bonnet vents and AC

[Doug]

hey there, I have a zed bonnet with no vents in it, but I'm told Zeds that had AC had vents to release extra heat buildup.

Firstly, is this so?

And if it is, will I have any problems running a 'plain' bonnet?

Thanks

[Alfadog]

The early cars were prone to overheat, so they added the vents when they introduced the 280Z (?)

My 240 hasn't had any problems, and it was driven up from Sydney about a month ago (about a 12 hour drive)

As far as I know, teh vents are good to have, but not essential if you dont drive your car hard and long often...

[jcdozier]

I think the heat problems started with the 260's that had all of the new emisions controls, although some 240's (mine) and some 280's have also had heat problems. My early 240Z would overheat in stop-and-go traffic during the summer. I back-flushed the coolng system, went to a larger radiator (the original 240 radiator was pretty wimpy) and installed a thermostat-controlled electric fan on the radiator and cured my overheating problems.

There are hundreds of Z's out there running with the plain bonnet. So long as your cooling system is "clean", you shouldn't have a problem. The electric fan is an easy installl that can provide extra cooling in high temperature situations.

[2ManyZs]

As long as your cooling system is in good condition you shouldn't have any problems. Radiator, fan clutch, water pump, thermostat should all be checked and if they are in good condition you won't have any overheating conditions while driving. If you have problems while sitting in traffic, you can add an electric fan to keep air flowing thru the radiator. One thing a lot of people forget is the fan shroud, if you don't have one you lose a lot of the efficiency of the stock fan. Without it and your stock fan won't draw enough air thru the radiator while you are sitting still.

Of course, you could get a 3 or 4 row radiator to replace the stock 2 row core radiator to improve the efficiency of the radiator.

The hood vents aren't really necessary but if you like the looks of them go ahead and put a set on. They certainly can't hurt anything, especially on a carburated car. They would allow some of the hot underhood air to escape, anytime you can remove the hot air you would be improving the air intake (the cooler the better)into the carbs and also allow the hot air to escape to prevent any chance of vapor lock. Just my two cents.......

[jcdozier]

2ManyZs comments about the fan shroud are spot on. Mine "disappeared" when I had the Z-shop install the oversized radiator, and was probably a big contributor to my overheating problem. The electric fan cured the problem, so I didn't worry about the shroud. (It's still on my list of things to get someday.)

I picked up a vapor lock trick from a Nissan mechanic - insulate the two metal fuel lines that run along the top of the engine. The quick and dirty way is to wrap them with plain old kitchen aluminum foil. Looks tacky, but works - someday I will get the real insulation tubing and put it on (it's on that list too).

[Doug]

thanks alot for your replies,

it is a carburetted (sp?) car, no emission crap on it.

it gets in before the emission regs by 2 months.

2mz's by 'put a set on', do you mean just cut a hole and stick 'em in or? this sounds interesting, if you wouldn't mind giving me some more info...

thanx

Doug

[Daniel]

Doug, Just remember those holes you cut to let heat out also let rain water in.That may not be a problem with you or perhaps you seldom get rain there, but I see it as a leaky roof that lets in moisture causing rust and making it difficult to keep the engine compartment clean.Just something to think about. Have fun!! Daniel

[jcdozier]

I have a '71 240-Z that "lost" it's shroud sometime in an earlier life. When I had stop-and-go overheating problems, I installed a thermostatically-controlled fan in front of the radiator - "cured" the overheating problem for me.

"Pull" is probably a little better than "push", but I didn't have the room on the back side of the radiator.

[2ManyZs]

Doug, it is possible to put the hood vents into an earlier hood. Yes, you have to cut holes in your hood and then drill holes for the mounting bolts(4). Like Daniel said though, it will allow water to enter the engine compartment, but it will also let hot air escape after you turn the engine off. It's a trade off. You should be able to find a set of hood vents without much problem if you decide you want them, in fact somewhere in all my parts boxes I have a pair. I got them years ago to put on a car then decided I didn't want to cut the holes in the hood. Or you could just find a later hood if that is possible.

And to answer a leter question, a "pull fan is a little more efficient as it will circulate the underhood air better than a "push" fan. It may not draw the air as well thru radiator as a pusher, but a pusher won't circulate air under the hood as well as the pull fan. It's a toss up, but any fan will draw much more air if it is in a shroud.

[Doug]

hmmmmm, I just had a thought, would it be feasable to put 'shutters' on there that I could close in rain and leave open when dry? Now, if I can only rig up a system to open and close from in the car I'd be set!!

[jcdozier]

"Shutters" sounds like fun . Be sure to let us know how they work when you get them installed.

In addition to hood vents, our good friends at MSA offer a couple of different options, (or did - my MSA catalog is 2-3 years old). They had a louvered steel hood - four rows of louvers - for about $400. The also had louvered inspection lids for about $45 + core (i.e., you send them your old ones). The catalog doesn't specify whether it's $45 each or for a pair (who would buy just one ).

IMHO the louvered inspection lids would be more for looks than cooling.

[2ManyZs]

I've got another idea, why not take an old hood, get one of the Chevy style cowl induction scoops and bond it on to the hood? But before you bond it on the hood open up a good sized opening under the scoop? Since the cowl induction scoop faces the cowl, the amount of water being sucked into the engine bay would be reduced to a very small amount. Might get some while sitting in the rain or when you wash the car, but some already gets in there anyway.

There are fiberglass hoods you can buy with the cowl induction raised center but I don't know if there would be a way to make it functional. BTW, they do look good on a Z. There are a couple places you can get just the hood scoop in fiberglass and you could go from there.

Just another thought from a tired mind.......:sleep: