More on the '60 FI problems

[George W.]

Trying to determine why steady vacuum at idle is 12 when most suggest it should be between 15-19.
1) removed valve covers and re-checked lash--all good at 12 intake, 18 exhaust.
2) The heads are from a '62 (3795896), but have the same cc(59.669) and valve size(1.72/1.50) as the 1960 3774692. Wondering if the rocker arm ratio is different on these heads, and if so, maybe someone can identify these rockers (they have an "O")--see photo below. Don't know if a different ratio would have any effect on vacuum, but???




3) Re-checked compression--140 in all cylinders
4) Re-checked timing and dwell
5) Did find something with distributor. When I pulled the rotor, I saw that the advance weights were "under" the breaker cam. Upon investigation I found that the shaft and weight base could be push/pulled about 3/8" (did not measure--but it is a significant amount of play). When pulled up, the advance weights react to the breaker cam, but still a bit sloopy/loose in my opinion.
When pushed down, (as I found when pulling the rotor) the advance weights go right under the cam. Now I know this is not correct, but I do not know if this is related to either the vacuum and/or the performance of this FI unit?



Below is a movie (not a great one) that shows the relationship of the advance weights to the breaker cam while in both positions.



Thoughts?

Thanks,
George
210 748 4693
geopar@gvtc.com

[Joe M.]

Re: More on the '60 FI problems

The O rockers are the sought after hi perf GM stock rockers.

[Timothy B.]

Re: More on the '60 FI problems

George,

You should pull the distributor and properly shim the lower gear so the weights ride against the autocam. If the car has a solid cam 12" sounds correct for idle vacuum.

[George W.]

Re: More on the '60 FI problems

George,

You should pull the distributor and properly shim the lower gear so the weights ride against the autocam. If the car has a solid cam 12" sounds correct for idle vacuum.

Everything I have read and been told is that the vacuum needs to be higher?

The play is not in the shaft, but in the cam assembly.

Am about to see hat I can do with this "play".

Am going to re-adjust the valve lash to 20 intake/25 exhaust and see if vacuum improves. (maybe the cam grind is wrong?) Purchased cam from SpeedPro and all specification match on paper, but???

[Timothy B.]

Re: More on the '60 FI problems

George,

I am pretty sure if you search the archives with that speed pro camshaft # the adjustment spec will show up. The more you loosen the lash the more vacuum the engine will have buy the less performance because of excess lash.

Who told you the idle vacuum should be higher.

The distributor shaft is moving up/down inside the weight base cam causing the problem you have. Shim the lower gear to tighten the up/down movement.

[John D.]

Re: More on the '60 FI problems

My 63 FI car has a Speed Pro CS113R cam.(097) At 900 RPM it puts out 16" of vacuum.
Now if it was the Speed Pro CS118R(30-30) cam it might put out 11-12' at vacuum.

Most people that call me say there 097 cam puts out at least 15" of vacuum at idle.
Nothing wrong with 12" George except for the fact that a stock 61 unit needs to massaged at tad to compensate for the lower vacuum.
Needs the weaker 30-30 enrichment diaphragm spring. Or play spring engineer and cut off 1/2 a coil from your 097 spring.
Those are some pretty heavy duty distributor weight springs for your engine set up. Typicall 914 springs have about 6-7 coils. Your springs look correct.
Are you weights #37? That's what they should be for an 097. I don't see the numbers stamped on yours?
Send your distributor to Don Baker and have him rebuild it & of course test it for you.

What Speed Pro cam did you buy? DId you save the box? JD

Lower gear shim should be .002 to .007. Don Baker sets them at .002. Your distributor needs some TLC.

[William C.]

Re: More on the '60 FI problems

Shim shaft, have the dist. curved to proper specs, check cam lift to determine if an '097 cam or '30-30 cam. vastly different lash specs, lift, and performance curve. The "O" rockers were generally used with the 30-30 cam, not the '097, so who knows what the overall combination really is? The 30-30 is a great cam for a 327, not nearly as good on a 283...

[George W.]

Re: More on the '60 FI problems

Speed Pro CS-113R
specs read .395 intake lift
.401 exhaust lift
.270 duration both intake/exexhaust dist shaft end play shimed to .004
the excessive play is in the advance unit----I'm pulling it apart to see what's up.

How would I go about measuring this camshaft lift/duration?

Should I change out the rocker arms?

G

[William C.]

