Finally got my 340 running half decent on all motor with the FITECH 1200 after battling a whole bunch of issues with E85. Now that i'm on pump gas, after a lot of logging and tuning, the system finally seems to be adjusting correctly.

I am ready to throw the boost back at it, but since this will be the first time boosting it on pump gas I am very worried about what I should be doing.

It's a 9.2:1 c/r 340 with ported w2 econo heads (about 295cfm), a 242/246 112LSA .609 lift cam and forged pistons. Boost supplied via intercooled procharger.

Right now I have autolite 65's in it. The pulley I have on the procharger was making 8psi when I was on E85.

Should I be worried about 8 PSI on this engine using 93 octane pump gas?
I have FItech controlling the timing.

My biggest questions are, will this be safe? What plugs should I use (2 steps colder, 1 step colder)? What should I do about timing? Where should my AFR's be to start?

I was figuring I'd back my total from 34 to 32 and then retard maybe 1.5 degrees for every pound (so total at max boost would be 20).

I'm new to boost tuning and felt much safer learning on E85, but I figure if I start very safe and sneak up on the tune little by little (maybe with the help of a pro tuner on a dyno) then I will be alright. If there is any serious risk of trying to do 8 psi on pump gas with this then I might have to invest in a meth injection kit.

Atleast 2 probably 3 colder on the plugs and watch the plug gaps .026-.028 is where id start at.
Just take things slow and make sure everything is happy.

I think it will take a bit more WOT spark than that, like 25.
That may be too much cam, or at least too much OL.
Needless to say: start rich. Stoichiometric, 14.7, 13.5 etc. are not relevant, you have to run as dark as you need to, I would begin at 12:1 or richer. In general, the same degree of anti-knock can be achieved by mix or spark, but retard kills more power.
160 thermo.

How efficient is your intercooler?What heat plugs do you have now?

I would start out doing the ignition as you described, do not go beyond 12:1a/f. Rich mixtures are hell on rings, ringlands, and make it difficult to read plugs. Start leaning out the engine to the mid to high 12s. When it feels sharp/ clean, start reading plugs for timing. Add 1 degree at a time. Use ngk plugs, watch the straps. Try to get your burn line ABOVE the bend on the strap if on pure pump, or on the bend with E10 blend.
Spend a bunch of money on several sets of plugs. Be diligent about plug reading. Much easier and cheaper to screw in plugs than change pistons.

On your deal your way safer running 3 to 6 lbs. at max RPM to start with on tuning it on pump fuel
I would screw in a set of Auolite 3932 or AR63, if you want the to run the extended gap plug with the blower I was taught to run a retracted gap plug on any motor under boost
Good luck, don't get greedy on the power

I have taken sooty plugs,made a pass and they cleaned right up and gave a new reading after the change!

I personally like the NGK stuff better, I think it's a little bit easier to read the timing mark. I'd use a -8 plug at that boost level.

Interooled 8psi, just start it fat around 12:1 A/F and your 20 degree mark will be plenty safe. You'll just have to sneak up on it from there, just carefully watching the plugs for detonation.

Good safe starting point though.

Trendz is spot on... buy a lot of plugs, take the time to make a pass and remove all 8 for inspection. Change the plugs, bump the timing, and try again. You can buy NGK race plugs REALLY cheap on www.rockauto.com (like $1.20 a piece)

NGk 4554
https://www.rockauto.com/en/parts/ngk,4554,spark+plug,7212


$1.34 each

Thanks for all the replies everyone! I'll try to answer some of the questions:

Intercooler probably isn't very efficient. It's a cheap eBay special, but it is large (31x3x12 IIRC) and is right up front behind the grille so it's getting plenty of fresh air.
Specs from the intercooler from CX racing (if they are accurate)

----Compress Air Flow Rate: <700Cubic Feet/Min, Rated to 600-800 Max HP
Working Pressure: 5~50PSI
Pressure Drop:2~5psi@35psi; 0.2~0.5psi@15psi-----


Plugs in it now are autolite 65's and heat marks seems to be pretty much center of the bend with 34 degrees, but they are difficult to read. It was much easier to read NGK's from my past experiences.

Cam was spec'd by comp for my boosted application. I thought it was really big myself, but they had all the specs of the motor, head flow chart, what I planned on doing so I put my trust in them. Originally I was going to run this setup at 15psi on E85 and try to make some big power, but the FITECH never worked correctly on E85 . I'll probably try again at some point.

Problem with reading plugs for fuel is the nearest track here is 3 hours away, and not a lot of safe back roads where I can get on it and shut it down right away. I was considering just bringing it to a dyno tuner to make tuning easier/safer but I was still having problems with the blower belt shredding when I last left off on E85. I would love to get it running decent myself so I can address any belt shredding issues before spending money on dyno time, I could worry about making power later.



So from what I am hearing from you guys, for a safe starting point I'll do the following.

160 T stat

NG4554's

Start with total timing at boost at 20 degrees and a 12.1 AFR

I am thinking I may have to address cooling system issues, as I was creeping up to 200 in traffic before WITHOUT boost (cheap radiator, cheap proform low profile electric fans). going to see if I can fit one of my high flow derale fans in place of one of the pro flow ones and hopefully that will keep her cool. I think a lot of it is from the intercooler blocking the radiator.


To be extra safe, I think I have two options. I was going to pick up a 5.0" pulley that would probably drop boost down to 4-6psi. Because I'd eventually like to make more power than that though, I figured for the $120 I'd spend on the pulley I can put that towards a $280 meth injection kit. This way I can be safe and fast. Do you guys think meth injection would be worth it? Possibly make it more complicated to read plugs/tune it (IDK, never used meth injection before).

When you start tunning you may have problems with crank case pressure from ring blowby even if you have a good evac system

I have dual valve cover breathers to a catch can, total seal gapless rings on the forged pistons. The limited time I was on E85 with 8 PSI I didn't notice any signs of blowby on plugs/no oil in catch can or residue around breathers. All I noticed was puffs of white smoke from the breather which I thought was a blown head gasket (and prompted me to do a compression test) but went away completely when switching to pump gas. Not sure if that was normal with E85 or maybe the gas stations here just had crappy moisture ridden E85 in their tanks.

I'd start out on C-16 or Q-16. Get a handle on it and then move to pump gas.

Sounds like it's capable of making some power

He only needs to run 100 oct to run full timing!A waste of $$ with C or Q at 8.50 a gal.

The cam events for different forms of boost (turbo, centrifugal, Roots/twin screw) will be different.
Just for fun: ask Comp the same question for the same boost derived from all 3 sources...?

Dizuster has a pretty good advise, I run NGK 9's in mine but I have a different set up, i run pump gas 93 in mine on the street but at the track I run C-16 waste of money maybe but to me it's good insurance I do turn it up a little from 8lbs up to 11.5lbs by my Fitech data logs. Just start out conservative on your timing and boost level till it's safe. The Fitech is pretty good about learning fuel tables as you go I really like mine.

My point is more that he should use a fuel close to his projected compression ratio after boost

You seem to always have trouble with your blower combo. 💩

Thank you for noticing.

The static compression ratio does not change with boost.
The dynamic compression ratio does not change with boost.
The charge mass increases with boost.
The calculations such as new CR = old CR × (boost + 14.7) ÷ 14.7 are completely wrong.