Mark Maras

http://xenonzcar.com/s30/files/1973 240z 1974 260z fuel system modifications.pdf Submitted by ZedHead (and maybe others) a while back. Many thanks. The factory printed this in 75. It has some history of the problem on 240 and 260 Zs. While I find it very interesting, I also have to keep in mind that the problem seemingly got worse the more solutions they threw at it. They never did solve heat soak and it continued into the 280's. IMO, the answer lies in the past. The early 4 screw carbs, manifold, possible differences in the steel fuel rail (2line-3line), etc. The fact is, the early Z's rarely, if ever, had this problem using a lone mechanical pump. But, I guess heat soak must have been a problem somewhere, or else they wouldn't have tried to fix it. Even now, there seems to be more complaints of this problem with 3 screw carbs even with the water passage blocked.

Try the fan. You've got nothing to lose except the problem. BTW, If adding choke improves the performance, The engine is running too lean AT THAT POINT IN TIME.

Hmmm. I was hoping that it would have had some effect. Specifically, It would have taken longer for the issue to arise, or perhaps wouldn't have been as severe. Looking at your engine build and ambient temperature in Panama, an under hood fan may be the answer. I'd also consider a vented 280Z hood or louver the access panels on either side of the hood. Just for kicks, the next time you're in the conditions that cause the heat soak (traffic), try pulling the hood latch to allow the heat to escape, just to see if that will prevent the problem.

Curious if there was ANY improvement after bypassing the steel fuel rail? I'm of the opinion that wrapping fuel lines retains heat that comes from the fuel rail mounts, but that's just a theory and probably only part of the problem.

What color are the plugs at 2 turns?

@240znz, are you still with us? We haven't forgotten you. Jalex, As I recall your heat shield is two piece. (can't remember which thread the pic was in.) It's possible that the gap in the shields between the carbs is defeating the intended function. Just a theory. Instead of all this guesswork on everyone's part (don't get me wrong, treasure hunts are fun) have you, (or any other member with the gremlin), considered using an infrared thermometer to measure the temp of the the fuel system components under the hood? You are still connected to the fuel rail by the valve cover aren't you? I think this was suggested by another member a while back. I'm sure that everyone (including you) would love to have raw data to peruse. I'd start at the firewall and work my way forward to the float bowls. The findings would invaluable to you and others with the same problem.

Jai, That message was for Mike. He can wave his magic wand and move this discussion of RedBird's problem to your older "Something's Wrong". "RIP Deanna" didn't seem like the right heading for discussions about Redbird's problem.

@Mike maybe we should take this new discussion of Redbird's gremlin over to Jai's old "Something is wrong" thread. There's sure to be more discussion on this new problem.

Using a voltmeter, measure the battery voltage twice. Once with the engine off and again with the engine running.

Because updates didn't follow model years, I'd check the 73 wiring diagram. 7/72 could, and likely does, have had some 73 updates.

I didn't know they existed. Interesting idea but I have to question how they can afford to give them away at those prices.

I've seen them rust. There has to be some iron in them.

Be careful in the bake cycle!

I prefer the body color. Black is a bear to keep clean. The texture of the bed liner would be a real dirt collector. And besides, you can't wax bed liner like you can a painted drive shaft.

Has anyone run 4 screw carbs on the later manifold? The answer may help point a finger at the probable culprit. Never had "the problem" with a mechanical fuel pump. Here's another puzzle piece to throw into the pile. What about a poor fan clutch? It would contribute to heat build-up sitting in traffic, not when the engine is off. Years ago I swapped the stock metal fan for a flex fan. The flex fan pulled more air at an idle than the original fan.

My early 71 started with a click of the key. If there was ever a problem with heat, the only thing I noticed was it took a couple of revolutions for the engine to start. No problems running at all. That minor change may have been heat soak, to a minor degree.

What carbs and manifolds did you use on the 72 motor? Cliff brings up another possible piece to the puzzle. I've been wondering if the problem lies in the 4 screw (early) carbs and the later 3 screw carbs. We'll leave flat-tops out for now. It's been reported that blocking the coolant flow to the later carbs makes little to no difference. I've not worked on 3 screw carbs. Is the coolant passage the only major difference between the two?

I'm hoping that @kats will translate it. Esso, actually, but they didn't need an answer man, they had a tiger tail one could attach to one's car. Precursor of the Union 76 antenna orange ball.1965, I was 16 years old, $0.30 gas, new cars were less than $3000.00. Good times except for Nam.

I'd guess, "Put a tiger in your tank, but that would date me.

Along with rerouting the fuel line you might want to try insulating your heat shield. Post #29 has Steve's source for it.

I think your first customer is in Panama.

Jarvo2, Yeah, that cam has always been kind of lurking in the back ground. It can't be helping the situation, that's for sure. jalex, Do you know anyone else in Panama that has a Z. I'm curious if anyone else there is fighting or has solved the problem?

No need to re-balance the carbs. Idle speed is your choice. The color of your spark plugs will tell you what to do with the mixture screws.

Good looking heat shield. Do I see a future garage business in the works? A bolt on answer to the heat soak problem would be a valuable addition to the owners who haven'r solved it yet..

Non-fiction-The Technique of Motor Racing, Piero Taruffi Fiction-The Red Car, Don Stanford