Rebuilt 263 w/ 70psi compression and 10In.Hg vacuum. What to do/test next?

[joe28704]

In an attempt to keep my rough 52' super wagon from being hot rodded in the future (by myself or others) I undertook to rebuild the engine and Dynaflow.
When running engine I could not get it to idle below 700rpm to set timing at 350rpm I did a compression test and vacuum reading. W/ throttle plates open, compression measured 70psi avg. w/ 5psi fluctuation (measured with two different gauges to confirm)Book minimum is 120psi! . Compression came up across the board by 25psi when 12V was put to starter. Vacuum was measured at port at base of carb leading to distributor and at manifold port leading to fuel pump, average was around 10in.Hg w/ approx. 4in fluctuation (also measured with a different gauge to confirm).
Block was bored out .060" over w/ EGGE supplied pistons and cast rings. Reground crank and camshaft, new Hyd lifters. All assembled by myself. I did not measure bore before carefully installing rings per EGGE instructions. Washed/brushed bores with soap and well rinsed. Rotella T 10-40 w/ Rislone ZDDP additive added.
Head valves were reseated only, machine shop said OK not to rework/replace valve stem guides. Shop has good reputation.
First 25 Minutes run time in park kept rpms up to 2000 and fluctuating then 15 minutes "run" time around neighborhood at around 10mph. Around one hour total run time to date.
A leak down test at TDC with a Harbor Freight tool was inconclusive and worthless however listening carefully yielded no sound thru carb, exhaust or open radiator cap but audible air escape from dipstick hole with a length of fuel hose to ear. Double checked head bolt torque.
There is probably more info to provide but please ask if I left something important(its obvious I did!!)
I have two burning questions:
1) Can the low compression readings be solely responsible for the low vacuum readings? (Do I have one problem or two?!)
2) What is the probability that the cast rings will "Seat" and restore compression if I drive it for "real" for some more hours?(Do I invest in title, tax, registration, insurance now or after I pull the engine for redo this winter.)
Like I told my mother, if all this was easy everybody would be driving straight eights with Dynaflows.
Thank you to any one who may provide me with some sound guidance on the next steps to take to get this old gal back on the dance floor.
Sincerely,
Joe Savastano

[322bnh]

Valves adjusted too tight? Timing chain installation?

[joe28704]

Thanks for asking. Forgot to add :
Timing chain was checked (for Hyd lifters) using dial indicator on valve spring cap as outlined on 1952 Buick service manual. Timing was correct per that procedure.
Hydraulic lifters (pretty sure not USA made, Ebay, no labels) were given two complete turns after no lash clearance when lifters were on camshaft base circle, per service manual.
Do you know of any other method to check if Hyd lifters could be culprit / contribute to low compression/vacuum?
Thank you.

[suntreemcanic]

Have you verified your lack of compression with a other compression gauge? Your low vacuum could be a separate problem.

[joe28704]

Yes I was lucky enough to find a second compression gauge and vacuum gauge to double check readings.
I could have a separate vacuum problem, but I carefully inspected intake manifold casting for cracks before installation. And got good visual of the four gaskets intake makes to head, all look real good, no audible air leakage, sprayed with starting fluid for rpm change none detected but at 850rpm hard to detect.
I'm willing to take carb and intake/exhaust off for second look but I'm looking for a real good reason to do so.
My big question is can such low compression readings ALONE lead to low vacuum readings, I just don't know enough (anything!) about engine flow dynamics to work that question out.
I took the car out for another run yesterday (again could not get engine to idle without dyeing below 850rpm, vacuum reading 11in.Hg) Ran it for maybe 35 min thru the neighborhood before I passed a cop; no headlights, no hood, no bumpers, no exhaust system, 10yrs dust on car, anyway hightailed it back home and took new compression readings and got on average a 7psi average increase over hot previous weeks readings. Are rings beginning to seat? Maybe its time to get the car all legal and put some real mileage on the car (how many miles do you think) to hopefully get rings to seat if they do at all.
P.S. don't see it burning any oil out exhaust, plugs not fouled/black.
Is it possible car will have to run several hundred miles for rings to seat and compression return to specs? (I got no experience on that issue).

