Adding 2.02 intake to J heads

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gliderider06

gliderider06

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Question. Would having 2.02 intakes be beneficial to have added the 1.88 J heads on a street car? When I upgrade the cam soon, I was thinking of putting 2.02's in. I have heard that it will not be beneficial if the motor is not seeing a consistent 4000 rpm and also that it will lose bottom end. I also heard that it can add up to 20ish HP across the board. I am upgrading the 360 soon with the Xtreme 268 cam, speed pro flat-tops and 3.91's in the rear. I have less than 1,000 miles on the heads and if it doesn't give significant gains, i'll skip it.
Thanks for your thoughts!
 
IMO, it is a win win. Bowl porting will take better advantage of the increased valve area.
I did this on a 318 a long time ago. It was worth it.
 
What rumble said ... ^^^^^.

As long as you're going to hang on to those heads for a while, then yes it's a worthy investment, imo.
 
Make sure, it's done right, with a bowl cutter, and a following valve job.
 
Yes it's a good upgrade, and doing it to a 1.88 head will leave the valve nice and high for good flow. Have the machinist at do a plunge cut into the bowl to open it up then just blend it in a little.
 
I guess I read "street car"..... it'll never know the 2.02 is there.
 
I'm with A body, that build won't know the 2.02 are there.
..XE268 is .477 / .480 and stock heads are good for about .485 lift
 
If you put in 2.02's it will increase your performance, who would want to do that???
 
gliderider06 said:
Question. Would having 2.02 intakes be beneficial to have added the 1.88 J heads on a street car? When I upgrade the cam soon, I was thinking of putting 2.02's in. I have heard that it will not be beneficial if the motor is not seeing a consistent 4000 rpm and also that it will lose bottom end. I also heard that it can add up to 20ish HP across the board. I am upgrading the 360 soon with the Xtreme 268 cam, speed pro flat-tops and 3.91's in the rear. I have less than 1,000 miles on the heads and if it doesn't give significant gains, i'll skip it.
Thanks for your thoughts!
Click to expand...

'The Old Adage > 1.88" vs. 2.02" Intakes

If > the current 1.88" Intakes are sitting low in the Valve-Seat, then an upgrade to 2.02" Intakes is worth 'every penny' of an investment.

But > if the current 1.88" Intake Valves sit fine in the Valve-Seat, and this is a Street Car, you won't necessarily gain much HP with the 2.02" Intakes, unless you're pounding in the 5000 RPM range.

The Comp-Cams XE-268 works great with 'J-Heads' with 1.88" Intakes.

Lift ....................... .477"/.480"
Duration................. 268*/280*
Duration @ .050" .... 224*/230*
Overlap................... 54*
LSA ....................... 110*
Centerline............... 106*

#901 Valve-Springs.... #104 lbs. Valve-Closed ~ #259 lbs. Valve-Open
 
I picked up a little time and speed with the 1.88 - 2.02 swap, BUT! This may not be true for you. It is application dependent as well as build dependent. My car was a 4spd & 4.10's at the track. The gain was small. It was a very long time ago. Those details are lost in time.

If your valve is high, I wouldn't waste the time on 2.02's on a street ride.
 
And remember that if you do a plunge cut/bowl hog you ruin the real potential of the 1.88 to 2.02 change.
 
krazykuda said:
If you put in 2.02's it will increase your performance, who would want to do that???
Click to expand...

It'll increase performance towards the end of the drag strip. Only by a couple of tenths at that. I read this as being a street car. I personally wouldn't spend the money.
 
IQ52 said:
And remember that if you do a plunge cut/bowl hog you ruin the real potential of the 1.88 to 2.02 change.
Click to expand...

Na, it's actually a 75 degree cut inboard of the seats, but any good machine shop he brings it to will know what to do. Also have the valves back cut if they have the ski jump lift on them. Remember you ALSO want a lot of flow very early in the lift just as the valve opens to fill that 365cid engine. Chrysler. put the 2.02 valves on the 340 for a reason and your build has 25 more cubes, headers, hi flow intake, and more HP!!
 
Hmmm. Maybe I can find another set of heads to work with. My current ones are really still fresh. I know a guy that has a set of 915's for 300.00. Might be cheaper/easier to start with a set that already has the 2.02's already.
 
Unless you are doing the porting yourself forget the $300 915's.

I can't give those POS away for 100-150/pair out here.

Find a set of later model 360 heads with induction hardened seat.
 
crackedback said:
Unless you are doing the porting yourself forget the $300 915's.

I can't give those POS away for 100-150/pair out here.

Find a set of later model 360 heads with induction hardened seat.
Click to expand...

If you get a set of 360 heads with induction hardened seats will the hardened part of the valve seat be cut away if you go to 2.02 valves???

Treblig
 
Treblig said:
If you get a set of 360 heads with induction hardened seats will the hardened part of the valve seat be cut away if you go to 2.02 valves???

