Is this guy's stuff any good? He seems to be a sleazy, used-car salesman type.
http://www.vetteheaders.com/servlet/Detail?no=33

I've heard of McJacks a lot when I was on CF. Don't remember anything bad though.

Quote:

No specs..??

I'd be interested in tube thickness, diameter, and flange thickness for starters.

-- Joe

To add to the above post I would like to the inside construction of the all important collector and the entry into the header from the head. Two key areas for horsepower.

I'm pretty sure they are Headman Headers.
Will

I know Jack personally... he is ok people.

I know for a FACT that his big block headers are made in house, one at a time. I have watched them do it. They are a quality part.

I don't know the origin of the small block headers, though.

Quote:

The word is Hedman and you avatar is offensive.

Quote:

Does this suite you?

Wouldn't want to offend any longer with a 10yr old TV ad clip about uninvited Christmas guest.
Will

Ron - (and this is for DaleD, too, actually!)

My recipe for perking up the L98 without breaking the bank.

The L98 has 2 main problems... exhaust and intake. It's that simple.

The LT1 picked up 50hp and a much nicer power band because it solved those problems.

Since I am sure you are on a budget, this is my menu to perk up the L98.

1. Exhaust... Long tubes if you can swing'm. Add bullet cats. They will keep the car sniffing well and not attract attention of the smog nazis. Also, they don't suck power like they used to. Think < 10hp lost; but the addition of the headers will be worth 20hp, so oh, well. Get the headers with an EGR port.

2. X-pipe... This is a given. True duals COST power, X-pipes make power. They even out the pulses from left to right and help scavange the exhaust ports. What happens is the vacuum from the left sucks the gasses out of the right and visa-versa.

3. Pipe and such back to nice mufflers... Borla? Magnaflow? Used LT1?

NOTE: For all of the above, you will want to get LT1 style hangers. This consists of a hanger at the transmission, a pair of hangers on the rear diff (camber bolts, actually) and hangers for the mufflers. They are not expensive when bought used via the likes of www.vette2vette.com.

4. Intake... this gets hard... but you have a couple of choices:
a. Port the hell out of the intake, or, upgrade the base and runners. Porting the plenum isn't going to help a lot. At least no where near as much as fixing the base and runners!
b. LT1 conversion. Nice trick, yes, but I like EGR (cuts down on detonation AND NOx - win-win). The Miniram is a good option and they are offering an EGR kit.
c. Super Ram is ok. It's just a pain to install.

5. Remove AIR pump and hardware. It's a mess... and robs you of power. The AIR pump only helps at startup, and if you install bullet cats at the headers, it won't matter as much.

NOTE: I am guessing that doing the above will account for nearly 60hp.

6. Now that the engine is breathing, finally, you can do some real engine upgrades. Roller Rockers will actually make a difference, now. A cam upgrade and even heads. At 110k miles, I would pull the heads and have them redone. The bottom end should be a-ok.

7. New injectors... FIC is the place to go and the result is well worth it. I would get get a marginally uprated injector. IIRC, the L98 is 22lb; I would go 24lb.

8. Get the damned thing tuned! This is where money comes in, really... you will want to get the engine tuned to match the new parts. However, doing the L98 is a pain with chips and stuff. TJ Wong or PCM for Less should be able to help get you REAL close.

I gained 10mph in the 1/4 going from a fully ported TPI setup (edelbrock base, slp runners, ported plenum) to a singleplane. Porting the TPI is just a waste of time, however, keep in mind this was with a 224/230* camshaft and good heads. I wouldn't expect much on a stock engine.

EGR is helpful for avoiding detonation during lean cruise, and some light load conditions where the AFR is still in the 15s. Obviously IDLE, AE, and PE modes don't use an EGR. For a daily driver with zero mods I'd keep it. For a car I care about, it puts too much carbon in the intake for me.

But - regarding headers...

I would be more concerned with tube diameter than tube length. Length does play an important role in blueprinting, but I highly doubt your going to be running enough cam to take advantage of any long tube header, and even if you were finding one off the shelf that just happened to be the right length would be like hitting the lottery. If they are available, why not - but given the choice I'd always go for what was available in budget that has the larger primary diameter.


I usually blueprint the build and swap it into the car when finances allow. I'm not a big fan of bolt on parts. Then again, nobody said what these headers were going on..

