Head combustion area

[stumo]

i would say unless you're building a monster (like Danny, Red Redding) then it's not worth worrying about.

Jim i would say that your problems were caused by too much ign (unresponsive knock sensor or PFC not showing it correctly) or too lean.


Many years ago i had a Vauxhall red top that ate it's pistons due to det, it was a std engine on Jenveys and MBE , it just wasn't mapped correctly.

 

[campbellju]

plus 2.0bar boost, track days, 1.2mm plug gaps and rubbish iridium plugs that fell apart. I did a lot of miles on the engine so I certainly got value out of it.

I'm using ERS in Burscough if you know them. If okay to re-use the head, in tidying up the edges and re-skimming it will hopefully sort a few issues out.

have you got nay new projects? Is the Jeep making a comeback?

 

[Fusion Ed]

It it does happen Ed, have seen my own and a few others and even an nme engine have this issue. It does not start because of it that comes from else where but once the area is damaged that is where it carries on the worst, this will also help reduce the hot spot that has caused the top of the deck to drop from excess heat in that area.

I've just mapped so many and never seen it as a problem... Not saying it cannot be made better.

 

[campbellju]

I saw the engine builder today about my original head that came off the engine. The det around the edge is comparable to another healthy head I've seen that was also no where near the sealing area of the gasket. The head surface is completely flat but a light skim to make it perfect won't hurt and I will re-build it anyway to replace the seals etc.

He understood the issue Doc highlighted and the logic of chamfering the edge but he hadn't done this himself before.

Unfortunately the milling machine he needs to do an accurate job he sold so he's going to contact someone he knows who's good at doing difficult engine jobs. He also mentioned a guy he knows who does head work for race bikes and will get me a price for porting/polishing the exhaust side.

It will take a few weeks to get the feedback from these other people but at least it's still moving forward.

 

[campbellju]

Update.

I picked up Steve's second hand head which had already had porting and valve work done. This was showing worse signs of det on the inlet side and the engine builder said he's seen a few SR20's like that. Anyone know why ours struggle so much on the inlet side? Lack of cooling? Doc mentioned a hotspot. Is this why others have always been looking for better solutions to the head's cooling?

After lots of reading about quench zones and their purpose I did the chamfering to the inlet side and left the exhaust side alone. Hedging my bets! My logic was that Steve's head and mine have shown no signs of any det on the exhaust side so it is not any causing the high boost combustion any issues. The inlet side has det which implies a hotspot that would benefit from chamfering.

A 6 thou skim has cleaned up the surface nicely and eliminated what was left of the det. We could have been more aggressive but I didn't want to risk changing the shape of the combustion chamber too much. 6thou I work out as 0.15mm which might raise the compression a little but the chamfering will reduce it too so I may have raised the compression a little but not too much.

The valves needed to be re-seated which is done. The head will need re-shimming but the builder can skim the shims as required. I also have my other head with shims I can use.

I have unused valve seals available from a previous build so bar some cost/time the engine builder should be able to finish off the head quite quickly.

As always with this car, it's cost me money but it's been an education.

 

[campbellju]

Quick update. After some minor shimming/rebuild issues the head is finally complete. Having 2 heads and 32 shims made life easier.

It's only 8 months since this thread was started!

The engine builder is busy again so asked I push back fitting the head to the block and doing the cam timing for another 2 weeks. :-(

Hopefully have the engine ready in a month (or so)

I'm potentially moving house in the next few weeks so as always the poor GtiR will fall to the bottom of the priority list again.

Progress at least

 

[campbellju]

I've just heard the new head bolts have arrived at my friendly Nissan dealer. I think that's the last piece of my engine jigsaw and it can be all finished off ...... though experience tells me there'll be something else

 

[The Doc]

About time jim!

 

[fubar andy]

Yes, good to see your almost done.

If you need a hand putting the engine in, just let me know!

 

[campbellju]

Thanks gents. Just been spending too much time fixing up the new house. Haven't had time to wash the cars recently let alone stick an engine in one of them. Help much appreciated Andy

 

[campbellju]

Dropped the new head bolts off at the engine builders this morning, he is swamped in cars and engines so has scheduled mine in for 6 weeks. Plenty to keep me busy on other home projects but frustrated as the engine is so close now. Would rather he finishes it off as a complete unit in case of issues but the glacial pace is annoying