l20b w/ l28 flat tops and a87 peanut head

[lynchfourtwenty]

could i run it on 92 octane? what would the compression be? im seein like just over 10.1 or so.. ? also would i have to have valve reliefs cut into the pistons or no?

Edited December 12, 2009 by datzenmike

[DISLEXICDIME]

if i remember right no. the comp is to high for pump gas espeacialy if the head has ben shaved at all go use the ozdat engine utility. it will tell you

[zed]

http://www.rbracing-rsr.com/compstaticcalc.html

I'm no expert, but I find accurately calculating the compression ratio is a very interesting part of engine building. Not difficult either.

I'm running over 11:1 on 95 octane - with no problems (Hainz said my HG is gonna blow soon - but she's done 5000miles already :D ). My motor is a peanut head L18 with L28 flat tops. No need for valve reliefs. My closest piston to valve clearance measured about .060".

It seems from my own experience and what I've read on Ratsun that this combination is unusually resistant to knocking. Bear in mind that 'squish' is critical to preventing knock; try to have deck clearance around .030 - .040".

Edited December 12, 2009 by zed

[datzenmike]

L20B with 86mm flattops = 1997cc

 

Open head......... 10.11

Closed head....... 10.87

 

Also a peanut head on stock dished pistons does not have the same quench area a flattops. Flattops have the best advantage as the whole area of the piston top covered by the head is the 'pinch' area. Stock L20B only have a 1cm wide ring around the piston edge that is pinched.

Edited December 12, 2009 by datzenmike

[BRE_dAtSuN]

Hey datsunmike I have l20b with 87mm flattop pistons on an open chambered u67.. I only get 91 here in cali unless I want 101 but there's only like 4 places I know that has it...but my ? To u is wat do you think my compression ratio is at?

[datzenmike]

Hey datsunmike I have l20b with 87mm flattop pistons on an open chambered u67.. I only get 91 here in cali unless I want 101 but there's only like 4 places I know that has it...but my ? To u is wat do you think my compression ratio is at?

 

Think?..... Hell, I'll work that out and we'll know for sure!!!

 

L20B with 87mm flattops with U-67 open chamber head would be a 2,043.9cc motor with 10.292 compression. This assumes a standard head gasket crushed thickness of 1.2mm and an un milled head.

[Dudeman]

I'm running over 11:1 on 95 octane - with no problems (Hainz said my HG is gonna blow soon - but she's done 5000miles already :D ). My motor is a peanut head L18 with L28 flat tops. No need for valve reliefs. My closest piston to valve clearance measured about .060".

It seems from my own experience and what I've read on Ratsun that this combination is unusually resistant to knocking. Bear in mind that 'squish' is critical to preventing knock; try to have deck clearance around .030 - .040".

 

Are you sure about that compression ratio? All of the calculating I've done comes out to 10.1:1, unless you've had your head or deck milled.

[BRE_dAtSuN]

Think?..... Hell, I'll work that out and we'll know for sure!!!

 

L20B with 87mm flattops with U-67 open chamber head would be a 2,043.9cc motor with 10.292 compression. This assumes a standard head gasket crushed thickness of 1.2mm and an un milled head.

 

I put a metal head gasket and arp studs but im not sure of the thickness I have to check again

[banzai510(hainz)]

you have good high octane gas!!!!!!!It will work but I suggest against it as a daily driver myself

[lynchfourtwenty]

i run 92 octane from chevron in the truck already, so as long as im not buyin race gas i dont care about the gas price..

 

so mike, do you think i could get away with this?

[Jason]

You'll have to run premium with this setup IMHO. My by buddy runs this and runs 94 octane with as much timing as he can without pinging. Set it up and back off timing with premium until the pinging stops and you should be OK. Mind, you better have a good cooling system to get this to work well!

[lynchfourtwenty]

awesome, so i could run premium an maybe an octane booster an be ok...

 

i dont drive the truck often, an it hauls shit on ocasion but not all the time.. i have a 3 year old (was new when i got it) 720 radiator, the guy at the radiator shop said it was a tri-core, but idk.. however the trucks never over heated on me the way it is.. i could easily put an electric fan on..