[suntreemcanic]

Joe, I just rebuilt my 263 straight eight last year and when I started it first time it had good compression right away. You mentioned you have pressure in the crankcase. How much? Did you check the ring gap? Did you bore it and install standard rings? Have you tried a cylinder leak down test? Were the new pistons shaped like the old ones? Did they have a large dome on top? If everything I mentioned is correct, then a cylinder leak down test will tell you where your compression is going. It will either come out the carburetor, the exhaust manifold or the crankcase. You can check your valve lifters and adjustment procedure, back off all adjustments and do your cylinder leak down test to check for valves seating correctly. When you have a problem like this, you have to question everything. Good hunting! By the way, that 263 I rebuilt went back in my 52 Super station wagon.

[322bnh]

Thanks for the update. As a test set the valve lash at 0.015"; if compression improves, try 1/2- 1 turn lifter preload. Modern rings need no special procedure to seat, but who knows how "modern" the available rings are for that engine. So seat them the old way: from 15 mph do a full throttle acceleration to 50 mph; let it coast down to 15 mph...repeat 10 times.
The high idle is probably a vacuum leak, could be internal to the carb even. Exhaust leaks will give you noise and witness marks...vacuum leaks are a "beach". Google "find engine vacuum leak".

[joe28704]

Thank you very much Suntreemcanic and 322bhn or your assistance!
Latest update:
Put 100 miles on car to "seat rings" and measure if any improvement in compression, measured no improvement in gauge readings after trip so I believe "rings not seated" can be ruled out. Subsequent re-test of three cylinders squirting 10-40 oil in them yielded NO improvement in compression. (?)
However 322bnh, following your suggestion of setting lash at .015" brought compression up to 125si on two test cylinders!!!(recall Buick book calls for two complete ball stud turns for lifter preload, that is what I originally set.
I found this in the internet:

"Conversely, too great a preload (more than .060") will produce excessive lifter pump-up, causing the valves to open longer and lift higher, drastically reducing cylinder pressure and hurting engine performance. The engine will also have very low vacuum, causing it to idle very poorly." (THIS DESCRIBES MY ISSUE !)


I then reset all lifter preloads to 1/2 turn, got same old low pressure readings and no improvement in vacuum.
I then reset all lifter preloads to 1/8 turn to get as close to zero lash as practical , got no improvement again.(Need to collect All cylinder pressures yet)
That is where I'm at now, got a glimmer of hope with 322bhn's insight, but normal pressure and vacuum readings are still elusive.
I plan to contact vendor of lifters to see if they have any "specs" but I doubt it since they are surely made in China.
My next activity is possibly to experiment with a hot lash setting with the engine running. Any thoughts on that?
I still am holding on the idea that low vacuum is being caused by the source of the low compression and will focus on bringing compression up to the 125Psi
I observed with a .015" lash on a hydraulic lifter. Do you see any danger in firing up engine with lifters set at say .015" lash (demonstrated to provide 125pi comp.)? I wish to test this to see if return of compression (Albeit not kosher for long term) restores vacuum so that would confirm there is no separate vacuum leak.
P.S., Suntreemechanic I have a ton of issues to inquire about our Wagons once I sort and correct this engine issue, your engine rebuild is motivational!

[Jenz38]

In fact I drive my 263 with solids, but I would give the hydraulics zero lash at running engine,check it by your ears, (then you're can be sure that the Valves are completely closed) .
I do it on sbc's also, and they should have min. one turn,( or one and half? ) tight after zero ,too ....

And for your measurements, don't drive you crazy with that..
If i have a rebuild engine in my hand ,they mostly runs rough like they have a wrong timing ...
I would suggest drive the engine for 1000 miles and I think,the problems with the too high idle, it will be fixed from alone...😉


M2C

[joe28704]

Thank you Jenz38
Your advice to " give the hydraulics zero lash at running engine , check it by your ears" to confirm would be:
Start with warm running engine then back off (currently 1/8 turn) pre-load until I hear "clicking" then tighten (give "pre-load") slowly until "clicking" just goes away?(zero lash). You then say "tighten after zero" to mean that's It, tighten lock nut at point "clicking" goes away?

If I start with say .010" lash (some clicking) and start to give it more pre-load (past zero lash) to the point of valves not seating well (two turns as I had w/ original setup), do you have any thoughts on what I should be hearing/seeing through that transition ? I will be monitoring vacuum gauge.

Thanks for your advice, I want to get the best compression I can get to see to what effect that has on poor vacuum, maybe I get a "twofer" (two for one ) when and if compression returns.

Weather will improve next couple of days , should give feedback soon. Thank you.