1975 EGR valve question
12-16-2014, 05:35 PM
#21
Team Owner
WELL..what I am getting at is that the other TVS was used for the VACUUM going to the distributor. SO when the coolant temp got high enough...the vacuum would work the ADVANCE pod as designed....BUT would not work when the engine is COLD.
Dub,
I am confused but intrigued. That intake-mounted TVS is typically for EFE. On what year was it used to control distributor vacuum? Never seen that before.
Dub,
I am confused but intrigued. That intake-mounted TVS is typically for EFE. On what year was it used to control distributor vacuum? Never seen that before.
12-16-2014, 06:32 PM
#22
Race Director
No need for sarcasm. You inferred that a car with full time vacuum to the distributor would not start and run properly. This is false, GM built millions of them before ported vacuum was introduced around the beginning of the 'smog era'.
The OP's engine can be set up similarly.
The OP's engine can be set up similarly.
I did not write what you wrote that I put in bold print. I never wrote that the engine would not START. Many of the Corvettes I get in my shop are such a 'mish-mash' of 'this and that'...trying to get it all to come together and run under all conditions is sometimes a FUN task.
I did not mean to imply that full vacuum is WRONG...and never wrote that it is WRONG....due to many variables that come into play. And that is where the 'balancing act' for me begins in order to get the engine to work correctly. AND YES...it is true....on some engines I need to use the TVS to get it to run correctly when cold....which is basically following what GM used anyway.
And 'hopefully' you will agree....just because a person buys boxes of parts and puts them on the engine DOES NOT make them right for THAT engine and can take some serious time to get all variables 'dialed-in' so it runs as they hope for.
And you have to wonder why GM started using the TVS'???? Why would GM spend money on parts if they are not needed if the engines were working perfectly before they implemented the TVS system for the distributor. And YES...I know and have read it before that NOT all of GM's ideas are good ones.
Just as an example....I have had a few customers over the years that think that BIGGER IS BETTER who put a double pumper carb on that had NO CHOKE plate...or even the casting to hold a choke plate.... and wanted me to get it to work like the original Quadra-Jet...meaning....they wanted to pump it twice and hit the key and it would idle as designed....OH YEAH and this is when air temps are about 40 degrees Fahrenheit. And they were being put on a later 70's emissions engine...with a smaller width air filter ( yeah that's good for being able to breathe) and the engine is so worn out....that I can spin the engine by turning the alternator belt manually when it is cold.....so NO ring drag....and when I check the PVC system...There is so much blow-by from the rings ...that the paper I use to see if it gets sucked to the valve cover grommet for the fresh air filter...it literally blows away from it.....and YET...they still want it running correctly....EVEN when I tell them their engine is shot and needs rebuilding....Try that one on for size.
WELL..what I am getting at is that the other TVS was used for the VACUUM going to the distributor. SO when the coolant temp got high enough...the vacuum would work the ADVANCE pod as designed....BUT would not work when the engine is COLD.
Dub,
I am confused but intrigued. That intake-mounted TVS is typically for EFE. On what year was it used to control distributor vacuum? Never seen that before.
Dub,
I am confused but intrigued. That intake-mounted TVS is typically for EFE. On what year was it used to control distributor vacuum? Never seen that before.
https://www.corvetteforum.com/forums...m-and-kit.html
DUB
12-16-2014, 06:56 PM
#23
I did not mean to imply that full vacuum is WRONG...and never wrote that it is WRONG....due to many variables that come into play. And that is where the 'balancing act' for me begins in order to get the engine to work correctly. AND YES...it is true....on some engines I need to use the TVS to get it to run correctly when cold....which is basically following what GM used anyway.
The OP no longer has the original manifold or carb. The hardware he's presently using has been around since the '50s and '60s. No need to confuse the poor guy further by inferring that his engine won't run properly without a TVS.
The shop that installed this stuff, for unknown reasons, did not hook up the vacuum advance to the carb.
12-16-2014, 07:30 PM
#24
Race Director
Jeeze dude, chill out a bit.
