V8 Issues under load

high mileage engines could get head gasket leak on inner side blowing under valley gasket,soke believe it was caused by imbalance of head clamping bolts ie outer row of bolts

yea, the outer 4 bolts cause the head to be pulled down at the 1 side. your's should be a 14 bolt rather than the 10 so worth checking. or even just undoing the outer 4 and re torquing them to 20lbs with nut lock and see how you get on.

I dont think its an timing issue. does it do it when cold?

though ive rarely seen it except on high mileage which might be expected anyhow

Ah OK, I hope its not the head gasket just got the thing back together was hoping to use it for a while! Checking the compression will confirm this?

dicomark10 - yeah does it when its hot / cold no change, only issue is that when its cold idle is bad also, especially now. Hardly runs on idle at all.

Also it done 109k; so a fair few miles.

well, it could be the amplifier if its fine when cold, the can be temperamental when hot. I take it yours is mounted on the dizy? (lil black box)
1 test is to get it hot and miss behaving then cool it with water and test quickly.

discomark10 said:

well, it could be the amplifier if its fine when cold, the can be temperamental when hot. I take it yours is mounted on the dizy? (lil black box)
1 test is to get it hot and miss behaving then cool it with water and test quickly.

Click to expand...

Yeah its right next to the dizzy. Cleaned out the connector earlier today. Sorry my last post was a little misleading - the issue with the spluttering happens all the time regardless of engine temp.

I now have a compression tester, I will give that a go tomorrow and see if any thing is a miss.

OK so I've done a bit to the V8 tonight but yet my problem continues...

I messed around with the timing, turns out it was set to 30 degrees advance so I backed that off and found that if it was set at 12 degrees it ran OK at almost idle (small amount of choke) but still fairly rough above idle, then I backed it off to 9 degrees as I read this was about right some where. Would not idle without 1/4 choke, and without choke idled very low and stalled. However at 9d the spluttering problem improved and the issue moved further up the rev range (4th gear 50mph, 5th gear 65mph) still only in 3rd, 4th and 5th. 1st and 2nd are fine, but it was still present which is annoying. I've left it at 9d as its behavior was generally more predictable, even if I did have to run 1/4 choke the whole time. Seems like the previous owner advanced the timing to make the idle run better - any one heard of this before?

I'm checking compression and fuel pressure tomorrow, but any thought between now and then please let me know!

Set it to 6-9 deg advanced at idle, any more can cause big damage!
The idle issue could well be down to the air idle valve at the back of the plenum, mine was ####ed and wouldn't idle.

discomark10 said:

Set it to 6-9 deg advanced at idle, any more can cause big damage!
The idle issue could well be down to the air idle valve at the back of the plenum, mine was ####ed and wouldn't idle.

Click to expand...

Yeah its set to 9 deg now, and I will leave it there.

Whats does this air idle valve look like and what do I need to do to it? Sounds like we are getting into the realms of tuning, which I have failed at before!

no, its just a controller that allows more air to go past the butterfly valve to drop the rpm.
https://www.google.co.uk/search?q=r...F%2Fwww.ebay.co.uk%2Fbhp%2Ftvr-plenum;225;169
the black think top left, just unscrew and replace

discomark10 said:

no, its just a controller that allows more air to go past the butterfly valve to drop the rpm.
https://www.google.co.uk/search?q=r...F%2Fwww.ebay.co.uk%2Fbhp%2Ftvr-plenum;225;169
the black think top left, just unscrew and replace

Click to expand...

I have carbs on mine, twin SU's. They only picture that came up in that link was for EFI plenum, is that right?

Oh ok then its not that, sorry my bad. then yes it down to the idle screw and mixture settings

discomark10 said:

Oh ok then its not that, sorry my bad. then yes it down to the idle screw and mixture settings

Click to expand...

Balls - when ever I mess around with these it normally gets worse. But I guess thats only ever been on chainsaws, until now......

What could possibly go wrong!

Thanks for the help Mark, I'm sure I will be back on tomorrow with another update.

might be worth watching a few vids on youtube on how to tune carbs

did you set the timing with the vacuum pipe off and blanked,
dose the vacuum unit stick to your tongue when sucked ,
basic setting for carb mixture ,all the way in then out 1 1/2 turns on both,
adjust tickover with idle screw,fast to start and back off when worm

Vac wont effect the idle

discomark10 said:

Vac wont effect the idle

Click to expand...

timing is set with vacuum pipe off and plugged
and if the diaphragm is split it will draw air which will effect idle,

Ill leave it to you lot

Ianski said:

timing is set with vacuum pipe off and plugged
and if the diaphragm is split it will draw air which will effect idle,

Ill leave it to you lot

Click to expand...

it would effect it if there was a leak your right

Sorry guys been away from my computer, in the engine bay!

I did a bit of digging as suggested on tuning SU's. SU recommend via their website, as Ianski said to remove the vacuum pipe - which I have to admit I didn't do, so I will go back out again this weekend and start again - thanks for the base settings Ianski I think I'm at nearly 3 turns. And yes the vacuum tube sticks to the tongue so all seems OK here.

Any way I did adjust it so that it runs OK on idle at the moment, but is a little unpredictable. During this I discovered that the throttle cable is fooked so new one on the way.

I also checked fuel pressure and compression. Fuel is fine, compression is a little low but consistent. I've put some oil on the top of the pistons just in case the rings weren't sealing correctly due to being sat for nearly 2 years.

And now I'm just waiting for parts to turn up so I can test to see if any of the above has made a difference.

Any thoughts would be appreciated. My goal is to get it to run for about a year - then the whole things is coming out and being overhauled! But I would like to use it for a little first as its been off the road for sooooo long!