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Old 04-14-2011, 07:11 AM
Dyna Dyna is offline
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Thanks for your answer. A Jag IRS from a V12 XJS 1981 and later all come with 2:88 rear end with LSD. Since I actually have a 89 XJS V12 as my daily driver I know this one revs about 3000 rpm at 70mph with 215/60-15 tires, if memory serves me right (not with the car at present). The tires I will use for the Burb will be 235/70-15 so youíre right I might not need an overdrive. I have a 700-R4 but also a 3speed with OD. Afraid that the 3-OD box might explode although. Preferably I would like to still have a manual box on the tree so to say, suggestions welcomed.

I donít really aim for a specific TQ/HQ numbers but rather the result. The more the better but I donít want a high reving unstreetable machine. At 5500 rpm this brick should be able to do 150mph in 1:1 gear with be 235/70-15 wheels. Iím pretty sure I need a ton of power for that. I think 475+ HP is the bare minimum when you consider weight and most importantly front area of the Burb.

So what is that nice roller cam , in your view? How much more would it produce compared to the Impersonator II - beside I would not lower the comp since I will drive on 91 (US) octane, and even possibly 95 (US octane). The AFR head especially the CNC once are a tad expensive too, and 421 might need bigger runners.. Hmm food for thoughts..

Why would you shy away from their rollers/rockers have you heard about a lot of failures? The issue with their heads form what I hear is casting quality which is very hard to see, while machined stuff is easier to check for faults and coming failures (the rockers looks like they are machined out of billets).

A Edelbrock performer RPM (7101 and 7104) actually has provision for the oil tube you only need to machine it in there since itís not there strait out of the box. Hence donít think there is a need to go for the 70-72 LT1 intake unless I got something wrong..

Sincerely Dyna

Originally Posted by SSedan64
A few ??'s.
What HP/TQ are you hoping for?
Does the Jag IRS have 2.88 gears? If so an OD Trans may not be needed.
OD Trans ratios:
Trans--------1st-----2nd-----3rd----4th Gear
TH700-R4----3.06---1.62--- 1.00----0.70

I'd shy away from ProComp Roller Lifters & Rockers. Some of their Aluminum Heads are Ok, the ones with larger 215cc or so Intake runners.

These are 2 SBC406 builds ChevyHiPerformance did a while back. Very torqy builds. Either of these with a nice Roller Cam would produce much more HP/TQ than these Flat Tappet builds below.
The Impersonator I, w/Vortec Heads.

The Impersonator II, w/Aluminum heads.

I was going to suggest an old Aluminum GM 70-72 LT1 type Intake as they have the provision for the Oil fill tube but, the prices have gone crazy. They're basically like a Edelbrock RPM Intake.
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