#1  
Old 06-05-2019, 01:30 AM
Rebel2324 Rebel2324 is offline
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Default Primatech header, efi, intake

Having issues with my 67 rebuilt sprint 3,8. Have had lots of work done on the carb and it continues to percolate. Tried 1 inch spacer and other things but nothing worked. Front two cylinders have gas deposits on spark plugs and I have gas in my oil as well as blue smoke on start and when rev. This is a rebuilt engine with a slight cam, stock intake and stock exhaust, So thinking I am doing harm to the engine, have possible glazed cylinder walls because of the percolating and rich front 2 cylinders (Is engine tipped down in front) , I was thinking of ditching the carb and putting fi tech efi.

That alternative would include getting rid of stock intake and getting a clifford with 4 barrel adapter. Getting a primatech header ( do not have) and a fitech efi unit (Already have). The header is not connected to the intake so the carb percolating issue should disappear. The header will reduce the under dash heat. There is no gas to heat up in the throttle body. One problem is finding a primatech header. Does anyone have one to sell??? Other issue is efi unit does not fit well on stock intake as it is spread bore but the clifford is square bore so that should be eliminated. I find the efi unit would sit really close to the valve cover, To close for my liking. Not sure if clifford manifold is further out. Custom make accelerator cable. I have the intank electric pump, sender and special tank.

Other potential solution. Plug heat passages going to carb, I will still run the electric fuel pump as it is in. Obtain a primatech header to reduce heat under carb.

Putting the efi on the stock intake does not seem feasible. The management controls are on the valve cover side, very close to it, the spread bore intake would have to be cut on the inside where the partitions are because they do not line up.

Anyone ever tried this before and if you have a primatech header to sell I am interested. Apparently there could be another run done shortly but I would like to get this thing running properly soon. If I can get her going I will then deal with the glazing if that is the issue.

  #2  
Old 06-05-2019, 05:51 AM
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Jeff Hamlin Jeff Hamlin is offline
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To me it seems gas in oil leans toward Fuel Pump issue.
Drain oil before next start up and inspect pump. Our Cammers are know to be warm blooded but I have never exasperated fuel peculation.
However as a precaution I use the steel shim sandwiched between composite gaskets and suffer no ill carb issues.
As a control test if possible install another known carb to be sure the carb is of issue.
I did this years ago to pin point what I thought was a cam issue.

Keep us posted.
Cheers.

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Last edited by Jeff Hamlin; 02-25-2024 at 11:10 AM.
  #3  
Old 06-05-2019, 09:06 AM
66sprint 66sprint is offline
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I had a fuel pump leak internally send gas into the engine oil. Very lucky I caught it before major damage done.
Have you checked the heat valve on the exhaust manifold to make sure it is closed and not pumping hot exhaust under the carb?
May be stuck.

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Old 06-05-2019, 11:36 AM
Rebel2324 Rebel2324 is offline
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The engine no longer has a heat valve on the exhaust manifold. I have changed oil again. Must have spent $1,000 on oil in 500 miles. I do have a shim under the carb although the bottom gasket was an issue which probably caused an exhaust leak and vacuum leak. It might also have sucked a bit of exhaust into the intake??? Since the carb empties itself when the car is hot and stopped, the first two plugs had gas deposits and I could smell gas very strongly in the shop after stopping the car once hot, I went to the conclusion that that was the cause of the gas in the oil. Also that exhaust intake passage in greatly debated on many forums with quite a few people blocking it off. The fuel pump is new (50528??) although I realize that doesn't mean anything. At present the car has the new fuel tank, sending unit and in tank electric pump installed without the proper fi lines installed.
So you both mentioned that the fuel pump may be one of the problems and Jeff mentioned making sure it is a carb issue by putting another one on the car. I could take the fuel pump out to check for issues with it. Changing carb would be a little more difficult. I could take the new tank out and put the old one in but I don't think I have another spread bore carb around. I have holleys but I think they are all square bores but I will check. I might be taking a shotgun approach to this issue but I have been fighting this a very long time. I appreciate both of your comments and assistance. Any further thoughts are really appreciated.

  #5  
Old 06-05-2019, 04:39 PM
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wayne228 wayne228 is offline
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I may have missed something in
my reading of the above but from what I understand you have an electric fuel pump in the tank and fuel making it's way into the first two cylinders. Assuming that is correct I would start by checking the fuel pump pressure. If it is too high it will override the float & overfill the carb bowl causing fuel to run into the intakes. This can also happen if the fuel pump does not shut down as soon as the ignition is turned off. Could also be a bad carb bottom jet seal. This would also cause fuel bowl draining and excessive gas in the cylinders while turned off. The gas could leak past the valves into the cylinder then past the rings into the oil.

