4.3l sohc v6?

[4pointslow]

Supersix Motorsports (my favorite place to shop for engine parts!) has their stage 3 heads listed as 236 CFM intake/176 CFM exhaust.
I have them on my original engine that has been pulled for the time being.
Boost dropped from pinning the boost gauge at 20 psi, to about 18 with just the heads and cams being installed. That means flow through the engine increased.
I am happy with the quality of the heads and all the work that was done to them. They really looked amazing when I installed them back in 2017.
All the porting, polishing, larger valves, etc made them look extremely different from the stock heads I pulled off.
I am sure if I can optimize my intercooler system I can break my own record of 12.80 in a 1/4 mile.

 

[CDW6212R]

That's great to hear John. That is a respectable flow level for what came from the factory. Most people know that the SBF 302 heads top GT40's may see about that 235cfm if fully ported, stock being about 190cfm.

The OHC designs have a higher efficiency for valve opening and timing, thus the higher rpm's. The boost helps a ton like actual displacement. What intakes can be used on the SOHC heads, the various models? Is there one that is aluminum at all, or are they all plastic? That might need flow testing, to see if it's a restriction worth working on. If they flowed 250cfm they would be a decent match to the heads, but if they were much less, than maybe that's something to work on.

I loved the talk of more stroke and bore. Almost any engine made has lots of room to grow bigger, if the parts are possible, and feasible, to locate.

Sleeving a block used to be about $75 a hole, I'm sure that is no longer a low cost process. What is the bore spacing, does anyone know? All of the SBF's are 4.38" bore to bore, thus the typical biggest size is around 4.030" to 4.060" at most.

 

[4pointslow]

The custom intake manifold that Ron Caster from www.bansheeautoparts.com used to sell with his M90 kits.
Just for reference. A top plate adapts the supercharger to this lower manifold.

I am also curious if the block could be sleeved as it would open up more possibilities for different pistons.

 

[CDW6212R]

Yes, I didn't know the 4.0 block had a possibility of a 4.0" piston. I read that just the other day about one that was sonic checked, having detailed thicknesses which looked like it might take a 4" bore in a rare case.

The 429/460 Ford block is well known to be able to handle a .120" over bore, and with sonic checking, some have reached .160" over, stock being 4.36" huge already. That's how those hit 521ci and bigger.

The 4" pistons are super common in various dimensions to fit countless Fords, Chevy, or Dodge engines. That bore could be a trick to getting useful gains in the SOHC, but again if the head/intake flow is up to it. That 236cfm head you mentioned can support good power, and boost pushes that up a ton.

 

[4pointslow]

For clarity,
All information in the past showed that the 4.0 SOHC block could NOT be bored to 4 inches.
Some one already had the block sonic tested and the test results showed that the block was too thin.
If anyone finds out otherwise I would like to know more about that.
I would also like to know about sleeving the 4.0 SOHC and if it is possible to do that to accomplish installing 4 inch pistons.

 

[CDW6212R]

You might want to revisit the information about a block being tested and failing the 4.0" bore. All blocks are different, which is why I referenced the Ford 460 block. Those have been tested many times, and the consensus was that any 460 can be bored .80-.100 over without sonic checking it. But some will have thick enough(centered) walls to take the bores out .160" over. That's a large variance in blocks, the core shift in the process of making them.

I doubt the 4.0 blocks vary that much, but maybe a small percentage could pass the threshold for a 4.0 bore. Now of course it is a huge deal to bore one all the way to its limit, knowing it cannot ever be bored again. The 351 Cleveland is kind of like that, 4.030" is no problem for them, but only rare 351C blocks can be safely taken to a 4.040" bore. Windsors are often bored to 4.060" without trouble, and those have the exact same 4.38" bore spacing. The Windsor blocks were evidently cast better. I have a 351C block that I had bored to 4.020", because it's safe to assume that 4.030" will be its limit, if checked.

 

[4pointslow]

Just reread this entire thread and this is the thread that had the statements about sonic testing the block and what not.
I guess it can be read differently by different people? I read it as the 4.0 SOHC is not possible to bore to a 4 inch "safely".
I found a website with a guy named Corey Weyer who had stroker cranks made, link is...

4.0 SOHC Stroker Crank's

Hey guys,I am not trying to solicite sales.I am thinking of having more of my 4 litre over head billet cams built to sell to the general public and also 200 of the 4130 stroker cranks.Its alot of investment.Question is -Do you think there are enough guys out there that want to build up there...

www.race-dezert.com

He also mentioned big bores in this statement.
"Hey Guy's,
It's been awhile I know but I've been trying put put my (cr8957jhhjdfbnap) life back together.
I have tested and run about every combo possible on a 4.0 sohc so any stroker or big bore setups you guys want to talk about let me know.
I will try to stay more on top of it but its kinda day by day for me as far as work goes. "

This was back in 2010 it looks like. No pictures and the guy seems to have disappeared. Shame, I am sure there are a few who would have liked to know more about his work.

 

[CDW6212R]

It's good to see that some people have put serious thought and money into the 4.0, even other DOHC heads considered. I read that thread which is short and hints at some nice cams and cranks.

But the real issue is always reliability and airflow through the critical parts. I think we can say the reliability is manageable within reasonable rpm's, whether that's 6000rpm or a little higher. The airflow of the heads and are a big deal, but with boost a lot of that is made up for if the flow is OEM lower level stuff.

Gaining displacement would be well worth while, even if the rpm's had to drop if for example the 2.9 DOHC heads didn't flow enough for a 4.5 liter engine. That would gain reliability, both with the better DOHC valvetrain, and the lower rpm's.

I would research more details about what acceptable cylinder wall thicknesses need to be on the various sides, thrust side etc. If a block could go 4.0" without a sleeve, or less than six sleeves, that may be worth it, to gain the common pistons available at that size. Installing a sleeve was not too expensive 35+ years ago, now that might be much different. And not every machine shop is competent at such a procedure.

I'm just pointing out possibilities, and concerns to build a nice reliable SOHC 4.0 block engine. A 302 engine you can get stroker assemblies for about $1000 still I think, I haven't priced those in years. If something feasible like that existed for the 4.0, than the transmission would be the only worry.