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  #1  
Old 07-13-2003, 05:29 PM
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Plug Question: Can a Bosch H9DC be used in a 2.3 8v?

In checking the owners manual, it seems I should have got H8DC's instead but I thought I'd ask- Can a Bosch H9DC be used in an 87 2.3 8v?

Thanks in advance,

Haasman
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Old 07-13-2003, 06:29 PM
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haasman

I don't believe going one heatrange hotter would make a lot of difference, unless you do a fair amount of balls-out driving.
In many cases, one heatrange hotter is actually recommended on higher mileage engines.
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Old 07-13-2003, 08:31 PM
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As a general rule, as compression/ compression ratio goes up, the plug temperature goes down. A cold plug is more easily fouled than a hot plug.

So, ... a high hour engine can benefit from a heat jump as , not only has its compression weakened, but a hotter plug will foul less from oil deposits common on h/h engines, [ burns them off better].
On newer lean burn engines. I would prefer oem spec...
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Old 07-13-2003, 09:17 PM
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OK, so what I am hearing is, it is OK to install Bosch H9DC plugs in the '87 190E 2.3 8v instead of the H8DC plugs.

The car has 215k miles.

Haasman
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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Last edited by haasman; 07-13-2003 at 10:05 PM.
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  #5  
Old 07-13-2003, 09:50 PM
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For a given cylinder head design, plug heat range is primarily a function of how much heat is released in each cylinder. The 2.3 has a larger cylinder than the inline sixes, and on average each 2.3 cylinder has to work at a higher level of power (which means more heat), so that's probably why the OEM plug for the 2.3 is one heat range colder than the sixes - 8 versus 9.

Unless you drive the car real hard, I don't think a "9" is going to be a problem, and a slightly hotter plug will usually reduce oil ash buildup on the insulator that is typical of older engines with higher oil consumption.

In the world of vintage 327 CID Corvette engines, GM always recommended an AC heat range "4" (AC44), but I learned long ago that 44s usually foul rapidly and heat range "5" (AC 45) works best for normal town and highway driving, and this applies to both the medium performance engines (250 & 300 HP) and Special High Performance/Fuel Injection engines (340 to 375 HP). Though the SHP/FI engines have significantly greater output, in normal street driving you can only use that output for a few seconds at a time. One average, in normal driving, all engines were running about the same power/heat per cylinder.

For hot lapping sessions I ran AC 43s with good results and when I ran my 2.6 in the '89 Silver State Classic Challenge, I ran a Champion BN60 racing plug that was probably a bit colder than Bosch heat range "6". For sustained high output you need to run a cold plug. Otherwise, excessive tip temperature can get the engine into preignition, which leads to detonation, and major damage in a hurry at WOT and high revs.

It's always best to err on the cold side because it's much better to foul a set of plugs than burn a piston or valve, but in the case of running a 9 in a street driven 2.3, I don't think it will be a problem.

Duke
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