I have a 1970 BB car with a 425 hp cam and 11 to 1 pistons, Holley Carb. and the LS-6 aluminum intake. All this thru stock exhaust manifolds and pipes (all original Chev. parts).

I have two questions.

First: Does anybody make a set of headers that fit this car without creating a ton of problems? The car is a full optioned model with PS, PB and Air. No AIR equipment. I don't want to have to beat on a header tube to get it to clear the steering gear box. Don't want the drivers side exhaust to melt my AC/heater box. Want all my accessories to bolt up without having a machinist on speed dial to make a bunch of custom mount parts. (am I asking too much here?)

Second: Exhaust pipes - Who makes a really good SS 2.5 inch dia. system that is low restriction. Don't want it to be obnoxious loud but want to get the exhaust out and not choke the engine down. (I looked at some of the Flowmaster adds and they make a nice looking 2.5" ss system. It's not cheap so am interested in opinions.

In lieu of headers, how about having the stock manifolds slurry honed? Does it improve the flow over stock, what does it cost, who does it.

I know that is a lot but I am looking to explore options for my car.

Bob

 

I just installed the Magnaflow X pipe SS system, I tried the Pypes system but sent it back because of the poor fit. This is a straight thru design and fit well, the only thing I had to do was bend the arm that is welded to the back of the muffler to get the tail pipe centered in the rear bezel. This system fits the stock manifolds if you go with headers you will need to modify the pipe from the X pipe to the collector.

 

If you want that engine to breathe you definitely want headers. For the purists who might buy the car, should you ever decide to sell it, you can save the stock manifolds. I have Hedmans with heat coating on my 69. They have 2" primaries and a 3" collector. The Magnaflow system mentioned by "gve" is mandrel bent, which makes a noticeable difference in performance and I would highly recommend it. I got the Pypes mandrel system and it required a bunch of cuts and re-welds to make it fit, so I'd steer clear of that. Between headers, good mufflers, & a mandrel system you'll feel a big difference.

 

Les,

How do the Hedman headers fit your car? Did you have to dent any pipes to clear the steering gear box? How about the pax side fit against the heater/ac fiberglass air box?

Many years ago, those were issues with the headers and it is why I stayed with the stock manifolds.

Any issues with mounting the alternator or AC compressor?

Thanks for your insight.

Bob

 

Bob
after seeing one forums member dyno pulls at 650hp thru about stock cast iron manifolds...i started to think that they are better than supposed ( or headers not as good as we think) and so i suggest to keep them.
this sayed, i use Hedman headers, 2,5" pypes and magnaflow straight thru mufflers. very loud with my L88 cammed engine and had to add car chemistry noise reducers to reduce exhaust noise

 

Bob,
I had no fitment issues on the driver's side. On the passenger side at idle I had slight intermittent contact with the frame. I had to put a slight dimple in one tube, thankfully before I sent them out for heat coating. I later changed my motor mounts and that may have been enough to prevent the contact in the first place. The dimple is so slight that I have to look really hard to find it. I would not hesitate to put them on again. Hooker also makes headers but I can't say how they fit. I've read about & seen less ground clearance with the Hookers, but I'm not sure if that's for smallblocks, bigblocks, or both.

For the end where the alternator bracket mounts, I used a nut on the stud to cinch the headers to the head and then used 4-5 washers between that nut and the bracket itself. I then secured the bracket with another nut. If that's not clear I can post a pic of it. I don't have A/C, so I can't speak to that. I hope this helps.

 

Dont even waste your time.

 

I did find a place that did the extrude honing. VERY EXPENSIVE. About $800 per manifold. That put the skids on that immediately.

Bob

 

Les,

Could you please take a couple of pics of both sides of the engine so that I can see the fit?

It would help a lot.

Can send to Bob3700@att.net

Thanks

Bob

 

Two emails with pics just sent. If you don't get all 8 pics let me know.

 

I'd keep your manifolds, the BB stockers flow pretty well, and go with a SS 2.5" system from Allan's with their version of the N11 mufflers.

 

I agree

Bob , not yet convinced about keeping the oem exh manifold?
look at this
http://forums.corvetteforum.com/c3-t...manifolds.html

 

Power is about combinations. So what if 632C2 switched to Long tubes? Would he see more power? Probably but that's isn't what he was after as he wanted it to look stock.

I just got finished installing the Corvette Central Magnaflow exhaust. The BBC Hedman Headers are out getting coated and will be installed once they are done.

Letting the Long tubes scavenge the exhaust is always a good thing.

 

I have Hooker headers and the Magnaflow stainless system on my big block '72. The Magnaflow system may fit a manual car but it sure doesn't fit an automatic. I wasn't too upset because I needed to adapt the pipes to connect to the headers. The head pipes that come with the kit run diagonally from the connection at the transmission cossmember over to the stock manifolds. Mine needed to snake quite a bit around the transmission so I bought some j-bends and welded up the adapter pipes and now they have plenty of clearance.


Mine did not need to be 'adjusted' or 'dinged' to fit around the stock steering, although I have since changed to a Steeroids setup.


On the passenger side of the car there isn't a whole lot of room for anything back by the A/C-Heater box but I didn't have to modify anything to get it to fit (a good thing since I had patched the holes and re-finished the box once already).


As mentioned above, the Hooker Super Competition headers have ground clearance issues. Not sure why but my Hookers have the single-bolt side of the flange on the bottom when every other header with fixed flanges have the two-bolt side on the bottom. It's not much but every little bit counts. Not sure if the deep transmission pan or the header flange is going to hit first.


The Hookers were very easy to install from below, with only a couple of washers needed to shim the A/C and alternator mounts.