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Discussion Starter #1
Searched and didn't find much. New to the site so if I goofed on the search and this has already been answered I'm sorry.

Long story short, the 468 BBC in ye' ol' B.O.A.T. ate a flat tappet lifter and a cam lobe on July 4th. Engine builder is guessing it's oil related. I've decided to drop a few bucks on the boat and want to get it back together while the weather is still nice. Motor came out of the boat this evening against its will. Current plans are to retain the Mark IV block and stroke it to 496-ish. I had a custom cam ground for an EFI Ford 408w and it made a touch over 500 ft/lbs at 2900rpm. The same guy is going to put together a "recommended" package for the boat motor which will remain carburated. On my 408w I used Canfield heads and was very happy with the performance. Cam guy is saying run a Canfield head for the boat motor (which I have no problem with). Canfield is AOK in my book so that's what I plan to run. My question is this, what exhaust manifolds should I be looking at? The current PCM manifolds are so poorly sized to the GM HI PERF heads it isn't funny. The previous owner spent a lot of money on a lot of things (Paul Pfaff worked on it at one point) but none of it really worked well as a package. I'm guessing budget restraints caused the previous owner to do whatever it took to just get it together and back on the water.

1974 Spectra 24XS. Motor when built should be in the 500/500 to 550/550 range. The boat currently has an enclosed engine hatch that I'd like to keep. The 2.5 year old grabbed the hot exhaust tip on the Yukon the other day and burned the #$#$ out of his thumb, lesson learned but I need to keep the boat very family friendly. I've seen cast Aluminum manifolds, stainless / DOM headers, and a few other variations. Most say "stock BBC style" or similar. I know from experience that the header requirement for my 408w with Canfields required custom headers. Does anything off the shelf work well with a Canfield head on a BBC?

Thanks!

Aloha
 

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BBC Canfield's have around ,625" raised exhaust port. This can cause alignment problems with your present - or any out of the box - thru hull exhaust systems. AFR/Dart/and many others have around .325" raised exhaust port that can also cause alignment problems - sometimes not, and sometimes not as severe. Brodix Race Rites have standard exhaust port placement.

If getting a better exhaust, most companies will make the riser's custom to where you want them. Before buying you can get an instruction sheet on how they want you to measure your tailpipe location so they can make them correctly for you. Of course, sometimes the less effective (hp wise but still decent) systems like Revolution's with their very short riser and thus use of longer rubber exhaust hose connection to tails will make for easier install. Rubber exh hose in longer lengths will move/bend easier than short connections.

Lightning Headers: www.boatheaders.com
CMI Exhaust: http://www.custommarine.com/headerapps/index.php
Dana Marine Exhaust: http://www.danamarineproducts.com/GroupCatProducts.cfm?CatId=75&group_id=10&page=1&CFID=422892&CFTOKEN=83872084
Revolution Marine Exhaust: http://www.revolutionmarine.com/
 

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Discussion Starter #3
What I'm curious to know is if the Canfield exhaust port "shape" works better out of the box with a certain manufacturers design. The current exhaust pipe setup has 3 sections of rubber hose that are between 6" and 8" long with two fiberglass 45* ish elbows along the way. I should be able to put together some sort of system without having to resort to a custom riser.

Here is a picture of the current mismatch of the PCM exhaust manifold to GM head:


I'm trying to avoid this ;)

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I have my exhaust off at the moment(Canfield CNC 355). When I get home tonight I will take a look at the gasket and see how bad it looks. I recall its pretty damn close.
 

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It is not just an issue with the port itself, it can also create a problem with access to spark plugs. Not that I would know this from experience or anything.

Paul
 

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It was a BBC with Brodix heads and banks exhaust manifolds. To put plugs in without cross-threading them you would just about have to take off the manifolds (which meant the whole turbo system). Needless to say, on the rebuild we are gong with different heads and I will find a way around the problem.

Paul
 

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There we have it, answers from experience.:)devil

Paul
I live in the I/O world thus deal with thru transom wet exhaust all the time.

Thus why I'm here - more jet,v-drive guys - to see what trends and info can be carried over. Many times it works well to hang out with people from other motorsports - they might be doing something everyday that you could use but otherwise never knew.
 
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