Hello, I am trying to get the surging or bucking at low speed out of my 1965 300hp. I am in the process of identifying my parts before I get started. Distributor is 1111076 and is correct. Vac reads on the mounting plate 238 ms 24. I have no idea what this translates toand I need to find out if possible or simply buy a new one. My supplement guide says 8 degrees initial timing, Centrifigual 0 @ 750 15 @ 1500 and 26 @ 4100, Vacumn advance 0 @ 4" HG AND 16.5 @ 8.2" HG. are these specs correct? Any help appreciated.
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Re: vac canister id help!
Michael-----
I don't know what the "238" vacuum control is for. The derivative number implies a vacuum control of GM #1116238. However, I can find no record of any such vacuum control ever having existed. Of course, you could be reading it wrong and it might actually be "236". The problem there is that a "236" would be stamped "MS 8" and not "MS 24". The "24" says that the control produces 24 crankshaft degrees of advance at full plunger travel. I don't know of ANY vacuum controls that produce that much advance, certainly none ever used on a Corvette.
The correct vacuum control for your distributor is the GM #1116236 which should be marked "236" and "MS 8". It produces 8 crankshaft degrees of advance and the plunger begins to move at 3-5 inches of vacuum. This is long-since GM-discontinued. Its Standard Motor Parts replacement, marked "B28" and known as VC 177 or NAPA VC1810 is also now discontinued.In Appreciation of John Hinckley -
Re: vac canister id help!
Michael -- the 238 vac advance you have on your 1111076 L75 distrib is correct per my Delco Remy Test Specificatons supplements. Howerver, this is NOT the vac can quoted in the tables of the '65 TIM&JG (says should be 236 -- aka Duke Williams special).
The MS (I think) is the manufacturer code; the 238 is part # 1116238; the 24 is 24 degrees maximum crank timing advance at 11.7 to 14 inches mercury.
The supplement figures you've quoted are from the '65 Shop Manual supplement, and they show same numbers for all '65 small block distrib's; which I doubt is the case.
Why you're having the bucking, I'll leave to others.Comment
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Re: vac canister id help!
Wayne----
Yes, I found it; I just wasn't going back far enough. Plus, some references are incorrect on this one and they "led me astray". The 1116238 was used only for the 1965 model year as far as Corvettes go and only for base and L-75. It was also used for some passenger car applications during the 65-66 period.
The 1116238 was discontinued in July, 1966 and replaced by GM #1115357. The 1115357 had somewhat different specs, though. It produced a maximum of 20 crankshaft degrees of advance at 16-18" vacuum and the plunger started to move at 7-9" vacuum. It was discontinued years ago.
However, a replacement is available for the 1115357. It's Standard Motor Parts VC169, aka NAPA VC1605. It's marked "B9".
Also, I should have said the 1116236 was marked "MS 16", as you mentioned. For some reason, I "halved" the figure thinking distributor degrees.In Appreciation of John HinckleyComment
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Re: vac canister id help!
Thanks for the help. So does this means the 238 can is correct, but the specs I have are wrong? What should the specs be for the 238 can? I mean 24 total for the can seems a lot and the specs I have in the supllement dont mention anything above 16.5 @ 8.2hg Thanks guys.Comment
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Re: vac canister id help!
Michael-----
Yes, I would now say the 238 is correct for a 1965 base or L-75 application. I agree that the 24 inches of vacuum does seem like a lot. That's one of the reasons I initially didn't think it was a Corvette vacuum control. But, I've now confirmed that it is. However, as I mentioned, as far as Corvettes go, it was used only for the 1965 base and L-75 applications. It was used on similar-engined passenger cars for 1965-66.
As far as I can tell, the 1116238 was only around for a quite short period. It looks to me like it was released in late 1964 for the 1965 model year and it was discontinued in July, 1966 in favor of the 1115357. So, it only "lived" for a little less than 2 years.
The specs I have for it are as follows:
maximum advance= 24 crankshaft degrees @ 14" vacuum
plunger travel starts @ 5-7" vacuumIn Appreciation of John HinckleyComment
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Re: vac canister id help!
specs for the 238 are adv start at 5-7 inches, all in at 12-14 inches, 25 degree (crank) advance.Bill Clupper #618Comment
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Re: vac canister id help!
Michael -- I confirm the spec's that Bill C. gives; mine are from Delco Test Specs Supplement to DR-324S and 324S-1 (1964 to 1976).
But what I would be concerned with is that the 1965 TIM&JG quotes the 1116236 vacuum can for ALL small block 1965 distributors. (and that the '65 Shop manual supplement seems to indirectly confirm this).
I cannot believe that a mild cam (base & L75) engine would require the same can characteristics as the 30-30 solid cam or the "151" 350 hp cam, with greater compression.
And we still haven't addressed your "bucking" symtoms; I thought Dude W. would chime in.Comment
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Re: vac canister id help!
The '65 300 HP 24 degree VAC was ill-chosen by GM. The best VAC to use for 300 HP engines with manual transmissions provides 16 deg. @ 15". The current replacement across all brands is stamped "B22" and is represented by the NAPA VC1802. For 300 HP/Powerglide use the NAPA VC1765 or equivalent in any other brand stamped "B20". This is a 16 deg. @12" VAC, and it is also best suited to all big blocks and L-79.
The "236" OE 8" VAC is represented by by the NAPA VC1820 or equivalent in another brand, all stamped "B28". This VAC is suited to engines that generate less than 14" vacuum at normal idle speed, which limits its functionally correct use to only OE SBs with mechanical lifter camshafts, L-82/auto, and L-88/ZL-1 that are converted to vacuum advance. I don't recommend it for L-79s even though the "236" was the OE VAC. The best replacement for the L-79 based on function is the "B20" 12" VAC because typical L-79s idle at 750@14".
Parts books are full of errors and many OE VACs were replaced with VACs that have different specs. It's a bloody mess, but one of the three VACs I referenced above is functionally correct for all '57 to '74 OE Corvette engines including ported advance engines that have been converted to full time and those where a single point vacuum advance distributor has replaced the OE dual point non-vacuum advance distributor.
My recommendations are based on sound, proven engine system engineering principals and comply with the "Two-Inch Rule" with reasonable idle speed in neutral for manual trans and Drive for auto trans.
B22 (16@15") - 283(with manual trans) /220-230-245-250-275 HP
.....................327(with manual trans)/250-300 HP
.....................350(with manual trans)/ALL base 350 engines
B20 (16@12") - 283 (with auto trans)/220-230-245-250-275 HP
.....................327 (with auto trans)/250-300 HP
.....................327/350 HP
.....................350 (with auto trans)/ALL base engines
.....................350 (with manual trans) ALL year L-82
.....................396. 427, 454/ ALL except L-88 and ZL-1
B28 (16@8") - 283, 327, 350 (with mechanical lifter cam)/ALL
....................350 (with auto trans)/ALL L-82
....................427/All L-88/ZL-1 (set idle speed high enough to comply with the "Two-Inch Rule"
DukeLast edited by Duke W.; July 8, 2008, 09:51 PM.Comment
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