Mate I don't want to rain on your parade but I think you need to take a deep breath and really consider what you need to do here. A pretty stock 289 isn't going to take the kind of air 2 paxtons are going move, It's going to want big heads with big chambers big ports and plenty of exhuast, or your wasting your time, its going to make a lot of heat and you need to get that down the pipes. I've worked on a couple of blown engines that were big dollar, big number at the wheels engines and we still had failures even with custom pistons, grout filled blocks and 4340 Scat rotating assemblies with H beam rods etc,custom mandrel headers etc etc.
I think you need to consider the engine a bit more or your wasting your time bolting 2 blowers on itor it will end in tears I just don't think the engine your are talking about will cut it or be able to use the air. Also can't see they can get Vac carbs to work on a blow through set up, have to be mechanical carbs, ie double pumpers.
You'll also want to consider oringing the block.
Below is a 383 SBC which has about 700 at the wheels at 80% throttle
Based on what you have said - So here is Boofs formula for you.
1) Block - clean it up or better still keep it in the corner of the shop and get a 302 block (since original 289s are getting hard to get).
2) Forged Pistons and molly rings
3) ARP rod bolts and smooth the sides of the rods. Better still get a set of H rods.
3a) Optional - Use a 302 crank and rods in the build - easy and cheep way to get more capacity [which is what your also doing with the super charger].
4) H Roller CAM - super charger grind with a wide cam angle (as suggested). Get Linked lifters.
5) Heads - get a set of AFR 185s or (my preference) TW 190 FACs.
6) Headers - 1 3/4" primaries into 3.5" secondaries to a 3" twin system.
7) Keep 8" though use 3.55:1 ratio diff with a detroit locker center. [Note: This saves 2K from converting to the 9" - use the money to get the heads].
8 ) Good quality high output ignition system - MSD 6A and matching coil.
9) Use double pumpers for carbies - I am with Shaun - odd they suggest vacuum secondaries!!!
9a) Option - Fuel inject it - MSII with manifold to built to suite [I have ideas here if you would like me to expand] [Phase 2 maybe].
10) Keep the C4 - get a kit for it to beef it a little and improve the shift.
This would be a fun (and relatively inexpensive) build. Keep us informed of how you go.
Hi Shaunp, thanks for the advice...but The reason I joined this forum is because after doing lots of research on this setup and coming back empty handed I thought I would join a forum ..and so I have ...My original question was "has it been done succesfully" and I stated that I would like to try and keep the engine as stock as possible ...yes the engine will be under lots of strain and I might have to consider using a scat crank, lunati rods even afr heads and custom exhaust...and yes I may have to use a 9" and a c6 auto..I might even have to buy a motorsport boss block...
But I just want to see if I can get a 289 with twin paxtons( the compressors are smaller than the single paxton kits that you can buy) to run a respectable HP range safely in the name of "havin a go" ...I bet people thought Mr Shelby was a little insane and eccentric when he built GT350/500's running Paxtons in the 60's to sell to normal street driving run of the mill customers...
so mate ..no, you are not raining on my parade, I respect that you may have many years experience working within the motor industry building performance engines., and your advice is taken into consideration.
I am just taking advantage of an opportunity to do something a little different. If cost me a little bit more to do ..well than so be it
now.... tips and tricks would be handy for strengthening the bottom end and cooling may be something I will have to upgrade.
I see your point on the 600vacs and will aproach it at a different angle
the clevo heads may help with porting and are sitting in my shed looking for a home
as I say I have a couple of weeks before I get home, and if I need to order some stuff and organise some machine work I have you guys in this forum to help come up with solutions
Just sharing a dream guys that is all
there is a difference between need and want ....and the want is needed
You can use the Clevo heads - far better than the (any) standard Windsor heads though not as good as the above after market heads. They will bolt on though they complicate intake manifold choices and you need to get Clevo headers (there are a few other minor aspects that are not important for the this discussion). You also have less engine room space as they result in a wider engine.
At the end-of-the-day to rebuild a set of standard Iron heads will cost close-ish to the replacement after market heads so why bother for a inferior product, less performance and has less safety in terms of boost / compression limits.
If you want it to look standard then paint the heads instead of keeping the shiny alloy look (which I really like).
Doubt you will find a dual quad manifold for a Clevor set up, you'll have to stick with windsor format. If you want an aftermarket rotating assembly don't mix and match, just buy a full Scat kit 4340 steel crank, H beam rods and forged pistons with suitable compression for the blower. If you start mixing and macthing they get hard to balance, H beams are normally heavier and you would likly have to add mallory metal in the crank.
So then the question is if you are buying new rotating assembly you may as well buy a stoker kit, price will be the same give or take. and go to 331/347. Harrop would do good cranks as well but they will be expensive.
You really need to strip the engine you have first and decide if you can use it. Or as Boof said just go buy another one to start with.
So before you buy anyhting else consider want compression you want to run then buy the heads and or pistons to suit. The bigger the chamber the more charge you can get in, boost etc
You could go up to 225 AFR heads with 2 blowers. I just think this is your opertunity to build something super tuff, so just consider the total outcome and life span of the the engine, just think it out carfully and you'll end up way happier in the long term.
The 383 Chev picture i attached broke 3 blocks across the valley, even when it was grout filled. Ended up having to buy a World Motown block, this was an engine full of expensive bitts, that was only used for hillclimbs, historic sprints etc, very limited street use even though the car had full rego and a QLD mod plate for the blower, but you could still hurt it, pretty easy. Running a lot of blower and moving air quickly, puts them on the edge, if they go lean on fuel it's all over pretty quickly, we also had issues of breaking ring grooves out of off the self forged pistons, had to get some made.
One more thing, you'll need to make sure your inlet springs are good enough also, the boost can cause valve float. So roller cam needs heavier springs than flat tappet, due to the steeper flanks, then you need heavier again for the blower (inlets only).
& then probably get 5,000 km's out of your cam before needing replacement. Horsepower is heaps of fun , isn't it.
(PRAYER) Oh thank you Wild Turkey American Honey & Cola in those small thin bottles, for giving me the strength to act like a half wit, and say stupid things at inappropriate times, semi-anonymously, on a public forum.
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