Hey Everybody! Here is the question... I am running a mostly stock BB 400ci with a pretty good size cam, edelbrock intake, rebuilt Q-jet for preformance, TA chrome headers, and HEI , turbo 400 W/ 2800 stall and 411 rear. What temp plugs should I run and what plug gap? I changed the plugs and they are a little ash colored but not much, with a 160 temp thermostat the cars runs at 190 which i think is OK but I was hoping to bring down the temp buy putting in a cooler plug. Stock is AC R44TS and I was thinking about ACR43TS but what gap for HEI? And will that help with the overall Temp? Thanks !! David
Hi David. 190*F is not too hot, it's pretty much right on the money. I'm using a 160*F t-stat on my 455 block right now and I think it's a mistake, particularly since I run synthetic oil- I don't see 161* until I hit the highway, then it's 190-210* depending on how hot and humid it is. The synthetic needs to be at a higher temp to get rid of moisture in the oil. Unless you have an overheating problem, which the 160* t-stat won't really fix- you're just covering up the problem, not solving it- cooling down the engine may actually rob you of performance. A hot engine is efficient, in general, so long as it doesn't damage anything. Don't forget that in a 15 psi cooling system like the one you most likely have, the boiling point of your coolant is not the boiling point of water at atmospheric pressure- the 15 psi system raises the boiling point from 212 to 247*F. The gap my '71 to '78 Chilton's manual calls for in a 1974 Buick 455 with HEI is 0.040". I have talked to various people about this, and it may be wiser to go to a 0.035" gap for a more intense spark- I haven't tried it myself yet.
hot or cold? Thanks chris, Yes I run a 15 pound cap. and know about the diffrecnce in the boling point of water under pressure, two things: do you run a 50/50 mix of antifreeze/water? As the anti has a higher boiling point than water it would seem that you would want more anti but... water dissipates heat faster than anti-fereeze. I have read that some guys run 100% water with an additive, but I have not tried that yet. Secondly, the stock gap for the plugs are .035 running points but I was told by a freind tha when you run HEI it needs to be at around .045 ? I was under the impression that the wider the gap the faster and cleaner the cylinder burn, maybe I am spliting hairs though! :grin:
There was a thread a while ago on plug gap, I'd have to hunt for it. I run 60/40 anti to water or at least i try to. probably more like 50/50 in practice though
I've never messed with colder or hotter plugs, to be honest. I use R45TS plugs, the heads are smog heads so I stick with the stock ones for right now
plugs back when our a-bodies were manufactured , u used the hotter plugs if most of your driving was city/stop & go , and cold plugs if your driving was mostly/all highway .
The heat range of the plugs has noyhing to do with the temp the engine runs . A colder plug will lose heat from the tip faster. If you look at the different plugs ,you will see that the porcelain of the cold plug contacts the side of the plug quicker ,and that is why it is colder.
:laugh: Okay Joe, that being the case.....which should i use, porcelain, or plastic.....my coffee wont stay over 90deg maby i need to re-gap my Mr coffee. Sorry Joe..couldnt resist.. Dave Dechent
Head Gapper!! I would like to see the "HEAD GAPPER" used for that!! Sounds like the name of a Rock Group!!:beer
If Dave does not straughten up, Dana will be using a Louisville Slugger to adjust the GAP!!:beer :beer :TU:
:eek2: Joe!!! You have one of those there head gappers??? Dayna said i could use a tune up anyway!!ou:
Is it too late to say something about plug gaps? With a good HEI set up, I'd run .045" I have had no problems with that gap. Also, I use as cold a plug as I can buy. It helps keep the knock and ping down with modern gas and older engines with high compression. My space gap... I mean - 2 cents Andrew
