I would swap to NGKs and try that first. Then drop the timing.

 

ugh, of course I was running NGK's before

 

+1 for Bosch platinum plugs not getting along with BBMs! I've only had bad experiences with those plugs.

-dave

 

fwiw, I ran ngk 9's all this season. 2000 or so street miles. No fouling problems at all. I'd start with changing to 7 ngk's at least w/ a .025" gap and bump timing down to 25.

 

googling xr7's or 9's doesn't find a place to buy them, anyone got a link? A friend told me that lopo's got hotter plugs than the HP engines and I did find that on ngk's site (4's vs 5's), interesting to know. Don't see 7's or 9's though.

 

Haven't fired mine yet but this is what I am using,

http://www.ebay.com/itm/NOS-NGK-Spa...Parts_Accessories&vxp=mtr&hash=item335d3db733

 

I agree on putting a better plug in it. If its primarily high rpm detonation I would take it to the track where you can see some numbers.
Pull the timing down to 18- 20 deg. and make some 1/8 passes. If it doesnt detonate pull the plugs and make sure there its not detonating.
Then bump the timing 1-2 deg. at a time until it doesnt go any faster pulling the plugs every run. If it detonates it will loose power and slow down or just not go any faster before you can hear it.

When you can hear it detonate its extreme.

 

I often heard my old shelby charger rattle if I got a subpar tank of oxygenated junk, so I guess I'm used to it When this engine was still carbed and NA it would rattle pretty easily, the stock timing curve was too aggressive. When I switched to EFI NA that all went away. Back then I was using xr5's I'm pretty sure.
We had an 86 5th ave that would rattle all the time too, we didn't care much about that car tho.

 

Matt is going to hook me up with a good deal on the NGK's hopefully!

 

Don't be afraid to take some timing out of it. 18 deg. wouldnt hurt it (maybe power).

 

This is some info I found on plug comparisons.
NGK B7S
Champion J4C
Accel 0123
Denso W22S-U
Motorcraft AZ2
Bosch W5E or W5EC
Autolight 313 or 353
AC Delco C42-1 or M41K
These are all the same non-projector and heat range but I haven't seen them all. I use the ngk and accel at .025" with success. 440 cu in ported 452 heads 16lbs boost on 94 octane with 1200cc min water/meth. Great mileage and zero fouling issues.

 

Oh yeah, 28 degrees timing.

 

My mentor recounted to me that 'back in the day' Ak Miller stated that almost all turbo engines of the time ran fine (or even best) at 26* under boost. My engine is very old school so that recommendation would apply. I moved to 26*, still with the boschs, and was able to pull cleanly to 5000rpm. Backpressure approached 4:1 at that point, tho air temp stayed at 160*. It was 55* and windy ambient.
I do plan to switch to the B7s's over the winter. And water. and more boost?

 

ok, Matt found ngk 2891's which are 7's projected, the b7s's are non projected. For a street car, 5-10psi, and given that I solved the detonation with 26*, I'm thinking I'd be better off with the protector style for low rpm/cruise burn? Or will it not make much difference so buy the b7s to be safer?

 

That would be a tuff statement these days. Combustion chamber and cam timing events alone can affect total timing.
Its not uncommon these days to see an intercooled SBC run total timing in the mid to high 30s with 30 psi boost.
Just to many variables. Non IC , A2W, A2A, 110 oct, c16, q16, e85, methanol.

 

Yes, but in the late 70's/80's when Ak was popular everybody had smog heads, reverse split cams, 8:1, and regular gas.

A truly modern head wouldn't need to be in the 30's for timing NA or boost.

 

If you wanna consider a modern head to be an LSX, Modular, most imports than yes you could say that about timing. Most of these type heads boosted are in the 20ish range or below.
Like I said combustion chamber is ONE big factor in timing.

SBC (not LSX), SBF, BBC, BBF, Chrysler, dont have fast burning chambers compared to the newer stuff. Even most of the big Bad MOFO heads dont have quick burning chambers in comparison.

 

What does a modern head have to do with this combo. What might be hurting you some is the 516 is closed camber correct? With the closed camber and steel head with probably a piston that is at least .070" in the hole... Makes for a detonation prone combo. Personally I would not add boost with that much backpressure. You are at he limit of the turbos anyways. See if you can find some small turbos to help kill the backpressure.

 

516's and .088 in the hole and .020 gasket so no quench whatsoever. The way the fab worked out I don't have room for much of a bigger turbo, the turbine and compressor housings are pretty tight. A wheel change would fit best, even though those can be ~$250 each I think?

 

I would think if that is your only option it is worth a shot. Adding boost at that high of a backpressure will probably not add up to much more power because it will take the boost just to overcome the added backpressure. Doesn't hurt to give it a quick try though.