Hi all! I have three issues I could use a hand with. 68 455 - c heads - Edelbrock performer intake - stock exhaust manifolds (are 350 and 455 exhaust manifold interchangeable?) 72 Quadra jet set up for 72 350 with Muncie m20 - still running points.

1) Plugs are gapped correctly for points ignition - dwell set at 30 - timing is base at 10 degrees (she likes between 8 and 10 it would seem) with vacuum plugged off and mechanical advance she’s in at like 28 degrees - with vacuum she’s mid 40s - I notice at idle she was chuggin a bit and running a bit “off” I set air / fuel with the vacuum gauge - I noticed when I’m cruising she likes to “surge” for lack of a better term - I just read somewhere here that too much vacuum advance could cause this? So just playing around I capped off vac advance and she smoothed right out - drove it around the block with vac advanced capped and she ran great - any thoughts or input? I like to run her at 70-75 on the highway - do I want to go with adjustable vac advance or?

2) there is a rattling in the front of my engine - I pull the belts and it goes away - I’m pretty sure it’s a) water pump or b) powersteering pump - any tips on how to figure which it is? Advice?

3) exhaust leak - I can feel it spitting on passenger side manifold - I’m going to double check pipes connection and check manifold gasket (new two years ago) but I’m definitely breathing it - is the 350 manifolds for 72 compatible for 455 from 68? Any advice or tips on this?

and lastly (bonus round) I rebuilt my 72 Quadra jet (just a rebuild kit) it was off my 72 350 w/ Muncie m-20 - I put it on my 68 455 (now hooked you the same m-20) I don’t get a lot of performance out of the motor as is - I assume it’s because the carb is set up for a 350 - any advice on this?

thanks as always all! Car is getting better and better each and every day!

 

You can easily make a custom vacuum advance stop to limit how much the rod moves. It’s been discussed here several times.

As for your noise, with the belts off can you spin the fan/pulley/whatever and hear or feel noise?

Your going to have to do some tuning beyond a rebuild kit to properly calibrate the 350 carb to work on a 455. Cliff Ruggles is a good place to discuss your project. Have the carb number, and as much info about the engine as possible.

 

Here's some info that might help the 350 carb work better with the 455 engine.


Year & Application.....Carb #...........Main Jet.........Primary Rod............Secondary Rod
1969
400/455.......................7029251........7031970.. ....7034849- "49B".........7033655- "AU"

1972
350..............................7042250.......... 7031969......7034850- "50B".........7045778- "CG"
455..............................7042251.......... 7031969......7034850- "50B".........7045779- "CH"

 

Geez not really much difference

user CFAIR posted this the other day

Just for reference my slightly warmed over Olds 455’s with the 17058553’s are set up like this. 74 primary jets, 49 primary rods, adjustable part throttle at 4.5 turns out, idle screws at 4.25 turns out ( .093 holes in the primary throttle plates). Float set at 5/16”s. Secondaries are: wrap screw set to 30 minutes past the hour (i.e. |), CK rods, M hanger. SMI (Sean Murphy Induction) has been through both carbs and both are Stage 2 on his site as I recall.

 

Will they bolt up? Yeah. Should you use them? No. Why bother swapping in a more powerful engine if you plan to choke it off with those crappy SBO manifolds. There's a reason why the factory used different manifolds on BBOs. Get the repro W/Z manifolds for a 69-72 BBO. They not only flow better, they are internally divided into individual runners.

 

thanks Joe - that’s what I was asking - I had no idea that they used different manifold between the two - or course I want the correct ones - will look into it

 

I’ll look into the vacuum advance stop deal reading up on the “Lars Grimsrod” link about vacuum advance to try and better understand what I need

I couldn’t hear or feel anything by spinning pulleys - but with belt on it sounds to be more the water pump - any advice on a quality replacement? Should I consider a “hi-flo” type as I will be adding a/c in the future? My car runs pretty cool as is

I’ll read up on Cliff Ruggles - thank you!

 

Thanks - I’ll have to decipher this when I get time - I have to do this systematically - Going to tackle water pump first and inspect timing chain while at it - then vac advance - then exhaust manifolds then I’ll tackle carb - appreciate the input!

 

thanks for the reply - round to tackle the carb lastly - will use this info when I dive in - appreciate it!

 

As far as your noise in the front of engine- Start it up and let idle, when noise starts squirt some water with a windex bottle or squirt gun,etc onto the belts. Noise will most likely quit and then come back as belts dry out. If so try new belts. You'd be surprised how much noise belts can make!

 

it’s a rattle not squeal - pretty sure it’s a bearing or pulley - and leaning towards water pump

 

Milodon and Flo-kool both make excellent aluminum body water pumps which would work perfectly for your eventual a/c upgrade. Just be sure to get the correct neck length pump so your pulleys continue to line up.

 

Keep in mind that the factory specs for carburetor jetting was in the days prior to gasoline with 10 percent ethanol. I would start with a slightly richer jetting to compensate.