The OP no longer has the original manifold or carb. The hardware he's presently using has been around since the '50s and '60s. No need to confuse the poor guy further by inferring that his engine won't run properly without a TVS.
The shop that installed this stuff, for unknown reasons, did not hook up the vacuum advance to the carb.
The OP no longer has the original manifold or carb. The hardware he's presently using has been around since the '50s and '60s. No need to confuse the poor guy further by inferring that his engine won't run properly without a TVS.
The shop that installed this stuff, for unknown reasons, did not hook up the vacuum advance to the carb.
AND from when I wrote the post that you added your .02 cents worth too...having to 'spell everything out in detail' for you has become expected.
And I NEVER wrote that HIS ENGINE would not RUN PROPERLY unless a TVS was installed. You evidently did not read what I wrote...and only read what you wanted to.
Thanks for the LAUGH. People rarely amuse me. This must have been be a joke. I thought you were trying to help the guy. My mistake.
DUB
12-16-2014, 07:38 PM
#25
Team Owner
Dub,
I am not being critical, just curious. My mechanical experience is very limited compared to yours. I have had a 1967, 1979, and now a 1974. The pic is a 1979 L-82 intake from my past restorations. There is no thermal vacuum switch (TVS) for distributor vacuum. Hence my question.
My 1974 does have the TVS for EGR and it does work. Last summer I tried both manifold and ported vacuum and to be frank the engine prefers ported. Much easier to get in tune. Perhaps not surprising as the engine is basically stock and it was designed to work that way. I did about 2,500 miles last summer with cold idle at 1,300rpm, idle in P at about 750rpm, and idle in D at about 600rpm; pretty close to specs. The car never stalled once. Timing is set at 12BTC, a little high but the car sure does run nice on the highway at 70mph at 180*F on 89 octane, 10% ethanol fuel. Yes, Mike that 10% is fine. Has been for 20+ years in my Corvettes. But you have to get the Viton accelerator pump. No doubt in my mind.
In any case Dub, I really appreciate your contributions to the Forum. You won't remember but two years ago you helped me with a minor fiberglass repair to my rear convertible deck. The compound you suggested sure did the trick when I drilled (and made a mistake) for the side bolts for the hardtop and had to fill in (plus a little touch-up paint). Brain farts are common at my age. All turned out well!
It's a little early but I don't post as often as I used to. But I will take this opportunity to wish you a Merry Christmas!
I am not being critical, just curious. My mechanical experience is very limited compared to yours. I have had a 1967, 1979, and now a 1974. The pic is a 1979 L-82 intake from my past restorations. There is no thermal vacuum switch (TVS) for distributor vacuum. Hence my question.
My 1974 does have the TVS for EGR and it does work. Last summer I tried both manifold and ported vacuum and to be frank the engine prefers ported. Much easier to get in tune. Perhaps not surprising as the engine is basically stock and it was designed to work that way. I did about 2,500 miles last summer with cold idle at 1,300rpm, idle in P at about 750rpm, and idle in D at about 600rpm; pretty close to specs. The car never stalled once. Timing is set at 12BTC, a little high but the car sure does run nice on the highway at 70mph at 180*F on 89 octane, 10% ethanol fuel. Yes, Mike that 10% is fine. Has been for 20+ years in my Corvettes. But you have to get the Viton accelerator pump. No doubt in my mind.
In any case Dub, I really appreciate your contributions to the Forum. You won't remember but two years ago you helped me with a minor fiberglass repair to my rear convertible deck. The compound you suggested sure did the trick when I drilled (and made a mistake) for the side bolts for the hardtop and had to fill in (plus a little touch-up paint). Brain farts are common at my age. All turned out well!
It's a little early but I don't post as often as I used to. But I will take this opportunity to wish you a Merry Christmas!
Last edited by Paul L; 12-16-2014 at 08:35 PM.
12-17-2014, 07:14 PM
#26
Race Director
Dub,
I am not being critical, just curious. My mechanical experience is very limited compared to yours. I have had a 1967, 1979, and now a 1974. The pic is a 1979 L-82 intake from my past restorations. There is no thermal vacuum switch (TVS) for distributor vacuum. Hence my question.
