vtdds71

(same post on ZCar.com - trying to cover more bases!) My '72 Z is finally back on the road again, and is actually running quite well. But, the engine is slow to fire up when cold, even with full choke engaged. Takes several seconds of cranking, then coughs to life, then immediately runs quite well on choke until reasonably warm. It will re-start instantly when warm, and when the car has not sat overnight. My sense is that the fuel lines are draining to empty after an extended shut-down, and the fuel pump (stock mechanical only) has to start from scratch to pump fuel from the tank to the carbs. Is there some type of one-way check valve in the system that is supposed to prevent this? Is the fuel pump malfunctioning? The engine has been "de-smogged". Carbs have been cleaned and rebuilt and show no sign of leaking, the gas tank was cleaned and re-lined, new fuel lines and in-line filter were installed, etc. Mechanical fuel pump may be original, but it does seem to pump plenty of fuel when tested. On a related subject, I did buy a Holley electric fuel pump from MSA some time ago, but have never installed it. Is this a good add-on for the early Z's? Is it better to use it in conjunction with the mechanical pump, or as the sole fuel pump in the car? Where is it best installed, and can anyone clearly describe the best way to wire it in (relays, etc.)? Thanks.

Again, thanks for the further info. The new 280ZX MC arrived from Black Dragon today, so I may just go ahead and swap it for the stock 7/8" unit, although I think the stock unit is pretty new, and in very good condition. I'm going on the assumption that the 15/16" unit does work better in the end with the Toyota caliper upgrade I've installed on my car. If it really doesn't do all that much, I'd just as soon keep the original and return the larger MC for a refund. Just getting to be a pain swapping all these parts around, re-bleeding the system, etc., so it would be nice to just hit the target the next time, and move on to a different issue on the car! Sounds to me like the correct length of the booster pushrod is a variable thing, depending on how much free-play you want in your brake pedal. I agree that a little gap between the pushrod and the MC is essential, but wonder how much to be safe. Maybe some close measuring and experimentation needed here. Thanks again.

Hey Blue 72 - Thanks so much for the great tip. I opened up the booster as suggested, and found the loose reaction disc inside. It's now epoxied onto the back of the actuating rod and ready to reinstall, except I just got a post from a similar thread on Zcar.com in which someone said I will also need to replace the actuating rod with one off a newer booster. He said there's no way to extend the OEM rod enough to adapt it properly to the larger 280ZX MC! Is this true in your experience, or were you able to adjust the original rod length to work correctly? Thanks again, you've saved me hours of frustration, I'm sure!

I have recently installed the 4-piston front caliper upgrade kit from MSA on my '72 Z, and am finding pedal travel to be way too long, as noted by others. I have ordered a '79-'81 280ZX master cylinder to replace the stock unit, as suggested, but others have said this should not be necessary. One person said the "reaction disc" may have come loose inside my brake booster, and that would cause long pedal travel and grabbing of the brakes. Removal of the booster did not detect any loose parts inside the vacuum chamber, and the booster had otherwise passed all the usual function tests (no loss of vacuum pressure from 19.7" Hg when engine shut off, either with or without brakes applied). I briefly tried to twist the two halves of the booster apart to check inside, but they were really tight, and I didn't want to risk damaging what may be a perfectly good booster. The booster vacuum line check valve seems OK, and I've carefully bled all the lines, especially the MC itself. ALL brake lines have been replaced with stainless steel equipment from Classic Tube, and rear brake cylinders are new. I'm ready to proceed with the larger MC installation, unless I've overlooked something else. Suggestions? Have others found the larger MC will actually give a large improvement, and shorten the pedal travel as hoped? I saw in a previous thread on this site that the actuating rod from the booster has to be lengthened once the larger MC is installed. How much longer should it be? Should I just measure the distance from the outside mounting flange of the MC to the base of the receiving cup inside the MC, and extend the rod by that difference? Thanks for any suggestions you can give me.