[datzenmike]

If you have the head just slap on and try it. If you get it cheap try it and if you don' t like it you can always sell for what you paid. Don't know how good US 92 gas is. If you have to bore and add the pistons and then find it doesn't work,... well all I can say is that's a lot of expense and work.

[lynchfourtwenty]

:( i just wanna do something different ya know.. but i dont wanna waste money.. im gonna do some pricing an stuff an talk with hrh an see what we can figure out..

 

would be a bad little motor tho eh?

[datzenmike]

Sounds like a fine build.

 

BTW was the A-87 cam the same as the L20B cam?

[Jason]

I don't think it's a good thing to need Octane booster, I'd try to stay under that point if I could. Remember if you're under load (ie carry stuff) the pinging will get worse so you'll have to back off timing even more. The cooling's important 'cause heat aggravates the pre detonation.

[lynchfourtwenty]

Sounds like a fine build.

 

BTW was the A-87 cam the same as the L20B cam?

 

not sure man?? thats a good question..

 

what are these http://www.google.com/products?q=l20b+cylinder+head+spacer&sourceid=ie7&rls=com.microsoft:en-us:IE-SearchBox&oe=&um=1&ie=UTF-8&ei=fyUkS7CoNY_WtgPuwYThDg&sa=X&oi=product_result_group&ct=image&resnum=1&ved=0CBgQzAMwAA ?

 

i cant find out how much they "space" it out tho.. an do you have to use 2 headgaksets? or no???

[lynchfourtwenty]

I GOT IT!!!!!

 

 

ok after playin around on that ozdat engine builder thing i think i figured out a good combo..

 

ok so..

 

SR20DE flat top pistons = 86mm bore pin height is 32mm but the wrist pin is 22mm

 

Z22E rods

 

Length 149.5

 

Piston End Bore 21

 

Piston End Thickness 25.4

 

Big End Bore 53

 

Big End Thickness 26.8

 

if its possible to machine the piston end of the rod to 22mm from 21mm

 

i could use the l20b crank..

 

using a 1.2mm head gasket?? not sure if thats correct??

 

and a peanut head

 

i get 8.6 compression..

 

is that right for the gasket thickness?

[lynchfourtwenty]

just gettin creative.. lol

[DISLEXICDIME]

remeber where we live lynch weed smoker the temp changes all the time. With my 11.5 . 1 l18 i have to adjust the carbs a few times a year because of the temperature changing the density of the air. slodat also had this problem with his lz20 that was built the same as my l18 . this was with us both running premium.

I also tried to use the same rad i used on my 10 to 1 l16 but it did not cool enough for the l18 so i had to put in a aliminun fiero rad . now my car runs to cold lol

 

if i do another l i think i am going to try to do the lz 2.3

[lynchfourtwenty]

good input mikey, thanks..

[datzenmike]

1.2mm is generally considered the crushed gasket thickness.

 

I get 8.66 so good going. You do get a monster -2.95mm deck height which accounts for an added 17cc of additional combustion chamber but with flattops and peanut this works. Could mill the head a bit if you wanted too.

 

 

Can I quote you on this???

 

 

SR20DE flat top pistons = 86mm bore pin height is 32mm but the wrist pin is 22mm

 

[lynchfourtwenty]

you can if that ozdat site is correct, which im sure it is..

 

do you think machining the piston end of the rod to accept the 22mm wrist pin would be ok?

 

 

i was tryin to shoot for close to 9.1 or so maybe a nut hair more.. so ya i bet a shaved head would work ok..

[lynchfourtwenty]

what made me think about this combo is Fineline has sr20det pistons in his lz motor.. an i was like How'd he doit?

[69FJWagon]

Hey Lynch that is the same engine set up in Lisas' pick up (521) that Troy built and its been going strong for 12-15000 miles running on Californias shitty ass super 91 octane with no issues, port work done and a Rebello Cam using a 38/38 outlaw weber carb it runs strong just not as strong as with the 44 Mikunis I had on it for a while, still a GREAT COMBO! and Troy figured around 10.2 on the compression