302 with weiand 174 spark blowout?

[jvail]

Here is my combo: stock '90 302 with Edelbrock RPM heads, 1 5/8 to 3" headers through hooker max flows dumped behind cab, hooked to t-5 tranny. I have recently added a weiand 174 and boost is between 8-9 lbs. I also am running e-85 through a race demon RS with the 775 size sleeves in it. My problem is that when it gets to about 5000 RPMs is always seems to backfire out the exhaust. I have a Innovate DB wide band and have tried jetting to 13:1 all the way to 10.5:1 (all on gasoline scale) and nothing seems to get rid of it. I am beginning to wonder if I am getting spark blow out? I have autolite 3923 plugs gapped at 35. I have tried advancing the ignition timing between 28* and 32* btdc, and nothing I do seems to get rid of it. I also have a new summit dist, and MSD blaster 2 coil. Everything seems to work well until I get up high in the rpm's. I am at a loss and could use some suggestions please? Thank you, Jon.

 

[mini274]

Is you distributor locked? and on most boosted engines the higher the Rpm the less timing you need my suggestion would be msd6al and a timing retard switch in cab so you can dial it in while driving but try retarding your timing first...

or if you got the buck check these out
http://www.summitracing.com/search/...D-Boost-Timing-Master-Ignitions/?autoview=SKU
that will do everything with your timing from inside the cab so no run then move the distributor

 

[jvail]

At first I had it locked at 28* then tried locked at 32*. Neither one seemed to make a difference. Now I have it set with 14 mech. advance and 14 initial.... still same problem.

 

[Jason]

High alcohol engines, whether methanol or E-85 are a bitch. Not to sound obvious but have you checked your advance? It may need to be dialed back a bit especially since the stuff you are running for timing was probably intended for gasoline which requires way more advance than e-85.

 

[jvail]

I have checked it where it is and at 32 degrees, with a dial back electronic timing light. I have not tried any less than 28* advance yet. From the info on the net is seems to say that e85 needs more advance than gas does. I will try that today.

 

[Jason]

That's correct. I had my alcohol head backwards.

 

[Davis]

You may want to close the gap a bit. I have found that I get blowout at high boost (20+ lbs) as well, and gap my plugs at .028 which is actually the factory gap for the Turbo Coupe (which ran 14 lbs factory). Also, an MSD or similar box would help with the blowout issues.

 

[jvail]

Well I got it figured out... New bpr6e plugs gapped at 20 and no more backfiring.... much smoother running and no hesitation. I had ended up calling the NGK technical support and they told me that even on N/A e85 engines you need to start with about 30 gap on plugs because it is much harder to ignite than gasoline. So now I am at 8-10 psi and much better!! Thank you for the help!

 

[skyy_4life]

yea first thing i was gonna say is close the gap some.

glad you got it figured, post some pics

 

[jvail]

I don't have any yet, but I will get some up soon (hopefully this weekend!) so everyone can laugh at my stupid truck. Don't feel bad about it I laugh too ! I still need to do a few things with it, but at least it is drivable now.