Stowell Posted March 12, 2012 Share Posted March 12, 2012 (edited) Ok. So I have a 77' 280Z but the efi has been swapped out to a Holley carb. Why they would ruin a perfectly good system beats me but they did before I bought it. So my problem is that when I start it up it will not idle. <Problem #1. Next when I do keep it running (have to keep giving it gas) the clutch acts as some kind of super gas launcher and when it's pressed to change gears the engine revs up to about 6 or 7k and I have to wait for it to come back down in order to change gears.<Problem #2. Well I decided to park it in the garage to fix it. I see that my headers are leaking air into the engine cabin and also the intake manifold is leaking GASOLINE ONTO THE ENGINE BLOCK! <Probblem #3. Well needless to say it's not going anywhere. I bought a new gasket thinking this was my problem.....wrong. Put the gasket on and it sealed my exhaust manifold leak but the gasoline is still leaking from the intake manifold. The pictures above show the intake manifold only has the screws on top to attach it to the engine. Now many people tell me that the headers are supposed to have some kind of extension that pushes the intake manifold down on the bottom....I do not see this whatsoever. So...in conclusion what am I missing here? I'm stuck in this pile of information that I can not use because I don't know if the headers are wrong...if the intake manifold is wrong...is it just the carb flooding it? Please help as this is my only mode of transportation. Thanks guys. Edited March 13, 2012 by Stowell Quote Link to comment Share on other sites More sharing options...
JSM Posted March 12, 2012 Share Posted March 12, 2012 (edited) First, your pics are not showing up. Second there are nuts on studs that hold the bottom of the intake manifold on as well as hold the header on. I would secure it first with all the nuts and then see how it runs. EDIT: If memory serves me correctly the red circles share holding the intake on: Edited March 12, 2012 by JSM Quote Link to comment Share on other sites More sharing options...
beermanpete Posted March 12, 2012 Share Posted March 12, 2012 The fuel leak is most likely from the carb or a fuel line. A leak in the intake manifold will show up as a vacuum leak. It sounds like you have both. Find and fix the fuel leak first as it is dangerous. The vacuum leak is annoying but won't burn the car down. Check the float bowl gaskets and the screws that hold on the bowls. Check the float valves for wear and dirt. Check the power valve diaphragm. Check the condition of all the fuel lines and the tightness of the hose clamps. Check the fuel pressure. If it is too high it will force the float valves open. It should be about 4 PSI. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 12, 2012 Share Posted March 12, 2012 The intake manifold isn't leaking gas, the carburetor or the fuel lines to it are. JSM's circles are in the right spots. There is a thick washer-shaped curved piece that goes over those studs to span the gap to the intake manifold and clamp it on the edges. The studs apply clamping force to both the intake manifold and exhaust manifold (header flange in your case). There's no reason for your clutch linkage to increase engine speed unless the pedal is rubbing on the throttle linkage. The PO might have run a cable linkage to your carburetor and the clutch pedal is pressing on it. Also, check the carpet down by your feet. Quote Link to comment Share on other sites More sharing options...
Stowell Posted March 13, 2012 Author Share Posted March 13, 2012 It's not the carb...the bottom of the intake manifold where it connects to the engine block is where the gas is dripping from. It's no where near the carb. I went out and bought 8mm studs that go into the block and they fit so I will try and see if that fixes my problem. Still any reason why it's not idling? Quote Link to comment Share on other sites More sharing options...
