problem with spark plugs....?

[big blue 72]

O.k. i got an HEI installed this past summer at The OHIO MEET which was the best time i'd had all summer and nowi have a question.
I changed spark plugs to R45T which is suppose to be a hotter plug , right?
well first i gapped them at .035 and it ran like s%it, then yestrday i re-gapped them to .045 on someones advice.
Do i need to reset the timing?
It still runs like it is bogging down and it also sounds like a rough pinging. Any help appreciated. Thanks
Big Blue

[Bowtiefreak]

Ummm, what heat range were you running. The lower the number the colder the plug on AC Delco. HEI's (if all stock) usually require the gap to be .035-.040 It makes a big diiference what your compression is and the gas quality,timing,timing curve,cast heads or alumn,temp that your truck runs at.

Usually an R45ts or an R46ts work best in most street applications. There maybe other problems that your not aware of (maybe)

[jewels.]

big blue,

when we did *my* HEI at the ohio meet, the plugs were gapped at .045. so, whoever told you .045 was correct. (i have even pulled some of my plugs to double-check their gaps, and thats what we had them set at).

but maybe the different type of plugs require a different gap. dunno. you *shouldnt* have to re-time everything just because you changed the plugs. in fact, fine69 would probably rip me a new one if i even hinted at touchin the timing on my truck. (dunno if he would do the same to you, but ya never know ) i wouldnt touch your timing. the timing was already set really really good at the meet. sounds like the plugs are the issue here. in fact, if you want to double check it, put the old plugs back in, and i bet the truck will run fine (which indicates the timing is fine).

hmm. not sure if i was helpful. maybe fine69 has an idea about your prob?

ciao!
jewels.

[Bowtiefreak]

Sorry, I didn't read the post close enough. If you are sure the timing has not moved then yes its probablly not that and its just the plugs. But I do disagree about the .045 gap being a standard to go by (although it has worked for me and thousands of other people over the years) Actually many service manuals show the plug gap at .035 in the early years of HEI. BUT .045 does work most of the times. It is a suggestion.
Jewels hope you don't take this as a (you don't know what your talking about) I am just throwing out some info.

Bowtiefreak

[lukecp]

I've used R45T's gapped at .045" before and the worked great.

So you are getting a pinging noise and the truck is sluggish? Since you didn't mess with the timing, and it ran fine before, i doubt that is the problem.

Did you put the plug wires on in the right order....might want to double check that......I've switched wires before by accident and the truck ran like crap.

[big blue 72]

thanks for the replies. i will try the old plugs at .035.
my other problem before all this was the fuel filter was packed with rusted, so i had to take it out.. now have new in-carb filter and a clear filter in front in the fuel line. .it sputters and wont take till i hit the back barrels. Think i still have debris in the carb?

[jewels.]

Originally posted by Bowtiefreak
Jewels hope you don't take this as a (you don't know what your talking about) I am just throwing out some info.

Bowtiefreak

ohhh - no no no no! i wont take it as that, because i *dont* know what i am talking about here! i'm sure you know a lot more about it too! i was just tryin to tell blue to not mess with the timing.

dont sweat it. i was just tryin to be helpful to big blue! he is such a nice guy! gotta meet him in person!

hope you get her fixed, big blue!
jewels.

[lukecp]

If swapping plugs dosen't work....your symptoms do sound alot like a vacuum leak.....

[tom hand]

Early HEIs the factory gapped at .065. They backed down to .045 because the were having problems with the coils burning up. I have run many at .035 because I was too lazy to regap the plugs. From the "seat of you pants feel" I could not tell the difference beyween .035 and .045, so I really doubt plug gap is your problem. I think you will find your problem is timing or a problem with the HEI itself.

[Fred T]

Sounds like a carb problem. I would guess your primaries have crud in them. Clean the carb first. Until you mentioned the filter issue, I was thinking you had the wrong jets. Also, stick a vacuum gauge on her, they make an excellent low dollar diagnostic tool. Most have instructions to tell what the gauge is trying to tell you.

