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Gains switching to larger intake valve

Posted By: 416challenger

Gains switching to larger intake valve - 09/15/09 02:13 AM

I will be freshening up my motor after this season and I was considering going from a 2.02 valve to a 2.05. What kind of gains if any can be had? The heads are Edelbrock RPM that flow the as followed-

Intake Exhaust
.100" 82.8 N/A
.200" 149.0 112.1
.300" 211.2 169.3
.400" 255.6 203.2
.450" 269.4 218.0
.500" 276.3 226.0
.550" 281.5 229.8
.600" 284.6 231.2
.650" 284.6 231.5
.700" 284.6 232.9

The cam is 262in 268ex @.050 w/ 675" lift. I would like to run 7.00 in the heat, I normally run around 7.09 @ 3800 da. Has anyone made a similar change, if so what kind of results?
Posted By: goldmember

Re: Gains switching to larger intake valve - 09/15/09 02:19 AM

Depends on the port.Simply installing a larger valve in the same port often won't help.
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 02:26 AM

Quote:

I will be freshening up my motor after this season and I was considering going from a 2.02 valve to a 2.05. What kind of gains if any can be had? The heads are Edelbrock RPM that flow the as followed-

Intake Exhaust
.100" 82.8 N/A
.200" 149.0 112.1
.300" 211.2 169.3
.400" 255.6 203.2
.450" 269.4 218.0
.500" 276.3 226.0
.550" 281.5 229.8
.600" 284.6 231.2
.650" 284.6 231.5
.700" 284.6 232.9

The cam is 262in 268ex @.050 w/ 675" lift. I would like to run 7.00 in the heat, I normally run around 7.09 @ 3800 da. Has anyone made a similar change, if so what kind of results?



82.8 CFM @ .100" lift??

Posted By: Bad340fish

Re: Gains switching to larger intake valve - 09/15/09 02:28 AM

On my ported X heads I changed from stock 2.02 valves to a race style 2.05 intake and it picked up .2, I don't recall how much MPH it gained. I also replaced the stock exhaust valves with SS valves as well so there might be some gain from that.
Posted By: goldmember

Re: Gains switching to larger intake valve - 09/15/09 03:01 AM

You bring up a good point. I have seen gains of .2 in the 1/8mile with a simple valve angle change,same valves. It's obvious that it was on different days so weather and track conditions cannot be ruled out.
Posted By: 416challenger

Re: Gains switching to larger intake valve - 09/15/09 03:29 AM

S/ST 3040-What did you mean by your comment???
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 03:42 AM

Quote:

S/ST 3040-What did you mean by your comment???



82.8 CFM @ .100" is not even in the ball park.

I've been through this before and I've never seen a 2.02"
valve flow more than 66 CFM @ .100" Being that far off at
.100" lift, only makes me question the 284+ at higher lifts.

I've seen similar flow numbers before, posted here.

Contrary to popular belief, this is a subject I know a little about.
Posted By: 416challenger

Re: Gains switching to larger intake valve - 09/15/09 03:47 AM

S/ST 3040- I was not aware that this number is abnormal(incorrect), that is why I asked. It is what is listed on the flow sheet. The heads were ported by a respected member from this site, so I assume the numbers were correct.
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 04:01 AM

Unless you send them back to the same guy to flow them with the
2.05 valves, you are going to be very disappointed. I can tell from
your flow sheet.

2.02" valve is capable of flowing at least 324 CFM @ .700"

2.05" valve is OK in an Edelbrock head but, you won't see any
improvement unless the valve job on 2.02" seat was no good
to begin with.


This is a set I did with the valves listed:

...........INTAKE........................ EXHAUST

.100"_____64.1___________________54.6
.200"____131.6__________________118.6
.300"____194.4__________________158.6
.400"____242.5__________________177.1
.500"____270.8__________________192.4
.550"____279.3__________________199.5
.600"____282.2__________________204.4

2.055" IN x 1.600" EX
Posted By: 416challenger

Re: Gains switching to larger intake valve - 09/15/09 04:08 AM

I am not hung up on the flow numbers. I am just looking for somewhere in my combination that I can make some improvement with minimal investment.
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 04:13 AM

Give us the whole build. Plus transmission, converter, race weight, gear and tire size.

