We have had a Genesis 427 on the road now for two years. It has been a solid performer with no issues other than a faulty intake gasket which the builder replaced, in my garage! Keith Craft offers Genesis blocks as a option. Or you can get a crate engine from Genesis. Our is in a Cobra. I can only imagine what it would be like in a Mark IV.
GT40 MKIV with a Big Block
- Thread starter fkemmerer
- Start date
I would probably go with a Shelby block. Just finished a Cobra project with a 482 ci motor from Keith Craft based upon this package and I'm very happy with the results.
Here's my Kieth Craft built Shelby 482 in my RCR MKIV. Open headers sound so good. 
YouTube - GT MKIV running with open headers
YouTube - GT MKIV running with open headers
Fred
Find onby a gearchart which i did for future customer of mine who also wants to build a MKIV with either a 427 SBF or a 482 BB.
Besides the T44 the 930 is the gearbox which are the closest fit you can find to it.
In my opinion it is a beautiful box, with perfect gearing for a torque oriented engine.
The 930 is perceived as one of the most rigid porsche gearboxes and it wil be suitable for your application. Check the gearchart and compare it to the dynocharts which are on KC´s website and you will agree that a 6 speed is way overdone. Check the RPM drops which are perfect for this torquie engines. If the top speed is to low for you there are plenty of longer final ratios available.
I made two charts, in order for you to see the big difference different height ratio tires make. So overall the final ratio choice of your gearbox also depends on your tire choice. ( find onby also a list for possible tires)
I will be happy to help you, to find the one fitting your needs.
Also in terms of weight the 930 box is the way to go. THere are two versions. the short and the long bellhousing one. Both are suitable for an RCR with out changes ( although you always could shorten the long one by milling of this 2 inches of the bellhousing). RCR offers complete adaptor kits for this gearboxes.
I could supply you with a fresh overhauled 930 with LSD for about 3500 Euro ( plus transport), but there are also good sources in US (RCR; CARQUIPP; GBOX).
Find onby two pics of 930 gearboxes ( on one of the pics the very right gearbox is a G50)
imagine this in a magnisia color and you have the closest look you can have to a T44
Here a pic of J7
THanks
TOM
Find onby a gearchart which i did for future customer of mine who also wants to build a MKIV with either a 427 SBF or a 482 BB.
Besides the T44 the 930 is the gearbox which are the closest fit you can find to it.
In my opinion it is a beautiful box, with perfect gearing for a torque oriented engine.
The 930 is perceived as one of the most rigid porsche gearboxes and it wil be suitable for your application. Check the gearchart and compare it to the dynocharts which are on KC´s website and you will agree that a 6 speed is way overdone. Check the RPM drops which are perfect for this torquie engines. If the top speed is to low for you there are plenty of longer final ratios available.
I made two charts, in order for you to see the big difference different height ratio tires make. So overall the final ratio choice of your gearbox also depends on your tire choice. ( find onby also a list for possible tires)
I will be happy to help you, to find the one fitting your needs.
Also in terms of weight the 930 box is the way to go. THere are two versions. the short and the long bellhousing one. Both are suitable for an RCR with out changes ( although you always could shorten the long one by milling of this 2 inches of the bellhousing). RCR offers complete adaptor kits for this gearboxes.
I could supply you with a fresh overhauled 930 with LSD for about 3500 Euro ( plus transport), but there are also good sources in US (RCR; CARQUIPP; GBOX).
Find onby two pics of 930 gearboxes ( on one of the pics the very right gearbox is a G50)
imagine this in a magnisia color and you have the closest look you can have to a T44
Here a pic of J7
THanks
TOM
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