redzedsled

Agreed! He did say that the difference of 7 thou was no big deal either, but why the difference once installed?

No, he was disenchanted and frustrated, with no answer except to machine the top of the pistons. Not something that should be done in my mind. I have seen a few threads where the piston and valves were on a collision course, it can't be good.

Hi Steve, I think I am going to go with the FelPro gasket, not sure of thickness. I think I might need a head gasket between my left and right lobes of my brain!

The ITM pistons were ever so slightly taller when they were both placed on the same wrist pin together for measurement.

The crank was from the original engine to my knowledge. The original connecting rods were used and were not replaced. They did remove 10 thou off the crank, and thus inserted the Clevite Undersized Rod and Main bearings if that tells you anything. I have read that some of the stroker engine guys use two head gaskets instead of one, but there has to be another answer.

Hello, My engine builder has just informed me that after mounting my pistons, ITM brand, item number RY2516-030, they are protruding above the deck of the block. The top of the P30 block was decked with about 5-7 thou removed, so that is not the problem. They measured the piston height to the old ones that came out before mounting (a slight difference of 5 thou) and after mounting them on the rod bolts and into the cylinder, they protrude about 30 thou above the block, Does any one have a theory as to why this would happen.

Thanks for the advice on calling Robello, they told me that he uses the Genuine Nissan part number 11044-N4221 in all his race engines. The larger firing ring, he stated, will not make a signficant difference. This is the only known gasket that Nissan makes that has all the water passages required.

Point well stated!

That is the beauty of this forum, many opinions and many options. Has anyone used the FelPro Perma-Torque head gaskets, I can get my hands on one of those very easy. The engine builder noted these were very soft gaskets years ago, but maybe these new type of FelPro gaskets have changed. Having not put one in my hands, I am assuming they have a steel core.

Steve, After reading carefully between the lines I see the importance of your comment on the oval firing ring having more clearance if you are to use the oversize valves. Point very well made...

I found this one on ebay, it is Genuine Nissan part number 11044-N4221. I imagine the firing ring would be 89mm round.

My engine builder is Heads Unlimited. They have been in business for over 40 years and the owner is doing the assembly has done many of these engines. Alf is the owner is doing the assembly work. Their website is http://www.headsunlimited.com/ BTW thanks for the English lesson

All very valid comments. The supercession chain suggests that all roads lead to the 11044-27L01, which is NLA. This is the gasket that I have in hand I'm sure. I have a copy of the Nissan Fast Supercession software but it is not current. All these part numbers are now obsolete within this chain according to my Nissan Dealer. With respect to the quality of "Stone", I would not disagree with you about their general quality, but this gasket I have really is world's apart when I compared them to the ones that were on the shelf at Dan's Z Shop. The other gaskets I have seen are very soft and require retorquing. The Felpro Perma-Torque brand does not require retorqing so I have learned. I showed the engine builder an aftermarket gasket, not sure of brand, and he thought the 11044-27L01 gasket was far superior. I still remain torn... I have trusted Beck Arnley and find their parts to be as close to OEM as possible. I just can't get my hands on one soon enough. I think my engine builder is losing patience with me, as he is chomping at the bit to get it bolted together. Time just does not permit.

Most all of the head gaskets I have seen do not have the oval firing ring. I do have a copy of the book you mention, but at this stage of the game everything is ready to be bolted up. Having said that I am running a very stock E31 head with the standard sized valves with 30 over flat top pistons. I did lay the head gasket down, and I commented to the engine builder that is was very close to the pistons and his response was "you want it as close as possible without interference". This engine builder had concerns about blocking off water passages though yet Dan at the Z shop (a Nissan technician), who works with Z cars as his profession, thinks the new style of head gasket with the oval firing ring is the way to go, despite the water passages being restricted with this gasket. In fact he had other 240Z head gaskets on the shelf, and all had the same water passage holes as I mentioned, along with the oval firing ring. I managed to find images of a Genuine Nissan head gasket for a 280ZX, part number 11044-P7911, and there is an absence of water passage holes entirely. See pics below for reference.

To be honest, I never really explored the larger valve option, so I really couldn't comment on the block notching. You bring some very interesting points in your discussion though. If the larger firing ring doesn't affect compression too badly, then may be the 280 HG would be the answer.

Steve, although I am running stock valves, another consideration is the use of over-sized pistons. If you use over-sized pistons like most would during a rebuild, it also makes the head gasket even closer to the firing ring edge. The stock bore is 83mm, and with say a 40 over piston it brings the bore up to 84mm. With a stock factory firing ring measuring 85mm x 89mm, that only leaves a 0.5 mm clearance around the head gasket in some areas. Just another observation I had along the way. A larger firing ring would provide more clearance, but how much does it affect compression. The later 260Z and 280Z head gaskets at least don't block the cooling holes coming up from the block. Still torn and have to make a decision quick whether to use the Stone head gasket!