Re: More on the '60 FI problems

Rockers are NOT the problem, but I can't say the same for the cam. Specs on your cam for a 283 are .2625, which with the 1.5 rocker arm ratio would give a lift of .399, less the clearance ramps, total lift at the valve will be .012-.018 less depending on lash, and the cam has identical inlet and exhaust lobes. Duration specs are meaningless unless they are stated including the clearance ramp that was allowed before the measurement started, and so varies with the cam manufacturer, (Chevrolet includes the clearance ramps as I recall) the mismatched inlet and exhaust lobes leave us with little to go on other than to say the system is likely mismatched, and will need some effort to make the cam and FI fall in love with each other. "tricks are for kids" as we used to say in the old racing days. When you have all the cam info fully known, it might be possible to adjust the engine to run, but the cam is not well matched to the engine as described.

[Timothy B.]

Re: More on the '60 FI problems

My thoughts about the 097 camshaft is that the idle vacuum is approx 12". Idle vacuum depends on idle speed so what RPM is called out in the book for the idle RPM.

[George W.]

Re: More on the '60 FI problems

Rockers are NOT the problem, but I can't say the same for the cam. Specs on your cam for a 283 are .2625, which with the 1.5 rocker arm ratio would give a lift of .399, less the clearance ramps, total lift at the valve will be .012-.018 less depending on lash, and the cam has identical inlet and exhaust lobes. Duration specs are meaningless unless they are stated including the clearance ramp that was allowed before the measurement started, and so varies with the cam manufacturer, (Chevrolet includes the clearance ramps as I recall) the mismatched inlet and exhaust lobes leave us with little to go on other than to say the system is likely mismatched, and will need some effort to make the cam and FI fall in love with each other. "tricks are for kids" as we used to say in the old racing days. When you have all the cam info fully known, it might be possible to adjust the engine to run, but the cam is not well matched to the engine as described.

Hi Bill,
Below are photos of the cam specs.

[William C.]

Re: More on the '60 FI problems

Idle speed is spec'd at hot engine as 800 for a 290hp (1966 Motors manual reference)

[George W.]

Re: More on the '60 FI problems

I have a couple of 914 distributors and there seems to be something missing under the cam lobe piece of the unit installed.
Below are photos of this area.
The first photo shows what appears to be a bushing or something ??? that the cam lobe rests on.

The second photo (of the unit installed) does not have this.

Hope the photos will show what I'm trying to describe.

After I get the unit in question out and dis-assembled, I should be able to post better photos.

Oops, I reversed the order of the photos:
The first photo is of the unit in question. Notice the area with red (something), this is the area in question. The cam lobes go right on past this area.
In the second photo I think you can see the "stop" piece.






Let me again extend thank yous to all who are trying to help with this.
Although the process has been lengthy and at time very frustrating, I am for the most part enjoying the learning experience.
G

[William C.]

Re: More on the '60 FI problems

What idle speed is the engine comfortable at and how accurately are the clearance set? feeler gauge, Hot or cold, Initial timing setting (distributor?)

[George W.]

Re: More on the '60 FI problems

My 63 FI car has a Speed Pro CS113R cam.(097) At 900 RPM it puts out 16" of vacuum.
Now if it was the Speed Pro CS118R(30-30) cam it might put out 11-12' at vacuum.

Most people that call me say there 097 cam puts out at least 15" of vacuum at idle.
Nothing wrong with 12" George except for the fact that a stock 61 unit needs to massaged at tad to compensate for the lower vacuum.
Needs the weaker 30-30 enrichment diaphragm spring. Or play spring engineer and cut off 1/2 a coil from your 097 spring.
Those are some pretty heavy duty distributor weight springs for your engine set up. Typicall 914 springs have about 6-7 coils. Your springs look correct.
Are you weights #37? That's what they should be for an 097. I don't see the numbers stamped on yours?
Send your distributor to Don Baker and have him rebuild it & of course test it for you.

What Speed Pro cam did you buy? DId you save the box? JD

Lower gear shim should be .002 to .007. Don Baker sets them at .002. Your distributor needs some TLC.

John, just for clarification, this is a 1960 unit (1707320).

Yes, I saved the SpeedPro cam box and have published photos of the specs (it is supposed to be the CS-113R Dontov 097 camshaft.)

I'll look at the weights and see if there is ant identifying characters.

I don't want to "cut" anything yet---but could be convinced once I know what I'm dealing with. What is a 097 spring?

The distributor was rebuild by a trusted source, but I do not know what calibration or tests were performed.