JK 24v 3liter ..at last!

Jim K
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Re: JK 24v 3liter ..at last!

Post by Jim K »

Oh, I see! Well, something we SHOULD have in our engines! :mrgreen:
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Jim K
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Re: JK 24v 3liter ..at last!

Post by Jim K »

Here is an important point to remember for anyone interested in changing cams in their 24v engines. Many think all 24v 3liter and 3.2 heads are basically the same. Well, they are not, and especially concerning the cam journals. There is one style for 164 series cars and one for 166/156 etc 3.0/3.2 heads. This journal difference is of course carried to the cams. To make a long story short, 164 cams will fit in later 3.0/3.2 heads, but not the other way around that is, later 3.0/3/2 cams will not fit in 164 heads, unless you do a lot of relief work to enable unobstructed cam rotation. Notice the pic where the different position of lobes is clearly evident.
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75evo
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Re: JK 24v 3liter ..at last!

Post by 75evo »

WTF? Then my cams won't fit? My 75 has heads from a 164 24v. And not to mention GTA cams have been fitted in loads of 164s.

Well I hope my cams came from an early 166/156.

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Re: JK 24v 3liter ..at last!

Post by Jim K »

What? Gta cams have been fitted to 164 heads? Yes, with a lot of work for intake cams, just like I did.

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Re: JK 24v 3liter ..at last!

Post by kevin »

Their is no early 166/156 :)

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Re: JK 24v 3liter ..at last!

Post by Saabretooth »

Jim, just checking, and I'm sure its been answered before in this thread.
Can the cams work with standard lifters of the 3.2 GTA engine? I recall that the answer is yes.... BUT.....

I just did a compression test and all the cylinders were doing in the region 250psi except for Cyl 2, which is just under 100psi

Car's in the workshop now to test if its a jamed tappet/spring.
Head's been skimmed 1.4mm which I've been told, raises the compression up to 11.1:1. last piece of advice I remember was that the engine is good for 7600rpm without balancing the crank.
Rev limiter is at 7300 on a FWD 3.2 GT, so I'm wondering if anythings the issue with the tappets, and if it would be better to use solid lifters instead?

Either case, high EO consumption, and periodic fuel smell in the cabin points to a potentially bent valve. I hope its not piston rings or liners. There's no white smoke out of the exhaust.

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Re: JK 24v 3liter ..at last!

Post by Jim K »

Hi Daries,
No problem with the hydraulic lifters, they are the same in all Alfa 24v engines. I just started my 3.2 with the -still secret- 10.3mm cams and it pulls great! If you have matched valve springs, I wouldn't worry about 7600rpm either.
Too bad about the half-dead cylinder, can be a costly issue! I hate to think about the work involved to pull the rear head off a fwd 24v car! :shock: Its worth switching tappets from another cylinder to verify if the problem 'moves'.

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Re: JK 24v 3liter ..at last!

Post by Saabretooth »

Did the compression tests again and all cylinders are showing 250-260 psi/ 18 Bar
So no issues with bent valves, or leaking piston rings....

Lambdas replaced, at least 3 times, and car runs fine on the throttle with matching lambda signals on the graph, but gets a lazier lambda reading for the rear bank pistons 1,2,3 when at idle..

Am wondering if its a fueling issue, or the map issue. Misfire signals come up for the rear bank rather often at traffic lights. Are the stock injectors and fuel pump sufficient to keep the car going?

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Re: JK 24v 3liter ..at last!

Post by Jim K »

If the fuel pump is good (and preferably tested for delivery/pressure) you shouldn't have issues with your power levels; same with the injectors. As for different lamda between the two cylinder banks... you need a genius for that one, like Festy! If anyone can figure it out, he can. 8)

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Re: JK 24v 3liter ..at last!

Post by kevin »

I have seen a few 24v engines with broken hydraulic lifters with standard cams . ( probable because my mate owned an Alfa workshop ) Only one lifter breaks . It looks like the piston of lifter punches through into casing . Does the engine make any ticking noises at idle or even rev up .

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Re: JK 24v 3liter ..at last!

Post by Saabretooth »

Really weird thing happened.
I changed out the Lambda
And still misfired at idle. But it improved the lambda signals

Changed out from 0.7mm gap plugs to 0.95mm gap plugs. Improved a lot more... But still misfired.

Changed out 5W50 oil (3 weeks old) to 10W60 oil and the misfires disappeared.


I'll keep an eye out for it the next few days.

No weird sounds from the engine.

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Re: JK 24v 3liter ..at last!

Post by Saabretooth »

Is it possible that its a mistimed rear cam, even its just a teeny weeny little bit?

With 1.4mm shaved off and the 10.0 cams, will that damage the engine if its even a little bit off?


The misfire @ idle is back again today, but 2 x only. Greatly improved over the last couple of weeks.

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Re: JK 24v 3liter ..at last!

Post by 75evo »

The cam sensor is on the rear bank. So a mis timed cam will very likely cause a problem. Maybe the ECU has a method to calculate the maximum tolerance between the arrival of the crank TDC pulse and the cam pulse. Maybe if it is mistimed and it exceeds the threshold of tolerance the ECU will flag it as an error.

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Re: JK 24v 3liter ..at last!

Post by Jim K »

WHAT DO YOU MEAN MISTIMED CAMS? :o You can shave the heads by a lot if you want and still be able to set the cams on their std marks so no problems anywhere. You properly tension the timing belt before you tighten the cam 19mm nuts at TDC, ie with the cam wheels loose. You then line up the marks in the rear of the cams with the head alloy one cam at a time and tighten the respective 19mm nut. When you're done, everything is timed correctly and all sensors will give properly timed signals.

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Re: JK 24v 3liter ..at last!

Post by kevin »

I think I will put money on a hairline crack in one of the coil packs or even tiny hole in suppressor below the coil pack . Take front coil pack cover of get car hot ( at night , turn lights off) and look for arcing . You might even see it in back bank under plenum . I have a 24v spider and 156 24v which my family members use in sa and had misfire issues that was intermittent . It was coil packs in the end .
The magnetic pick up on back makes no difference even if cams are 2mm out with extreme lift cams . I know from setting my cams way off marks while experimenting on the dyno . Don't try this as it gets very close to valve touching piston time .

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