2.02 or 2.05 that is the question

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345man2

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k guys finally pinned my winter build for my duster, 416 bottom end voodoo hydral tappet, pump gas, air gap, 4 speed, ported j heads, now the question how much would it benifit me to go up to a 2.05 valve or should i stay with 2.02:D
 
from my experience, your heads need to flow quite a bit to really even take advantage of an over sized valve. when i got my super commando's, the larger 2.08 valve actually HURT flow, because we're using a 4.030 bore and not a big 4.1XX from an R block. they had to go back to the machine shop and i had to have the valve unshrouded. that being said at the end of the day the machine shop told me they actually would have flowed better with a smaller valve. granted mine were 2.08, but it takes alot to of porting to get a smallblock mopar head in the 280/290 CFM range, and with you mentioning a flat tappet i doubt you're spinning this thing to 8000 RPM. it's probably a toss up on a street driven 416. it'll be a torque monster down low anyways..i'd probably spend that money elsewhere.
 
Pick the smallest valve and port that will provide the adequate flow for the HP and RPM level you desire.

CFM flow without velocity is as bad as velocity without flow.

Given the limitations of a stock J Head in port volume, even ported the port won't flow enough air to support a 2.05 valve. The second issue is valve shrouding you didn't say what your bore is, but unless it is quite a bit larger than stock you can have a problem with valve being shrouded by the cylinder wall. For theses reasons I think sticking with 2.02 would be your best bet, at least until you can step up to a more race oriented head like a W series that has the port that can support the larger valve.

Regards,

Joe Dokes
 
if they are flowing in the 260 + cfm area go with the 2.05. have them profile out the wall next to the valve. the long stroke will keep velocity up high even at low rpms
 
I know while I've been discussing with my machinist about building power on a 318 or 360, and the one thing that he said is that even upgrading from 1.88's might gain you a tenth in the quarter, but it's not a difference you'll be able to feel. And he told me (and some goofing with Desktop dyno seems to confirm this) I'd make much better gains putting in bigger exhaust valves than going bigger on the intake. (not quite twice as much)
 
345man2 said:
k guys finally pinned my winter build for my duster, 416 bottom end voodoo hydral tappet, pump gas, air gap, 4 speed, ported j heads, now the question how much would it benifit me to go up to a 2.05 valve or should i stay with 2.02:D
Click to expand...

What valve manufacturer are you using for the 2.02? I would go with Manley .100 long chevy 11/32 valves and keep the current valve size but have someone who know's how to port and do valve jobs on mopar heads do that work.
Those heads can support pretty decent power, but it's real easy to get too much money in them compared to some new heads.
So just be careful of that.
 
Even 1.78-1.50 318 heads ported can flow enough to support 400+hp, it seem like you shooting for 450+hp 2.02 are fine. Look at RHS heads flow enough for 500hp with 1.92 valves. Bigger ain't always better.
 
2.02 to 2.05 won't gain anything unless it yields a good flow increase which is unlikely being its only a 1.5% increase in valve size
 
running the 202 nailhead design and looking for ROUND 500 HP JUST DONT KNOW IF THE SWITCH TO 205 is worth the cash or not:D
 
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