Diseazd Posted January 17, 2012 Share #265 Posted January 17, 2012 I agree with the Captain........Install a set of working carbs and eliminate carbs as your problem. This thread is going to last forever. Link to comment Share on other sites More sharing options...
240260280z Posted January 17, 2012 Share #266 Posted January 17, 2012 I now think it is a vacuum leak because at WOT the manifold and engine bay vacuum/pressure difference approaches 0. However, with the partial throttle opening under light acceleration, the manifold vacuum will increase with rpm and more air will flow into the manifold down stream from the throttle valve due to the increased vacuum with RPM . This plot of the data shows it: Link to comment Share on other sites More sharing options...
Zedyone_kenobi Posted January 17, 2012 Author Share #267 Posted January 17, 2012 Everybody breath and take a break.I am going to install new intake gaskets next and report back in a week or two. Link to comment Share on other sites More sharing options...
Zedyone_kenobi Posted January 20, 2012 Author Share #268 Posted January 20, 2012 PIcking up my intake manifold gaskets today.. .should have them on this weekend or at least by monday. Link to comment Share on other sites More sharing options...
steve91tt Posted January 20, 2012 Share #269 Posted January 20, 2012 Before you put on the new gasket you might consider spraying a little carb cleaner around the intake ports on the head while it's idling. If you have a gasket leak the car will stumble when it sucks the carb cleaner through the leaky spot. I've used this technique before with good success. If you don't see any sort of idle change when you spray the carb cleaner you don't have a significant leak. Link to comment Share on other sites More sharing options...
Zedyone_kenobi Posted January 20, 2012 Author Share #270 Posted January 20, 2012 (edited) I agree Steve, I would bet you I do not have a significant leak. Since my idle is so steady and my vacuum at idle is fairly strong and steady. However, I have bought into the thought I have to have a marginal leak down stream of the carbs that is aggravated by the higher vacuum inside the manifold at part throttle as RPM climbs. All the clues point to this. I can still try that trick though... It cannot possibly hurt anything.Just to be crazy anal, i have ordered a set of new carb insulators from courtesy Nissan so every gasket in the intake system will be OEM new. I am using Fel Pro intake/exhaust gaskets, which I trust.For all I know I have a slightly cracked insulator...so I will replace them and inspect the old ones. Edited January 20, 2012 by Zedyone_kenobi Link to comment Share on other sites More sharing options...
Zedyone_kenobi Posted January 21, 2012 Author Share #271 Posted January 21, 2012 Intake came off with complete ease. There is a bit of buildup on the top of the intake valves and a nice thin layer of soot in the exhaust runners nothing alarming on either side. But I was wondering if it would be advisable to scrub and clean it out. It will no doubt cause a bunch of junk to fall in the cylinders. Better to spray some sea foam while it's running instead? Any advice before I assemble it all back? Link to comment Share on other sites More sharing options...
Captain Obvious Posted January 22, 2012 Share #272 Posted January 22, 2012 It sounds pretty normal to me. I wouldn't go poking that nest. You don't want that stuff to fall into your cylinders.My (amateur) advice is to put the new gasket on and forget you ever saw anything in there. If you clean it off, it's going to come back anyway. Link to comment Share on other sites More sharing options...
Zedyone_kenobi Posted January 22, 2012 Author Share #273 Posted January 22, 2012 I agree, but I was thinking if I wanted to take this down time to rebuild the head. I know my rings are top notch due to the compression test, but I would not be surprised if my valve guides were a little worn. Meh, forget I mentioned it. Link to comment Share on other sites More sharing options...
Zedyone_kenobi Posted January 24, 2012 Author Share #274 Posted January 24, 2012 Will be installing the new gasket this week sometime. The felpro on bottom is far beefier than the MSA gasket on top. All surfaces are clean and I am currently running a thread straightener on all the nuts and studs. Also ordered a new set of thick washers as my set looks very tired. Link to comment Share on other sites More sharing options...
madkaw Posted January 24, 2012 Share #275 Posted January 24, 2012 (edited) Could you please speed up the process a little-we need some closure here:)Is that sealant I see on the old gasket? If so,don't use any on that new gasket Edited January 24, 2012 by madkaw Link to comment Share on other sites More sharing options...
Diseazd Posted January 24, 2012 Share #276 Posted January 24, 2012 Could you please speed up the process a little-we need some closure here:)Is that sealant I see on the old gasket? If so,don't use any on that new gasketDitto that.... Link to comment Share on other sites More sharing options...
Patcon
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