Low manifoild vacum reading

[Galaxie352]

Hi guys

Anyone inn here have some experience with manifoild vacum ?
This is not a FE, but i assume the technical would be the same.
I have been helping my father putting his 59 biscayne together. I have som trouble with engine inn this car too get it running okay. This is a stock 283, but it sounds like it have a lot of cam inn it. I am reading 5HG manifoild vacum ported side on the carb. I have also conected straight too the manifoild and still gets the same reading. I was thinking a vacum leak, so i went over with some brake clean around the intake manifoild when the car was running and did not notice any RPM inncrease. I changed the inntake gasket thinking it maybe had a leak bottom of the head. Did not help either. Compression checks out ok. Leak down tests checks out ok. Timing checks out okay. Disconected all vacum lines that can cause leak. I am thinking maybe there is something wrong with the camshaft at this point and are considering taking the engine out again. My Yblock is reading over 15 HG and are running great. Any Tips/Tricks/Experience ore advice on what to do here ? Camshaft next ? Flattet ore wrong timed ? Oh, one more thing. The car drops a lot inn RPM when putting it inn drive. Have tried to inncrease the idle, but it does not help. And, when give it a little trottle inn drive it tends to surge a little before it respond. Sometimes it dies. At one point the car was chasing RPM at idle. This car makes me sad :'(

Best Regards
Robin

[machoneman]

Was the engine recently rebuilt? New crank/cam combo set up wrong (too retarded). Or, your harmonic has slipped the outer ring and it's running retarded. Check the elastomer (between the hub and ring) to see if it's badly cracked or the material is sticking out (i.e timing is way off).  Then, slowly advance the timing while looking at your vacuum gauge. If it picks up vacuum (like a lot) well beyond the normal 6-8 degree initial, the hub has slipped.

[1964Fastback]

+1

And if it is an old engine, maybe the timing chain has slipped.

If you aren't sure about the harmonic balancer, look on here or the internet in general about making or buying a piston stop and finding true TDC and comparing that to the marks.  Cheap and easy.

Also, remember the cylinder numbering, distributor rotation direction and firing order are all different on the Chevy from the FE.  I know it's simple but if you are used to working on your FE all the time...

Pat

[Mr Woodys Garage]

Seal Up All The Breathers, And Then Put The Palm Of Your hand Over The Oil fill Tube. my Bet Is You Will Feel A Vacuum. Those Years Of Chevys Had A Problem With Intake Seal Towards The Rear Of The Intake Surface, And Will Not Seal/Sit Down Properly Due To The Breather Cannister At The Rear Of The Intake Valley. Pull The Intake If Test #1 Indicates A Vacuum. If You Look On The Bottom Of The Intake, Or Top Of That Cannister, You Will Find The Culpret. Intake Tightens Down, But Cannot Seal.

[Galaxie352]

Mr Woody. That one was interesting. I have not tought about that. This engine have the rear breather ore the draft tube that goes down on passenger side of the engine,and also the canister innside the valley. Have tried to advance the timing, the vacum stays the same. I will do the test that mr woodys says. And move on to the camshaft. 1 TDC do line upp with the harmonic balancer.

Thanks everyone =)
Best regards
Robin

[Mr Woodys Garage]

You Will Have To Seal That Tube To Do The Test...Tape, Or A Plastic Bag With A Hose Clamp Or Rubber Band Should Do The Trick.

[Gaugster]

As part of the vacuum hose checks where you able to disconnect or isolate any automatic transmission or power brake (if equipped) lines? Sometimes they are hard-line vs rubber.

The breather check is great tip!