I took part in the recent SLP header group purchase (Thanks Steve Spohn!) and bought the 1 3/4" NON-Air coated versions for my 1988 GTA with 5.7 (350).

The car has run Edelbrock headers since April 1999. When I first got the Edelbrocks, I took a grinder to them and cleaned up the very messy welds that connected the flange to the tubes. At the time, I also ground off the AIR tubes (for off-road purposes-you know ).

At the strip, the car has run many 14.0s at 99 to 99.6 mph with closed exhaust (no cat, off-road remember ) on Pep Boys Ultra Zs (255s) cutting 2.00 60 ft times.

The car has also seen 30 mpg several times and over 140 mph on occassion.

With today's warm weather, I pulled off the Edelbrocks and test fitted the SLPs so I could be sure of the fit. Everything fit fine but now I'm going to send the 'Y' pipe off to be coated. While I was at it, I measured both brands of headers.

The Edelbrocks have two size tubes. Half are 4-11/16" around (using a cloth sewing tape measure) = diameter of 1.4928 (4-11/16 divided by 3.14 [pi]). Not sure of the thickness of the tubing and coating so I would guess about .060 (60 thousandths) off that, would equal about 1.486" inside tubing diameter.

The other Edelbrock tubing measures 5-1/8" (all measurements are about 5" from the flanges) which equals 1.632", minus about .060, equals roughly 1.572" inside diameter.

So, Edelbrock tubes are 1.486" and 1.572" internal diameter. This could be rounded to 1-1/2" and 1-5/8" (almost) internal diameter.

The SLPs measured 5.5" everywhere, which equals 1.7515" minus about .060 (for the estimated thickness of the tubing), equals about 1.745" internal diameter.

So, the SLP tubes are 1-3/4" internal diameter (rounded off).

The port (at the flange) openings of the Edelbrocks (remember, I ground out the messy welds before getting them coated) are, at best, described as an squared oval. Not quite rectangular and some ports are "rounder" than others.

The measurements here range from 1-1/4" by 1-7/16" to 1-3/16" by 1-7/16". The difference could easily be explained by the grinding I did.

The SLPs measure 1-5/16" by 1-1/2" on EVERY port. Interestingly, the tubing gets larger about 1/8" from the flange.

At the end of the shorty headers, where they bolt to the 'Y' pipe, the Edelbrocks measure 2-3/8", as do the SLPs.

The 'Y' pipes are quite different.

The Edelbrock 'Y' pipe is 7-13/16" around which equals (7.8125" divided by 3.14) 2.488" minus about .060 equals an internal diameter of 2.428".

The SLP 'Y' pipe is 7-1/16" around which equals (7.0625" divided by 3.14 [pi]) about 2.249" minus about .060 equals about 2.189" internal diameter.

Hmmm.

The Edelbrock 'Y' pipe is not completely the same size through its length with a couple of places 'squeezing in'.

The SLP 'Y' pipe is fairly consistant.

The point where the 'Y' pipes join (single cat on my car-if the cat was on my car ) is one of the largest differences between the two brands.

The Edelbrock tubes get (the best I can describe) mashed together to blend in to the single large pipe.

The SLPs have a much nicer 'collector' at this point and merge to a single large pipe (forgive me-I didn't measure this but they both appeared the same diameter).

Other notes: the SLPs, where the tubes joined at the collector, where the 'Y' pipe bolts to, was much more 'profesional' appearing.

Also, the SLP 'Y' pipe collector points in a different direction (more straight to the back of the car) than the Edelbrock (which angles about 30-45 degrees toward the transmission).

Ease of installation was about the same. However, it seems my car keeps getting lower to the ground, even when on jack stands. Or could it be my 45 year-old belly getting a wee bit bigger?

It appears there may be better plug clearance on the SLPs. Not sure. Any comments here? Also, I've had to run the shorty Accel 276 plugs for clearance on the Edelbrocks and the plugs always seemed 'just a little' rich. And not much choice in the shorty plug heat ranges. What do you guys run?

Other than the small 'Y' pipe on the SLPs, and the total lack of bolts, gaskets or instructions, I am, thusfar, satisfied.

Track times will be necessary to make me smile. To be totally honest, I will be surprised if the SLPs pick up more than a tenth or two over what I've already run.

BUT, I've got much bigger plans for the near future and the Edelbrocks would definately be too small.

The Edelbrocks aren't that bad, from my experience (at least the ones I have after cleaning up the welds). Maybe the track times will prove me wrong.

Sorry for such a long post but I thought some people might like a direct comparison of measurements between the two brands.

jms

 

Cool. Hopefully, some people looking for comparisons between the two can see this post.

 

Thank you for posting that JMS. That will back up my data and pictures I posted back in August regarding how much better SLP headers are over Edelcrock's.

 

keep us posted with your results

 

I have some results on my comparison but there needs to be some explanation.

