[Pistons protrude from block - thicker gasket?]

 

This is why you use the USED gasket to set your clearances, not a new one. You can waste a new gasket to check them (compress it, then throw it away) if you want to, but most guys just keep the old FelPro sitting on the wall to aid in clearance checking. There will be no measurable difference between clearances arrived at using a used gasket, as opposed to wasting a new gasket. You just save the cost of the gasket.

 

 

Thanks, that all makes sense; and confirms what I thought, that the thickness of a compressed gasket can be counted on before installation.

 

It also confirms what I thought, that use of clay is most relevant for determining piston to valve clearances.

 

For piston to head clearances, you can measure the amount of pop-up and you can measure the thickness of a compressed gasket; unless I'm still missing something, then the difference of the two numbers is the measured piston to head clearance (and should provide the exact same number as claying the chamber).

 

It would seem that a listing of expected compressed gasket thicknesses for all common gaskets would be a useful resource. Has anyone ever put one together?

 

I envy you and others who have multiple old gaskets lying around, and a wealth of knowledge (I hope to gain from). My project is the first time I have ever been so involved in an engine for my car, and is likely to be not only the first but the last engine I build (I have owned my car for 34 years with a couple of used engines and a couple of rebuilds done by others; I am trusting this one will last me another twenty years of cross country pleasure driving with maybe a head job in 10 years).

 

So can you tell me what the compressed thickness of a Felpro 8799 is? I have heard it is about 1mm, but is that .040 +- .001 or .042 +- .001? I have no idea.

 

Do Cometic MLS gaskets change in size when compressed, or are they the same height as advertised (I read this in another place, but again i have no real world experience or knowledge)?

 

Thanks for your continued patience.

[Pistons protrude from block - thicker gasket?]

Give my your data on compressibility repetition of various gaskets, and try that angle.

 

They say to use a previously compressed gasket as it's a known quantity. If you change to a different gasket, the 'thickness' uncompressed is what compressed again? Nobody knows.

 

The only way to KNOW thickness is to do a physical CHECK.

 

This is a problem with engineers, they calculate. They recalculate. They BUILD it and wonder where that knocking sound comes from...

 

This is one of those things where you measure to PROJECT your needs, but ASSEMBLY and CLAY CHECK is the ONLY way to KNOW what you have.

 

If you do this for valves in a dynamic state the results are similar. Same for the piston to head clearance... the way to know is to physically measure.

 

Anything else is just a guess.

 

I still am confused by part of the process.

 

In the end - when you do the final assembly of the engine, do you use a new head gasket?

 

If so, how do you know the compressed height of that new gasket will be the same as the used one you had for your measurements?

 

If not, how many times can you re-use a head gasket? I thought it was advisable to use a new one every time.

[Pistons protrude from block - thicker gasket?]

EXACTLY! They are NOT 'zero deck height' engines, 0.020" range is not anything to be concerned about...and changing gaskets without an actual PHYSICAL CLEARANCE CHECK is foolish.

 

Assemble the engine, determine what you need, DO NOT GUESS!

 

I understand how measuring is the only way to know exactly what clearances will be; however, I am a bit confused on a number of things.

 

If I understand correctly, a head gasket should only get used once - and all instructions for measuring clearances say to use a used gasket in the process. So any measurements taken would only be valid in the field for a new head gasket that compressed to exactly the same thickness as the one you used in your measurements.

 

If it is valid to say that using a new version of the same gasket as the one used in measurements will give the correct results; then why wouldn't it bevalid to say "if your pistons protude .025 from deck then you will need a gasket of xxx thickness - and your options at that thickness are zzz or yyy"?

 

I am not the first person to use a P() on a block with flat tops - I am assuming not the first whose pistons protuded .025 (I have in this thread learned that all engines protude in the .020 range), I am just looking for experience in selecting a gasket.

 

Also, the fellow who built my engine has built many engines, but not a lot of Datsuns. His concern is mostly from stretch at higher rpms (if I understood him correctly) which of course is something a static measurement can not tell.

 

I am not trying to be argumentative, I am just trying to get my engine in my car - which I had hoped would happen in June, and is ready to get assembled today - assuming I have a head gasket I can safely use.

 

I remain confused - sorry.

 

 

Also, I can understand how clay measurements may be more necessary to determine piston-to-valve to deal with head shaving and various lift cams. I have an extremely modest cam (Don Potter mild street, designed for stock springs) so I am really only concerned with piston-to-head clearance - which should be able to be determined by measuring height above block and knowing head gasket thickness. Please correct me if i am wrong.

[Pistons protrude from block - thicker gasket?]

