On 10/3/2024 at 10:11 PM, IanS said:

Are all cylinders the same?

Just thinking back 40 years pintos were notorious for trashing cams due to bad lubrication. Ford changed the cam spray bar to fix.

So cam cover off and examine the cam, whilst you are at it check valve gaps.

Yeah all reading roughly 100psi. It's a brand new cam as well, I'll double check valve gaps though.

On 10/4/2024 at 10:39 AM, Foz said:

Definitely odd to have low but even readings - did you do the compression test with the throttle wide open ?  Closed throttles can give a low reading.

Yes throttle was wide open.

I also found oil on the spark plug threads, does this indicate oil passing by piston rings? The block was re-bored, just wondering if they have over-bored/honed and now it is oversized for pistons???

Edited October 5, 20241 yr by LewisH

I take it you've got all the plugs out when you do the compression test, you want it spinning over as fast as possible to get an accurate reading?

Have you put a timing light on it to check what it's actually doing rather than just swapping timing maps?

It should read correctly if it’s new. 

Is the new cam an upgraded cam?

Most non standard cams require timing to be set, often with vernier pullies or offset keys.

2 hours ago, IanS said:

Is the new cam an upgraded cam?

Most non standard cams require timing to be set, often with vernier pullies or offset keys.

It is possible to get the cambelt out one or 2 teeth on a pinto and it will still run, although not too well - don't ask how I know 😜

It's worth checking the cam timing to make sure it's correct.

 

On 10/5/2024 at 6:14 PM, richyb66 said:

I take it you've got all the plugs out when you do the compression test, you want it spinning over as fast as possible to get an accurate reading?

Have you put a timing light on it to check what it's actually doing rather than just swapping timing maps?

Yeah all plugs out and throttle open.

When I first installed the Megajolt I checked the ignition timing with a strobe on the base map and then again on the pinto map. Looked to be correct. 

Edited October 6, 20241 yr by LewisH

9 hours ago, IanS said:

Is the new cam an upgraded cam?

Most non standard cams require timing to be set, often with vernier pullies or offset keys.

Brand new, this was installed when i first assembled the engine after re-bore and new head etc. I checked the timing against the quoted figures from Kent, however I'll double check along with tappets etc. 

Afternoon all,

Bit of an update...difficult to grab an hour these days, but managed to get out this afternoon to check timing and tappet clearances.

The cam timing looked slightly out, I have advanced this on the vernier pulley as much as I can - this was a big improvement with compression, jumped from 100psi to 130psi. 

I then checked clearances, all inlet valves were tight. Re-tested compression and I now have around 140psi on all. 

Although I am pleased to get some progress, I am still wondering if 140psi is low for a tuned pinto?

If it is low, do I carry on advancing the cam timing slightly to see if this keeps improving? It is set currently to roughly 108ATDC (Kent quoted figure for FR32). 

Any help much appreciated.

Does it run any better now or are you still having the same problems ?

3 hours ago, Foz said:

Does it run any better now or are you still having the same problems ?

Haven't got that far yet unfortunately. My thinking was continuing with advancing the cam timing to see if it helped raise compression even more. I just wasn't sure if it was a good idea? Also not sure if raising compression correlates directly to better running engine. 

 

Randomly changing the valve timing isn't really the way to do it, you could end up burning out your valves, if you have the setup from the machinist then you should be using a dial indicator to set them up as per spec.

I have checked the timing using dial indicator to spec, but the compression numbers still seem low to me, I'm just not sure what I should be getting?

My head is skimmed and the block has also been re-faced, I was thinking that this could change the required cam timing from the Kent quoted figures and perhaps it needs advancing slightly?

The pinto in my 2B had a CR of about 10:1 and ran nicely with a Kent FR32 set at 108 degrees.  

As they are all balanced I suspect your low compression figure may be a red herring, I think I got a compression figure around 13 bar (190ish psi)  but I had Webers not bike carbs and its easy to open them fully.   Have you tried what Trev suggested ?

On 10/4/2024 at 10:31 PM, RedTrev said:

What about the sliders in CV carbs, should they be lifted during compression test? If left down will they restrict the airflow enough to lower the compression reading? Just a thought 🤔

I've not tried this. I'll have a go this afternoon and report back, thanks.