Sealik

Well...you have to pull a needle to determine size. You definitely need a fatter needles....but the 46s(?) might be a little to much for the 1800..?..38s would be a better 'fit'. I've got a LZ23/240Z 46mm SUs with RA needles and it runs a little rich at idle and WOT...cruising is good though, between 14-16 I have a wideband to monitor A/F ratios , somewhat simplifies 'searching' for the appropriate needles

These might help... http://www.zcarz.us/TechnicalInformationPageCarburation.htm http://www.jetlink.net/~okayfine/sutech.html Size of engine??? What needles are you running? Running rich at just idle...or....? Wide band A/F ratio gauge is rather handy when setting up SUs

Haynes Techbook 10240 Weber Carburetor Manual....(includes SU carbs) Here's some links on setup...etc. http://www.sw-em.com/su_carbs.htm#SU%20carb%20applications http://www.ztherapy.com/technical_stuff/spotterguides/zcar/240spotter.htm http://classicmotorsports.net/articles/simple-carbs/ http://www.z-car.com/510/S_U.html

Thanks Tony...you could be right because those marks on the pistons don't look fresh. I started the L last week...ran like ****...but it did flash up, chugged actually with bad gas and all Assuming it sat longer than the previous owner stated. What I'm trying to find out is where the stock flat tops sit relative to the block at TDC Then I could add my .5mm (above deck) and determine stroke...then compression ratio. Factoring in the head that has been shaved at least .010 of course I calculated the stoke at 86...assuming a stock negative deck height of 3mm Bore 86.2 Hg....1.2 E31 volume...42.4cc Deck height... .012 inches Would be 10.62 without the shaved head? Or... 9.84/2mm HG without the shaved head? First time calculating Cr sooooo... Maybe Edit....measured the stroke...it is 79mm Disregard my CRs

Thanks...I am somewhat baffled on what the PO did Wasn't sure on the negative deck height for the stock 280 flat top piston.....3mm????? So....if that is correct....add .5mm for mine that are above deck...multiply that by 2, add 79...equals...86 inch stroke? Think I'm gonna need 2 HGs to drop the CR below 10 and clear the valves........

Hello... Have some queries on my recent purchase. It's a 69 510 with a L28 in it. Price was good...and...can't quite say no to any older 4-sale Datsuns in this locale Looks like someone started this project years ago and never quite finished. Bolts missing here and there, old gas, no carbon on head...etc., still has the cross-hatching marks in the cylinders from honing/boring. The block is a N42 with P79 50 pistons...assuming the cylinders were bored 50 over Pistons are above deck by about .5mm The head is a E31....looks like it had recent work on it Also looks like it's been shaved...From front of engine..4.228, then 4.231 at center and 4.240 near back of head. Wedged it seems... Stock head is....4.248??? Additional marks on head Head ,intake (E46?) and SUs are from the 71 240Z I believe....SUs need to be cleaned etc. Anywho......trying to figure out my options to get the pistons to clear the valves, slight contact as seen per pic Looks like the block hasn't been decked....but I read somewhere that with different crank/ connecting rod/ pistons from the 240 and or the 280 will give you the .5-.6mm positive piston deck height??? Cam is stock(?)...around .413 Don't really want to pull the pistons and get reliefs cut into them.....but.....will a 2 mill HG work? Thanks Oh.....here's the ride... And 1 of my 720 4x4s with a recent LZ23 that I built....