performance, 99% of the time, you will be correct.

'Pre-jetted' carbs may get you in the ballpark, but dialing it in after running it will get you inside the diamond!

Being your friends Big block is pretty close to stock, and he is used to a 'universal performance carb', perhaps he will be happy with it as is. Good luck and keep us updated.

[ejowrench]

When I said  'as is', I meant as with YOUR prepped Q-jet, not 'as is' with the aftermarket carb. Just wanted to clarify that. I'm sure your Q-jet will perform better.

[Marx3]

Marx3, Thank you for the cam specs. This cam is very close to stock. [as you already know].

Yeah, it felt pretty stock too, which would be plenty to hurl a tiny Nova down the quartermile :-).

I believe Cliff said in his book, something like- if you install your a carb on a performance [modified] engine and you believe you will need to make changes for optimal performance, 99% of the time, you will be correct.

Hehe, you gotta love that sentence !

'Pre-jetted' carbs may get you in the ballpark, but dialing it in after running it will get you inside the diamond!

Being your friends Big block is pretty close to stock, and he is used to a 'universal performance carb', perhaps he will be happy with it as is. Good luck and keep us updated.

I am positive it will be a huge improvement! I will keep you posted!

Actually I built an 800 cfm unit for a pretty serious Buick owner for his 70 GS .60 over, Hemi-killer cam etc that he wanted to appear stock long ago, and he has just recently out it on so I can swing by him and make the final afr tuning.. He was using an 850 Holley DP which the engine was dynoed with ( can t remember the exact numbers, but plenty of HP an alot of TQ ) The Holley was doing good. He put the ball-park Qjet on yesterday and took it for a quick testdrive. He calles to tell me how amazing the throttle response was. It made the car feel like a much better driving car just because og the Qjet. It had a slight stumble when going from cruise to wot, but I found that he had not connected the pull-off yet... :-) The Qjet was doing 10 times better than the Holley even without the pull-off :-) I love

[ejowrench]

As I say all the time to my friends who read Hot Rod: Holley is for racing, Q-Jets are for street! After many years of a Holley carb on my daily driven Chevelle and now a Monte Carlo, a modified Q-jet now resides for good.

[Marx3]

The car in question has been raced, and I intend to do modified rebuilds for more serious streetcars, like sub-14 second cars. I would like too at least :-)

Uhh, a monte Carlo, what year? I've had a '75 and a '76 :-) I love the lines of the 73-77.