This is the first time I have posted, so hope I'm not screwing things up here.

Just wondering if anybody is running an aftermarket intake on there 280z. I bought a 71 240z with an L28 engine that has a Clifford manifold and a 500cfm Carter. there is also a 390 Holly that came with the car. From what I can determine, the 500 is prob. to much carb and I would be better off installing the 390. Is anybody using this setup?

Play with this link a little for sizing carbs by CFM

http://www.gtsparkplugs.com/CarbCFMCalc.html

I plugged in 2800 CC 7000 rpm and .80 VE which is fairly reasonable that chugged out 277 CFM required

even at .90 VE which is pretty high you only need 311 cfm...

390 is the closest choice you have and should be plenty of carb.

I have a friend with a straight six Ford running a 390 cfm carb on his straight six. It's plenty of carb and too rich sometimes. The 500 cfm is stupid large. Sometimes more is not better. Overly carbed with run very poorly. Too rich, slow to rev, lack torque, kill plugs, etc, etc. The 390 may also do some of that but less so. That is one of the beauties of the SU carbs. They change their flow based on manifold vacuum. Just change the needles and adjust the mixture for modded engines. The biggest problem with SU's is they have 40 yrs worth of use on them with little to no maintenance. Rebuilt (ie: Z therapy) I understand they can be quite enjoyable.

Charles

PS Merry Christmas, Santas almost here...

Of the 2 carbs you have, the Holley 390 is the best for what you have now.:disappoin

Get a pair of rebuilt SU's and it will be more than 'enjoyable', its down-right fun! :love:

Bonzi Lon

Most Holley conversions were done by people that simply couldn't figure out the SU's. I'd track down an SU set-up. That would be the best option.

Thanks for the input guys. ( thanks for the link Patcon ) Thats pretty much what I expected to hear. This is my 4th Z and I have owned countless British cars, all with S.U.s. I agree, you cannot beat a good set of S.U.s ( that are not wore out and sucking air ) and I am used to tuning them. Will sell this setup and find a good pair.