[cdowns]

if you had a bunch of rust and crud in the filter chances are the strainer inside the tank pick pickup is loaded up as well

[jewels.]

hey guys, i dont mean to be a pain, but note.....

he said he didnt have any problems until he changed the spark plugs.... (those of us at the ohio meet know this because we helped him work on the truck, and it ran good then...) so, since the problem appeared with new spark plugs, the problem is obviously the plugs. his carb is fine. i saw it. nothin wrong there.

i promise you - its a plug problem.

good luck, big blue!

jewels.

[Fred T]

Not trying to disagree with you Jewels, but where did blue say there wasn't a problem until he changed the plugs? I only find that he went to a hotter plug, that it ran lousy after that, but he didn't say how it ran before. I was assuming he switched plugs because he had a problem.

Obviously, it helps to have all the info. I'm still thinking he has more than one problem, and that what he did with the plugs has made the other problem worse. We'll have to wait and see what happens when he puts the old plugs back in. Hopefully that will fix it.

Let us know, big blue. We're waiting.

[big blue 72]

O.k, put the old plugs in @ .035 and it still doesnt run.
guess the 31 year old quadrajet has gotta go. this would be the second rebuild.
kinda sad. im kinda thinkin the primaries are clogged again.
Any good quick fixes?

[lukecp]

Spray it down inside and out with a can of carb cleaner.....usually a good temp. fix for a gummed out quadrajet.

[jewels.]

try cleanin out the carb with cleaner? an inexpensive fix that might do it for ya....

dunno...
thats all i have for a suggestion...

jewels.

[big blue 72]

thanks, but already used a whole large can within 2 days..............................................................................aaand nope, no vacuum leaks either .
Fuel line?

[ddsmith]

Hey everyone,
I figured I would steal some information from one of my favorite books(The Doctor's Guide to Automotive Ignition) and share it with you. I always like it when some really smart person puts information in a form I can understand. Granted this doesn't give you a starting point when using HEI in a non stock application like our trucks but it is very good info. I think .045 is a really good starting point for the HEI setup in the trucks and work it from there. In theory, the largest gap you can adequately fire is the best but increasing gap is limited to the ignitions ability to fire where it is suppose to. When you increase resistance across the gap the spark starts looking for an easier path to ground. Sometimes through wire insulation, through the advance mechanism, and other bad routes.

1. If you tune your vehicle often. i.e. change plugs,
Then increase plug gap .006 from factory recommendation. This will result in a 4% increase in gas mileage, noticeably smoother operation, no change in power.

2. If you only tune up the truck when it is running bad,
Then decrease plug gap .004 from factory recommendation. This will allow an additional 5000 miles between tuneups, increase in full throttle power 2%, lose of 3-5% in mileage.

3. If you mostly drive easy, light throttle,
Then increase plug gap .010 from factory recommendation. This will increase mileage 6%, noticeably smoother operation, 5% loss in full power, requires plug change 1/3 more often.

4. If you drive to achieve maximum power, full throttle race,
Then decrease plug gap .010 from factory recommendation. This will provide 6% improvement in power, better starting with fouled plugs,7% loss in mileage when driving slowly, 25% decrease in frequency of tuneups.

[lukecp]

Out of curiosity, how would decreasing the plug gap change power? Wouldn't less spark be exposed.....or would the spark just be hotter and shorter than with a long plug gap?

I haven't really played with the plug gaps on my truck....it has always seemed good at .045 so i haven't messed with it. If backing them down to .035" will give me 6% more power i would do it....i get crappy mileage anyways....lol.

