I was wondering if one of you guys could shed some light on my situation. I have a 64 L76 365hp 30/30 cam solid lifters 2818 carb. pertronix ignition with number matching distributor now for my question, using a dial back timing light I have about 36 degree timing at idle (800 to 850 rpm) with the vac can disconnected and carb plugged off. Now heres my question I have a B28 can on my dizzy and taking a vac reading from the nipple on the right side of the metering block I am only getting about 3.25 of vacuum, but when I take that nipple out and cap it off then connect the vac gauge to the nipple on the base of the carb im getting about 15 at idle and the car seems to run smoother at lower rpms (less jerky) so should I leave it on the bottom with full mainifold vac? and is the B28 can ok or should I go to a B26? also is the 36 degrees ok as far as timing? Thanks in advance.
Jim

 

Yes, you want MANIFOLD VACUUM. Right John?
If I remember right, but wait till someone also confirms, (my batting average has been low lately) the B-28 should be ok with the vacuum reading you're getting BUT you want 36°, and all in, at around 2800-3000 rpm with vac can disconnected and manifold base port plugged.

Gary

 

Vac advance should be connected to manifold, not ported, vacuum.
15 in-hg is too high for a 327 with a 30-30 cam. Either your gauge is not accurate, the cam is lashed outrageously wide, or you don't have a 30-30 cam. A properly lashed 30-30 cam (.025/.025) should develop no more than 8-9 in-hg @ 850 in a 327.
Never seen a 2818 with a vacuum nipple in the base.
Base timing (with the advance weights tied and vac advance disconnected and plugged) should be 10-12 * BTDC for an L76
Vacuum advance adds 16.5 * to base timing, so with vac advance connected and weights tied, spark timing should read 26 -29 * BTDC at 850.

 

"using a dial back timing light I have about 36 degree timing at idle (800 to 850 rpm) with the vac can disconnected and carb plugged off."
Are your timing readings correct?
That is a lot of timing at idle and that would make the 'all in' timing way too high.
You should have 36* total timing around 3000 RPM with the vac adv disconnected.
Initial timing should be somewhere between 12-16* depending how the curve is set up.
If you do have 15" HG at idle then the B-28 might be too aggressive. I would use a B-20 one which is all in at 11-13" HG, this will help with possible detonation.
As previously stated, the vac adv should be connected to manifold vacuum and allow no more than 16* advance.
Joe

 

Someone has been into your carb with the wrong parts - no 2818 ever had a vacuum port in the baseplate - those came in later years.

 

The 30/30 cam was put in last year, as far as my gauge Im going to check the vac using a different gauge this weekend. I did set the valves @ 30 cold last time I adjusted them a couple months ago if that makes a difference. I used the EOIC method I read on the forum here. As far as the 2818, it is a 2818 stamped but the base is not correct since it does have that vac nipple but that seems to give me the full manifold vac in comparison to the side of the metering block which I plugged off. Also im going to use some rubber bands and lock the weights and see whats going on with the timing. I just need to get this thing fine tuned and feel that im pretty close. Thanks for the response.

 

Hey John,
Thanks for the photo you always come through, My base plate has one long oval hole and two other holes so it is incorrect, however everything else seems to be correct. Im just wondering if the base plate makes that much of a difference since my metering block vac is so low when I don't have it capped off? I appreciate your expertise on this, I have had this car for 30 years and its running the best it ever has and I just want it to be fine tuned like it should be and that's why im asking all these questions.

Thanks,

Jim

 

Thanks Joe, im going to take this information I got from you, John, and the others that responded this weekend and do some more checking and testing, I appreciate the help.
Thanks,
Jim

 

Get the p/n of the cam and post it here if you can.

EOIC method is an excellent method, especially with a cam that has very long clearance ramps like the "346".

Difference in idle vacuum between the 30-30 lashed at .030/.030 and .025/.025 is about 1 in-hg. So, yes there is a slight difference, but 15 in-hg is far too high!

 

[QUOTE=jimstingray57;1587537007]Hey John,
Thanks for the photo you always come through, My base plate has one long oval hole and two other holes so it is incorrect, however everything else seems to be correct. Im just wondering if the base plate makes that much of a difference since my metering block vac is so low when I don't have it capped off? I appreciate your expertise on this, I have had this car for 30 years and its running the best it ever has and I just want it to be fine tuned like it should be and that's why im asking all these questions.

Thanks,

let me rephrase that it's the manifold that has the long ovAL hole not the carburetor, but the base plate on the car now is from a different Holly I presume.