I saved the following thread a while ago because it had some interesting considerations and numbers.  Quench and piston rocking,  I've also seen that you either want to be in the "quench" area or completely away from it.  If you're not in it but too close you can actually create a detonation zone.  No facts to back it up, just a consideration.  Some people seem to think that the Datsun "quench" heads weren't doing any quenching at all.

 

http://forums.hybridz.org/topic/106806-long-rod-short-piston-combo-l28-tech-questions/?do=findComment&comment=999867

 

Numbers-wise, .025" = 0.635mm.  So with a 1.25 mm HG (after installation), you'd have 0.615mm or .024" "quench" zone.  So your mechanic might be right, depending on which part of the discussion in the thread I linked you look at.  BRAAP suggests that .014" quench is "perfect" (Post #16), but two others stop at .028" and .025".  

 

So according to Braap (if i read correctly), then with .025 protruding and a Fel-Pro (1mm compressed, I believe) then it should be perfect.

 

So which gaskets are 1.25mm compressed (for safety, and slightly over .020 quench)?

[Pistons protrude from block - thicker gasket?]

The E88 and P90 headshave totally different shaped combustion chambers.

 

In an E88 the piston can stick above the deck (and probably the gasket) with no ill effects; on the P90 this can't happen.

[Pistons protrude from block - thicker gasket?]

Yes, they are cast - but getting a 1.5mm head gasket would be much cheaper.

TEP has 1mm and 2mm MLS in stock.

It looks like there is a TOMEI 1.5mm; just wondering if there are others?

[Pistons protrude from block - thicker gasket?]

I have an F54/P90 combo with ITM .040 oversize flattops that is just about ready to get put together.

 

The fellow doing my machine work has let me know that my pistons protrude from the block deck by .025 and he feels i should use a thicker gasket than the Felpro one I have sourced.

 

Any suggestions on an appropriate gasket?

 

Any other solutions?

 

Thanks

[P90 vs P79 part numbers ?]

That makes sense - since it is the different part.

 

Except it should only show up when searching for a 1983 (the only year with the P90A head with hydraulic lifters).

 

So would a P90 share all of the same valve/rocker parts with a P79 then? I think so (and hope so).

[P90 vs P79 part numbers ?]

NissanPartsZone.com has good diagrams providing most part numbers...

 

...however, in the "Camshaft and Valve Mechanism" page for the P90 (81 & 82 L28ET) most of the parts in the diagram are not in the table (hence no part numbers are provided). see http://www.nissanpartszone.com/Page_Product/PartDetail.aspx?ModelName=280ZX&ModelYear=1982&ModelSeries=S130&FileType=268&SelectConditions=%281%3d2S%3b2%3dL28ET%3b3%3dJ%3b4%3dMT%3b5%3dF5%3b6%3dT%2fR%3b7%3dFED%3b%29&ShowConditions=%281%3d2S%3b2%3dL28ET%3b4%3dMT%3b%29&seeDesc=False&goBack=True&SectionNo=&ComponentsNo=130&PartSortBy=PartCode#ctl00_cphView_pnlPartList

 

For the P79 the table is virtually complete. see http://www.nissanpartszone.com/Page_Product/PartDetail.aspx?ModelName=280ZX&ModelYear=1981&ModelSeries=S130&FileType=268&SelectConditions=%281%3d2S%3b2%3dL28E%3b3%3dJ%3b4%3dMT%3b5%3dF5%3b6%3dC%3b7%3dFED%3b%29&ShowConditions=%281%3d2S%3b2%3dL28E%3b3%3dJ%3b4%3dMT%3b6%3dC%3b7%3dFED%3b%29&seeDesc=False&goBack=True&SectionNo=&ComponentsNo=130

 

Are most of the unlisted parts in the P90 table the same as in the P79 table?

 

I wonder, since some parts are different; such as item 13234, the rocker adjust screw, is part no. 13234-21000 for the P79 (which is available) but is part no. 13234-P9900 for the P90 (which is "Limited Availability").

 

Is there another source to find P90 part numbers?

[Can't find flat top pistons]

OK, I get that ITM are good for stock RPM range (that is all I am aiming for).

 

I have heard that people have had issues with their rings and it has been suggested to get Hasting 2C6142 instead (chrome upper ring).

 

Thoughts, feedback...

 

 

PS. Any hope in the world of finding a set of OEM oversize anywhere? Really hoping someone bought a set, and then decided to go forged when they did their build, and have these available to sell to a good car (mine is a 72 240z that i have owned for 34 years, and am hoping to build a good strong, long lasting engine for).

[Can U20 valve springs be used in a L28 ?]

Didn't want to risk it, and couldn't get a defnitive and authoritative "yes, they would work" so i ordered OEM L6 valve springs.