My 1974 does have the TVS for EGR and it does work. Last summer I tried both manifold and ported vacuum and to be frank the engine prefers ported. Much easier to get in tune. Perhaps not surprising as the engine is basically stock and it was designed to work that way. I did about 2,500 miles last summer with cold idle at 1,300rpm, idle in P at about 750rpm, and idle in D at about 600rpm; pretty close to specs. The car never stalled once. Timing is set at 12BTC, a little high but the car sure does run nice on the highway at 70mph at 180*F on 89 octane, 10% ethanol fuel. Yes, Mike that 10% is fine. Has been for 20+ years in my Corvettes. But you have to get the Viton accelerator pump. No doubt in my mind.
In any case Dub, I really appreciate your contributions to the Forum. You won't remember but two years ago you helped me with a minor fiberglass repair to my rear convertible deck. The compound you suggested sure did the trick when I drilled (and made a mistake) for the side bolts for the hardtop and had to fill in (plus a little touch-up paint). Brain farts are common at my age. All turned out well!
It's a little early but I don't post as often as I used to. But I will take this opportunity to wish you a Merry Christmas!
I am not being critical, just curious. My mechanical experience is very limited compared to yours. I have had a 1967, 1979, and now a 1974. The pic is a 1979 L-82 intake from my past restorations. There is no thermal vacuum switch (TVS) for distributor vacuum. Hence my question.
My 1974 does have the TVS for EGR and it does work. Last summer I tried both manifold and ported vacuum and to be frank the engine prefers ported. Much easier to get in tune. Perhaps not surprising as the engine is basically stock and it was designed to work that way. I did about 2,500 miles last summer with cold idle at 1,300rpm, idle in P at about 750rpm, and idle in D at about 600rpm; pretty close to specs. The car never stalled once. Timing is set at 12BTC, a little high but the car sure does run nice on the highway at 70mph at 180*F on 89 octane, 10% ethanol fuel. Yes, Mike that 10% is fine. Has been for 20+ years in my Corvettes. But you have to get the Viton accelerator pump. No doubt in my mind.
In any case Dub, I really appreciate your contributions to the Forum. You won't remember but two years ago you helped me with a minor fiberglass repair to my rear convertible deck. The compound you suggested sure did the trick when I drilled (and made a mistake) for the side bolts for the hardtop and had to fill in (plus a little touch-up paint). Brain farts are common at my age. All turned out well!
It's a little early but I don't post as often as I used to. But I will take this opportunity to wish you a Merry Christmas!
NO problem at all.
'Things' change...and I notice changes and analyze these changes and see it these changes warrant further investigation in WHY these changes were made. Case in point (off subject) GM used hot water shut off valves....THEN decided to not use them...then brought them back in again. SO...if you year model does not have one...WHY the heck not put one in. Unless you are a purist and want it the way it was made ...and if so...do not complain about heat or your A/c not working as efficiently.
What many here on the forum may not understand that is I work on many eras of Corvettes...and I take notice in the improvements and changes that GM does in many cases.
I am aware that GM began using the TVS for the distributor a year later (1980). And to apply what I wrote above about eh hot water shut off valve. If a person feels that a TVS will make the engine run better...put one in and test it. REGARDLESS if it did not come with one. AND I am sure that using one of the other TVS' would work if it was check to make sure it is a normally CLOSED TVS...and NOT a normally OPEN TVS. SO a little bit of hose and a 'T' fitting. No big deal...and if it works...what is the harm.
ALSO....take a minute and read and try to think about this. The TVS for the distributor is used to make it so the initial timing setting is used (and yes I know all about centrifugal advance) UNTIL the engine gets hot enough to open the TVS and allow vacuum to get to the advance pod. AND it is KINDA FUNNY...how GM does somewhat the SAME THING on a computer controlled engine. The timing is set with a lead disconnected as required. AND....the engine is in OPEN LOOP when is cold and it is running off of initial setting of components. BUT...once the O2 sensors get HOT enough....the engine then goes into CLOSED LOOP....and the computer takes over (so to speak) and it is able to do what it was designed to do. Does anyone see the similarity???? Distributor TVS's and OPEN LOOP....HMMMM.
