Three pondering questions on 4.6 DOHC and IRS swaps
07-03-2009, 12:18 PM
#11
No, heads and intake have to match. The B heads need a b head intake, the C heads need a C head intake. The 99/01 Cobra and 03/04 Mach 1 have the same basic intake. So 99-04 heads use one intake, 93-98 heads use another.
That guide I posted lists all possible intakes you can use for each head.
That guide I posted lists all possible intakes you can use for each head.
07-03-2009, 12:51 PM
#12
5th Gear Member
Join Date: Nov 2006
Location: So Cal
Posts: 3,569
I will address the IRS question 
What are your goals and why this swap? If your goals are nicer ride for a DD, than you are good. If you are looking to run some high HP numbers for good launches on the 1/4 OR improvement on the twisties, you will be better off keeping your current SRA. Of course, you will need to invest $$$ into the SRA to out perform the IRS on the twisties, you will need to beef up the IRS to handle the 1/4. Even with IRS upgrades, you will never be rid of its wheel hop.
I say, keep the SRA and go CO's/PHB or WL and beat the IRS silly on the track AND the corners.
Jazzer
What are your goals and why this swap? If your goals are nicer ride for a DD, than you are good. If you are looking to run some high HP numbers for good launches on the 1/4 OR improvement on the twisties, you will be better off keeping your current SRA. Of course, you will need to invest $$$ into the SRA to out perform the IRS on the twisties, you will need to beef up the IRS to handle the 1/4. Even with IRS upgrades, you will never be rid of its wheel hop.
I say, keep the SRA and go CO's/PHB or WL and beat the IRS silly on the track AND the corners.
Jazzer
The only part that is untrue....
99% of IRS cars with the known remedies (bushings, decent tires, a good shock/spring setup, FLSFCs) have eliminated wheel hop. The other 1% are freaks of nature. There's more than a few Cobras running 10s with nothing more than the mods I've listed. Then they just start snapping axles....
OP, consider that you although you will be adding 85 lbs to *** of the car, weight distribution will improve.
As far as ease of swap, it could go either way....my swap took 12 hours because EVERYTHING went wrong. Subframe wouldn't line up on the donor car, shredded wheel studs, exhaust fitment, brake issues....I have SEEN it done in 3 hours before, though.
If you plan on power levels above 450 I strongly recommend keeping the SRA......Level 5 axles are STUPID expensive and the stockers WILL eventually snap.
07-03-2009, 05:47 PM
#15
I might just go with control arms and rebuild the SRA in the end now. Im looking for more that 450hp out the back and I dont feel like dropping a ton in beefed up IRS axles or having stockers snap and take out the hole side suspension.
07-03-2009, 05:50 PM
#17
My buddies 03 cobra convertible just dyno'd in at 450hp (I think he said) with only a mild tune and cat back. Mine right now is probably around 300hp (wild guess, no dyno or track runs yet) on the SOHC.
Also IRS= independent rear suspension SRA= straight axle
Also IRS= independent rear suspension SRA= straight axle