[Head gasket thickness - a few questions]

I am trying to assimilate everything I've read in many threads - and having a bit if a hard time. So a few questions...

 

1. what is the OEM gasket thickness compressed?

I have read 1.25, 1.2 and 1mm; shouldn't be a big difference, but would like to know

 

2. do deviations from stock thickness result in tightening (or loosening) of the timing chain?

if so, is it an issue

 

3. what is felpro compressed

again I have seen 1.2 and 1mm

btw. is this the right Felpro for a F54/P90 combo  http://www.carpartsdiscount.com/auto/parts/catalog/nissan~280zx~81.html?3593=274533

 

Thanks,

 

Rick

[WTB: 87mm (.040 over) cast flat top pistons]

I am building a F54/P90 with an AZC 4barrel for my 72 240Z street only car. Looking for 87mm flat tops, only need cast (and want their longer life).

 

If anyone has an OEM set they don't want - great.

 

Seems everyone is out of the ITM.

 

Does anyone else make them?

 

I really don't need or want to spend on forged.

 

Thanks for any leads.

[Mismatched head and block - which gasket]

Sounds reasonable, but...

 

I've decided to completely avoid the issue, and will be using an F54 block to go along with the P90 head.

[Mismatched head and block - which gasket]

Please don't tell me to search - as you will see, I have. And the answers vary and contradict.

 

I would like people to provide explanations for the answer, and not just a vote.

 

 

Here are some, match the head posts:

 

http://forums.hybridz.org/topic/93164-preparing-78-280z-for-turbo-swap-reusing-stock-block/?p=878887

 

http://forums.hybridz.org/topic/68264-which-head-gasket-l24-p90-turbo/?p=642230

 

http://forums.hybridz.org/topic/68264-which-head-gasket-l24-p90-turbo/?p=642327

 

http://forums.hybridz.org/topic/68917-p90-head-on-a-77-block/?p=1105677

 

Here are some match the block posts:

 

http://forums.hybridz.org/topic/92946-putting-p90head-on-a-75-280z-block/?p=877438

 

http://forums.hybridz.org/topic/70335-n47-head-on-a-flat-top-l28/?p=665985

 

http://forums.hybridz.org/topic/66997-felpro-head-gasket-question/?p=669237

 

http://forums.hybridz.org/topic/47953-wrong-headgasket/?p=413493

 

http://forums.hybridz.org/topic/105907-p90-head-on-n42-block-na/?p=990794

 

http://forums.hybridz.org/topic/102185-shaving-p90-head/?p=956811

 

http://forums.hybridz.org/topic/66997-felpro-head-gasket-question/?p=629556

 

Here are some that talk about gaskets with extra holes:

 

http://forums.hybridz.org/topic/101675-head-gasket-confusion/?p=952624

 

http://forums.hybridz.org/topic/98875-90mm-gasket-coolant-holes/?p=929474

 

And here's one from TonyD saying to machine block and head to whatever gasket you have:

 

http://forums.hybridz.org/topic/101675-head-gasket-confusion/?p=953209

 

 

So what is the real answer, and why? Please, if you don't know why, don't post and wait for someone to come with an explanation.

 

Also, is it less relevant on a lower power street car (my application)?

 

[p90 head on a 77 block?]

The advice given in this thread is contrary to what I have read in other threads.

 

Could someone please confirm:

 

- if you have mismatched head and block, should the head gasket match the head (as indicated in this thread), or the block (as indicated) in other threads

[N42 block P90 combo question.]

rick240, browse through the FAQ's and you'll probably realize that none of what you're planning is really worth spending money on.  Seriously, I'm just trying to help.  You could get an old 280Z or 280ZX engine complete and spend time tuning it to run right, without even cracking it open and probably be better off and save money.  

 

I've owned my car for 34 years now. It had 75,000 miles when I bought it, and over 300,000 now. I've put in rebuilt 240 engines and used 240 engines - and it is again due for something.

 

So although I could save money by putting in a used engine, I intend to put in the best engine (and drivetrain) yet. And I want to do the major refresh now and not have to need to consider it in 3 - 7 years down the road because I chose a used engine again. I want this one to be as close to new as possible, so with maybe a top end refresh in 10 - 12 years this'll be OK for me to drive when I turn 75 in 21 years   Always assuming we can still drive carburated vehicles in 20 years.

 

The F54 block was introduced in 1980 for NA and turbo engines.  Don't listen to your adamant friend anymore.

 

I was pretty sure of that - thanks for confirming.

 

 

But with a carburated P90, is there any advantage to a F54 over a N42 block?

[N42 block P90 combo question.]

Yeah, I think the head shave is beyond what i need for my street driving. I think i will be just P90 head rebuild without shave (mild cam, rockers and HD springs), and put on a block (flat tops, minor overbore, balanced and polished crank).