Stowell Posted March 13, 2012 Author Share Posted March 13, 2012 Sorry about the pictures fellas. They're up now. I took a picture of the brand name of the manifold. Just in case. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 13, 2012 Share Posted March 13, 2012 Follow the flow path of the gasoline from the filter through the lines to where ever it ends. It doesn't flow through the intake manifold. You're missing the clamping washers. Each stud or bolt holds between the intake and exhaust splits its clamping force between them. It's probably not idling because you have a huge intake manifold vacuum leak. You have quite a bit of work to do to get things right. If you've been trying to run it with the gas leak and the vacuum leak, you're on the edge of an engine fire. Lean backfires and gas fumes are a bad blend. The pictures are better, at least they are equally gigantic. Good luck. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted March 13, 2012 Share Posted March 13, 2012 It's not the carb...the bottom of the intake manifold where it connects to the engine block is where the gas is dripping from. It's no where near the carb. I went out and bought 8mm studs that go into the block and they fit so I will try and see if that fixes my problem. Still any reason why it's not idling? Your pictures show poor sealing to the head on the bottom half of the ports. The lower mounting bolts are missing or not installed properly. There is also what looks like fuel stains on the inside of the ports. The carb is probably allowing gross amounts of fuel into the manifold and the fuel is running through the ports and leaking out at the joint with the head. Check the fuel pressure. If the car still has the original fuel pump from the fuel injection system it will have way to much pressure and force the float valves open causing a flooding condition. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 13, 2012 Share Posted March 13, 2012 (edited) I haven't seen this noted before but wouldn't the 60 - 90 psi of a stock EFI unregulated pump crush the floats in the Holley? Just a thought, there may be more work to do if he's got the EFI pump on. Just noticed that the OP has been driving this around like this, with the intake half-bolted on and the Holley pouring fuel in to the manifold leaking on to the hot headers, revving to high RPM. It's got to catch fire eventually. Edited March 13, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
Stowell Posted March 13, 2012 Author Share Posted March 13, 2012 It's not the original pump. And the gasket came like that and for some reason shifted to that position when the exhaust manifold was put on. It won't move to the correct postition. I'm not driving it at all since I found out the gas was leaking. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted March 13, 2012 Share Posted March 13, 2012 On the original z engine the intake and exhaust manifold flanges are close to the same thickness.when you bolted it to the cylinder head they were then clamped with the same pressure under the bolts with the shared thick washers.this is why aftermarket header gaskits are hard to seal on a z.the intake and exhaust manifolds must be the same thickness-this can be corrected by machining .get the original mounting washers-try courtesy nissan.holley carbs can be made to work but its probably jetted rich and the power valves are probably blown.my pic wiould be a set of z therapy su carbs with oem nissan manifolds. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 13, 2012 Share Posted March 13, 2012 Here's what they look like - http://www.thezstore.com/page/TZS/PROD/14037N36 Don't know why MSA calls them "spacers", maybe because they span the space between the manifolds. Even the pros are confused. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted March 13, 2012 Share Posted March 13, 2012 It's not the original pump. And the gasket came like that and for some reason shifted to that position when the exhaust manifold was put on. It won't move to the correct postition. I'm not driving it at all since I found out the gas was leaking. The gasket is installed correctly. The intake manifold shares mounting hardware with the exhaust manifold. There are several studs that are common to both manifolds. These studs do not pass through a hole in either manifold, they are between a port on each. A very thick, large diameter washers spans the gap between the two manifolds and a nut is placed over the washer to tighten it down. It appears that you are missing some of this hardware, or it is not installed properly. Your fuel pump may be correct, but you should measure the fuel pressure anyhow to verify what is it. Even a fuel pump designed for use with carburetors can be intended to be used in conjunction with a pressure regulator. If the pressure at the inlet to the carb is more than 4 or 5 PSI if could force the float valve open, or at least raise the fuel level required to close it. Either way the result is the same, flooding. Since you say there is no fuel leaking on the outside of the carb then it must be leaking inside which will happen when the fuel pressure is too high, of if the float valve or float itself fails. In the case of the Holley, the power valve can also cause internal flooding, as has already been said. Quote Link to comment Share on other sites More sharing options...
Stowell Posted March 14, 2012 Author Share Posted March 14, 2012 Bought the studs I needed and position the gasket properly. Put the manifold back on and the leaking gas problem is fixed.....now fate has somehow slapped me in the face and now my "flap" on my carb is sticking.......wow. The red item (if you can't tell I'm completely ignorant when it comes to carbs) is somehow sticking when the flap is opened. Don't know what the heck is going on here. Also here is a picture of the fuel pump I'm using. And also for some reason THAT's not kicking on either. Touch it to the positive of the battery and it works. Wire it to an ignition fuse and nothing. Btw these problems did not exist before the installation of these studs.....what happened? Quote Link to comment Share on other sites More sharing options...
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