Throttle Body expansion

[Sgreg]

Does anyone have the latest tuner info on the 63mm bore TB vs. stock in a ZR-1 with upper end P&P, headers and AM exhaust ? Any improvement with the bigger bore ? Some used to feel it was a negative performance mod if heads are not ported as well.

[Sgreg]

I didn't know this was such a tough one. Anybody on pros and cons of going to a 63mm TB for a upper ported ZR-1 with headers and AM exhaust ?? :dontknow:

[GOLDCYLON]

Jeffvette told me once unless your going bigger in CDs the enlarged TB is a waste of money even with the top end port with matched heads and long tubes. I asked about this when I had my top end done.

[Jeffvette]

Spend the money elsewhere.

[Sgreg]

I think it is Marc who does the 63 MM TB with the first level mods; not sure though. If he does, the tuning specs most probably include more fuel. Makes sense that too much air creates a bog in acceleration. I always assumed head work on a 350 inch motor might call for enlarging the TB. I guess Jeff is saying not necessarily so. So until you get to a 368 inch or more cube motor, the larger TB just isn't needed. Man, I almost pulled the trigger on a bigger TB; glad I didn't.

[XfireZ51]

Greg,

Both Lgaff and myself have 63mm TB with just top end done. What we found is that the bores on the plenum itself need to be matched to the enlarged TB bores otherwise there's no sense to doing it. I can't tell you that I make more power than a top end w/o a 63mm TB. I can tell you I don't have any bog when getting on it. I'll let Lgaff speak for his experience.

[GOLDCYLON]

Dom did you adjust timing?

[XfireZ51]

GC,

There are changes to VE, SA and other tables to optimize for all the modifications made. I can't point to specific changes made for the 63mm
throttle bores.

[GOLDCYLON]

Got it