[ddsmith]

I think it has to do with the large turbulance when accelerating at full throttle and the large gaps has a harder time getting the flame started under these conditions. Misfires/ lack of flame front kills power. Like I said he's the expert and has done more testing than I could dream about. Jacob's has been studying and developing ignition systems for a long time. This book was copyrighted in 1984. He did have a specific in his 6% improvement of power at about 4000 RPM. No I'm not a Jacob's employee and as a matter of fact I'm a little ticked of at their product. It was warrantied for a year and the first time I ran it years after my purchase it failed due to failure to tighten all the connectors at the factory. They told me I could buy another one. Poor customer support does not alter my opinion of the information in the book. Oh and the reason I bought the Computer Ignition was because it allows opening plug gaps up .025 from the factory recommendation. Provides 8-12% increase in power, 11-23% increase in mileage, and raises time between tuneups. I'll probably get another one sometime soon and will install it immediately on the truck after checking all the connections and give you guys some feedback.

[GMC Jim]

All HEI distributors are NOT created equal!!! I (and others) have posted information that the centrifigal advance timing of any distributor should match the factory specs for that specific engine.
Example: an HEI unit from a 1980 Chev truck; 8 cyl, 305 cu. in.; is calibrated for 6 to 10 degrees centrifugal advance and a total advance ( cent. & vacuum) of 14 to 22 @ 2000 engine RPM.
If this distributor would be installed in a 1971 8 cyl., 402 cu.in engine; ther would be some decrease in performance. The 402 specs are 10 to 13 degrees centrifugal advance and a total advance (cent. & vacuum) of 28 to 35 @ 2000 engine RPM.
The most accurate method to meet specs for the engine in which it is installed, is to have a distributor rebuild service center set the centrifugal advance curves. These facilities use a combination of weights and springs to match the engine design advance "curve".
Example:- a 1971 402 cu. in. engine specifies the following centrifugal ( degrees @ RPM). 0 @ 930; 2 @ 1260; 16 @ 2400 and 30 @ 4400.
Also the vacuum advance 0 degrees @ 8" vacuum and 20 degrees @ 17" vacuum. As a final check ( using an adjustable timing lite); the total advance ( cent. and vac. ) should be 28-35 degrees @ 2000 RPM.
Over 10 years ago; I had a used HEI unit re-built including the advance curve set to the engine. I installed new spark plug wiring made for HEI usage; gapped the spark plugs to .045.
Noticed an immediate improvement in power and performance and somewhat better gas mileage....... Hope all this info helps......( there is more info in the FAQ's, also!)............Jim

[GMC Jim]

Regarding spark plug gap for engines using the HEI distributors.------ Checking thru GM/AC/Delco; 1971-80 Tune-Up Specifications, Manual SD-100; the large majority of GM engines specify a .045 spark plug gap for HEI units. Some heavy-duty and California emissions engines call for a .060 gap in the years 1975 & 1976. Many 6 cylinder HEI equiped engines use a plug gap of .035.

[junkyardjohn]

WOW!! IN THE TIME IT TOOK ME TO READ THIS POST, I COULD HAVE CHECKED OR RESET THE TIMING, ADJUSTED THE CARBURATOR, & PULLED A COUPLE OF PLUGS TO SEE HOW THEY WERE BURNING.

[lukecp]

Wow....alot of great info on this thread

I agree....stock HEI advance curves are more of a emissions curve than a performance curve. I have said it before, and i will say it agin. Buy a Crane adjustable vaccum advance and re-curve kit if you have HEI. Very easy to install, and it gave me about 1 more MPG out of my truck, and more power.

I have seen some Jacobs advertising for their Mileage Master igniton products claming much better fuel mileage.....i wouldn't mind trying one out, but they cost a pretty penny, lol.

[ddsmith]

I have seen some Jacobs advertising for their Mileage Master igniton products claming much better fuel mileage.....i wouldn't mind trying one out, but they cost a pretty penny, lol.

Imagine how happy I was when mine didn't work and was out of warranty. I've sort of been holding them accountable by not purchasing anything from them for over 10 yrs. Maybe I'll relax the punishment soon.