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Old 06-05-2019, 04:47 PM
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wayne228 wayne228 is offline
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I just remembered a quick check test to see if its a carb leak.....Unbolt the carb from the engine, leaving the fuel line attached. Slip a piece of cardboard or paper between the bottom of the carb & engine. turn the ignition on to activate the fuel pump BUT DO NOT CRANK THE ENGINE OR START IT. after a minute or so shut the ignition off and remove the cardboard. If it has fuel on it the carb has a leak or the fuel pump is over pressurizing it.

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Old 06-05-2019, 05:23 PM
66sprint6 66sprint6 is offline
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I've seen the gas tanks with the in-tank pumps, but I thought that they were for FI use and created a high pressure condition.
I think it's only 6 pounds or less for a typical carb, isn't it? Anything more than that would overwhelm the carb, so a good regulator is crucial.

  #8  
Old 06-05-2019, 06:34 PM
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wayne228 wayne228 is offline
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I agree, the EFI type can go as high as 100 PSI. That will blow the seals & the float seat in a Rochester in a nano second. I do not like the pressure reducer regulator route as it has the potential for a failure that will also smoke the Rochester. I use an inline fuel pump that is rated for low pressure applications.

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Old 06-05-2019, 10:35 PM
Rebel2324 Rebel2324 is offline
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I should have been a little more clear on the fuel delivery. When these problems occurred I had a regular fuel tank, correct 4 barrel mechanical fuel pump that ran off the motor supplying gas to the original multi times rebuilt carb. Since whatever I did or had done to the carb, including shipping it to the US more than once to have it looked at and nothing helped, spacer etc etc I decided to switch to fuel injection. The change of gas tank, to electric fuel pump etc just happened last week and the car has not been run since as I didn't like having to notch the inside of the intake to go from spread bore to a square bore FI unit. Summit sold be a spacer and it may work but the fuel openings don't line up. Thinking if I get a primatech header that takes away the gases faster, is further away from the intake, has no crossover to the intake and a square bore clifford intake that is supposed to flow better, has no passage to the exhaust, is a square bore and bolt that to a FI unit that carries no gas in the unit itself to percolate, has self tuning capabilities and that kind of looks cool, the problem would be solved. So I bought the tank, electric pump and FI and started installing it last week. I try to stay stock wherever possible but I don't want to harm the engine and I do want to enjoy the car.


Last edited by Rebel2324; 06-05-2019 at 10:48 PM.
  #10  
Old 11-22-2019, 02:19 AM
Rebel2324 Rebel2324 is offline
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Thought I would post a short update on my progress so far. As mentioned I was having problems with what I thought was carb percolating and gas in the oil. I ended doing the following. Installing a new efi gas tank with an intank fuel pump using the oem fuel line as the return line and installing a new line to the efi unit. Closing off the carb heat passage which goes from cylinder 3 up to the base of the carb and then down to cylinder 4. I used the special expoxy type compound as was previously outlined in a OHC post. Thanks a heap to the member who explained the steps to this. It's interesting that I have seen later intakes that did not have that passage. I installed the fitech unit using a different spacer than Summit recommended. The one they sell to go from square to spread was totally inadequate to me. I put about 500 miles on the car since then but ended up changing the exhaust to a more quiet muffler after that. In those miles the car seemed to make better power although I have no facts to prove it. The engine cranked slightly longer than a normal efi car so I was adjusting the fuel delivery when cold which helped but I still would have needed to fine tune that part. The oil now smells like oil, obviously there is no percolating as there is no gas in the efi unit to percolate. The plugs look healthy and I didn't notice smoke out of the exhaust although I would think there still would be unless the cylinders were glazed and the spirited driving unglazed them. Unfortunately since I changed the exhaust it runs rough. I have to clear the computer and restart the learning faze, Also unfortunately winter came at that time and I had to park the car. I'm hoping that in the summer I can clear the computer and put some miles on. If I get time this winter I may also take the cover off and look at the cam and internals. I am working on restoring another car so that may not happen. Anyway thanks for reading. The fitech ran very well however in hindsight I would have tried the holley sniper with timing control and would not have needed a spacer. I would also still like to get an older header and intake as they are much lighter and don't have the heating passage. Thanks to all that helped me out. This is a great bunch of members and I hope to meet some of you when I eventually go to a Pontiac meet.

  #11  
Old 11-22-2019, 09:06 AM
66sprint6 66sprint6 is offline
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Glad to hear that you are having some success. These engines can be finicky at times. I heard that Brent (I went to visit him a long time ago at his shop just south of Red Deer, Alberta) was considering doing another run of the Primatech headers. I'm not sure if that is/was happening.
Just curious as to where you are located.

  #12  
Old 11-22-2019, 10:37 AM
Rebel2324 Rebel2324 is offline
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When I originally posted I talked to Brent and he said he might do some at the beginning of next year but was very busy. He rebuilt my engine. I'm in Winnipeg which is 800 miles from him. If I found the first style Primatech header I would go for that. There seems to be some issues with the newer ones.

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