Heands and Jetting

[dkramer]

All,
I recently put new heads on my 88 200 2.4L Merc. I bumped the compression approximately 15psi. I was approximately 120psi on all 6 cyl. before and I am now 135psi on all 6 cyl. I have not changed the jets as of yet and have done a few short runs and checked the plugs afterwards and they are still oil coated nothing pointing to any lean condition. I also added velocity stacks not too long ago. My question is should I up my jet size in my carbs and if so how do I tell what jet I have now and also what jet would I move up to? Any info would be appreciated. The motor is running good but I don't want to lean it out and cook anything.

Thanks,
Dave

[dkramer]

where is the merc carb gurus at, i need some help with this.

[terry taylor]

HI. I realy don,t see an area for concern ,you appear to have a very safe margin. I run 140 psi. 87 octane Canadian upping compp. aparently improves throttle response low end midrange power any change is needed it,s mids.because you are at full spark advance with least throttle openning[cruising rpm] if short burst results are as you explain mixture is fine no need for change [upping octane a littlemay make you feel more comfy but then again may not be necc.given your plug cond.] PS.I am not a guru but i am happy.thanks

[Fast Fred]

the size is stamped on the jet. try to get a look at the piston crowns as well as plugs:cool:

[dkramer]

I run 93 octane all the time just to be safe. I just don't want to lean the motor out. I will pull the plugs and check them again and also take a look in at the cylinders to see what I am seeing. If I were to up the jets could I cause any harm? I will take a look at the jets and see if I can get the sizes off of them as well. I will keep you posted.

Thanks,
Dave

[terry taylor]

HI. DKRAMER It is important to note In your changes and some others a side benifit smaller comp. increases as yours is better fuel economy. the fuel oil supply is there for standard com,chamber volume. Your decrease in comb . chamber vol.draws from same supply but uses less of it each stroke. hence better milage, My point is t his creates richness adding a [little] more oil should make you comfortable extreme high rrrs[racing drags] is a diff. area this post along with my other is my pleasure. THANKS

[dkramer]

I typically run 50:1. Do you think that is enough oil?

[terry taylor]

HI. Yes that is Mercs. recommended along with most other mfg,s. Also synthet ics 100% that is are far superior in ever aspect a few more $s well spent. Y our engine will thank you for it. thanks.