Jim

 

Ok the following is the cam information,
Its a Melling performance, 22410 not sure if that's the PN but the following info is off the tag. Cam lift .323 Int and Exh.. Valve Lift is
.485 both intake and exhaust, Lobe CTR is 110 intake & 118 exhaust
Lash Hot is .030 intake and exhaust, SAE Duration in 294 both intake and exhaust, .050 duration is both 254 intake and exhaust,
SAE Timing BTC=35, ABC=79 BBC=83 and ATC = 31
.050 Timing BTC=16, ABC=58, BBC=64 and ATC = 10
I hope this tells you something but I was assured this is a 30/30 cam.
Thanks,

Jim

 

From the internet. It has to be accurate.


Standard 302 (30-30) cam, P/N 3849346
Casting #3849347
254 duration @ .050" (intake & exhaust)
.485" lift (with 1.5 rockers)
114 deg. lobe separation
Exhaust Max lift @ 116 deg. BTDC
Intake Max lift @ 112 deg. ATDC

 

Yes, those are "30-30" specs.

Your 327 should develop 8-9 in-hg @ about 900 RPM. In your first post, you said, " I have about 36 degree timing at idle (800 to 850 rpm) with the vac can disconnected and carb plugged off." If this is true, then that's why you have so much vacuum. Set your base timing to 12* BTDC with the vac advance disconnected and plugged. Make sure that the advance weights are restrained, or remove them and tie the autocam to the nested position. Idle timing should go to 28-29 with the vac advance connected. Untie the autocam and reinstall weights and springs.

After that's done, and you still read 15 in-hg, then either your gauge is NG, your lash is around .045/.045, or you have a SBC 427.

 

Thanks 65 tripleblack,
I will try what you said this weekend if it doesn't rain, I appreciate your help. It would be nice to have a SBC 427. I will put my results in here after I check things out this weekend.

Thanks,
Jim

 

65 tripleblack,

Ok in between rain storms I was able to make some checks, first I used rubber bands to restrain the weights, I plugged off the vac can and the carb vac. and set the timing at 29 degrees, I then connected the vac gauge and it showed 14 hg, I gave it some throttle to ensure the timing would not advance and it didn't. when I reconnected the vac line the timing was showing 45 at about 850 idle, I then took the rubber bands off the weights and blocked off the vac can and checked the vac off the carb and it read about 13.25 hg with timing @ 29 degrees, I did retard the dizzy to get the 29 degrees at the beginning and without driving on wet roads the throttle does seem to be crisp and slight to no hesitation, but I will have to test drive to see if its good. The vac is still higher that the 8-9 like you guys say but I don't know why and this engine seems to like plenty of advance and really don't have any detonation issues. so decipher this info when you get a chance and I will be ready for the next set of orders.
Thanks,
Jim

 

I told you to set the base timing at 12*.........not 29*. "Base" timing is with no vacuum advance and no centrifugal advance.
Reread and follow the instructions.

The 30-30 cam will take all the timing you can throw at it and not detonate. That is because it is such an inefficient (junk) cam and bleeds off too much cylinder pressure! The fact is, is that anything more than factory settings plus about 2-4 * will cause peak cylinder pressure to occur too early (earlier than about 14* ATDC), resulting in a severe loss of power.

 

Ok 65 tripleblack,
this evening I pulled the car out of the barn and went to set the initial timing @ 12 like you said, in order to get to 12 I had to raise the coil out of the original bracket so it would not interfere with the vac can when I rotated the dizzy toward the firewall, anyway rubber bands installed on the weights and the carb vac was plugged off, idle was set about 850. The car didn't want to run very well at all, it was sounding real retarded, but anyway I left it there then I connected the vac advance and it was about 29-30 but the car was still sounding too retarded but anyway I left it like that then shut it off and removed the rubber bands on the weights then started it and checked the vac, it was about 13.5 to 14, it was too late to take the car for a spin but just the sound of it seems to be doggy with the dizzy retarded so far. So anyway that's where im at and have no clue what to do next, I will probably not get a chance to drive it until this weekend to see how it does. so I hope this doesn't fry your brain like its doing mine, but a friend that has two 66 vettes, hasn't seen an engine quite temperamental as this one is and like I said before I have had this car since 84 and it runs strong but not quite fine tuned like I want it to be.

Thanks,

Jim

 

In post #1 you said that the car jerks when moving at low engine speed. This is because of too much spark advance.

Next thing I would do is verify the clocking of the harmonic damper to make sure it hasn't slipped. It's also possible that someone installed the wrong timing cover with different timing mark clocking. I have no picture of the timing tabs for comparison.

If you have a piston stop, you should use it to verify engine timing marks.

 

Here's a review of the timing tab variations:


http://www.crankshaftcoalition.com/w..._TDC_lines_SBC