273-4 vacuum leak

[plycuda]

Hello to all. I'm writing to ask advice about a (likely) vacuum leak. I have a '67 Barracuda Convertible with a recently-rebuilt 273-4 Hi-Po (not by me; a local machine shop), .030 over; Hughes did the heads (ported and "larger" SS valves). Compression is estimated at 9.2. Cam was size recommended by Hughes staff (can't think of specs at the moment; it's a 'mild lope 340' from Comp Cams). Exhaust is from '69 340 Engine. Carter 4-barrel is the original PN (new from Edelbrock in '02); rebuilt a few weeks ago. We've replaced both gaskets (one over/under the 1" aluminum spacer), checked to hoses (advance, gauge and PVC hose). Engine is not fully broken in yet (two 20-minute runs); this is just the "assembly" stage! We've now started setting it for street break-in runs. Engine RPM is extremely slow to return to set idle unless I hand-cover the carb (which then immediately returns to set idle). Any advice? Thanks.

 

[MVRCorp]

The best way I've found to check for an intake leak is to spray the mating areas of the heads and carb with WD-40 or similar sprays and listen for RPM change on idle.

 

[redfastback]

what is the timing at? anything left unplugged at the carb?

 

[plycuda]

Hello,
Thanks for the replies. We found the problem; intake manifold bolts were not torqued. Redid them and no leak! The suggestion to retorque the intake AFTER the two 20-minute initial break-in runs was part of the written instructions from the machine shop (I didn't READ everything first)!
BTW: today we complete the reassembly. Engine running, PS unit in place, console installed, carpets and seats back in place. Ready for some on-the-road break-in travels.
Thanks again