Hi All The PO of my 1975 308 GT4 had removed the driver’s side air pump. Noticed that this port on the vapor filter was pulling vacuum and probably had a hose on it at some point. Is it ok to just plug or does this need to pull air in order to function correctly? I’ve been having some stumbling at around 2800 RPM so have messed with jets (was at 55 but now running 60 idle, 210 AC, and 135 main and about 5.5 to 6 turns out on the mixture screws) and the problem still persists so started looking for a leak. Bases of carbs seem fine, but this was pulling a noticeable amount of air. Before I plug and do something catastrophic wanted to see what was advisable. thanks! Image Unavailable, Please Login
And didn't remove the passenger side air pump? Not part of your problem, but if you do a search on "air injection nozzles" you should get some prior threads on the best way to remove the 2V air injection system (and unblock the exhaust ports). For your runability issue, you might give the ignition advance behaviors an initial look with a timing light just to make sure both banks are advancing quasi-correctly and reasonably smoothly with engine RPM. Have your R2 points been removed, and you are running an R1 only system (or has it all been changed to some aftermarket system)?
Thanks for the response Steve. I actually had a light on it today but as I was doing it alone (and it’s my first time looking at timing on a 8 cylinders!) it was pretty challenging! At idle, on cylinder #1 (closest to distributor on front bank) I can see two red marks on the fly wheel with the timing light set to 0 (picture attached). As I advance the timing on the timing light to 10-12BTDC those are still visible and then they move as I increase rpms which I took to be a good thing. On cylinder 5 (farthest from distributor on rear bank) I don’t see any marks at all from idle to 4k…this, I imagine is a bad thing. Also while I was hunched over the engine I noticed the car really stinks of gas and burns the hell out of my eyes. I wonder if that rear bank is so retarded that it’s not igniting the fuel completely? Apologies for the silly questions: trying to learn about this as I go. Am unsure about the R2 points as I didn’t pull the caps (and wouldn’t know exactly what to look for) but will try to pull them off and make sense of it tomorrow. On another note was considering changing to a Pertronix or other EI solution. My car is a Series 1 (10196) which I read on Birdman’s site means Euro timing and cams. Do you happen to know if there’s a different Pertronix or other EI system for the series 1 cars? Thanks again this forum is a real gem Image Unavailable, Please Login Image Unavailable, Please Login
I think you may not have the cylinder numbering correct as the three red marks in your photo are what you should see when the timing light is on cylinder #5 (i.e., PM5-8): Image Unavailable, Please Login Cylinder #1 and Cylinder #5 should each have three marks on the flywheel (your flywheel looks like it has been resurfaced so some of the lettering is cut off). Usually people put corresponding paint marks, or nail polish marks, on the pressure plate housing to see them better, but, in your case, the red marks are added directly onto the marks on the flywheel edge. For Cylinder #1 there would be something like: 7 deg (BTDC) = this would be for R1 only at 1000 RPM of the 1-4 distributor PM1-4 = TDC for pistons #1 and #4 -3 deg (ATDC) = this would be for R2 at 1000 RPM of the 1-4 distributor and the actual "mark" is the straight line near each group of characters. Likewise, for Cylinder #5 something like: 7 deg (BTDC) = this would be for R1 only at 1000 RPM of the 5-8 distributor PM5-8 = TDC for pistons #5 and #8 -3 deg (ATDC) = this would be for R2 at 1000 RPM of the 5-8 distributor If you do a search on something like "flywheel marks", you should get some prior threads with examples of other people's flywheel marks. But my point was to check how the advance mechanisms are working as the RPM is increased (not what the static idle timings happen to be). The Pertronix is an "R1 only" solution. Doesn't make any difference whether Series 1 or 2 or US vs euro. You have a lot of homework and sorting to do .
Thanks again Steve this is a really generous response and very helpful. I do have a lot of homework to do! I have the WSM but it's not terribly easy to understand (and in other places references to a test bench which I don't have) so have been scouring this forum and elsewhere to see if there's a step by step process I can follow. I am very new to working on cars but managed to set the timing on my Datsun roadster with some help from the forums so hoping I can figure this out with the response you sent. I think I have a plan: You're absolutely right, I mixed up the cylinder numbers and that the picture was of the marks visible when I had pushed the car until #5 was at TDC. When timing light was connected to #5 I could see those marks but none were visible when connected to #1. I imagine the easiest way to proceed is continue to push the car until I can see some sort of lettering #1 is at TDC and then add new marks in a different color so I can spot them easier (as you note the flywheel has been resurfaced so it's really hard to make the lettering out, especially as RPM increases). Once that's done I need to verify whether I have R1 only or still running both. Found these threads you're on from many years ago which should help me understand the R2 points. https://www.ferrarichat.com/forum/threads/308-distributor-r1-r2-problem.29993/ https://www.ferrarichat.com/forum/threads/308-gt4-twin-distributors-timming-elec-timming-and-carbs-adjusting.294241/ Thanks again
Erik mark the timing marks directly on the pressure plate in white paint marker and write the value next to it. Way way way easier to see.
Success! New marks for both banks are done and timing advanced to 10 (the front was around 7 and rear was at closer to 3 so definitely wasn’t done correctly last time). Thank you both for the help. Car runs much better but still a stumble around 2800 I ended up also picking up a Pertronix MR 183 Flamethrower 1 but now realizing I maybe should have gotten the series 2 flamethrower? Ugh learning curve is steep! Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
