Holley with excessive tickover speed

gbtv8 · Post by **gbtv8** » Wed Jun 01, 2011 6:54 pm

Hi guys, I'm hoping someone can help me. I recently fitted a holley carb to my 3.5 rover v8 in my Scimitar GTE. (its a 390 on a dual plain manifold). I have ran the scimi for 2 year on SU's with no problem and fancied a change. I have completed the fitting but when I started the eng. I can't get the revs below 1200rpm. I've stripped the carb and checked all orifices, it had a rebuild kit in before I fitted it (it is second hand) and I have checked for vauum leaks etc. The mixture screws will richen the carb and speed up the revs but if you try to slow it down it just stutters and dies. It starts easy and doesnt need the choke. The tickover screw is not required and when trying to throttle it doesnt like it untill after about 1600rpm. Starting to pull my hair out now and i havent got alot left to start with.

mgbv8 · Post by **mgbv8** » Wed Jun 01, 2011 8:15 pm

Have you got the info on setting the carb from the holley website or youtube??

What engine did this carb come from ??

It sounds like the butterflies may be to far open at idle.
Do you know what jets are fitted ?
Do you what what marks are on the power valve (if it has one)
And do you know what vacuum you are making at idle ??

These carbs are not to bad to set up once you get your head around the basics and have certain data available.

Regards
Perry

Stu E · Post by **Stu E** » Wed Jun 01, 2011 8:35 pm

Don't know about the Holley, but I had the same problem when I changed my SU's for an Edelbrock. The fix was to put a PCV inline between the flametrap and port I used on the carb, only cost a couple of quid from Reel Steel.
Stu

mgbv8 · Post by **mgbv8** » Wed Jun 01, 2011 8:45 pm

Good point Stu!!

Has gbtv8 got all vac ports blocked off properley???

gbtv8 · Post by **gbtv8** » Thu Jun 02, 2011 5:15 pm

The carb came off another Rover eng. The butterflies are totally closed and all vac ports are blocked off.
I got info for setting out of a Holley book. I'm not sure what size power valve is in and I cant see why it should effect tickover. I looked at the main jets yesterday and appear to be marked 52 although again would this directly effect tickover. If so what should it have?

mgbv8 · Post by **mgbv8** » Thu Jun 02, 2011 6:13 pm

If the power valve diaphragm is leaking the fuel will seep into the inlet manifold. Worth a look when you have it off next.

gbtv8 · Post by **gbtv8** » Mon Jun 06, 2011 2:03 pm

I may have cracked it. I went back to basics and thought that my problem had to be something that I had done. So what had I done? I had overhauled the carb. using an original holley rebuild kit. This contained a new power valve and all the gaskets needed for the job. At the suggestion of mgbv8 I thought I should check the power valve anyway just for piece of mind. Every thing appeared fine. What else had I done? I had removed, cleaned and replaced the primary butterflies and upon replacing them I put them in upside down, hoping to improve air flow over the pitted butterflies. I put them back in the correct way, at the suggestion of a work colleague, and checked that the gap between butterfly and venturi was minimal, if anything at all. I replaced the carb. and set the mixture screws to the basic setting, rechecked the float heights, opened the choke, blipped the throttle and 'hey presto' it started and appeared to be better, smoother and more responsive straight away. I didn't have time to run it to full temp. because I had to see to family matters but I am optimistic. I'll try to set it up tomorrow and report findings.
Thanks for help so far,
Col.

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