 

Any advantage to F54 over N42 for block?

 

I was certain that all 81-83 had F54 but just talked to someone and he was adamant that only turbo were F54. He's wrong on that - right?

[N42 block P90 combo question.]

If you shave your head by .080 what does that make the volume of the combustion chamber?

[N42 block P90 combo question.]

I assume I should have them shorten the valves too by .030?

 

 

No, you don't shorten the valves, you shim the towers up 0.030". There are 0.015" thick shims and 0.020" thick shims available.

 

A couple of questions.

 

1. When i read the DatsunZGarage article (http://datsunzgarage.com/p79/) I conclude that however much you shave the head, you shim the towers by that much to keep timing chain, etc lined up, but then you need LONGER valves by the same value. The answers here imply you do not change valve length -

 

2. How much can you safely shim the camtowers in a P90? MSA on their site where they sell their camtower shims states it should never be shimmed more than .045" but it seems the general wisdom talks about .080" shaving and shimming.

[Can U20 valve springs be used in a L28 ?]

Hi,

 

I have an opportunity to buy some new valve springs for my rebuild. In the ad they were identified as Nissan Competition, but I am afraid they may be just stock.

 

Part numbers are:

 

13203-25502

 

13204-23000

 

In Google searches they show up as Nissan Spring-Valve. So I suspect plain OEM not performance.

 

Am I right?

 

From reading threads I have seen rule of thumb that stock springs should not see more the .460 cam lift.

 

Some of the cams I am considering are in the .470 and .475 range.

 

Would these springs work, or should i keep looking?

 

UPDATE: I have found parts diagrams that identify them as for Fairlady 2000 (the U20 engine). Are they stiffer than stock Z, or do I need to keep looking?

[Valve Guides]

Are OEM valve guides for a P90 still available? Any links or partnumbers?

 

Would you also want to use stock valve seals (in my case I am not building a big engine; just a P90 with between 9.0 and 10.0 CR and a mild cam with headers)?

[p90, carbs and fuel pump options]

I am about to build out my new engine for my 240z with a P90 head on a 280 block (probably an N42).

 

I am running the Arizona Zcar Holley 4-barrel conversion and am thinking that the simplest would be to just install the mechanical fuel pump in the P90 (since it has the cutout).

 

What all would I have to do to do this?

 

Is there a good, quiet, electric pump alternative i should consider?

 

Thanks,

 

Rick

[Subaru Diff Clarification]

This weekend while working cleaning parts at a friend's house he mentioned that changing the input flange requires a certain amount of precision to ensure that things don't bind in the diff which can result in bad noise.

 

Are there any tricks people employ when swapping the flanges?

 

I'm jusr surprised that no-one has built a Subaru r180 input flange to Datsun driveshaft u-joint adapter.

[Custom Cylinder head building.. What's Involved?]

The round exhaust ports, (with the liners still intact), are excellent for mild race and hot street engines. Also of note, All the round port heads, (N-47, MN-47, and P-79), have a smaller intake port. At approx 1/2 “ into the port, the port takes on a “D” shape, this helps bias the port centerline which in turn helps to aim the incoming air flow toward the center of the cylinder. This is great, but for maximum effort high RPM breathing, that smaller port is a hindrance to overall flow. These “D” shaped intake ports compliment the round exhaust ports nicely for mild to hot street, and mild race applications. Especially for a street engine that is asked to have some civility at part throttle conditions like having to drive through town back and forth to work and in stop and go traffic on your way to your favorite bonsai back road. These "D" shaped intake ports and round exhaust ports found on the N-47, P-79, and MN-47, in my opinion, offers the best performance with the least compromise in around town drivability and low end and mid range torque.

The square exhaust ports of the N-42, E-88, and P-90, allow for considerable exhaust port alteration allowing the engine to breathe freer at the higher RPMS, though low rpm performance will suffer as a result. The Intake ports of these same heads are also larger than the intake ports in the N-47, MN-47 and P-79, so less carving.

 

In short, the N-42 offers more “all out” potential, but at the cost of low rpm and part throttle drivability. This same radical head on a street engine that is to be driven around town would be a poor choice. This N-42 works best at WOT and above 4000 RPM, where as the round port heads do their best, (depending on how they are set up and built), from as low as 1500 RPM up to 6500 and will have decent manners around town.

 

Hi,

 

I have been doing research about how to build the right engine for me and came upon this post.

 

If I read it correctly, for someone like me who will be driving around town, and driving across the country, no racing, and really wants decent performance in the 1500 - 6000 rpm range I would be better off with a N47 based engine?

 

Thanks (I appreciate knowledge from experts),

 

Rick