2.02" J heads... or 2.08" intake valve / 1.650"exhaust?

2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/06/11 08:39 PM

Okay, I know this is going fifty-eleven thousand directions...but...

We have a B&M supercharged 1972 Dodge Dart. It's basically got a stock long block 1974 360 with 60,000 miles on it that has a SpeedPro (I think it is) .429" lift camshaft and a roller timing set in. Currently the supercharger is sitting on a Holley Street Dominator aluminum intake manifold that I milled the carburator flange flat on for the supercharger. It has an Acell Super Coil and a Holley 750 cfm double pumper carburetor.
The car runs great/strong but I've been thinking about a head swap since I have a set of ready to go 2.02" J heads sitting here collecting dust.
My original intent was to just swap the heads and be done.
Lately I've been wondering about valve sizes.
Would it be beneficial to run the larger 2.08" intake valve?
What about the larger 1.625" or 1.650" exhaust valve?
Eventually I'll be going to a larger camshaft, though nothing crazy. Something with ~.480" lift.
Should I just stick the 2.02" heads on there or stuff larger valves in another set of heads?

Will the big block 2.08" valves work in the small block heads (length)?

In a factory casting head can you fit 2.08" (I) & 1.650" (E) valves?

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Posted By: 9secondsatellite

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/06/11 09:37 PM

what actually works great in that head is sbc chevy .100 long valves. they are almost identical in length. i went with 2.02 and 1.625. now keep in mind you'll have to go with 11/32" guides,retainers,locks and seals when doing this. there are a lot of different brands and choices(read inexpensive and options) for valves by using this setup.you'll also lighten the valve train with that combo.

Posted By: 340B5

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/06/11 11:20 PM

Stick w/the 2.02, unless you want to do a bunch of headwork to un-shroud the 2.08's

Posted By: ademon

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 06:01 AM

2.05 is common on X&js

Posted By: sshemi

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 10:17 AM

Quote:

Stick w/the 2.02, unless you want to do a bunch of headwork to un-shroud the 2.08's

Not worth it in my opinion

Posted By: Joesixpack

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 04:17 PM

put 2.02 s on as is. 2.08 wont work with low lift cam, and low compression ratio.2.08 on that combo will loose lots of bottom end torque...port will stall...to effectively use 2.08 and gain any benefit...you would need to increase port volume from intake port opening down...including unshrouding below valve,narrowing guide....blending chamber floor...increasing static compression ratio...and adding .100 lift to cam....change rocker arm ratio...then once you have the bigger intake charge rammed on top of the piston you got to get the exhaust out of there quicker also...so more work on exhaust port....plus you would need to do some work on intake manifold to make that intake volume larger....lots of work for very little return.....an effective combination that includes all areas must be considered.....better and or bigger carb...bigger exhaust tube primary diameter..looser stall TC,more gear ratio...with no other changes other than swapping on the 2.02s i think you will have a quicker 60 foot time...better mid range....possibly 300-400 more rpm on top end.

Posted By: MR_P_BODY

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 04:30 PM

Quote:

put 2.02 s on as is. 2.08 wont work with low lift cam, and low compression ratio.2.08 on that combo will loose lots of bottom end torque...port will stall...to effectively use 2.08 and gain any benefit...you would need to increase port volume from intake port opening down...including unshrouding below valve,narrowing guide....blending chamber floor...increasing static compression ratio...and adding .100 lift to cam....change rocker arm ratio...then once you have the bigger intake charge rammed on top of the piston you got to get the exhaust out of there quicker also...so more work on exhaust port....plus you would need to do some work on intake manifold to make that intake volume larger....lots of work for very little return.....an effective combination that includes all areas must be considered.....better and or bigger carb...bigger exhaust tube primary diameter..looser stall TC,more gear ratio...with no other changes other than swapping on the 2.02s i think you will have a quicker 60 foot time...better mid range....possibly 300-400 more rpm on top end.

You do realize he is hanging a super charger on it...
but it isnt worth the bucks to put the 2.08 in it...
dont need it with pressure... exhaust is more important
on a pressurized engine

Posted By: HotRodDave

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 05:26 PM

The 2.08 properly un-shrouded will flow more at low lift than a 2.02. Listen to what you are saying, by your reasoning a .250 in diameter valve will flow more at low lift than a 6 inch valve. The bigger valve will flow more at low lift up to the point the port stalls, the port will stall at a lower lift with a bigger valve. The bigger valve has more open area around the valve at lower lift, port velocity will actually increase with the larger valve because more air will be flowing through the same size port

When some one claims there 2.02 valve J-heads went slower than when they had 1.88s and "no other change" you can count on it being because the chamber and throat were not opened up properly.

Posted By: MR_P_BODY

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 05:57 PM

Quote:

The 2.08 properly un-shrouded will flow more at low lift than a 2.02. Listen to what you are saying, by your reasoning a .250 in diameter valve will flow more at low lift than a 6 inch valve. The bigger valve will flow more at low lift up to the point the port stalls, the port will stall at a lower lift with a bigger valve. The bigger valve has more open area around the valve at lower lift, port velocity will actually increase with the larger valve because more air will be flowing through the same size port

When some one claims there 2.02 valve J-heads went slower than when they had 1.88s and "no other change" you can count on it being because the chamber and throat were not opened up properly.

What I said was it wasnt worth it... period... yes
the bigger valve flows more if its unshrouded

Posted By: Leon441

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 06:24 PM

What part of there will be a Supercharger on top of this thing are you guys not reading. All of this debate about valve size and port velocity. Sure it is a great debate. But, with boost it is far less important on the intake side.

Leave the valve sizes alone. Run a cam that is meant for a blower.

Enjoy.

Leon

Posted By: MR_P_BODY

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 06:26 PM

Quote:

What part of there will be a Supercharger on top of this thing are you guys not reading. All of this debate about valve size and port velocity. Sure it is a great debate. But, with boost it is far less important on the intake side.

Leave the valve sizes alone. Run a cam that is meant for a blower.

Enjoy.

Leon

Exactly

Posted By: daniel_depetro

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 09:51 PM

Thanks for the suggestions/info. guys!

Posted By: HotRodDave

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 10:26 PM

Quote:

put 2.02 s on as is. 2.08 wont work with low lift cam,

This is why I explained the valve size thing, not directed at you p-body

. Even NA the differance from 2.02 to 2.08 is very small but I do get tired of hearing that a bigger valve flows less at low lift crap

Posted By: sshemi

Re: 2.02" J heads... or 2.08" intake valve / 1.650"exhaust? - 08/07/11 10:28 PM

Quote:

Quote:

put 2.02 s on as is. 2.08 wont work with low lift cam,

This is why I explained the valve size thing, not directed at you p-body . Even NA the differance from 2.02 to 2.08 is very small but I do get tired of hearing that a bigger valve flows less at low lift crap