1971 240Z

Restores, Revamps and Repairs
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Moddy
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Location: Palmerston North

Post by Moddy » Tue Oct 28, 2014 6:25 pm

Nothing. Just turns over and huffs out the carbs every few cranks. I say huff coz its not really a backfire coz its not ignited. It just HUFFS out the carbs. Ive just spent the arvo rechecking the cam, crank, leads, dizzy, spark, carbs, fuel pump and hoses/lines. Only thing i couldnt recheck was the compression coz i dont have a tool. Did a 'thumb' compression test and seemed good. Mate suggested the dizzy might need shifting so loosened it and rotated it while cranking and it didnt even nearly start while i was turning it through retarded to advanced. Im seriously at a loss. Im gonna recheck the valve clearances tomorrow coz my mate has my feeler guage. I dont understand why it wouldnt even stumble or fire even once. I must be missing something relatively obvious but i cant for the life of me work out what it is.
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nzeder
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Post by nzeder » Tue Oct 28, 2014 6:32 pm

Did you at anytime drop the dizzy/oil pump drive? Could this be 180 degrees out? Seen this before.

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djz
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Location: Christchurch

Post by djz » Tue Oct 28, 2014 7:20 pm

If you've got a timing light use it when turning the engine over, that will give you an indication if you're anywhere near the correct ignition timing.
Nissan 280ZX 2 seater RB26 powered.

Greensheep
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Location: Auckland

Post by Greensheep » Tue Oct 28, 2014 9:20 pm

Looking at the work that you have done and presuming that you haven't touched the oil pump
My next thought is that the valve timing may be out
Put the crank on top dead centre and check number 1 inlet or exhaust valves have correct clearance and look evenly spaced
One chain link out is all it takes and the engine won't run or even fire.
It's always a good day when you drive a Z

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Moddy
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Location: Palmerston North

Post by Moddy » Wed Oct 29, 2014 12:05 am

Thanks for the help guys. Unfortunately ive checked all these things more than once now. The cam especially lol. I actually did have it on wrong to start with but i worked that out before id even finished assembling the head. Its definitely at TDC with the #1 piston at the top and the lobes on the #1 cylinder making a nice upside down V. *Sigh* i just want to throw it out and put in a RB. Why must my wallet be so empty!
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djz
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Post by djz » Wed Oct 29, 2014 7:05 am

I think your cam timing is out, the lobes should be pointing up.

Image

Image
Nissan 280ZX 2 seater RB26 powered.

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Moddy
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Location: Palmerston North

Post by Moddy » Wed Oct 29, 2014 9:37 am

Thanks DJZ. Sorry, typo, my bad. I didnt mean lobes were making an 'upside down' V. The lobes on #1 make a right way up V as per the FSM and the pics you linked. I actually referenced these exact pics to make sure i had it correct. God this is so frustrating. Anybody want to buy a l24 lol? Oh well. Back to the garage. I think im just gonna pull the whole thing down again and start from the beginning. Maybe i missed something somewhere. God i dont know.
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Moddy
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Post by Moddy » Thu Oct 30, 2014 6:30 pm

Sooooo... i learned a lesson today, much to my own embarrassment and disappointment. If someone tells you they've checked your valve clearances and theyre "all good" it pays to at least stick a feeler guage in one or two just to make sure. The lesson, obviously, is never assume ANYTHING when assembling an engine.

I misplaced my own set of feeler guages some time ago now and have been waiting to borrow some so i could double check my clearances and ensure they are all good, especially considering the trouble im having starting the beast. So anyway as i said previously, i decided id recheck absolutely everything including the cam/crank alignment, valves, dizzy, spark, carbs, etc. Pulled the cam cover off and rotated engine to TDC. First thing i noticed was my cam was NOT perfectly aligned. It had been very slightly advanced when id checked it the day before last and id put that down to chain stretch. Well now it was at least a tooth out. So i pulled the cam gear, realigned it, reassembled it, rotated it through several rotations and rechecked it and now its almost bang on the mark. Id say barely even .5mm retarded on hole one which is expected from a chain with a little bit of wear in it right? As they stretch the engine will retard and then you shift the sprocket to hole 2 and then 3? Sweet. cam properly aligned. Check.

Then i moved on to checking the valve clearances and was horrified to discover THIS ->

Image

And that isnt even the WORST of the gaps! Those were just the two i decided to take a photo of so i would have some evidence of my folly to remind myself in future. So yea, as you can tell my clearances were so up the f*** its no wonder she wouldnt start. Especially when you combine that with the cam being out which then of course means the spark would have been out of time as well. Jeeze. So anyway, they're all adjusted nice and tight now to spec. 0.008 on the inlet and 0.010 on the exhaust.

