7040273 Carb poor idle

[ArlingtonJudge]

Hello All
New to the forum and looking for some guidance.  I have a numbers matching 1970 Pontiac GTO Judge.  The engine is a stock Ram Air 3 bored 60 over with a stock replacement RA3 cam, 225/237 duration at .050 with .407/.407 lift.  CR is around 9:1.  The engine had been rebuilt by someone other than me and I have no details on the build.  The engine had sat for a long time with out being fired so I went through it, checked the bearings, new gaskets etc.  Could not find any information on the cam that was installed so I installed a known RA3 cam.

 I rebuilt the carb with no modifications and have not been able to get the engine to idle very well.  Idle screws have no affect, and there was no throttle response.  When I did manage to get it running (at fast idle) it ran very rich.  So started dissecting the carb to measure everything.

Idle tube restriction   .033
Idle down channel     .052-.055 
Primary rods             #39
Primary Jets              #70
Secondary Rods         BV
Secondary Hanger      O

From Cliffs book I'm thinking that the Idle tube restriction should be .038 and the down channel opened up to .059??  Any help is appreciated  THanks

Leon S

[novadude]

What size are the idle and main air bleeds?  Also... I'm not a Pontiac guy, but that looks like a lot more duration than a stock RAIII cam? 

[ArlingtonJudge]

the idle air bleeds are .046 and the main bleeds are .069 with a port coming from an adjustable screw

The cam is a H-O racing specialties HC-56.  the specs noted are off the cam card. 

[Kenth]

Stock cam for 1970 RAIII engines is the 068 (9779068).
Maybe this cam was in your engine?

Your new H-O racing specialties HC-56 cam is more like the 744 (9785744).

[ArlingtonJudge]

This is the cam I removed and replaced with the HC-56

[Cliff Ruggles]

Why is the compression ratio 9 to 1?  It should be much higher if it's a "stock" Ram Air build....

[Kenth]

This is the cam I removed and replaced with the HC-56

Looks like a Crane H-294.
Brand   Model   AID   AED   ID050  ED050   IL1.5     EL1.5   LSA
Crane   H-294   294   304   238     248           .500   .530           114

[ArlingtonJudge]

Guess i should not have used the word "stock".  Unfortunately I don't know much about the build other than hardened seats and bored 60 over. 

[ArlingtonJudge]

Thanks Kenth - good information to know,  I searched every place I could think of and could not find any information on that cam