Technical Tips > Engines - Carbies - Exhausts - Dissys

pinging suspect new manifold

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Gray-man:
Hi new to this & need help,fitted a Holley intake manifold to my 74 vette,alloy low rise no part No. visable may be underneath, car pings badly now,timing is spot on,balencer is good,replaced accel dizzy with GM HEI, pinged as soon as i fitted manifold,could the wrong one or a badly fitted one be the cause,would appreciate help i'm stumped

Cameron 77C3:
G'day  Gray-man, welcome ;42

What type of manifold, ie dual plane, single plane, etc, etc.?  Part number would be very handy.
What type of carburettor and size,
What have you set the timing to and how did you set it?
What fuel are you using?
What type of engine is it (ie S/B, B/B standard, performance and so on)?
Did you fit dissy and manifold at the same time or had you been running the dissy OK before manifold change?
Last but not least, why did you change the manifold?

Cam

gtc:
One of the causes of pinging is incorrect (too much) spark advance. Although you say that the timing is 'spot on', how do you know that the spark advance curve is correct for the new intake+carbie combination?

TPI-383:
Has the GM HEI dizzy been regraphed to suit your engine combo or is it standard. If it is standard it could be pulling too much advance too early. Why did you remove the Accel dizzy,Was it a problem? Most aftermarket dizzy's have adjustable advance and can be tuned to almost any engine combo.I would be checking this first. You could try disconnecting your vac. advance from the dizzy and blanking the line to the carb. Take it for a drive and see if the prob is the same or improves.When does it ping? On most of the engines I have built I have had the dizzy regraphed and do not use vac. advance so timing is more consistant.I personally have not had much luck with vac. advance on performance engines.Where are you located,maybe I can recommend a place to help with regraphing dizzy.
Cam, wasn't there a post on how dizzy advance works on this site before.
Tim

Cameron 77C3:

--- Quote ---Originally posted by TPI-383
...........Cam, wasn't there a post on how dizzy advance works on this site before.
Tim
--- End quote ---


Yep

There is this thread http://www.nswcorvettes.com.au/forum/viewthread.php?tid=6499

And this thread http://www.nswcorvettes.com.au/forum/viewthread.php?tid=6435

And this thread http://www.nswcorvettes.com.au/forum/viewthread.php?tid=6500

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