-- Joe

Thanks guys. I am working with these guys that I met at Corlisle: www.corvetteplenums.com
Their advice was using their CNC porting on the stock plenum, also on an Accel type base plate and runners. Then either aftermarket or ported stock heads, Lingenfelter 219 cam, larger throttle body and injectors and headers.
Good advice about the stock LT1 system and the bullet converters. They also advised a custom tune.
The car is a completely stock A4 91 coupe with FX3 and performance rear end.
My goal is to keep up with the crew that I hang with on their occasional back road runs. Most drive stock C5s with Borla exhausts. Two of them have C5 Z06s and one of them has a supercharger on his C5. There is also a C6 Z06 and a stock '08 vert that is damn quick in its own right! Throw in a few L98s, a straight axle with fuel injection and some LT1s (one is on the bottle) and they are quite the bunch.
I am not looking to thrash them all (no way could I afford that) but I don't want to be left in the dust either.
AND, yes I am on a budget. I have agreed to keep the spending on the mods to a modest level. Usually my idea of modest and her idea of same are worlds apart. :pain10:
I have been able to stay married to her for 41 years with 4 kids, 10 grandkids and 6 different Corvettes so I want to maintain peace at home. Hafta obey the rules.

Quote:

Was that was on your 500 hp supercharged motor? Hardly a comparison for a stock or mildy modified motor. Porting the TPI and switching to the big tube runner setup will offer modest gains over stock. But it isn't sufficient for a large, monster built engine.

Matthew

Quote:

Normally, I would agree that bolt ons are nearly pointless. This is why I am not a fan of cold air intakes and muffler elims. They do nothing to fix the root cause of the problem.

The L98 is SO restricted that my suggestions will bring real power now and the potential for future power capacity.

Quote:

Yep, that is why I said:

Quote:

-- Joe

Quote:

True.. I just can't get over the crappy cam, smoggy heads, etc.

The bottom end is fine, and a lot of guys with 20 year old Fbody's have run 11s on stock bottom end without failure.

It's just so simple to turn an L98 into an 11 second car, I don't see the point in wasting time with porting TPI and bolt ons. I figure either do it all, or don't do anything.


Btw, stock bottom end, AFR 190s, 230/230 cam, 1 3/4" headers, and miniram = 11.50 car at around 112mph all day.. Really old known fbody combo.

-- Joe

Bump.

Paying a bunch of money to CNC the plenum is a waste of money, All it does is help complement other intake mods. You can siamese the runner entries and knock odwn some bosses some and behind the TB thats about it.
Takes me about 30-45 min tops. Dont expect big gains from that alone or at least gains youll feel s.o.t.p. without doing plenty more.

OK. On a budget. What about this from headers to exhaust pipe:
These bullett cats:http://www.summitracing.com/parts/MPE-59959/
These headers but ceramic coated and with O2 bungs:http://cgi.ebay.com/ebaymotors/Hedman ... ories?hash=item4cec139059
This exhaust system (with the above bullett cats welded in)
http://www.parts123.com/parts123/yb.d ... 50g~Z5Z5Z5~Z5Z5Z50000050F
As far as mufflers go, not sure. I had elims on a previous 87 and they were too loud. I replaced them with Magnaflows and they were OK but a bit too quiet. I like that 60s muscle car sound(but not the cherry bomb rasp).

Budget or not... don't buy an exhaust system. Buying tubing, fittings, and mandrel bends and taking it to your local exhaust shop will always be cheaper and will probably fit better than a "bolt on" exhaust system (which uses clamps that leak).

If I was starting from scratch I'd like to do a single 3" equivalent oval pipe out the back, this would be the lightest weight system, and those oval pipes are only 2.25" tall. I'd stick a single 3" high flow cat on there to pass smog, test pipe otherwise, and run 2.5" to each front header, no collectors, but use a tri-Y system.

I have a hard time believing those bullet cats can flow as well as a larger cat. They have less cross-sectional area. And they cost twice as much.

I wouldn't touch those headers, thin flange and tubing. I do like the looks of the Hedman Elite line though, and the price is right.

Quote:

They look like Hedman's to me too.

BTW: I'm pretty sure this is the company that refurbs, ports, and coats stock L98 manifolds. If you need to stay stock (like in CA), it's not a bad option. Sells them on eBay too.

Quote:

If you're talking about larger, like 3.5" cats, I agree. More cross-section will always flow better. But, if you're talking about one center cat, I've never seen a center cat do as well as small bullets.

For what it is worth, the highflow bullet cats flow very well.

Think of the flow rates of the stock LT1. There was a chart somewhere that compared the LT1 cat with several aftermarket units. I found this:



The old center cat on the L98 is the killer of that exhaust system. The single cat just can't flow enough.