Can someone tell me what the intake vacuum pressure should be for a 1969 W30 engine? I am getting around 6"-8" pressure which seems really low to me. I know normal engine should be around 20". From what I understand, due to the big cam, the W30 should read lower than this. I know the low vacuum is why they didn't have power brakes, but this just seems too low. What should I expect to see for a W30 engine?

 

if you can get to 15 your doing great

if its the over 300 duration camshaft i doubt you can get that

 

I have the 328 duration cam. Is 6"-8" vacuum normal for this cam? I am having issues with hard starting and rough cold idle which is why I am asking about the vacuum pressure thinking I may have a vacuum leak somewhere. I quickly checked for any leaks but didn't find any. I just want to verify if what I am getting for vacuum is correct or not before looking for the problem elsewhere.

 

Have you checked timing, could be cause of hard starting..?

 

hopefully someone with that cam will answer, that cam is tough on the idle...as mentioned i would check timing,idle speed for the hard start its possible the cam could be worn or valve train worn or low compression, but i know a low vacuum with that cam is normal how does it run when warmed up

 

Timing has been checked (14 deg BTC) as per service manual. Idle speed checked (850rpm), compression checked (165-175), engine has very little miles after a complete rebuild many years ago so I dont think worn components is an issue. It seems to run pretty good when warmed up but does smell like it's running very rich. I tried adjusting the idle screws but they don't seem to have any effect. It could be that I have a carb issue, though it was just recently rebuilt, it was sitting with gas in it for quite a while. I just wanted to make sure my vacuum was good before digging in to the carb.

 

850 rpm...that enginge is hardly running sure that is right?

 

[QUOTE=Billb442;592832]I tried adjusting the idle screws but they don't seem to have any effect. QUOTE]

There's your problem right there. Either bad carb, vacuum leak or improper timing. Verify TDC and go from there.

 

I might push the idle up to around 1100 and see how the vacuum is and recheck you idle mixture, with a lopey idle finding the right mixture can be difficult

 

According to the assembly manual the warm idle speed in neutral should be 900rpm. So I adjusted up to 900rpm. It didn't really help any. Double checked timing. Looked fine.

joesW31- Thank you for the info. Do you have any link to the info that the idle screws do not have an effect on W30 engines? I had not heard that before.

 

sounds EXACTLY like my high compression 403 from about 2 yrs ago.

I had overheating and poor performance too.

You may need to deviate from the factory timing settings to attain joy.

Here's what worked for me
HEI [pre-computer] on ~10:1 403 using #6 heads
Comp cams 290H ?? {seek a thread on that for details}

Poor or no idle
absurdly rich gas stinky exhaust
*No* effect from idle mix screws despite internal mods per the book.
[Idle air bypass opened]
Stalling out below 1000 rpm, vacuum dropped off to 4-5 and then die.
overheat at idle
top speed about 60 mph
sluggish acceleration
severe overheating after 2 mile test run.

Adjusted timing higher, far past factory specs for similar motors.
Much happier engine!!

Vacuum is back, idle can be set down
Pings under load => modify distributor curve to limit the vacuum advance as required
put in weights/ cam [dist'r] with less total mech. adv.
set TOTAL timing to about 36 at 3000 rpm, let the staticn fall where it may.
Now hard to start due to advanced timing.
Retard timing to start, back where we were before.
SOLUTION: hook vacuum advance to MANIFOLD, which brings back lots of timing for IDLE and vacuum at idle, yet leaves static timing late before engine starts, for easy starting.

VOILA'

easy start
ZERO overheating EVER, with a ballsy 403 using the stock 307 radiator. 210 F and stable says the gage. Superb throttle response. Lots of torque. No [detectable] detonation- though I am rather hard of hearing now.

Go ahead, try these things.

13000

 

I did the same thing on my 455 with the 328 cam. The problem with the ported vacuum on the carb is that it pulls great vacuum with the throttle plates closed (advance plate moves) but when you get into the gas and the ported vacuum drops to 8 or 9 then the timing retards. Not the best thing for an engine you want to accelerate. I don't have the vacuum solenoid on this engine yet, I understand that it is supposed to only allow vacuum to the distributor in 2nd and 3rd gears. Maybe that will help as it idles high after its warmed up.

 

Thanks for the tips. The car just went to the shop to get some body work and get painted (finally!) so I will have to wait until I get it back to try the suggestions out.