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l28 build


taylor76zharris

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Hello, Im starting my l28 buld in a few weeks on a motor that i got for free. F54 block and p90 head. it is a turbo motor but i want to go old school and go back with carbs. I want to get close to 200hp and i want to use either dual webers or the stock su carbs.

I know i need new flat top pistons, main bearing, rod bearings, maybe e33 head (i heard they have a better quench area). what else should i need.

Thanks

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Well first you need to figure out where that e33 head came from since it doesn't exist. 
 

For the block, get new everything( bearing and rings etc) You don't need forged pistons, and you could even bore it out a little. To anyone that tells you to get forged pistons: That depends on what rpm he is going to be making power. A perfectly matched cam can easily make enough power below 7k rpm. 

 

Stick with the P90, and shave it, and get it professionally ported. Then match a sufficient cam to it. I've only met one person who was right around the 200whp mark with SU's. 

 

If you went with Triples then that's an everyday thing. My friend is making 216whp with mikuni's with his new motor and the most important and costly part was the machine work on the head/cam. 

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E31 i ment, sorry was in a hurry before class. I was hopping someone would say stick with the p90, a lot less fuss trying to find an e31. this will be my first rebuld ever so i hpe it goes smoothly. The L series seems like a fairly simple one to start with.

 

So spend some money on the head and cam, got it.

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Spend the money on the head. I'd budget 2000-3000 dollars in headwork, or 60-80hrs, depending on if you're paying with cash or with your personal time and tools.

 

With a P90/flat-top piston configuration, shoot for 9.0-9.5 :1 compression unless you want to run a very late intake valve closing, or you are willing to work around detonation with either race gas or conservitive timing. You can get away with a little more, but it becomes much harder to work with very quickly above 9.5:1, although some folks run 10:1 and higher on pump 93. Cam accordingly.

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No....You have completely missed the message here.

 

Headwork. Not a valve job, Headwork. That means getting it ported, flow tested, ports touched up, flow tested, match the intake manifold to the cylinder head, pick a cam appropriate for the port flow, intake manifold flow, and desired torque peak, and then tuning it all to play nice together. In addition to all the above, you would install new valves, have the seats recut, install springs suited to your cam lift and seat pressures, install the correct spring shims, measure for and install the correct thickness lash pads, and ensuring that you are using new or reground rocker arms with your new cam. Some folks say you don't need them...others, including myself, wouldn't install a new cam without reground rockers.

 

A flat-top L28, with a P90 head, will net you 8.8:1 compression, approximately. Shave the head until your chamber size is reduced enough to produce the compression you want...but you'll need to have the valves unshrouded BEFORE shaving, because the chamber size will increase 1-2cc with this operation.

 

If you're not ready to spend either a LOT of garage time with the correct tools and patience to finish the job, or spend the equivalent in cash money to someone who is, just put together a flat top bottom end with quality parts, and install the P90 head. A set of nice headers, a properly sized cam (talk to you cam grinder about that) and make sure you set up your cam geometry, and call it a day.

 

Skip the dual webers, if you're talking about the DGV downdrafts. They're *ususally* more trouble than they are worth, and don't have any real advantages over a set of SU's. If you are talking about the Weber MCHH sidedrafts, then they *MAY* have some advantages, but you will need to construct a custom linkage. I don't know the answer on that one.

Edited by Xnke
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You are on the right track. This is what I would suggest:

 

- Flat tops

- P90 head with fresh vavle job

- Choose a street cam with 460 or less lift so you can use the stock valve springs. Something with an advertised power band of 2000 to 6000RPM

- New, correct thickness lash pads to match your new cam

- SUs with SM needles

- Header

 

This setup should allow you to run upwards of 35 degrees of total advance on pump gas. Don't shave the P90 head anymore than to just get it clean and flat. Properly tuned, this setup will make 200 crank HP all day.

 

Pete

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I've got a F54 / p79 combo and the head is not shaved at lot. CR is around 9.0/9.5 as other people have suggested above. It is a great combo with plenty of torque. The Cam on my engine is coming from Rebello.

Do not forget to think about timing management with your engine; to get the most HP out of your engine, you'll need something appropriate.

 

Regarding part supplies, I got everything from http://www.clarksdiscount.com/ They were great with me, very responsive & very fast (order done on Monday in France, parts were at home on Friday). I've got nothing but good comments so I share the link.

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http://www.store.partsdinosaur.com/page278.html

 

This guy was a pleasure to work with and the cheapest i could find when i ordered ITM dished pistons for my turbo setup...

 

Also a cam regrind is another good route. There are a few recommended places to have your stock cam regrind just search.

 

BTW datsunllc gets a thumbs down from me and don't ask why :(

Edited by Randall
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I've got a F54 / p79 combo and the head is not shaved at lot. CR is around 9.0/9.5 as other people have suggested above. It is a great combo with plenty of torque. The Cam on my engine is coming from Rebello.

Do not forget to think about timing management with your engine; to get the most HP out of your engine, you'll need something appropriate.

 

Regarding part supplies, I got everything from http://www.clarksdiscount.com/ They were great with me, very responsive & very fast (order done on Monday in France, parts were at home on Friday). I've got nothing but good comments so I share the link.

 

Thanks for the clarkes discount tip. Great prices!

 

Pete

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Wow thanks for the heads up, i was going to buy from him. :icon11:

Also thanks for the parts numbers, very helpful.

 

Ordering pistons today from clarks,. I just want to make sure im getting the right ones because the part numbers dont match but they say they will work with my engine (l28 f54). Part number is RY2700-20, Im guess ing those are 20+. I was hopping to get standard bore which it looks like they dont cary. They do have very good prices though, compared to everyone else.

Edited by taylor76zharris
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I've got a F54 / p79 combo and the head is not shaved at lot. CR is around 9.0/9.5 as other people have suggested above. It is a great combo with plenty of torque. The Cam on my engine is coming from Rebello.

Do not forget to think about timing management with your engine; to get the most HP out of your engine, you'll need something appropriate.

 

Regarding part supplies, I got everything from http://www.clarksdiscount.com/ They were great with me, very responsive & very fast (order done on Monday in France, parts were at home on Friday). I've got nothing but good comments so I share the link.

 

Thanks z-ya. i found some good pistons on ebay.

 

What do you mean about timing management? like adjustable cam gear? is the distributor adjustable?

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You don't need an adjustable cam gear for the build you are doing. You just need to make sure everything lines up with the stock timing marks as per the manual. If you don't have a book on how to do a rebuild on an Lseries, get one.

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