Valve Clearance? |
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Valve Clearance? |
last337 |
Aug 19 2013, 02:33 PM
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#1
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Member Group: Members Posts: 421 Joined: 4-December 12 From: New Orleans Member No.: 15,221 Region Association: None |
Can someone explain this to me? I have been fighting with this thing for some time now. I had so many problems for so long with my engine just dying and after pulling my tank and changing fuel lines and filters I am back running again.
Now I am having another issue where I will get my dual carbs tuned just right at operating temp and be running just fine. However, after a while I start to hear backfiring again. The only thing I havent done in a while is set my valve clearances. Actually it has been a long while since I have done that and I am suspicious about it being the culprit. I understand how if my timing was off or my mixture was off I could hear pinging or backfiring through the exhaust. But I dont know why my valve clearance would do that only as the temp of the engine changes or just seemingly by itself at times. Can someone explain how proper valve clearance is so critical? |
r_towle |
Aug 19 2013, 02:42 PM
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#2
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Custom Member Group: Members Posts: 24,586 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
Valves set to tight will remain open longer than they are supposed to.
Creates hard starting, low power, and backfires up the intake. Valves too loose creates lots of valve tappit noise and lower power due to not opening enough. Valves are set cold because as the engine warms up, the aluminum push rods get longer...so you end up with zero lash when hot. Setting them hot sucks, but can be done....wear gloves. If your carbs are getting worse as the motor gets hotter, you need to be looking at possibly intake leaks, and possibly linkage binding up when hot. Here is how I put gaskets on the carb setup to prevent boiling the fuel when the motor gets hot. Another "car runs worse when hot" issue. It also prevents intake leaks. head rtv sealant gasket phenolic spacer gasket rtv sealant manifold then rtv sealant gasket spacer (sometimes, not always...unless I have having boiling issues) gasket rtv sealant Now, I use the sealant very very thin. Its just smeared on both sides of the gasket to ensure a tight seal to the head and the spacer. I have found that most of my leaks are head to manifold and not manifold to carbs...but that is my experience. Sometimes I have needed to trim the gasket and the spacer to get around and away from the cylinder head tin which can intrude on me trying to get a tight seal down there... One more issue when hot. Distributor advance plates with OEM grease from 40 years ago stop moving. The grease is more like glue now... Fix is to remove advance plates, take them apart, clean and re-grease. Put it all back in place... Its another super hot thing when the motor is running...cant touch the distributor. RIch |
last337 |
Aug 19 2013, 03:29 PM
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#3
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Member Group: Members Posts: 421 Joined: 4-December 12 From: New Orleans Member No.: 15,221 Region Association: None |
Thanks for the info! I guess I need to go through it again then.
Do you know where I can buy the phenolic spacers? I cant seem to find a vendor for anything other than the paper gaskets. |
last337 |
Aug 19 2013, 04:05 PM
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#4
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Member Group: Members Posts: 421 Joined: 4-December 12 From: New Orleans Member No.: 15,221 Region Association: None |
I see a few on ebay but would rather get them somewhere else.
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monkeyboy |
Aug 19 2013, 04:50 PM
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#5
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Senior Member Group: Members Posts: 808 Joined: 8-June 08 From: Los Angeles, Ca Member No.: 9,147 Region Association: None |
HAM sells them
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last337 |
Aug 19 2013, 05:08 PM
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#6
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Member Group: Members Posts: 421 Joined: 4-December 12 From: New Orleans Member No.: 15,221 Region Association: None |
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euro911 |
Aug 19 2013, 05:25 PM
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#7
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California |
Thanks for the info! I guess I need to go through it again then. Do you have a 2.0L or a 1.7/1.8L?Do you know where I can buy the phenolic spacers? I cant seem to find a vendor for anything other than the paper gaskets. There's a guy on the board (Carl), who goes by MRRAGPICKER that sells 1.7L and 1.8L spacers pretty cheap |
jsayre914 |
Aug 19 2013, 05:27 PM
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#8
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Speed Up !!! Group: Members Posts: 3,188 Joined: 10-February 08 From: Timonium MD 21093 Member No.: 8,696 Region Association: MidAtlantic Region |
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Dave_Darling |
Aug 19 2013, 05:29 PM
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#9
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
http://haminc.biz -- Len Hoffman, Hoffman Automotive Machining. Knows more about Type IV cylinder heads than probably anyone alive.
The standard "gaskets" used in fuel-injected applications are phenolic block spacers. So all of your favorite Porsche or 914 specialists will carry them as well. (My favorite is in my sig, but I'm a bit prejudiced.) --DD |
last337 |
Aug 19 2013, 05:31 PM
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#10
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Member Group: Members Posts: 421 Joined: 4-December 12 From: New Orleans Member No.: 15,221 Region Association: None |
Thanks for the info! I guess I need to go through it again then. Do you have a 2.0L or a 1.7/1.8L?Do you know where I can buy the phenolic spacers? I cant seem to find a vendor for anything other than the paper gaskets. There's a guy on the board (Carl), who goes by MRRAGPICKER that sells 1.7L and 1.8L spacers pretty cheap I have a 2.0L. How different are the 1.7 and 1.8? |
euro911 |
Aug 19 2013, 06:12 PM
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#11
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California |
I believe they all have slightly different ID diameters and the 2.0L only have 3 stud holes instead of 4.
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r_towle |
Aug 19 2013, 06:23 PM
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#12
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Custom Member Group: Members Posts: 24,586 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
Get the right ones or they won't line up.
Get 2.0 liter spacers. So, seeing as you don't have them, there is a phenomenon named hydro lock on carbed cars that can happen when you stop the car. These motors actually get hotter right after you stop them, as a heat sync. This can boil the fuel, overflow that fuel into the cylinder, then you cannot turn over the motor because its now filled with enough fluid to hydro lock the piston in place. Spacers help prevent this so you isolate the carbs from the motor with some plastic....phenolic spacers are the normal thing we all use, cause they can be bought everywhere. Rich |
last337 |
Aug 19 2013, 06:42 PM
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#13
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Member Group: Members Posts: 421 Joined: 4-December 12 From: New Orleans Member No.: 15,221 Region Association: None |
Get the right ones or they won't line up. Get 2.0 liter spacers. So, seeing as you don't have them, there is a phenomenon named hydro lock on carbed cars that can happen when you stop the car. These motors actually get hotter right after you stop them, as a heat sync. This can boil the fuel, overflow that fuel into the cylinder, then you cannot turn over the motor because its now filled with enough fluid to hydro lock the piston in place. Spacers help prevent this so you isolate the carbs from the motor with some plastic....phenolic spacers are the normal thing we all use, cause they can be bought everywhere. Rich I have never had a problem with the motor locking up to that point where it wont turn over again but then again I dont do much stop and go driving. If I do stop it is usually for a beer and a burger (IMG:style_emoticons/default/beerchug.gif) Anyways, trying to understand a bit more...I know that dual carbs are preferred to singles because of the long runners and the fuel turning back to liquid in the runners. What other effects does the heat radiating to the intake and the carbs have on the engine performance? |
r_towle |
Aug 19 2013, 06:45 PM
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#14
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Custom Member Group: Members Posts: 24,586 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
CALL gprparts or pelicanparts.
You want the following, in my opinion. Engine is 2.0 liter type 4 motor. Two phenolic spacers Four gaskets, head to intake manifold. Two sets (could be four pieces) of weber manifold gaskets. If you call, John at GPR or the team at pelican will help you fast and simple. Rich |
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