Straight or Angle Plug Heads ??? - Team Camaro Tech
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post #1 of 15 (permalink) Old Oct 21st, 03, 06:56 PM Thread Starter
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I am about to order a new set of Pro Action Iron Lightning Heads and I was wondering if I should buy angle plug or straight plug heads ???
What is the advantage of going with one or the other ??? Thanks, Tom

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #2 of 15 (permalink) Old Oct 22nd, 03, 12:39 AM
 
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You're SUPPOSED to get a little better performance with the plugs tipped toward the spark plug. It's been debated. Watch the headers you use. Different clearance issues with the different heads.
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post #3 of 15 (permalink) Old Oct 22nd, 03, 05:02 AM
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Just make sure they will be compatible with your existing headers/exhaust manifolds before you buy them.

1968 Camaro 383 517hp/500tq, Autogear M22, Marina Blue
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post #4 of 15 (permalink) Old Oct 22nd, 03, 05:06 AM
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I've been told several times that there is no difference in performance, but only better access to the plugs when using headers with the angle type.

Matt Jones
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post #5 of 15 (permalink) Old Oct 22nd, 03, 06:29 AM
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I called every header manufacture I found a number for looking for header recomendations. Doug's and Hooker were the only ones that actually stated to me that they had headers that would fit my sportsman II's with slant plugs. I had bought an assembled engine that had the slant plugs, I would have gotten straight plugs if I were ordering them. There is no clearence improvement with slant plugs.

As for slant plug performance, it's not worth enough on a street machine IMO. If you are in competition it might be different. Kinda like indexing the plugs.

...Dennis

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post #6 of 15 (permalink) Old Oct 22nd, 03, 08:33 AM
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I talked to a guy once that had run a set of GM "over the counter" angle plug heads. He said that he preferred them to conventional GM straight plug heads because they were less detonation prone on his stock cammed street engines.

I would never consider the angle plugs for anything I build. The potential for manifold issues seems to outweigh any significant performance advantage that might be gained IMHO. I have a friend that is trying to deal with this issue right now. He is wanting to borrow my Hookers to see if they will fit his angle plug heads. Too much hassle in my book.

-Mark.
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post #7 of 15 (permalink) Old Oct 22nd, 03, 03:22 PM
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Gentlemen,

While it is debated how much of any performace gains come from the angle plug heads... I can tell you from experience that there are not that many headers that will fit unless you specifically requested headers for that type of application. Usually headers that will fit the angle plug application start in the neighborhood of the $580.00 and up category. I have Hooker Super Comps from my last motor and had to modify them to fit the new angle plug heads that I bought. Unless you have the means to modify the headers or the extra money to purchase new ones than I would suggest that you lean twards the straight plug design.

Best of luck,
Tom
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post #8 of 15 (permalink) Old Oct 22nd, 03, 03:36 PM
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I concur with DJD. Doug's or Thorley's are the only small tube headers I found that would work with my angle plug heads, power steering and manual trans.

The heads I have are the LT1-style service replacements from the early 70's (492's I believe). They bascially fell in my lap and I jumped on them. I went with Doug's Headers and they're beautiful--great fit, no massaging.

I've had zero signs of detonation as well for what that matters. They sure as hell woke up my stock 327/210!.

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post #9 of 15 (permalink) Old Oct 22nd, 03, 07:45 PM
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my pro toplines are angle plug heads, and i'm running over the counter super comps, and they fit excellent. there also is better plug access than with my old straight plug heads and the headers that fit them. now my car is an automatic, with power steering, but i believe if you throw in a manual trans things get dificult in a hurry. i can only speak of a p/s, auto car. as for performance, my understanding is with the old "bathtub" chambers, angle plugs made a difference, but with the new "fast burn" style chambers, like the pro toplines have, it makes very little difference. i would just go with what your headers are meant to accomodate, and if your getting headers too, like i said, with mine the angle plugs have better clearance. but if you have a manual, straight plugs are probably going to be easier to get headers for.

Sean

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post #10 of 15 (permalink) Old Oct 22nd, 03, 07:59 PM
 
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In the same vain...any ideas on how to get out plugs 5 & 6 with straigh plug heads using headers. I can get the socket on but it's impossible to use a rachet. I'm sure there are alot of creative ideas other than drop the headers every time you want to change plugs. I just picked up a '69 Z/28 with the original 302 and aftermarket headers. I'm flexible but come on.....
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post #11 of 15 (permalink) Old Oct 22nd, 03, 08:09 PM
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Tom,
The angle plug heads are for greater detonation resistance period...If you're not running at the ragged edge with high cylinder pressures or low octane fuel you don't need the angle plug heads. High cylinder pressures could be due to a compression ratio too high, a cam with the exhaust valve closing too early, or a very agressive ignition timing curve with the above. They are for racing applications where a bit more cylinder pressure without detonation could be the difference between winning and losing. If you're having -or will have- a mild pre-ignition problem from the head swap they could be of use. If not, there seems to be a lot of exhaust interfence problems associated with running the angled plugs. It's your choice.
The theory (if you're interested)in which the angle plug heads work: The spark plug is pointed toward the exhaust valve. This starts the flame kernel in the area of the hot exhaust valve (an area which can be an ignition point (at high temperatures and pressures). In other words, with straight plugs (if the cylinder temperature and pressure are high enough) you can have multiple ignition sources (the hot exhaust valve and the spark plug). If the fuel air mixture lights off too fast the cylinder pressure rise will be too quick (detonation) instead of the smooth pressure rise you are looking for to make power you will shock your cylinder components with a hammer like impact. I hope this helps.

Regards

-DEC
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post #12 of 15 (permalink) Old Oct 23rd, 03, 10:31 AM Thread Starter
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Thanks for the info.!!! My money tree has shed all it's leaves for the year, so I guess I'll have to wait until it grows more.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #13 of 15 (permalink) Old Oct 23rd, 03, 10:40 AM
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DEC - I won't disagree that slant plugs "may" help prevent detonation some but I don't think it was a real thought back when Chevy made available over the counter 202 slant plug heads. Compressions were routinely 11:1 back then in performance small blocks and often guys would run 12:1 on the street without a hint of detonation on pump gas.

If slant plugs were the answer to detonation in modern heads they would be the norm and would cost more. Sportsman II's cost the same straight or slant plug...

...Dennis

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post #14 of 15 (permalink) Old Oct 23rd, 03, 05:00 PM
 
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Quote:
Originally posted by DesertRod:
In the same vain...any ideas on how to get out plugs 5 & 6 with straigh plug heads using headers. I can get the socket on but it's impossible to use a rachet.
Just use a spark plug socket w/ the hex pattern cut into the outside of the socket on the end. Slip an open end wrench on it and enjoy. It's the only way to remove some of the plugs when you have headers.
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post #15 of 15 (permalink) Old Oct 23rd, 03, 07:17 PM
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Rick,
There is one error in my explaination: what reads as "a cam with the exhaust valve closing too early" should be "a cam with the INTAKE valve closing too early". The intake valve closing point will have a great effect on how much pressure is trapped in the cylinder not the exhaust. It also will greatly effect the breathing as well. The later the the intake closes the better the ability to breath at high rpm's -as there's much less time to fill the cylinders at high rev's- but on the other side if you close it too late the cylinder pressures suffer at low rpm's (i.e. a soggy bottom end). Sorry about the boo boo. It was late.

-DEC
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