With the Edelbrocks, I dynoed 224 hp and 302 torque (about a month ago). I was running rich, according to the a/f ratio.

Best time (last year) with the Edelbrocks was 14.06 at 99.6 mph.

The 1-3/4 SLPs went on a couple of weeks ago. The Y-pipe exit location was different than the Edelbrocks (which followed the stock routing). Last week, I had a local muffler shop install a 3"- 45 degree connector (about 8-12" long) to connect the SLPs to my Edelbrock cat-back (no cat).

The short piece ended up getting three crimps in it. Most of you have seen the crimps larger pipes can get.

I know this didn't help and I WILL get a mandrel bent piece very soon.

At the track, this past weekend, I turned in a 14.02 at 98.47 and would probably have went a little better (later in the event) but had some tranny issues come up later on.

Please understand about the Edelbrocks I had on. I had removed the A.I.R. lines and ground smooth and opened up the flanges quite a bit.

The SLPs haven't, at least at this point, impressed me all that much.

Install was straight forward. Fit is good. Quality is ok but not what it should be for the money.

And did you know that the flange openings are actually 1-3/8" square? The tubing is actually 1-3/4" after the flange.

I have a set of GM Fast Burns (and the Scoggin-Dickey intake) to go on later and I will have to grind out the flanges at least 1/16" each side and about 3/16" to the top (Fast Burns have a very pronounced 'D' port).

On the car, I feel a very slight loss of bottom end torque. Mid to upper rpms (as if a TPIs 4500 to 5000 is upper rpms) feels slightly better. Not $560 worth ($440 for headers, coated, and another $120 to get the 'Y'-pipe coated).

I do realize they will be a much better choice when the other combo goes together.

I did another mileage check (mileage checks quickly tell me when something needs attention) Sunday morning. On the same route and about same outside temp, I had previously seen 30 mpg (sometimes a little over) with the Edelbrocks.

Now, it was a little more windy this time, but my mileage was 28 mpg. Not a lot of change but some. However, the wind was enough factor that I'll call it pretty well even.

Would I remove my Edelbrocks and get the SLPs if I didn't plan on bigger/better things and didn't have to worry about smog stuff?

Considering what I know now---probably not.

But remember, MY Edelbrocks were better prepared than those that are thrown on the car, by most people, without doing some work.

My observances.

jms

 

Just a couple of thoughts,...

I bought my first set of SLP's directly from them, and the phone rep made a point of letting me know that I would need the installation kit(gaskets, bolts, etc.,) and the catalyst adapter(the 45° elbow you're missing). Wish someone would have told you, you'd need these things to complete the installation.

I agree with you that the quality could be better considering the price. I had to grind off a lot of welding slag on the inside of the tubes near the flanges and the collector.

You mentioned that with the Edelbrock's your plugs were showing 'rich'. Have you looked at them since the SLP's were installed? My feeling is that you may be running a little leaner than before, hence the drop in low-end torque. Will you be doing any tuning to compensate for the SLP's increased efficiency(a slight bump in FP might help out).

All advertised pipe diameters describe outside diameter. I prefer a micrometer for this type of measurement as it pretty well removes any chance of error in measurement or conversion. Same goes for inside diameters.
If the pipes are 14 ga, which I believe both of them should be, the wall thickness is 0.064". So you should subtract 0.128"(two walls) from the measured outside diameter if you don't have an inside mic to do that measurement. The tailors tape is fine in a pinch, but not noted for extreme accuracy(who cares if one inseam is 3/1000th longer than the other right?).

 

Very true on the method of measuring. The tape was useful in a direct comparison of the two sets of headers.

Haven't checked the plugs yet. Will put a few more miles on them to get a more realistic overall comparison. After a few more miles, I'll bump up my fp to see what it does.

The very slight loss of torque is not a problem on my L98.

The main thing that bothers me on the SLPs is that for that type of money, they should have included the bolts and gaskets.

Another thing, I bought the coated versions of their headers but the 'Y' pipe was not coated (cost me another $120 to get done by Jet-Hot). Is the 'Y' pipe not part of their headers?

And if they are a direct bolt-in, why do you need the 45 degree adapter? I know the answer, as do most others.

Sort of like--- "Would you like cheese on your cheeseburger? Just 50 cents more!"

jms

 

OUCH! $120 for just the y-pipe?

Next time you need to coat something, try ordering from http://www.techlinecoatings.com/. They sell coatings directly to guys like you and me. Most of their exhaust coatings can either be air-cured or are safe in the oven(assuming the wife/girlfriend don't kill you for putting car parts in the oven ).

And I totally agree that the 'extras' should be included with SLP's headers. Guess that's one of the downsides to dealing with them. On the upside, their tech support is really good and they actually have phoned me - on their dime - after the sale, to see if I was happy with the product.