After downloading the Stone Gasket Catalog online, the profile of their gasket for the L24 is part number JA-01067, which is exactly like the gasket I have from the regrind kit. This gasket supercedes part numbers 11044-U8720 and 11044-27L00 respectively. The L24S, and L24E engines on select models also use this gasket. Whatwith depleting Genuine Nissan engine parts available we are at the mercy of the aftermarket companies who are making one size fits all gaskets it seems. Or does Nissan have pure logic in mind when blocking off some water passages from the block to intently restrict water flow as some have suggested. It seems that the L24 blocks after the 240Z era began to utilize less cooling passages up through the block to the head to support this notion. This is noted in the image of the 280Z block where fewer holes are running vertically though the block and into the head. Is the firing ring size more important than the distribution of cooling through the earlier L24 blocks according to the gasket maker Stone in this case. Often with Nissan supercessions, parts and their fitment can become lost in translation, and Nissan parts support centers here in Canada are not very helpful. This issue will arise for more Datsun 240Z owners as they try and locate the correct head gasket for their restoration. I see many of this type of new design gaskets being purchased online, so I hope to see more thoughts and insights.

Yes, this is the section where the passages are blocked.

Hi Zed Head, See earlier posts for comparison of Original and Stone gasket...

Thanks very much for this thread link. I think it proves my theory that the gasket is similar to the F54 block based on the water passages drawing you so kindly mentioned. The F54 block was for the 280ZX and the bore would have been 86mm, perhaps the later L24 blocks were equipped with a reduced number of water passages. I asked the engine builder if he felt he could punch in four more holes in the gasket and use it, but he was very apprehensive. This gasket is not your typical composite head gasket it is very tough and most likely difficult to punch. Still at a loss why the later blocks had reduced cooling passages.

I don't have ability to put the gasket on the head at this time. But I found a pic of a F54 block and this gasket seems to fit the cooling passages of this block. There seems to be more water passages in the E31 and P30 blocks than the block shown below. Please see reference pics below with a side by side comparison of head gaskets. original on top, new gasket at bottom. Please see passage holes indicated in red to show which holes are blocked below:

Please see attached images of the head gasket. It is supposed to be a graphite type head gasket and was confirmed it was from a 240Z Regrind Kit. When I looked at it on top of the block at the engine builders, there were a total of four holes obstructed from the passages that extends into the block. It is stamped L24 Nissan and Stone. Dan at the Z Shop, from whom I purchased the gasket has suggested that this is the correct gasket as the later L24 gaskets had limited cooling passages. He had a generic Felpro gasket on the shelf, with the fire ring measuring 89mm round, with all passages present. The 280ZX gasket he had on the shelf actually had the water passages blocked completely, and was also 89mm round. So which begs the question are all of the cooling passages really necessary, and why would they change the design. Can anyone help me to understand why they would block off these passages to the block, yet leave selective passages open.

See reference pics below showing ring dimensions. Aftermarket generic head gasket at top and original head gasket off E31 head at bottom. Nissan superceded to 11044-27L00 and 11044-27L01 most likely because of the size this oval ring. The only issue is the Datsun 810 and early Maximas gaskets dont have the same cooling holes as the original gasket.

Thanks to all who gave their valued opinions, I really appreciate it! I managed to find a Nissan Head Gasket from a re-grind Kit. I believe it to be from a Datsun '77-'81 Datsun 810 or a very early '82-'84 Maxima. It is stamped Nissan and "Stone" on the gasket itself. The slightly oval openings are just as my original gasket was at 85mm x 88.5mm designed for a 83mm piston. I would have taken some pics but I had the engine builders awaiting the gasket to button everything up. The mechanic placed the gasket on the block and it mated up perfectly. Thanks to the Applewood Nissan boys in the parts department who outsourced the gasket, they just may have bailed me out! My only concern is that the original gasket had different openings for the water passages at the bottom of the head. There seems to be two types of head gaskets for the 240Z out there, one with numerous water passages, and the other with selective passages. The engine rebuilders are going to call me in the morning with respect to any blocked passages as it was closing time when they called me with the fitment. Does the fact that this type of gasket has fewer cooling passage holes (to match the head) effect the cooling of the block? I have tried to research many other similiar message threads but come up empty as to the proper answer.

Nismo has just stated that 11044-E4620 is now NLA and Out of Production.