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Old 07-18-2013, 06:02 PM
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Olds 403 having some trouble need advice

Well i finally got everything else on the car put together and took it for its first test spin today, had some issues though.

First, i can't get one of my carburetor bolts to draw down, the threads in the manifold are stripped. Will having only 3 bolts Torqued to proper spec cause a vacuum leak? It's a Qjet carb and i use the THICK gasket.

Second, while the car is in gear and in drive/reverse it trys to stall sometimes. At idle my RPM 1100-1000, In gear RPM drops to 700. When it wants to die it drops down to 600-500. Could my Torque converters stall be too low for this cam profile? When i had the transmission rebuilt i was told the new Torque converter was standard stall and i don't know what that is. It's a Th350 from a 79 Trans am.



Engine specs

.040 Over
Stock spec pistons
Fel pro gasket, compressed thickness somewhere between 0.037 - 0.040, not 100% sure there

350 Rocket heads from 69, had them CC'ed, 66CC
Stock valve sizes, 1.94 int/ 1.63 exh i believe?
They have been ported, had my machine shop check them out and they told me i really lucked out here.

Cam
Comp cams thumpr, dick miller recommended me this cam profile
42-600-5 - Hydraulic Flat Tappet Camshafts

Lift : 491 / 476
Duration: 278 / 296
Range 2000-5800

Intake
Edelbrock 3711 performer low rise
Range idle - 5500
Dual plane

Ignition
Stock dizzy recurved, DUI DYNA MOD ignition module/ coil.
Moroso adjustable vacc advance
Moroso Pickup

Carb
Factory 800 CFM 403 Q-jet, built to this motors exact specifications by Ken @ Everyday Performance

Exhaust
Hedman headers
Primary Tube Diameter (in):1 3/4 in.
Collector Diameter:3.000 in.
2.5" full dual exhaust the whole way back.

Beyond that, the car is an 88 Monte carlo SS, TH350 B&M rebuilt, 3.42 gearing in the stock 7.5 rear.

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Old 07-18-2013, 10:35 PM
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fix the threads in the intake manifold
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Old 07-19-2013, 12:12 PM
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Quote:
Originally Posted by vinniekq2 View Post
fix the threads in the intake manifold
THIS! Yes, it will cause a vacuum leak. Get a helicoil kit for that thread size. It's very easy to install.
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Old 07-19-2013, 01:53 PM
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It could be that the re curve in the distributor is letting it advance early and when put in gear it reduces rpm and its retarding the timeing and the engine trys to stall! Try setting the initial timing in gear and have someone hold the brake with it in reverse! Set the carb idle and adjust bleeds screws in gear also! After fixing the carb stud!!!!! Adjust carb bleeds with a vacume gauge or RPM gauge if necessary!Your cam and convertor aren't causing the stall in my opinion unless the lifters are adjusted wrong!!!! That Thumper you have is very street friendly and your issues are in the engine tuning!

Jester

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Old 07-19-2013, 05:48 PM
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Thanks for the tips. I adjusted the rockers again after break in just to be sure. Would it be the same to just dial back idle speed until it sits at what it does in gear then make adjustments? I'm j/w because i don't have any help
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Old 07-19-2013, 06:30 PM
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never torqued carb nuts /bolts down ever. wrench tight if it needed more 1/4 1/2 turn the most!! over thinking leads to a striped thread.
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