I also discovered a leak in the carb manifold when i was fiddling with the dizzy yesterday with my mate so ive repaired that and reassembled everything and now im just going to leave it to harden overnight before i cross my fingers and turn the key tomorrow morning. If she doesnt start now im seriously just gonna bin the engine hahaha. Ive got a bloody L31 lined up to trade with my mate and he didnt even care if i had the head fitted to the L24 or not! I thought id drive it for a bit before i swap but now im kinda regretting the decision.

Is anybody still running the L24 and had experience with the L28/31? Im curious as to whether people actually prefer the revvier L24 to the torquey L28 or L31?
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nzeder
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Post by nzeder » Thu Oct 30, 2014 9:21 pm

That is some gap you had there.

Re the L28/31 question you can make them rev too so don't fall in the l24 is more revvie thing but the extra cc and torque is very nice. But what is your plan/usage of the car? A good L24 can very nice on the road.

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Moddy
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Post by Moddy » Thu Oct 30, 2014 9:26 pm

In terms of the 'revvie' thing, i was just quoting my friend. He wants the L24 coz his dad rates them more than the bigger engines. He reckons they rev better and make top end power or something like that. Doesnt make sense to me but im pretty happy to trade my L24 for his L31 with LD crank :D Id originally planned on putting in either a V8 (1UZ or LS1) or a RB of some sorts. I dont want this car to turn into a never ending project in the quest for more power that will inevitably come with one of those engines and despite the problems, its actually really nice working on the old carbied engines. As time goes on the idea of just having a L-series with some sweet triple webers is becoming more and more appealing.
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marrow
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Location: New Zealand

Post by marrow » Thu Oct 30, 2014 11:02 pm

Well, 'no replacement for displacement', you could always get yourself an l28 and convert it back to run triple carbs, with a lighter flywheel to make it feel more 'revvy' if that's what interests you.
That would sound excellent too

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Moddy
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Post by Moddy » Thu Oct 30, 2014 11:55 pm

Hahaha, just to clarify, im not after 'revvy' haha, ive always bin after displacement. Im just wondering if any of the more experienced zedders on here know of any reason why someone would want an L24 instead of an L31. Doesnt make sense to me. The L28 or L31 can be made into weapons with relative ease. Yep, i dont get it lol.
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nzeder
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Post by nzeder » Fri Oct 31, 2014 12:00 pm

Spend $$ on making a zed handle better will give you more fun for $$ than a larger engine. That is my opinion only I have owned a few zeds over the years and the biggest improvement on a road zed is suspension upgrades. I have owned L24, L26 stock L28 and a L32 powered cars. A stroker is very nice the torque is great for pull out of the corners aka to go with your suspension upgrades. A L28 stock with triples and good exhaust setup sounds great and will go well on the road - my first race car was just that a stock L28 bottom end, stock head just a mild cam triple 40mm webers (or mikuni I had both and ran both). The car was an auto to start with just had a high stall fitted. With suspension mods it was fast on the road just down on power and gear choice on the track vs manual 240z with more work.

My current racecar project will be getting a stock l28 with triples again this is so $$ can be spent on things like ignition timing, suspension and the nut behind the wheel. After a few seasons of running again a fresh L28 will be built with some lighter pistons rods etc to extract more power. But a stock L28 with triples will do me for now.

So I would stick with the L24 and put the $$ on suspension/brakes first then go for more power but again my opinion.
Last edited by nzeder on Fri Oct 31, 2014 12:49 pm, edited 1 time in total.
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Moddy
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Post by Moddy » Fri Oct 31, 2014 12:30 pm

Thanks for the feedback Mike :) I've actually got a whole host of suspension upgrades waiting to be fitted. Im just trying to sort out some weld on stubs for my coil overs. I figured instead of doubling up on the work I'd just fit the whole lot at once. Now experience tells me that once I've stiffened up the ride I'm going to need to brace the chassis to prevent cracks forming etc. Is it your experience that these old girls need some extra bracing once you've stiffened them up? I was intending to start with strut braces front and rear as I'm trying to avoid a cage. Possibly make some braces to bolt across the frame rails to stiffen the bottom too?
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Greensheep
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Post by Greensheep » Fri Oct 31, 2014 6:34 pm

Difference between the L24 and the L26 was a longer stroke which made the engine very torquey
Difference between the L26 and the L28 was a larger bore which bought the engine back square again
Depending on the bore of your L31 whether it is a squarer engine or not
Generally speaking a well balanced square engine will be revvy
How much was spent on balancing your friends L31?
If you increase the hp too much the rails in the chassis will need strengthening I think there is a thread on the forum showing the photos of a 240z having rail strengthen and extended
Personally you can beat the handling and sound of a well put together L series as it pulls toward 8000 rpm :D
It's always a good day when you drive a Z

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