TRI POWER experts-please help.

[Richard S.]

Are there any differences....any differences at all.....between the 67 427/435 TRI POWER carbs I have.....and 68 or 69 427/435 TRI POWER carbs....thanks for the help.

Rick.

[Wayne M.]

Re: TRI POWER experts-please help.

Are there any differences....any differences at all.....between the 67 427/435 TRI POWER carbs I have.....and 68 or 69 427/435 TRI POWER carbs....thanks for the help. ..Rick.

Rick --- for sure; the center carbs. The outboasrd LIST 3659's were the same for all three years.

'67 center with 4-sp is LIST 3660; with auto, LIST 3888
'68 center w/4-sp LIST 4055 (first design, stamped 3925517)
4055-1 (2nd design '68 and all of '69) 4-sp, 3940929.

auto trans: 1968 (!st design) LIST 4056 # 3902516
auto, 2nd design '68 and all '69 LIST 4056-1, #3940930.

Hey Rick, my late '69 L68 complete set-up was bought from a guy around Bromont Quebec, in the late '70s.

[Richard S.]

Re: TRI POWER experts-please help.

Thank you for taking the time to post a reply. I'm sorry I was not more clear.....aside from the numbers difference....of which I was aware, and which was the reason for my question....are there any physical differences in the 67, 68 and 69 center carbs of 435 horse Corvette carbs....thanks for the help.

Rick.

[Michael F.]

Re: TRI POWER experts-please help.

NO all will interchange, if you include the intake for 68/69 you lose about 10hp on top end according to what I read back in the day.

[Wayne M.]

Re: TRI POWER experts-please help.

Thank you for taking the time to post a reply. I'm sorry I was not more clear.....aside from the numbers difference....of which I was aware, and which was the reason for my question....are there any physical differences in the 67, 68 and 69 center carbs of 435 horse Corvette carbs....thanks for the help.

Rick.

Rick -- OK; main jets for the 4056-1 is "61"; for the 4055-1 it's "63"; for the 3660 it's "64"; for the 3888 it's "62" All power valves are "65"; all outboard 3659 metering plates are "-3" (dash 3).

the primary venturi diameter for 4055-1, 4056-1, and 3660 and 3888 is 1_3/16"; the 3659 outboards are 1_3/8" dia. Inlet needles & seats are all the same.

The throttle bore dia's for those with 1_3/16" venturi is 1_1/2". For those with 1_3/8" venturi, it's 1_3/4".

The above does not mention 4055 or 4056 (with no dash -1) but that's all I have.

I know of other differences such as center carb throttle lever, brackets for throttle cable, fuel lines, but I'll leave those to the real experts .

[Richard S.]

Re: TRI POWER experts-please help.

Thanks Wayne.....sure sounds like you are one of the "real experts' to me....

Between 67 and 69 do you think Holley/GM did anything to improve the performance or function of the center carb??

[Richard S.]

Re: TRI POWER experts-please help.

How can I find out what Holley did to the 67 center carb: 3660A

1) In early 68 when it changed to 4055A...and

2) In late 68 when it changed to 4055-1A.... and this number was used in 69 as well.

Would Holley be able to tell me what was done at each change?? Thanks.

[Jamie F.]

Re: TRI POWER experts-please help.

The later center carbs have a vent cap and lever on the float bowl which is not seen on earlier carbs. A list with a -1 after the 4055 indicates the presence of the vent cap.

[Rick L.]

Re: TRI POWER experts-please help.

Sorry to resurrect this thread, but this is exactly the type of info I am trying to get. In the last post the author states that the 4055-1 change was the addition of the fuel bowl vent. I've been looking around for a 4055 and every single one I have looked at has had the vent. I can't believe that they've all had the fuel bowls changed, so anybody have any info about why I am seeing this?

Thanks,
Rick L.

[Wayne M.]

Re: TRI POWER experts-please help.

Sorry to resurrect this thread, but this is exactly the type of info I am trying to get. In the last post the author states that the 4055-1 change was the addition of the fuel bowl vent. I've been looking around for a 4055 and every single one I have looked at has had the vent. I can't believe that they've all had the fuel bowls changed, so anybody have any info about why I am seeing this? ....

Rick -- can't answer your direct question but a Tech Service Bulletin, dated Jan 31st 1968, describes 3 x 2 carb hard starting after hot soak, being alleviated by addition of fuel bowl idle vent (center carb) in early October produced vehicles; (lists 6 parts required to field correct on earlier cars). Now whether this early October Holley plant change was ALL the mod's done under 4055-1, or if this was the first appearance of the dash-1 LIST number, I can't say.