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Discussion Starter #1
hey, im getting a vacuum reading of 14 at idle, is this low?as rpm increases the reading goes up .... 351c 2v with edelbrock intake and comp cam 256H camshaft... car starts up and runs real smooth ... there is a slight engine vibration.

Also im losing engine oil... no visible leaks/smoking, could it be the intake is leaking internally?


but the car runs/drives real good.
 

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too many variables to tell if its good or bad

my bone stock 351C 2V with 110K on the clock. my timing at 9 BTDC
vacuum is 20 in park and 17 in drive

when RPM increased the vacuum should go down

my vac gauge is connect to the ported carb port not direct manifold and I have that vacuum tree thingy on the water pump disconnected.
 

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Discussion Starter #3
my timing is at 12 Initial
32 Total



too many variables to tell if its good or bad

my bone stock 351C 2V with 110K on the clock. my timing at 9 BTDC
vacuum is 20 in park and 17 in drive

when RPM increased the vacuum should go down

my vac gauge is connect to the ported carb port not direct manifold and I have that vacuum tree thingy on the water pump disconnected.
 

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that seems way low
should be 6 initial for factory
. my engine likes a little more.

and 38 total

you need to get your dizzy checked out and calibrated,
 

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256H is a very small cam for a 351C - 206/206 @ .050" , .468/.468 lift - vacuum reading should be higher at 12* static timing.

I see no reason it shouldn't be able to manage up around 18" of vacuum, but that also depends on static timing and how you have the carb tuned. If you have tweaked and tuned it and the BEST it can manage is 14", you definitely have something going on, whether it's worn rings, bad valves seats etc.

As far as the oil loss, it could be pulling it from under the intake. If you have a friend follow you, let off the gas at 30-40mph and downshift to second. If it puffs a bunch of gray smoke out the tailpipes, then you have either an intake leak, or your rings are giving up the ghost.


too many variables to tell if its good or bad

my bone stock 351C 2V with 110K on the clock. my timing at 9 BTDC
vacuum is 20 in park and 17 in drive

when RPM increased the vacuum should go down

my vac gauge is connect to the ported carb port not direct manifold and I have that vacuum tree thingy on the water pump disconnected.
Vacuum gauge should always go on manifold vacuum, ported vacuum is 0 at idle.


that seems way low
should be 6 initial for factory
. my engine likes a little more.

and 38 total

you need to get your dizzy checked out and calibrated,
Agree his total timing is low, but let's focus on the oil consumption/low vacuum issue, as distributor calibration/total timing has nothing to do with idle vacuum readings.
 

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yeah i meant the dizzy can not the gauge. post fixed.
 

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Discussion Starter #7
I will have a friend follow me and try that mate , just a question how come the car runs brilliantly..pulls hard ... starts right up .... no issues except the oil consumption?
256H is a very small cam for a 351C - 206/206 @ .050" , .468/.468 lift - vacuum reading should be higher at 12* static timing.

I see no reason it shouldn't be able to manage up around 18" of vacuum, but that also depends on static timing and how you have the carb tuned. If you have tweaked and tuned it and the BEST it can manage is 14", you definitely have something going on, whether it's worn rings, bad valves seats etc.

As far as the oil loss, it could be pulling it from under the intake. If you have a friend follow you, let off the gas at 30-40mph and downshift to second. If it puffs a bunch of gray smoke out the tailpipes, then you have either an intake leak, or your rings are giving up the ghost.


too many variables to tell if its good or bad

my bone stock 351C 2V with 110K on the clock. my timing at 9 BTDC
vacuum is 20 in park and 17 in drive

when RPM increased the vacuum should go down

my vac gauge is connect to the ported carb port not direct manifold and I have that vacuum tree thingy on the water pump disconnected.
Vacuum gauge should always go on manifold vacuum, ported vacuum is 0 at idle.


that seems way low
should be 6 initial for factory
. my engine likes a little more.

and 38 total

you need to get your dizzy checked out and calibrated,
Agree his total timing is low, but let's focus on the oil consumption/low vacuum issue, as distributor calibration/total timing has nothing to do with idle vacuum readings.
 

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5,056 Posts
too many variables to tell if its good or bad

my bone stock 351C 2V with 110K on the clock. my timing at 9 BTDC
vacuum is 20 in park and 17 in drive

when RPM increased the vacuum should go down

my dizzy vac can is connect to the ported carb port not direct manifold and I have that vacuum tree thingy on the water pump disconnected.
revised
 

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I will have a friend follow me and try that mate , just a question how come the car runs brilliantly..pulls hard ... starts right up .... no issues except the oil consumption?

How an engine runs is not always an indicator of overall engine health. I had a C-30 Chevy dually that ate a quart of oil every 500 miles - still started right up, ran strong and pulled well, but it was tired and ready for a rebuild. Engines that are cared for can just wear out gradually and you may not notice the difference until you actually have a metric to judge against - quarter mile times, dyno runs etc. Not saying your engine is definitely ready for a rebuild, but have you ever done a compression and leakdown test?
 

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Discussion Starter #10
I had a garage here do a compression test and it was fine ...
The oil consumption only started after the cam change ... any pointers??
I will have a friend follow me and try that mate , just a question how come the car runs brilliantly..pulls hard ... starts right up .... no issues except the oil consumption?

How an engine runs is not always an indicator of overall engine health. I had a C-30 Chevy dually that ate a quart of oil every 500 miles - still started right up, ran strong and pulled well, but it was tired and ready for a rebuild. Engines that are cared for can just wear out gradually and you may not notice the difference until you actually have a metric to judge against - quarter mile times, dyno runs etc. Not saying your engine is definitely ready for a rebuild, but have you ever done a compression and leakdown test?
 
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