Adv. Timing on a high comp, big bore.

[nakomis0]

Welp. I have a 440 with around 11.5:1 comp.

Dispite the Sparks recommendation of not adding a degree key to a 440, or any high compression motor, I installed thier key.

I felt a snappy throttle response through out the powerband.

Just for curiousity I called sparks to see thier reasoning about not recommending the key on high comps.

From my understanding of what he was saying, they don't recommend it because its increasing the compression to much and causing pre detonation.

But i still don't understand, I could understand more if it was only very high compressions like 12:1 +, but a mild 11:1 with thin gaskets?

Even if the increased comp. does cause pre detonation, couldn't this be fixed with a 50/50 mix of 93&110 octane fuels?

I've still been running only 93 octane with the near 11.5:1 comp and the 6 degree timing advance key. I cannot hear any pre detonation. But I do plan to run slightly highter octane in the future.

I'm just wondering about these keys and what you think about running them on higher comp, 440s.

[woprs50]

i still dont know if my 400 has and advance key in it but it had a JE 11to1 piston and would spark knock on 93 octain and still did with a half and half mixture of 93 and 110 the only way it didnt do it was straight 110 my motor is apart right now and im going to pull the flywheel off to see if it has and advance key in it and if it does its going by by

[cals400ex]

Originally posted by woprs50
i still dont know if my 400 has and advance key in it but it had a JE 11to1 piston and would spark knock on 93 octain and still did with a half and half mixture of 93 and 110 the only way it didnt do it was straight 110 my motor is apart right now and im going to pull the flywheel off to see if it has and advance key in it and if it does its going by by


maybe your jettting is just too lean.

[woprs50]

it had a 172 main jet in it and it still had stock exhaust and the plug was a little dark the guy i bought it from said that it was jetted for when he had a Duncan double barrel pipe on it but im gettin the FCR 40mm before it goes back together plus i ported the head and got sparks exhaust so ill have to rejet it when it goes together

[cals400ex]

Originally posted by woprs50
it had a 172 main jet in it and it still had stock exhaust and the plug was a little dark the guy i bought it from said that it was jetted for when he had a Duncan double barrel pipe on it but im gettin the FCR 40mm before it goes back together plus i ported the head and got sparks exhaust so ill have to rejet it when it goes together


i could have still been lean on the pilot/fuel skrew or the needle taper, diameter or the clip position.

[nakomis0]

Originally posted by nakomis0
Welp. I have a 440 with around 11.5:1 comp.

Dispite the Sparks recommendation of not adding a degree key to a 440, or any high compression motor, I installed thier key.

I felt a snappy throttle response through out the powerband.

Just for curiousity I called sparks to see thier reasoning about not recommending the key on high comps.

From my understanding of what he was saying, they don't recommend it because its increasing the compression to much and causing pre detonation.

But i still don't understand, I could understand more if it was only very high compressions like 12:1 +, but a mild 11:1 with thin gaskets?

Even if the increased comp. does cause pre detonation, couldn't this be fixed with a 50/50 mix of 93&110 octane fuels?

I've still been running only 93 octane with the near 11.5:1 comp and the 6 degree timing advance key. I cannot hear any pre detonation. But I do plan to run slightly highter octane in the future.

I'm just wondering about these keys and what you think about running them on higher comp, 440s.

[04'400ex'er]

Originally posted by nakomis0
Welp. I have a 440 with around 11.5:1 comp.

Dispite the Sparks recommendation of not adding a degree key to a 440, or any high compression motor, I installed thier key.

I felt a snappy throttle response through out the powerband.

Just for curiousity I called sparks to see thier reasoning about not recommending the key on high comps.

From my understanding of what he was saying, they don't recommend it because its increasing the compression to much and causing pre detonation.

But i still don't understand, I could understand more if it was only very high compressions like 12:1 +, but a mild 11:1 with thin gaskets?

Even if the increased comp. does cause pre detonation, couldn't this be fixed with a 50/50 mix of 93&110 octane fuels?

I've still been running only 93 octane with the near 11.5:1 comp and the 6 degree timing advance key. I cannot hear any pre detonation. But I do plan to run slightly highter octane in the future.

I'm just wondering about these keys and what you think about running them on higher comp, 440s.

I would definately run at least a 50/50 mix or even better a 70/30.
the 70/30 will usually run cooler then stock so with the overheating problems you get with the keys, i would definatly run one of those mixes.

[SHADETREE101]

do you notice any heatingissues. i have the same set up in a 416. just to be safe i am running straight 110. i do think that i am noticing the engine getting hotter, but maybe that's just paranoia of the new engine. can anybody tell me what there bikes temp is on a stock one, i do have a raytech gun to check it.

[ewalker302]

It's my opinion that sparks is just covering their own rear end with their reccomendation about not running the key in a built motor. Much the same way pipe manufactures always reccomend a much larger main jet with their pipe than needed.

I've never seen a thread here blaming the degree key for overheating problems, but since it must raise the temp at least a coulple degrees, they are just making sure that they cant be liable for someone running the key and claiming that is what caused overheating/destruction of their engine. Just like a pipe manufacturer dosen't want to hear about ppl messing up their bikes running lean.

Just a liability clause.

If I was running a worked motor, I would get some type of temp guage to monitor engine heat instead of worrying about the degree key.

:bandit:

[nakomis0]

Ewalker, that pretty much what I was thinking. (or hoping)

I been running this setup for a few months now, still only on 94 octane. My temps. are still reading normal. No pinging under loads.

Once summer temps start getting above 85* I'm not gonna trust running the lower octane. I'm sure i'll jump to a min 50/50 mix.

[Quadzilla]

Nak,

What kind of base and head gaskets you running? If you are running EX gaskets, you are not getting 11.5:1 comp (prob more in the mid to high 10's). If you have XR gaskets, then you should be getting 11.5:1.

My guess is that you are running EX gaskets because I am not aware of anyone else running over 11:1 running pump gas with XR gaskets. Pistons are typically built using the XR gaskets as a reference for compression, not the thicker EX gaskets.

I'm running custom Cometic gaskets that C&D has make up for them. They are a bit thinner than XR gaskets (8 thousandths on the base and head gaskets each). I'm running a 70/30 mix of 110 and 93. I've not tried to run straight pump gas yet. Not sure if I want to. I've seen a couple of EX's being towed back with blown motors because they were running 11:1 on pump gas.

Let us know what gaskets you are running. Thanks

[nakomis0]

I'm running the C&D recommended thinner cosmetic gaskets. 11:1 piston.

From what you said, I'm starting to think maybe I should run a higher octane. Temps have been still low around michigan, mid 70s.

I wouldn't recommend pump gas in the summer heat. But I think I would trust (Sunoco) pump 94 octane in the cooler months.