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Opinions on best option: truck manifolds are too big on 5.3 LS

15K views 12 replies 9 participants last post by  kossuth 
#1 ·
Hello,

I'm installing a 5.3 LS from a '03 Silverado in my 1937 Chevrolet 4 door. As you can see in the picture the exhaust manifolds aren't going to fit. I'm wondering what is the most reasonable option. This is going to be a daily driver for my wife and we're not looking to win any races, just carry our family around. I have read that these years motors had very good manifolds and that shorty headers wouldn't be any better than stock manifolds, but I'm not sure if stock manifolds would clear in this situation. I usually work on old stock motors and I'm not sure about the reliability of new headers. We intend to drive this car for the rest of our lives and are looking for the most reliable option. I'm not sure about all the available stock options.



Thank you,
Brandon
 
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#5 ·
is there a Dorman replacement manifold for the vettes from Advance/Schucks etc etc?
Make sure they have an exchange policy and explain to the senior curmudgeon what you're doing. take em home and try. You may even need a vette manifold on one side and a truck on the other.

For longevity and less heat radiating into the cabin, Id definitely use a cast manifold, you could even have em coated to look nicey nice. Id do all your mockery and test firing before you get em coated though
 
#6 ·
headers

We are installing an LS2 truck motor in a 57 Chevy with the same problem. Patriot makes a very nice ceramic coated header that works with a reasonable price. Purchased them through Ecklers. Another option we toyed with was having the flanges milled to bring the stock manifold in closer to the block but it removes way too much material by the time you get enough angle for clearance.
 
#9 ·
Manifolds

You could look into the 97-99 Corvette stock LS manifolds. I am putting a 5.3 into a 47 Chevy and found the same clearance issue. I have ordered a set of the vette units but have not received them yet, so the jury is still out. Seems to be the main units to use in this case for clearance. If you chose the vette units I recommend going to a Corvette forum and contacting the vette owners. The first upgrade they do is pull the stock exhaust and replace. A much cheaper price from them than auction sites, saved me a good amount.
 
#11 ·
Sanderson's were the only thing I could find (at the time) for my 59 with a 454HO.

I bought the cast iron headers and had them coated later.
Very happy with them, and the coating that was done almost locally
seems to be holding up as well.
Been six years on the car---just fine.
 
#13 · (Edited)
I found this thread through google looking for 5.3 deck heights. Why this showed up I have no idea but I have something to add to this even though I'm sure you have figured something out by now, I'll offer these suggestions.

1. All factory truck and 99-02 fbody manifolds are very large and boxy because they are cast iron
2. Factory 98 fbody manifolds are actually stainless steel. So you could cut the flanges off and weld an extenstion to it.
3. Vette manifolds are well,,, Vette manifolds and their application and fit can almost always be questioned.

In case you guys didn't know, the Ford 302 exhaust port spacing is exactly the same as the spacing on a GM LS motor. ford headers to lsx - LS1TECH Thus, what alot of guys in the LS world do with swaps is they purchase a set of 302 headers that will work and cut the Ford flange off. Then purchase a set of GM Performance LS flanges and weld them up GM Performance 12480130 - GM Performance Header Flanges - Overview - SummitRacing.com . You have a much larger pool of vehicle types and header configurations to compare by throwing a 302 Ford into the mix. Obviously the ford ports are rectangular so you will need to oval them out with a pipe expander or something like this with some heat http://www.amazon.com/Lisle-32000-Exhaust-Pipe-Shaper/dp/B0002STSO4 .

Also don't overlook the possibility of modifying a shorty header off an Fbody to fit like I did.



 
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