I'm about to attempt to tune a 66 427 425 horse engine with an unknown solid lifter cam. 650 Holly vacuum secondary. Engine idles high (to me) at 1000+ rpm. Has 12-13 hg vac at idle. Would a B26 VC181 vac can be ok to use? I am going to start from scratch of course on the dist and carb and go from there. Who knows what's been done to it to try to get it tuned. Owner says he has to rev and slip the clutch to get it going without a stumble. Thanks in advance guys.

 

Here are the specs on B26 and VC1810 (different). Specs from papers by Lars et al.


VC1765 B26 Starts to open 5-7 fully open by 11-13 8 degrees
1965 396 Impala High Perf
or 1966-67 Corvette Exc. High Perf.
B20 1966-67 Impala 427 Exc. High Perf.
1966-68 327 Powerglide Exc. High Perf.
1969 307 All
1969-70 396, 427 Cam., Chev High Perf.
1970 400 2-bbl
1970 307 MT
1973 Camaro 350 High Perf.
Comments: This part is still available through NAPA stores. Sold by Wells under part
number DV1808.

VC1810 B28 Starts to open 3-5 inches Fully open 5.75-8 inches 8 degrees
1965 409 High Perf.
1965 327 High Perf.
1966 327 High Perf.
1964-67 Corvette High Perf. FI

Comments: This VC1810 High Performance unit has now been discontinued by NAPA/Echlin. It crosses over to AC/Delco part number D1312C, and VC177 in
Standard Hygrade – both of these numbers are available at this time, but could also be discontinued soon due to the age of these cars and components. Wells still sells it under their part number DV1810, and Borg Warner has it under part number V329. GM part number is 88924985, and is still available. (This info courtesy of Henry at Ole’s Carbs). Another good source for the vacuum advance control units (under the Wells part numbers) is from “My Parts Garage.com”


langg

 

Dave -
As you know, I do a huckuva' lot of testing of vacuum cans and distributors. For your application, pulling 12-13 inches at idle, the B26 unit is cutting it a little too close: The B26's pull in their full stroke right about at 12.5 to 13", so you'd stand a chance of the can not sucking all the way in at idle, producing inconsistent timing. I'd run a B28 on that engine and shorten the stroke a tad so it produces 12 to 14 degrees of advance. That will give you a very good setup with stable timing and good throttle response, assuming you combine that with about 16-18 degrees initial timing and about 38 degrees total (assuming you have stock iron heads).

Lars

 

Thanks guys, it indeed does have iron heads. Actually a picture of the car I'm working on is in Nolan Adams book Vol II under 66 year IP's at the back for 427 425 HP cars. Red vert.

 

The vacuum can that's in it now is numbered MS 236 16. Is this on ok to use? Having trouble finding a B28 VC1810.

 

No, that's the stock unit, and it won't work with your modified engine's vacuum level, as noted above. You have to run a B28 to get it to work at your limited 10" of vacuum.

Don't know why you're having trouble getting the unit. You just log on to MyPartsGarage.com as noted, give them your credit card number, pay them $5.28, and 2 days later the part shows up on your doorstep...

http://www.mypartsgarage.com/catalog...sult/?q=DV1810

Lars

 

U could map the engines vacuum since u already have the idle vac (=12-13"). Raise your RPMs to 3000 and read vac. U can also take a reading at freeway cruise under a little load. This will give u what your eng makes for vac.

Next take your Mighty Vac brake bleeder connected to your vac can on the distributor and can pump it down to measure vac when full advance is added (or rather when adv starts to drop) and then vac at which no adv is added (vac adv has fully dropped out). This should show you what any particular vac can will do for your engine timing and help u choose a vac can to match. To measure the amount of adv requires testing with eng running with vac can installed and like lars mentions u can make adjustment to the vac can stroke on the dist - i recall by adj the can mount in the dist. BTW, if u didnt notice, what was meant by "starts to open" is actually the vac level the vac adv drops out (low vac/no adv). And "fully open" is actually max adv provided by the vac can at high eng vac (low rpm/high vac/max adv).


Good luck Dave,
cardo0

 

We were trying to find one locally so we could finish the job yesterday. We ended up ordering one out of Phoenix. Will be here this morning. The tune went well. The biggest issue was no advance off idle. Stock dist springs, vacuum can not working with 11" of manifold vacuum. Just changing the advance springs to bring total mechanical advance in at 2500 made a huge difference in this engine. The 650 street avenger float level was too low also. I think I need to change the power valve to a 5.5 instead of the 6.5 that it came with due to the low vacuum. Thanks again