FE-FC Holden Discussion Forum

my 186 goes like a slug.
as you may know? i know nothing about this engine but the inlet manifold is opened up way way bigger than the inlet port.the engine seems newish plenty of compression etc.biggish cam ,commo dizzy double valve springs,350 holley,it should go heaps better than it does?
just wondering if the turbulence created would be that detrimental to performance.
thanks all

Waynos,
manifold and head ports should ideally be the same size however i new someone who had a similar problem and when i dismantled the timing case i found the timing was out a couple of teeth. I repositioned the timing and the motor went like a charm. This may be the problem but before dismantling the engine i would do all the usual things like checking points,air filter, fuel pump etc
Regards brett

thanks heaps ,
she runs sweet,everything is fine but it should run better.my dad reckons its the carby and i think it could be the manifold.
i rebuilt the carby so wont believe him, but he's usually right

In addition to what Brett F said,

Mismatched ports can be a problem but most likely wouldn't be too noticeable at low RPM.Would present a compounding problem at mid to high RPM range, unless of course they are very badly mismatched ??? then even low RPM breathing problems could be encountered.

 Fitment of performance parts that aren't a proven  combination can also be a poor performance contributor, for example :- a camshaft with a high end RPM profile on a standard engine just isn't going to perform unless other performance oriented parts designed to compliment each other are fitted as well.

There could be a myriad of other factors contributing to less than expected engine performance including checking the items  that Brett has mentioned and other parts and/or tuning problems .

With regards to Brett's comments,I had a 253 in a an old commy wagon that I used for work.It had a mild cam,mild ported heads,extractors and Holley carb and it wouldn't pull a sailor off ya sister.After putting up with it for a long time I eventually sold the car but swapped the motor before I sold it.After pulling the motor apart I found that a "guru" mate of mine had advanced the cam timing too much ( a tooth or so) and this was the problem.It can happen.Cheers,Jamie.

well i'm just being lazy with the motor side of things cause i'm gonna build a supercharged 179 soon.
i just wanna drive it for a while and enjoy it a bit.i guess the price of fuel has made it a bit easier.
it's a slug but i cannot complain.
I'm DRIVING IT!
thanks for the posts
waynos

hey never heard the sailor off ya sister quote, i will use that forever more,hahahahahahaha

it actually seems more noticeable at low revs,it goes better as it starts picking up at higher revs,maybe its just the wrong combo

That's exactly what the 253 did.... ::)

Yep, same here  ::), years ago, when I first started my apprenticeship, standard 253 in HQ Monaro.

Fitted 35/75 cam in an otherwise standard engine, went worse than the standard cam for obvious reasons that weren't obvious to me in my early days as an apprentice.

I know better now ;D

hey i think it goes too good for the cam to be out(maybe i just dont wanna believe it cause its more work than i wanna do over chrissy)
what my post was supposed to be about but i didn't explain properly is thatmy inlet manifold is about 1/2 an inch bigger than the port?

Waynos,
If you want the motor to suck in air and fuel the inlet manifold should be smaller than the inlet port of the head. it sounds like you should remove the manifold, lay a inlet gasket on the head, scribe a line using the gasket as a template, measure from the edge to the line. This will give you an idea on how to gasket match the inlet port. Do the same on the inlet manifold, if the opening is larger than the gasket then you need to open up the gasket to suit.
If you want the exhaust gas to escape the the exhaust manifold opening should be larger than the exhaust port to allow flow.