200GT, 2.5L....91 or 87 Octane??? (UPDATE)

[walleyehed]

As Dhadley knows, I've been told to run 92-94 Octane in this engine, and for fear of ruining the shops machine work, I have ran 91, which is <br />as high as is available at 3600ft, for the last 2 months.<br />My question is, and this is for you too, DH, has anyone been running any lower octane in the GT/XP series (Early '80's) 2.5L, and how has the success been if so???<br />91 is very pricey, and I'd like to go to atleast 89 if I can.<br />I still have the sea-level jets in, and timing set for break-in period, and it's been more than long enough to start working this set-up for some extra R's, but do I dare get away from the 91 Octane????????

 

[Dhadley]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

I never ran anything except 87 but that was always with stock deck height and uncut heads. stock port timing also (I assume your ports are stock).<br /><br />With a set up like yours where its been running fine I'd suggest going richer on the mid and hi jets and then test with the 87. Then sneak back up on the leaner jetting.<br /><br />Now, when we put small bore heads on a big bore motor we always go to 93. In that case, really bad things happen if you dont.<br /><br />I just cant help but wonder why they insist on hi test if the heads arent cut. I asked Dan why and he said thats just what they do. But there has to be a reason.

 

[walleyehed]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

Thank you for the response, DH...<br />Being at 3000ft and above, I've always had to drop 2-3 sizes (Lean) after break-in due to being sloppy rich at this altitude, and man it's rich....<br />I guess I better call Dan and ask if they cut these heads any...I don't think they did.<br />Another question I have for you, and this could very well be related to how rich it is due to going 3 steps richer on the idle circut for boyesens, even though I've not done that in the past, again, due to altitude....My Idle is very rough...it never dies, or spits back or coughs, but it's very rough. Matter of fact, this engine doesn't really smooth-out until you hit 2K, then smooth as silk from there-up. Not one of the charactoristics I'm used to seeing with boyesens..<br />Any hints on smoothing up the Idle???<br />Thanks, Sir!

 

[Dhadley]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

What Ive found is that the riching up is to protect the reeds from a possible burning on initial start up. If your motor doesnt sneeze then it'll be fine. Since it is too rich now at idle, especially where youre at, I'd go back leaner.

 

[walleyehed]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

I'm a gonna try the original sea-level bleed air orfices and see how it runs....<br />Thanks!

 

[Dhadley]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

Keep us posted (so to speak).

 

[walleyehed]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

Changed idle bleeds back to .033's...only notice less smoke at Idle...still not "Real" smooth, and it won't Idle at 650...about 700 is as slow as it will run without dieing...no sneezing though!<br />I ran about 70 gallons of 87 oct. last week, after running about 50-60 gallons of 91,(all in 4 days..????:-( ) and I can't say I noticed a bit of difference, and the plugs look the same.<br />I'm still retarded about 3 degrees and I think I'm going to start bumping that up and see what happens(WOT).

 

[Dhadley]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

What pistons did you use?

 

[walleyehed]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

New Wisecos...3173P3

 

[Dhadley]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

Good, it should be able to get to 650. We just gotta keep plugging along. (so to speak)

 

[walleyehed]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

I've still got the QL77JC4 plugs in it I've had since break-in....I suppose it would be wise to screw a new set in..???

 

[Dhadley]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

It might not hurt. I had over 250 hours on those in my cf before I put new ones in. Didnt really see any difference but ya never know. Cant hurt.

 

[walleyehed]

Re: 200GT, 2.5L....91 or 87 Octane??? (UPDATE)

You have email coming, subject: PROP....