Paul,
And YES...I also run into engines that prefer ported vacuum. Like I wrote before...NOT all engines are the same.
I am glad to read that your repair worked out for you....and you also have a MERRY CHRISTMAS.
DUB
12-17-2014, 08:51 PM
#28
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Well I enjoyed reading all this. A lot of info. I'd like to learn as much as I can about it before taking the car to a shop in the spring for an estimate. This helps a lot. Much appreciated.
12-17-2014, 09:54 PM
#29
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Dub
If you are still following this. Are you able to tell if my carb. is compatible with the Elderbrock intake which has the provision for the EGR valve just by looking at the photos ?
That carb. cost about 800.00 according to my receipt and I am hoping it is still useable if I change intakes.
If you are still following this. Are you able to tell if my carb. is compatible with the Elderbrock intake which has the provision for the EGR valve just by looking at the photos ?
That carb. cost about 800.00 according to my receipt and I am hoping it is still useable if I change intakes.
12-17-2014, 10:09 PM
#30
Dub
If you are still following this. Are you able to tell if my carb. is compatible with the Elderbrock intake which has the provision for the EGR valve just by looking at the photos ?
That carb. cost about 800.00 according to my receipt and I am hoping it is still useable if I change intakes.
If you are still following this. Are you able to tell if my carb. is compatible with the Elderbrock intake which has the provision for the EGR valve just by looking at the photos ?
That carb. cost about 800.00 according to my receipt and I am hoping it is still useable if I change intakes.
Yes.
12-18-2014, 10:48 AM
#32
Team Owner
Just make sure that you match that carb to the new intake. I can't tell if it is square-bore or spread-bore. This one on my former 1967 was square-bore.
You don't have to remove it for a peek. Just check the model # on-line.
You don't have to remove it for a peek. Just check the model # on-line.
Last edited by Paul L; 12-18-2014 at 10:51 AM.
12-18-2014, 11:18 AM
#34
Team Owner
Left (passenger) front mounting pad. Should be something like 14XX (model) plus YYYY (date). The one in my pic is a #1406 (square bore, 600cfm).
12-18-2014, 06:27 PM
#35
Race Director
ericupnorth,
I would like to HIGHLY ADVISE you in getting a hold of 'paul 74'...and ask him where he got the nice fuel filter you can see in his photo he posted in POST # 32. And get the shop to remove that inferior rubber hose set-up coming off the steel line that you have now. Rubber hoses AFTER the fuel pump require a dedicated maintenance/inspection interval....that many people do not do until it is too late.
paul 74,
I would like to know where you got the billet filter also. I use the AN fitting design but they are a bit larger and also would like to know the micron valve of the filter if you have that information.
DUB
I would like to HIGHLY ADVISE you in getting a hold of 'paul 74'...and ask him where he got the nice fuel filter you can see in his photo he posted in POST # 32. And get the shop to remove that inferior rubber hose set-up coming off the steel line that you have now. Rubber hoses AFTER the fuel pump require a dedicated maintenance/inspection interval....that many people do not do until it is too late.
paul 74,
I would like to know where you got the billet filter also. I use the AN fitting design but they are a bit larger and also would like to know the micron valve of the filter if you have that information.
DUB
12-18-2014, 06:29 PM
#36
Race Director
Dub
If you are still following this. Are you able to tell if my carb. is compatible with the Elderbrock intake which has the provision for the EGR valve just by looking at the photos ?
That carb. cost about 800.00 according to my receipt and I am hoping it is still useable if I change intakes.
If you are still following this. Are you able to tell if my carb. is compatible with the Elderbrock intake which has the provision for the EGR valve just by looking at the photos ?
That carb. cost about 800.00 according to my receipt and I am hoping it is still useable if I change intakes.
with Mike Ward. You should be good to go.DUB
12-18-2014, 07:35 PM
#37
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Hi Dub
You mentioned in one of your previous posts that Edelbrock liked the rubber lines over the metal. I am guessing the shop involved probably followed the installation instructions and doesn't deviate unless the customer knows enough to override and requests the modification and at the same time the shop in doing so is not exposed to liability. It does however seem a lot safer to use the metal lines. I am going to ask them to modify mine to something similar to what Paul has. It also seems to give easy assess to the fuel filter and is right out there as a reminder to change the thing once in awhile. Been down that road before...well actually off to the side of it.