Posted By: 416challenger

Re: Gains switching to larger intake valve - 09/15/09 11:42 AM

My combination is-73 Challenger, 418 cid, 11.55:1 comp, Edelebrock RPM heads, Vitor intake, 950HP carb, 262in 268ex 675" lift, 727 tran, 9 1/2" 4800 converter, Dana 60 w/ 4.10 gears, 28 x 12.5 ET Street tire, and the weight is 3720 w/ driver. I have ran a best of 6.92 @97.2 and 10.98 @120.7 w/ 1.50 60' time.
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 01:09 PM

Honestly, that is not bad for 11.55 compression and 3720 lbs. (505 HP)
Since you mentioned "improvement with minimal investment", I'd start
looking for places to take out weight. That's about as cheap as you
can get.......and effective.

Everything else looks pretty decent together. Maybe another 1.5 point
compression with another 10º cam, an 8' converter in a 2.74 low gear
904. Nothing really as cost effective as whittling down the weight.

After I got as much weight out of it, as I could, then I'd swap to a 2.74
904 with a matching 8" converter. Only then would I start messing with
the engine. The weight alone (200 lbs.) should get you 7.0s.

Good luck.
Posted By: cgall

Re: Gains switching to larger intake valve - 09/15/09 01:33 PM

Probably no gain unless you unshroud the valve by machining the combustion chamber.
Posted By: theclutcher

Re: Gains switching to larger intake valve - 09/15/09 02:00 PM

Quote:

Probably no gain unless you unshroud the valve by machining the combustion chamber.


if that is shrouded, you can expect very little then bore size comes into play.
imo...
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 02:18 PM

Quote:

Quote:

Probably no gain unless you unshroud the valve by machining the combustion chamber.


if that is shrouded, you can expect very little then bore size comes into play.
imo...



Anytime I've tried unshrouding the intake valve (straight wall side) on an
OEM head, it hurt flow. I haven't tried it on the RPM though.

Attached picture 5483757-DSCN1743.JPG
Posted By: moper

Re: Gains switching to larger intake valve - 09/15/09 02:20 PM

Quote:


Intake Exhaust
.100" 82.8 N/A
.200" 149.0 112.1
.300" 211.2 169.3
.400" 255.6 203.2
.450" 269.4 218.0
.500" 276.3 226.0
.550" 281.5 229.8
.600" 284.6 231.2
.650" 284.6 231.5
.700" 284.6 232.9

The cam is 262in 268ex @.050 w/ 675" lift.



If the port already stalls at .550 then adding more valve without adding port volume ahead of it isn't going to do much. I don't think shrouding is an issue. Or it's less of one than many think. I am curious tho... with those flow numbers, why such a small duration and huge lift? I would think more power will be made staying in the .650 range but adding another 15°-20° of duration at .050. I wouldnt have specd a cam any taller than .630 for those heads.
Posted By: 416challenger

Re: Gains switching to larger intake valve - 09/15/09 05:12 PM

The car runs on pump gas, so I really do not want to raise the compression any more. I was kind of leaning toward lightening it up. I have a steel hood and will probably go to a fiberglass hood. I also will be going to a 29.5" x 10.5" ET Drag and was thinking about a low gear set in the transmission. Anyone know the weight of a steel Challenger hood?

Moper- The only reason for the high lift is I reused the 1.6 rockers that I had, with 1.5 I would have 632" lift.
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/15/09 05:21 PM

At 3720 lbs. there should be plenty of places to remove weight
without spending any money. It obviously gets harder (and more
expensive) the lighter you get.

