it may seem like a stupid question, but im haveing alot of trouble. heres my problem..... i have a tuned port injection "block" with a 600cfm edelbrock carb slapped on top with no changes to the rods or jets. im getting major detonation with my crapy bosch platinum +4's, and i have to keep the base timeing down to 4 and use 92 octane to keep it from detonateing like crazy going up any hill. my main question is, what kind of spark plugs should i be useing? should i go by the book (in the store) and get some spark plugs that are recomended for my car? i know the heads have a higher compression than normal because they are tpi heads, and thats probly whats causeing me this problem, but i cant aford new heads. my car runs fine but im getting ****ty gas milage. im lookin into getting some ac delco rapid fires seeing as how its so recomended by all u guys. theres also the heat range issue, but i figure if i use plugs that were ment for a tpi engine it should take care of the problem, am i right? i want to do it right this time and get the proper plugs for my engine, changeing the spark plugs are a pain even without the emmisions equipment, so i dont really want to do alot of "experimenting" with different heat ranges. also what about gapping the plugs? how do i know what to gap them to now that i have this odd engine combo? is there some kind of formula i can use to figure out what heat range/gap setting i need?

 

Bad news for yea. The spark plugs are not gonna fix this unless they are so wrong it's not even funny... I personally like the OE # A/C Delco with second choice Autolite. TPI Block and heads should be ok, I don't understand, what's up with the compression ? Whatcha got for pistons ?

 

im not sure what ive got for pistons, but its basicaly a stock tpi engine block with a carburator intake manifold and a 600cfm carb on top. tpi heads are suppost to have a higher than normal compression. and i also heard from alot of people that bosch platinum +4's are really bad for detonation. the spark plugs are the only thing that could be causeing my detonation problem. ive played around with the timeing curve, the springs in the distributor and the base timeing, NOTHING helps. i also tryed changeing the rods and jets that also didnt help stop the detonation. it makes sense for it to be the plugs because its the only thing i havent changed. what i need is a colder heat range spark plug, all i really want to know is if a plug that was designed for a tpi engine would be cold enough.

 

Regardless of your induction type (efi or carb), you *should* be getting the same amount of fuel in your cylinders, providing your carb is tuned correctly. In their basic form they are just different methods used to deliver fuel and air. Therefore, I would run the spark plug that's listed for your engine with TPI. If you pull your old ones and find that they are the correct heat range then the problem is likely being caused by running too lean, which means you need to tune your carb some more. When you pull your old plugs, take a close look at them because they are a window into what's going on inside your engine. If you're getting detonation or preiginition you'll probably find that the ceramic is very white, indicating that they've been too hot.

I've seen test reports on the +4s and they suck. After a while the spark begins to jump to only one sidewire (path of least resistance) which carves a trench through the insulator, after that sidewire gets burned up the spark move to the next one until all four are burned up. In the process, the four piece of insulator pie break off and the sidewire also detriorates until it's buried way down in the insulator. In short you've spent $50 on plugs that break in your engine.

 

well... i got me some #2 ac delco rapid fires. not much to look at but i hope it will help. much to my dissapointment they are half an inch longer than my bosch platinums, requireing me to take off both headers to fit a socket in along with the plug do i have to gap these? it says on the box to gap it to vehical specs but the parts counter guy said they are already pre-gapped. is he full of bs or was he right? oh well... im probly gona install them as is. wtf is with these things being so *** damn long????? ill be surprised if i can fit the wires on between the plugs and the headers......

 

also.... there wasnt much wrong with my bosch platinums other than haveing brown carbon on the electrode and grounds, i cant find my haynes manual either to tell me what that means..... but then again ive only been running these plugs for about 4 months now so i guess they havent had enough time to decompose.

 

dude if your motor was running good before you should have no problems... first off are you using the stock distributor with that carb? if so thats a no no since the distributor is computer controlled, even though it should still work, your timing is probably way messed up (is your distrib. 180 off?) also check the timing chain.

 

the engine is completely rebuilt, new timeing chain and all. i had to set the base timeing to 4 degrees just to keep it from detonateing when going up any hill. i tryed adjusting the timeing curve with my adjustable vacume advance canister and even that wasnt enough to stop the detonation without setting the base timeing to 4. it was at 8. my car also has NO cat and NO egr set up(no emmisions system, just a pcv valve and a breather). i was told this can increase the chance of detonation. but im not about to install an emmisions system any time soon or buy a new intake manifold with an egr slot. im sure these rapid fire plugs will fix my problem because they are alot colder than the bosch platinum +4's. the car was running fine, but i was getting such bad gas mileage its not funny. i was getting alot better gas mileage when i had the base timeing cranked up originaly at 8 degrees but any decent hill i went up would cause detionation. i use 92 octane too. i have 6 of the rapid fires in my engine now, but i guess im gona have to take off the other header to get to no.6 and and no.8 no the distributor isnt stock, its a pro-form Hi-Output HEI coil in cap distributor. just haveing the car running "good" isnt enough for me, i want it to be running at its best(without the emmisions system)

 

why not just use a wrench to take the plugs out instead of taking the headers off?

 

how can you get a wrench in there?

 

Use a 5/8" open-end wrench.Spark plug reading chart

Pete

 

yeah.. if you can get a spark plug wire on it you should be able to get a wrench on it unless ya have some really odd bend headers or somethin

 

well the actual hex part of the spark plug seems to go quite deep into the head. but ill give that a shot if i ever need to change them again thanks for the info