Anyone have a suggestion for what are the best plugs to use for a dead stock 9.7:1 HJ 5.0L with HEI dizzy and coil but with original HJ cap? Just whatever a blue 5.0L uses? Just wondered if the extra compression makes much of a difference.

I just ordered a set of NGK BPR5FS-11 to give a try. I have seen on a few sites that people have had trouble with the higher compression red 308 with full vacuum advance available at idle, running with 1.5mm gap (BPR5FS-15).

I also just found 8 x new BOSCH SUPER plugs in my shed from probably the 80's, they are to suit VC-VL and WB V8. Bosch H 9 BCY, they are resistive type, copper core. On the back it says 0 241 225 809 (with -388 after that in small text). I cannot find a cross reference for these plugs anywhere.

Edited by user Tuesday, 15 June 2021 10:06:32 AM(UTC)  | Reason: Not specified

Thanks Smitty. The 1.1mm gap NGK were cheap, so if I have to replace no great loss.

This car is pretty much untouched mechanically, however probably 25-30 years ago the prior owner fitted a high energy coil and Scorcher ignition plus a 650 vacuum secondary Holley. When it was at the wreckers I got it from it had a weepy head gasket, so they changed the head gaskets and re-fitted a Holden points dizzy, which is the wrong one (off a HT-HJ 253). It always ran well enough for me to move it out of the shed and give it a run up and down my street (Private Road).

However when I got it running the last time it was running like a pig. I bit the bullet, refitted an original choke operator to the manifold and fitted new stainless repro choke pipes. I had an original 7043284 Quadrajet rebuilt a while back and refitted it, plus the correct late HQ - early HJ air cleaner, plus all the right hoses etc. It now starts and idles right, auto choke works like a dream. It will still need fine carby adjustment on a dyno but goes OK. I ordered a new PCV valve for it and a new PCV source filter for the side of the air cleaner. I even found some of the 38mm pre-heat duct for it from the air cleaner intake down to the exhaust manifold stove. It does still have a miss in it under power, but that is probably a combination of dirty plugs, old dizzy and coil. It has relatively new Eagle silicone leads on it.

I was going to fit a VK HEI dizzy to it that Dr Terry has to rebuild for me plus an original WB HEI coil. However I also have a like new correct HT-HJ 308 dizzy, but it needs cap, points, rotor button, condenser etc. I went looking for those and it was going to be well over $100 for it all, but I stumbled across these new Goss replica HEI dizzy, rotor button, cap and coil for $195 from Spark Plugs direct. Same as this:

https://www.ebay.com.au/itm/202488711470

I know it is cheap Chinese junk (although the coil says made in USA on it), however this car would be lucky to do 5kM per year so its not going to wear out! With new ignition and the right plugs I'm hoping it runs sweet again. I wouldn't be surprised if the plugs come out all gunked up as it has been over fuelling and blasting thick black carbon mixed with condensation out the exhaust. Since I put the Quadrajet on that has stopped.

There was a nice solid non-original 12V ignition source there for the coil too, added when the aftermarket coil was on it that I didn't realise was there, and last week I accidentally dislodged that and it shorted to the TH400 dipstick and turned itself into melted green insulation and smoke both inside the car and under the bonnet. I have to trace it back to its source under the dash and will replace it rather than try and bridge the wiring at the ignition switch (pink to yellow).

I don't know what advance curve is in this Goss dizzy, but when I get the VK one back from Dr Terry I'll try and get it re-graphed to the same as the original HJ 5.0L one and use it if the Goss one has a non-suitable curve in it. I'll probably pull the cover off the Goss dizzy module too and make sure it has heat sink compound under the module and some light oil on the advance mechanism, but as for a low kM unit that will never really rev or work hard there isn't much else to go wrong in it.

Edited by user Tuesday, 15 June 2021 1:29:26 PM(UTC)  | Reason: Not specified

Yeah I've done a few of them over the years with small cap and Ford rotor button, but they are hard to find in good condition now hence why I grabbed this kit. Plus I'm running out of original HEI coils, I had a dozen but now down to 2. This kit comes with a socket type HEI coil so I can run all the original leads, in the past I had to run a non original coil lead.

Normally I just bridge the pink and yellow wires at the ignition switch for the 12V feed, I'd rather not screw with this car's harness though so I might actually solder a wire across the ignition switch spades below the plug connection.

I also only have one original Bosch Aussie made cap and one rotor button left for HT-HZ, and this el-cheapo comes with a cap and rotor button.

HJ's had 10deg initial with 36-44 total. Centrifugal starts at 360-660, intermediate 17-21 and final is 26-32. The VK spec dizzy I have (923 last 3 digits) is a little different, it is 6deg initial, total 34-42. Centrifugal starts at 1000, intermediate 8-12 and final is 20-24. The big difference is the vacuum advance. HJ is 9-13. VK is 14-18. So if the cheapy doesn't go so well I'll get the one back from Dr Terry and get Scorcher to rebuild it to original HJ specs.

I'll grab a Bosch module and keep it spare.