What to expect to the wheels
355 cubic inches
Flat top Pistons hypertonic rods
Comp cam xfi 268
Stock ported and polished heads with 2.08 intake valves,1.9 exhaust
Lt headers
T56
Stock rear end and gears
What should I be expecting to the rear end and what would be a good tune to use for this setups
Seeing as you didn't post about resolving the factory gearing is not encouraging either.
Your valve sizes are wrong, or at least I hope like hell they are wrong because 2.08/1.9 aint gonna happen.
Far as "what would be a good tune to use" CUSTOM is the ONLY answer, do not even start it till you have a baseline from a tuner.
If the heads are good I could see 380rwhp and low 12s if you fix the gears. If the heads are not good it could be a lot lower.
Seeing as you didn't post about resolving the factory gearing is not encouraging either.
Your valve sizes are wrong, or at least I hope like hell they are wrong because 2.08/1.9 aint gonna happen.
Far as "what would be a good tune to use" CUSTOM is the ONLY answer, do not even start it till you have a baseline from a tuner.
If the heads are good I could see 380rwhp and low 12s if you fix the gears. If the heads are not good it could be a lot lower.
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If you meant 2.02/1.6 did they charge a bunch extra for replacing seats, because to use those valve sizes correctly in LT1 castings you need new seats. If they didn't then either the valve is not in the seat right or the seat is machined so thin as to likely fail, and if they did replace the seats well I wouldn't be inclined to trust someone who wouldn't just tell you to use 2.00/1.56 as some of the best proven LT1 castings do.
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If you meant 2.02/1.6 did they charge a bunch extra for replacing seats, because to use those valve sizes correctly in LT1 castings you need new seats. If they didn't then either the valve is not in the seat right or the seat is machined so thin as to likely fail, and if they did replace the seats well I wouldn't be inclined to trust someone who wouldn't just tell you to use 2.00/1.56 as some of the best proven LT1 castings do.
What are the rods then?
So is it really 2.08 and 1.6 valves? 2.02 is more likely, 2.055 maybe.
Who did the heads? Are they ported all the way through or just had bigger valves installed? Port matched or full runner?
Compression? Deck height? Head gasket thickness? Chamber size?
You need a custom tune for that cam, be it from a tuner who has done a dyno tune on THAT cam before, being off the shelf someone might have a file, or a dyno tune. You should bring it to 6600rpm at least when you take it to the dyno.
At this point, you are to far along to worry about it. Get it on a dyno with a capable tuner and see how she does.
I say 350whp.
Part number for rods/pistons?
Who ported the heads and what do they flow?
It's hard to say what you'd make. I could be anywhere from 340-400rwhp but it's all in the details. The XFI 466 is not a bad cam. It's a little on the small side for the typical H/C car but the lobes make up for that. Those valves are too big if we're talking about the stock seats in the heads. The largest you'd want to go is 2" and 1.56", anything bigger shrouds the chamber and has no advantage. Without any flow data or pics of the ports/chambers it's really hard to say. Most people rave about Lloyd Elliot on here when it comes to hand porters and go for the LE2s.
Part number for rods/pistons?
Who ported the heads and what do they flow?
It's hard to say what you'd make. I could be anywhere from 340-400rwhp but it's all in the details. The XFI 466 is not a bad cam. It's a little on the small side for the typical H/C car but the lobes make up for that. Those valves are too big if we're talking about the stock seats in the heads. The largest you'd want to go is 2" and 1.56", anything bigger shrouds the chamber and has no advantage. Without any flow data or pics of the ports/chambers it's really hard to say. Most people rave about Lloyd Elliot on here when it comes to hand porters and go for the LE2s.
Last edited by camfreak; Dec 28, 2015 at 08:01 PM.









