Carbs on 2.7 cis engine issues
 

ok quite awhile ago i upgraded a 76s 2.7cis engine and swapped the stock engine to carbs . we altered and tuned the engine to match, changing the ventures and jetting , hotter plugs , recurved the dist. the lot ... the car was stored for awhile and how we are getting it back on the road .

the issue is it will start under protest ( spitting through the carbs ) once going idals well , runns smooth .. but when driving there is a lag / spit through the carbs when you put the foot down . it just does't want to go . it seems i have to keep the rev's up constantly and then go . also lacks power that i expected .

any ideas?

Porsche cis to carb swap - YouTube

Was it ever running great after the swap to carbs (before you stored it)?

you're lean. what are your jetting and carb specs?

Sounds lean. Have you balanced the carbs, adjusted the idles, etc?

Todd

You should get an afr meter too check the hole rpm range

that's the tricky bit , i never drove it prior to the last tune as i was busy but my mechanic advised he had it running sweet . ( and i believe him ) but i wonder if his idea of sweet and my expectation is different .
when the video was done and the engine was rough tune (prior to change of ventures / jets ) i had the car for 1 week to do some work and took it for a drive. it was hot light up the rears no issue.

i do wonder if as the engine is NOT a rebuild but aged and burning a little oil if that throws off the af meter and makes you end up leaning it out

do you have and AFR instrument in the car?

i don't , running stripped out R-Gruppe less is more layout

How long was it stored? Sounds like gummed up carbs in need of significant cleaning.

+1, sounds like the carbs need to be pulled and cleaned out.

If the carbs are old Webers, sending them to Paul Abbot for a complete overhaul would be money well spent. My 2.7 was giving all sorts of troubles with starting and running poorly, but once they were properly cleaned out and jetted correctly, it's been great.

Also, the pistons/cylinders and cams you're running can make quite a difference. It took some time on a dyno to get mine tuned optimally.

Good Luck on your project!

car was stored for 6 weeks , than brought home and sat for 12 months but started monthly . carbs where stripped / checked and installed at the start .
i think a tune on a rolling road first then look at carbs again plus cam change

I would check all of the basics (Paul Abbott's website (Performance Oriented) has a good install, set-up, tune doc), but because it seems to be spitting back through the carbs while you are "putting the foot down", but otherwise running ok, It sounds like it's going lean momentariily ...when you push the accelerator down, which causes the carb accelerator pump(s) to squirt fuel to meet the increased demand. The carb accelerator pump volume might be a bit too low. To test this, I'd adjust the nut on the pump rod (loosen, I think) to increase the pump/squirt volume to see if the lag/spitting decreases when you put the foot down. Mark the original location of the nut on the pump rod, so you can get back to where you started.

regards,
Al

First, I would make sure your idle jets are clear. If so, checking your plugs will give you an indication of what may be going on.

I was having a similar problem with my Webers. When I would lift off and then push the throttle down, as when going through a turn, it would pop and spit through the carbs for a second then clean up.

I lowered the float level slightly on the right hand carb, and now it runs like a dream.

The float levels were within spec, although at the high end, so I didn't think that could be the problem. Turns out with the new crap gas we get now it made it rich enough with the slightly high float levels to foul the plugs.

Adjusting the float levels down to the lower end of spec fixed my problem.

cheers for the feed back , we will give all the ideas a try