Are my intake valves sinking?

rickman74 · Posted: Sun Jul 05, 2015 6:24 am Post subject: Are my intake valves sinking?

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Hi I installed these new 040 heads from brazil about 3 years ago. I've always been running real hot on the highway (400-450). I decided the pull them off and check the compression ratio. I calculated the cc volume at 48 cc which gave me a cr of 8:1 with my deck height of .06. I want to lower it to 7.5 so I've ordered .02 barrel shims to increase the deck height which gives me a lower cr and hopefully a cooler head.

I put a straight edge across the ends of the valves and the two exhaust valves are sitting lore than the intakes. It seems like the intake valves are sinking, what do you think?

I tested cylinder compression and I have 145 psi all around, which led me to think that high compression was the source of my problem.

If the intakes are sinking do I need a head rebuild?

All help appreciated.

Bleyseng · Posted: Sun Jul 05, 2015 6:55 am Post subject:

.08" is pretty big deck height and will make a less efficient running engine. Tighten the deck but use dished pistons to get the CR you want.
What are you setting the timing at?
_________________
70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles

rickman74 · Posted: Sun Jul 05, 2015 7:14 am Post subject:

I set my timing at 28. Don't want to spend the money on the dished Pistons, this is an exercise to see if lowering the cr helps my high heat readings.

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50352

I would have a tendency to tighten the deck to .040" and then run the timing a few degrees more retarded, maybe 26° BTDC at full mechanical advance.

What fuel system are you running? Have you had you AF ratio checked? Are you sure you have identified the correct timing mark on your pulley? Maybe its time to buy a degree wheel pulley.

http://www.geneberg.com/product_info.php?cPath=7_223&products_id=810

rickman74 · Posted: Sun Jul 05, 2015 11:30 am Post subject:

hi wild things, I'm running a 34 pict 3 carb from air-cooled net with a svda can. The dimple on my pulley is accurate for 0 TDC, i've checked it with the heads off. I've never done an AFM test, but judging from the sooty chambers I'm not running lean. I've tried every combination of timing and the heat is hot or worse.

How about those intake valves? I've checked an old set of 311 heads I have and they have similarly uneven valve stems. Is this head pooched?
m

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50352

I would have to see better pictures of your heads before making a comment about them.

captincanuck · Posted: Sun Jul 05, 2015 7:34 pm Post subject:

My valve was slightly sunken, but not much. Didn't look to bad. Right?

Popped the valve out to have a closer look and this happened.

New head time for me. (Had great compression BTW)
_________________
1979 Westfalia "FireFly" Subaru 2.2 with Subaru gears 5spd.
Build Thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=634777&postdays=0&postorder=asc&start=0

Wasted youth · Posted: Mon Jul 06, 2015 2:54 am Post subject:

Are your intake valves sinking? Can't tell by your photos, but like captincanuck, I made some irritating discoveries:

http://www.thesamba.com/vw/forum/viewtopic.php?t=614510&highlight=

borninabus · Posted: Mon Jul 06, 2015 7:47 am Post subject:

i was able to keep my deck reasonable--not optimal, but reasonable-- by opening up my combustion chambers.

http://www.thesamba.com/vw/forum/viewtopic.php?t=478262

i was very pleased by the results Smile

_________________
88 Van WBX, A/T - 13 JSW TDI 6M/T - 2012 Touareg TDI Sport

Bleyseng · Posted: Mon Jul 06, 2015 11:50 am Post subject:

rickman74 · Posted: Mon Jul 06, 2015 4:24 pm Post subject:

OK OK!
I dropped my heads off at german supply. Scott will send them out for a rebuild, he's also gonna get me some dished pistons . Does anyone know how many cc's the dish adds?
Thanks for your input.

Bleyseng · Posted: Mon Jul 06, 2015 6:34 pm Post subject:

Stock VW 94mm bus were 15cc, stock 914 94mm were 10cc

I hope to visit my brother in law soon in Markham and go eat at Congee Queen! Love T town!
_________________
70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles

captincanuck · Posted: Mon Jul 06, 2015 8:55 pm Post subject:


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