You mentioned in one of your previous posts that Edelbrock liked the rubber lines over the metal. I am guessing the shop involved probably followed the installation instructions and doesn't deviate unless the customer knows enough to override and requests the modification and at the same time the shop in doing so is not exposed to liability. It does however seem a lot safer to use the metal lines. I am going to ask them to modify mine to something similar to what Paul has. It also seems to give easy assess to the fuel filter and is right out there as a reminder to change the thing once in awhile. Been down that road before...well actually off to the side of it.
12-18-2014, 07:45 PM
#38
Race Director
Hi Dub
You mentioned in one of your previous posts that Edelbrock liked the rubber lines over the metal. I am guessing the shop involved probably followed the installation instructions and doesn't deviate unless the customer knows enough to override and requests the modification and at the same time the shop in doing so is not exposed to liability. It does however seem a lot safer to use the metal lines. I am going to ask them to modify mine to something similar to what Paul has. It also seems to give easy assess to the fuel filter and is right out there as a reminder to change the thing once in awhile. Been down that road before...well actually off to the side of it.
You mentioned in one of your previous posts that Edelbrock liked the rubber lines over the metal. I am guessing the shop involved probably followed the installation instructions and doesn't deviate unless the customer knows enough to override and requests the modification and at the same time the shop in doing so is not exposed to liability. It does however seem a lot safer to use the metal lines. I am going to ask them to modify mine to something similar to what Paul has. It also seems to give easy assess to the fuel filter and is right out there as a reminder to change the thing once in awhile. Been down that road before...well actually off to the side of it.
And 'sometimes'..the WARNINGS that are given are due to some BOZO who did a modification WRONG and then went running back to the manufacturer saying..."Well,,,you did not tell me I couldn't" Kinda like the reason that places that sell COFFEE....has to let you know it is HOT. Because someone ...had no clue.
DUB
12-18-2014, 08:32 PM
#39
Team Owner
Dub,
You are asking me to go back many moons. I sold the 1967 in 2008.
Whatever. The banjo fitting into the carb and in-line filter is standard Edelbrock stock. I don't know the micron value. From the filter down to the pump I used standard steel tubing flared to 37* AN. Yes, I have cutting, bending, and flaring tools. To those who may not know, AN is an army/navy standard for military usage. It is a single flare compared to the usual 45* double flare. All the fittings are available right down to the fuel pump from Russell.
I normally document my projects and had pics of all of this conversion from Holley to Edelbrock about two computers ago. Sorry, some things get lost with trying to go from one computer to another.
*Edit* - I looked and this is all I could find. I bent and flared that tubing. Even biologists like me can do a couple of things right!
You are asking me to go back many moons. I sold the 1967 in 2008.
Whatever. The banjo fitting into the carb and in-line filter is standard Edelbrock stock. I don't know the micron value. From the filter down to the pump I used standard steel tubing flared to 37* AN. Yes, I have cutting, bending, and flaring tools. To those who may not know, AN is an army/navy standard for military usage. It is a single flare compared to the usual 45* double flare. All the fittings are available right down to the fuel pump from Russell.
I normally document my projects and had pics of all of this conversion from Holley to Edelbrock about two computers ago. Sorry, some things get lost with trying to go from one computer to another.
*Edit* - I looked and this is all I could find. I bent and flared that tubing. Even biologists like me can do a couple of things right!
Last edited by Paul L; 12-18-2014 at 08:41 PM.
12-18-2014, 08:34 PM
#40
Edelbrock did not design that carb. It is a copy of a very old (ancient) Carter AFB carb that came on many GM vehicles in the 50s and 60s, including Corvettes. It was superseded by Holley which in turn was superseded by Qjets until EFI appeared in the 80s.
Not one Carter-equipped car left GM with a rubber fuel line, AFAIK.