StealthElephant

I've got 10.7:1 compression.

I've got a non-CC HEI distributor and a stock replacement coil. 45,00 volts I believe.

I was running .035 gap when the car was getting 7MPG...but the timing was crap.

My 2nd set of plugs that I'm running now are at .040 gap, they have 700 miles on them.

I have 6* initial timing right now. I'm getting about 9.7 MPG on the 2nd set of plugs.

Before I had been running 9* initial timing and I was getting 8.7 MPG on the same 2nd set of plugs.

I'm going to change my plugs and I'm wondering if I should bring my gap back down to .035, I was even thinking of going down to .030. Also I'm running R42LTS, the coldest plug for the Vortec head. Should I move up 1 heat range?

I'm really not quire sure where to go timing wise. I can't imagine going up 1-2* is going to give me any significant gas milage increase...yet I feel strongly that I should be able to get 12MPG. I dont' think I can realistically go any lower either. I'm running full manifold vacuum. WOT is very strong...the motor is screaming now, I'm not pinging anywhere. I'm at 6* intial now, I wasn't pinging at 9* either, I WAS pinging at 11*.

The car has a very nice stable idle, good response. My only issue is bogging when going from no load to WOT, I've been told I have a pump shot/secondary issue. Reference Thread

I just don't know where I should go from here. I've got brand new 8.8mm moroso wires. The coil is brand new, only 300 miles on it, the Accel distributor was brand new. I'm happy with the performance of the engine, I feel confident when I go to the track I'll be happy. It's the fuel economy that still has be baffled. I pulled the front 4 plugs (1,2,3,4) for general inspection and 2 were black (running rich) the other 2 were perfect. I think #3 and #2 were rich. [This was when I was getting 7MPG, #1 plug was out a fe days ago as I rechecked TDC on #1, the #1 plug looked perfect] I didnt pull the back 4 because they are a PITA to get to.

My only though is that since I drove the car about 400 miles getting 7MPG when I first got the engine running, that I completely clogged my cat from running so rich for so long. I dunno if my compression is limiting me from getting good gas milage...but whatever. Any final thoughts would be appreciated. If 10MPG is all I can get then I guess I'll have to live with it.

ede

i'd set the timing for 34-36 total. have injector stuck hurting the milage?

IHI

iTrader: (1)

I might move the heat range up to a 44 and at the very least a 43. Your plug gpping around .035 is about right, I've never kept track of mpg with mine but have done a .035-.050 with no noticable power difference-that is my moitor though not anybody elses and the larger the gap the harder the coil has to work to arc it, I did notice a definate temp diff. in my 6AL box when I had 'em gapped wide though. If you have a true 10.7:1 compression I'm not sure your small cam has enough overlap to shed some of this to make it pump gas freindly and be an all out performer. I would'nt worry so much about intial timing, rev the motor up to 3K and check to see where it's at for total timing. I've read time and again the Vortec usually like total in the 30-33* total with the effiencent burn, but I'd get the right heat range plug first so it is effeicent. Again, I say you compression is to high for an iron headed sbc and the small spec of the cam your running, for all out you may consider a mix of racing fuel with your 93 octane. A cam in the high 240* low 250*@.050 duration would be alot happier with your compression and iron heads.

I know for the right amount of $$ anythings possible, but for all practical purposes my 11.5:1 motor with aluminum heads and 248/252 cam is about all I want to try for maxing out pump gas, your not too far away with your iron heads.

StealthElephant

Well right now I'm at 30* total timing and WOT feels really good.

I still can't get my gas milage to 10MPG. The timing is retarded as far as realistically possible at 6* initial getting 9.7MPG. 11* initial pinged. 9* didn't ping but it got 8.7MPG.

OMINOUS_87

I would run with an NGK TR6. 6 will be the proper heat range for your setup, in NGK terms. You might want to keep the gap in a reasonable range since your running with factory ignition parts. .040 max IMO with 10.7:1

With a cam that small your mileage should be alot better than what you are experiencing.

StealthElephant

Whats the equivalent of that plug to AC Delco as far as heat range is concerned?

OMINOUS_87

No idea, I only run and recommend NGK.

You can find a very large selection of NGK at NAPA.

They should have TR6 in stock.