Hi guys, I was wondering if I can convert my 390 to a SOHC 427. This motor will be going into a '67 mustang coupe and will do some bracket racing so I do need the horsepower. If you could please let me know wether or not it is possible, please let me know.

Thanks!

-Brad

 

I dont think it's possible. For one thing, the 427 uses 4.23" bores, while the 390 uses 4.050" bores. You'd need a .180" overbore to achieve 427 specs. This is nearly impossible with most 390 blocks. The most you should expect is 410ci, with a 428 stroker crank. All SOHC 427's were side oilers, and the top oiler block might not handle it, but I think it should. Also, you'd have to block the passages to each lifter so that you dont lose all your oil pressure. Then you'd need a plate to cover the timing chain.

If you got this far, you'd have to procure the SOHC heads. This alone would be a major problem. Then, you'd have to have the chain, sprockets, and cams for it. I'm sure the SOHC takes special cams, so you'd have to have custom cams ground for it.

The SOHC 427 was notorious for breaking timing chains, as it was so long it'd stretch and break. It was a high revving very powerful race engine though.

I really think it's impractical to convert your 390 to a SOHC 427. You'd probably be money ahead to buy one when it comes up on ebay.

There is a lot you can do to the 390 to get a lot of performance out of it, if you'd like suggestions on that just ask. I think a intercooled centrifugal supercharger for that 390, like ATI's P-600B would be just the ticket...

 

The SOHC also required special pop-up wedge shaped pistons that I bet would cost a small fortune to make for a 390. Also the SOHC heads have oil drainback passages that do not exist in other FE castings. For that alone you may be S.O.L. no matter how much money you have.

 

unless you arevmade of money or it's growing in your yard, I'd abandon the SOHC plan!

Take a look at Ebay for 427 SOHC parts and you'll see what I mean. Virtually unusable 427 SOHC parts fetch obsurd prices. Good parts are off the chart.

I don't think you could buy all of the parts for less than $20k. then converting the 390 block to be compatible would be almost impossible. Now, you might be able to get a custom compatible block from somebody like Shelby. He's making all new 427+CI all aluminum blocks.

 

Nope. Can't be done. It would be EXTREMELY rare to find a 390 with enough meat to bore it to 4.23.

A Shelby block would work fine with drainback mods. My non-cammer Shelby based engine is going to finish up at around $18,500. I don't think you would be able to build a cammer for less than 25k. Other than the WOW factor, no need for a cammer. A well built wedge FE with modern components will put out just as much or more HP.

-Scouder

 

Building a 427SOHC should be done for nostalgic purposes only. You can get just as much power out of todays aftermarket wedge heads as you could the SOHC heads. The price of the SOHC parts are outrageous just like everybody else says. If you are wanting to spend tons of money on one then we can point you in the right direction.

 

It would be a neat trick to see Edelbrock FE heads make as much power as the SOHC heads. You'd have to be smokin some mighty good stuff to read those figures on a dyno.

 

The stock SOHC heads flowed out at 355int./248exh. @ .600 lift. Keith Craft can get your edel heads flowing 380cfm on the intake and around 250 on the exhaust. There are dove heads flowing even higher numbers. There are tunnel port heads that have had some extensive porting done that flow far greater volume than any of these heads.

 

Here's some factory hp ratings for comparison:

427-8V LR - 425HP @ 6000RPM
427-8V MR - 485HP @ 6300RPM
427-8V HR - 540HP @ 6300RPM
427-8V SOHC - 657HP @ 8300RPM

 

8300 RPM??? That sounds like nothing but nascar engine material to me. Even if you could build one, would you really want to be spinning that fast on the street?

 

Well I guess it wouldn't have to be 427 CI, I just was thinking to go "cammer" so that part doesn't matter. I am looking for some form of forced induction by means of a huge 8-71 blower or a 6-71 blower. I will be fine staying at 390 cubes, that won't be an issue. I have located multiple used 6-71 or 8-71 blowers, and the only problem would be making some sort of intake manfiold for it. If you guys could please shed some light on how I could find a manifold or have one made to hook up an 8-71 or 6-71 blower.

Thanks Guys!

-Brad

 

I think Blue Thunder makes an intake for the superchargers?

http://www.bluethunderauto.com/

390/427/428 6.71 blower manifold

 

8300 RPM in an FE...I love it :-)

I saw a 30ish cuipe on Ebay once with a 427 SOHC installed, not sure what it sold for, but it was i the $30k range the last I saw it.

The coupe was nice, but I'm sure any buyer was interested in the motor.

 

No need for smokin anything to put out cammer numbers with a wedge head. My Ebocks flow 381/259. Keith Craft is building streetable FEs that go well over 700hp. Sorry, but cammers and tunnelports are being eclipsed on a daily basis by new, easy to get, reasonably priced square port stuff. I sold my tunnelport heads because they only went 304/182 and I could not get them to flow near CNC ported edelbrocks without spending a fortune on already expensive 30 year old heads, and I saved 40lbs to boot.

Would I like to have a cammer? Yep. They are still the most exotic FE ever produced, but by no means the pinnacle of FE performance like they once were.

-Scouder

 

Hi guys, does anyone actually have pictures of a blown 390 or of the manifold itself? Blue Thunder does not have pictures of the manifold on its homepage. I am interested in a manifold more for an 8-71 blower, but a 6-71 blower would be nice too; I just want forced induction. N/A will take you a distance, but not nearly as far as forced induction.

Thanks!

-Brad