82 replies to this topic

[bigmatt4]

few head shots

Attached Files

•  DSC00499.JPG   821.25K   11 downloads
•  DSC00507.JPG   518.21K   9 downloads
•  DSC00509.JPG   786.46K   9 downloads
•  DSC00578.JPG   1.03MB   16 downloads

[bigmatt4]

still have to refit ported 12g 295 head and electronic dizzy

So whats this then?




Hopefully if you say you now have the correct head and are fitting the correct size exhaust system, you will find a vast improvement. an exhaust exit of 1 1/8 inch as stated recently is most likely not helping at all.

we started with the 12g940 head just eliminated porting to be the idle fault by fitting stock block standard head ended up being a process of elimination job to find fault

Edited by bigmatt4, 29 August 2011 - 09:17 AM.

[Yoda]

My thoughts were that using a small bore head and a restrictive exhaust would give all sorts of issues. Hopefully with the correct size head and exhaust, we might have a chance of sorting this.

[AndyMiniMad.]

I mentioned in earlier posts that the exhaust should be looked at...I dont know enough about webber carb jetting to comment on the other points raised in this thread....But at the risk of repeating myself.....You should sort the exhaust before faffing around with anything else....Its one of the most important parts of a performance engine and often gets overlooked.

[bmcecosse]

An 850 head on a big bore block is just madness - it will tell you nothing. Why do think oil was being sucked down the exhaust guides?? I really do believe you should fit the proper head and a single SU carb and get it running nicely like that. If it still won't work - the only factor left is the camshaft.......

[bigmatt4]

An 850 head on a big bore block is just madness - it will tell you nothing. Why do think oil was being sucked down the exhaust guides?? I really do believe you should fit the proper head and a single SU carb and get it running nicely like that. If it still won't work - the only factor left is the camshaft.......

oil down guides because when i removed the head there was oil in exhaust port 1 and 4 and you could see on the exhaust valve stems and the back of the exhaust valve yet the cylinders were clean and oil free.
As mentiond before 850 head was on lt to diagnose fault ie removing modifications to eliminate that possibility. The 850 head will not be staying on the engine and the camshaft is not the problem we are on our second camshaft we started with a 649 cam and have downsized to a RE13 camshaft thinking the cam was too big for street use.
The 940 head will be refitted this weekend when the new extractors arrive.
the exhaust from the extractors back is 1-7/8 the extractor pipes are only 1-1/8 28mm we are upsizing to 1-1/4 32mm

Edited by bigmatt4, 29 August 2011 - 10:37 PM.

[AndyMiniMad.]

(the exhaust from the extractors back is 1-7/8 the extractor pipes are only 1-1/8 28mm we are upsizing to 1-1/4 32mm)...

Good man... That will make a difference....Im not saying it will cure the problem, but it wont do any harm to have the proper sized exhaust manifold fitted.
Oh!! I also have the RE 13 OT cam in my 1380 and im very happy with the performance of the engine. Its a bit lumpy bellow 2300 revs but then smooths out and pulls very strongly all the way to 6500...It wont idle smoothly at anything bellow 1100 revs and even at that stutters and pops. But remember that the engine WANTS to be reving at at least 2300 revs (coming on cam) and is simply not happy below that rev limit, so you will never get it to behave properly at idle...its the sacrifice we make for the oommph higher up the rev range.

[bmcecosse]

The 850 head has just confused you - throw it away...... Exhaust valve stems NEED to be lubricated - never fit seals on the exhaust stems on a hard driven engine...........

[bigmatt4]

The 850 head has just confused you - throw it away...... Exhaust valve stems NEED to be lubricated - never fit seals on the exhaust stems on a hard driven engine...........

think you need to read all of my posts i started with the 940 head lots and lots and lots of tests with proper head last effort was trying 850 head . but a thick coating of oil in the ports is a little more than lubricated

[bmcecosse]

I have read them all.....and I say again - you are over-worrying this, and the weber carb isn't helping either. And perhaps the daft 850 head may have had worn guides/stems?? It's really not relevant to your engine.

[b34k3r]

Has new Fletcher LCB manifold with 34mm pipes, back to ported 12G940 head (pictured above) and has a smoothish Idle at around 1100rpm. It not perfect, but its close enough, goes like a cut cat!

[Yoda]

1100 rpm is fine with that cam etc. Mine runs a 286 cam and idles around 1100/1200 depending on the weather

Edited by Yoda, 04 September 2011 - 07:45 AM.

[b34k3r]

This is how it runs.
note it is from a cold start and it rattles a little til it's warm

Edited by b34k3r, 05 September 2011 - 10:53 AM.

[b34k3r]

This is how it goes on the open road.


Th camera mounting is poor its not quite THAT bouncy to ride in.

Edited by b34k3r, 05 September 2011 - 10:54 AM.

[Yoda]

Looks and sounds awesome. well worth waiting for!