Treblig
Click to expand...

They are only hard under the exhaust seat. You can install a variety of seat materials in a head that's not factory hardened.


IMO, any engine over 315 CID (or with a bore size of 3.9 or greater...especially if the valves open on the bore centerline....hint, hint,hint) should have, at a MINIMUM, a 2.02 intake valve.

In fact, a 340, with a 4.04 bore SHOULD have a valve of 2.100 diameter. The problem is...that the port can never be made big enough to support that diameter valve.

Emissions is what drove the 1.88 valve, not low end horsepower.
 
madscientist said:
They are only hard under the exhaust seat. You can install a variety of seat materials in a head that's not factory hardened.


IMO, any engine over 315 CID (or with a bore size of 3.9 or greater...especially if the valves open on the bore centerline....hint, hint,hint) should have, at a MINIMUM, a 2.02 intake valve.

In fact, a 340, with a 4.04 bore SHOULD have a valve of 2.100 diameter. The problem is...that the port can never be made big enough to support that diameter valve.

Emissions is what drove the 1.88 valve, not low end horsepower.
Click to expand...

x2.
I don't bother using any 1.88s. They all get either 2.02s or 2.05s if there's a good amount of porting.
 
gliderider06 said:
Question. Would having 2.02 intakes be beneficial to have added the 1.88 J heads on a street car? When I upgrade the cam soon, I was thinking of putting 2.02's in. I have heard that it will not be beneficial if the motor is not seeing a consistent 4000 rpm and also that it will lose bottom end. I also heard that it can add up to 20ish HP across the board. I am upgrading the 360 soon with the Xtreme 268 cam, speed pro flat-tops and 3.91's in the rear. I have less than 1,000 miles on the heads and if it doesn't give significant gains, i'll skip it.
Thanks for your thoughts!
Click to expand...

Based upon this ^^^ scenario.

Going to 2.02" Intakes would not greatly improve power. If anything, between 1200 and 4000 RPM's, the 1.88" Intakes will perform slightly better than the 2.02" Intakes on the Street with the Comp-Cams XE-268.
 
On our "old reliable" iron head 360 bracket engine we met in the middle with a 1.96 intake valve. skinny stem chebby valves are cheap! :)
 
2.02'S will give some more power for sure (I've done the same mod on my old 340 that had 1.88 J heads on it when i got it. but there is a trade off (no free lunch here!) It moved the power increase in the upper rpm range & hurt the torque in the off idle-2500 rpm range. After 2500 er so air speed picks back up & away you go!
 
69 Cuda 440 said:
Based upon this ^^^ scenario.

Going to 2.02" Intakes would not greatly improve power. If anything, between 1200 and 4000 RPM's, the 1.88" Intakes will perform slightly better than the 2.02" Intakes on the Street with the Comp-Cams XE-268.
Click to expand...

What is this based on? A 1968 340 has as much or more low end than a 1972 340. There is absolutely ZERO data that supports a loss of low end power with a 2.02.

In fact (and testing supports this) the bigger valve will INCREASE low lift flow, which by all accounts will help with low end power.

Again, the issue becomes this; how big can you go before you lose????? The answer is...it depends. Can you get enough port area to support the bigger valve? If not, the head will lose power ALL across the power band.


Typically, Chrysler P-car heads have a horrible flow curve ( I could care less what numbers they flow) and every time you increase intake valve size WITHOUT compensating for the CORRECT runner volume increase, you only make the head worse.

Have you ever looked at the flow curve of P-car head with 2.08 intakes and just a bowl job? That combination will get it's doors blown off by heads with a 1.88 valve.

But the problem isn't with the big valve. It' with the incorrect port. There is more to it that big valves and bowl hogs.
 
69 Cuda 440 said:
Based upon this ^^^ scenario.

Going to 2.02" Intakes would not greatly improve power. If anything, between 1200 and 4000 RPM's, the 1.88" Intakes will perform slightly better than the 2.02" Intakes on the Street with the Comp-Cams XE-268.
Click to expand...


If this were a 340, especially a post-71 version with the shorter pistons - I might agree. But based on the OP's 360, I think this is off base. As the Mad Scientist noted - even if we disregard the better placement of the seat and proper approach angles - the 2.02 valve by virtue of it's larger cicumference increases off the seat flow by roughly 20cfm which affects low rpm usage especially given the max lift at the valve of around .450 on this cam. We're talking about a 3.58 stroke - not a 3.31, which makes a significant difference in off idle/low rpm performance over a 340. While a 340 might feel soft depending on the rest of the combo - a 360 will never "feel" soft with them.
 
Good points made here, but in reality its sort of a cost vs performance gain thing here. Hes talking about a street car, so its going to be only a small amount of improvement really. The 2.02 will make more power, but it wont be drastic.
 
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