Going up 1.5" in tire will lower your drive shaft RPM over 300
RPM at the same speed. Wrong direction, I think.

With 4% slip, I have you figured at about 6250 engine RPM, currently.
Posted By: theclutcher

Re: Gains switching to larger intake valve - 09/16/09 01:10 PM

Quote:

Quote:

Quote:

Probably no gain unless you unshroud the valve by machining the combustion chamber.


if that is shrouded, you can expect very little then bore size comes into play.
imo...



Anytime I've tried unshrouding the intake valve (straight wall side) on an
OEM head, it hurt flow. I haven't tried it on the RPM though.


That is interesting,
Have only seen the opposite.
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/16/09 01:37 PM

Quote:

Quote:

Quote:

Quote:

Probably no gain unless you unshroud the valve by machining the combustion chamber.


if that is shrouded, you can expect very little then bore size comes into play.
imo...



Anytime I've tried unshrouding the intake valve (straight wall side) on an
OEM head, it hurt flow. I haven't tried it on the RPM though.


That is interesting,
Have only seen the opposite.



Hmmmm..........3 notebooks full notes and a flow bench is pretty handy.

Attached picture 5485887-DSCN1396.JPG
Posted By: theclutcher

Re: Gains switching to larger intake valve - 09/16/09 01:52 PM

Quote:

Quote:

Quote:

Quote:

Quote:

Probably no gain unless you unshroud the valve by machining the combustion chamber.


if that is shrouded, you can expect very little then bore size comes into play.
imo...



Anytime I've tried unshrouding the intake valve (straight wall side) on an
OEM head, it hurt flow. I haven't tried it on the RPM though.


That is interesting,
Have only seen the opposite.



Hmmmm..........3 notebooks full notes and a flow bench is pretty handy.



cant argue with that, just the few Ive had experience with always picked up, big or small block when opening up that area.
wonder what the difference could be?
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/16/09 02:04 PM

Scott.....I know the OEM big block heads do like opening that
up, the more, the better, I understand but, it always screws
up the high lift flow on my small block heads.

Dwayne Porter and I discussed this once in conversation
as, we both found the same thing.
Posted By: theclutcher

Re: Gains switching to larger intake valve - 09/17/09 12:59 PM

Hi Vic.
At what lifts you see the reduction?
Would not come into play too much if cam doesnt see time spent at that lift point.
wondering if plusses if any at low lift more than offset the loss at high point.
what have you seen?
Posted By: TheOtherDodge

Re: Gains switching to larger intake valve - 09/17/09 01:18 PM

Hey Josh! Long time no talk!

I think switching to the 2.05 valve is more expensive/time consuming than the improvement you will see (valve job, cut seats, new valve, set up springs, intake gaskets, head gaskets, antifreeze, oil, etc).

I would concentrate on weight, particularly the hood where you will get a lot of weight off the nose.

Tell your dad "hi" for me!
Posted By: S/ST 3040

Re: Gains switching to larger intake valve - 09/17/09 01:31 PM

OEM SB Casting #974 Manley Pro-Flo 2.02" x 30º BC

.............BEFORE.........................................AFTER

.100"_____62.0____________________________62.4
.200"____127.3___________________________128.9
.300"____188.9___________________________192.1
.400"____241.8___________________________240.2
.500"____269.8___________________________268.0
.550"____268.0___________________________****
.600"____269.2___________________________266.2
.650"____269.9___________________________268.3
.700"____273.3___________________________268.3

**** - Turbulent/Noisy
Posted By: afxcoronet

Re: Gains switching to larger intake valve - 09/17/09 01:34 PM

Josh, just leave it alone, and get started on the Dart...
Posted By: 416challenger

Re: Gains switching to larger intake valve - 09/17/09 04:50 PM

James- I figured since I was already going to be freshing the motor I would ask the question, but It sounds like it isn't a worth while investment. Now I just have to find a hood.

Curtis- The Dart isn't going to happen anytime soon, we just put Mackenzie is preschool.
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