2.02 valves in 73 340 heads?

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zig

zig

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I am in the process of rebuilding my 340. It was a bone stock 73 340. I am upgrading pistons with stock bore to some early replacement pistons to get 10.5:1 or whatever was stock early on. Also looking to upgrade cam with duration of 270-280. I am debating on the intake still of keeping the stock or something different. Also doing headers. A friend of mine keeps telling me to upgrade the intake valves from the stock 1.88 to 2.02. Any experience with this?? I was planning on doing some light porting to match the gaskets. Maybe a little bowl work also. Not much..

I want to take the heads in this weekend to get hardened valve seats and a full valve job. Just wondering if it is worth it to upgrade the intake valves. Looking for a healthy street engine. maybe 350 hp or so..
Thanks for the input...
 
Well, 2.02 is bigger= more flow= more power. You will be holding your power potential back with the smaller valves. jm2c! might as well have the machinest grind the seats open for the bigger valves.
 
zig said:
I am in the process of rebuilding my 340. It was a bone stock 73 340. I am upgrading pistons with stock bore to some early replacement pistons to get 10.5:1 or whatever was stock early on. Also looking to upgrade cam with duration of 270-280. I am debating on the intake still of keeping the stock or something different. Also doing headers. A friend of mine keeps telling me to upgrade the intake valves from the stock 1.88 to 2.02. Any experience with this?? I was planning on doing some light porting to match the gaskets. Maybe a little bowl work also. Not much..

I want to take the heads in this weekend to get hardened valve seats and a full valve job. Just wondering if it is worth it to upgrade the intake valves. Looking for a healthy street engine. maybe 350 hp or so..
Thanks for the input...
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If you are running pump gas your engine will ping with 10.5 pistons and full advance unless you are willing to run a cam to negate the static compression. Don't buy pistons till you get it apart, check and measure bore wear and deck height. Bore and hone with torque plates and ballance the rotating assy. 73 heads should already have induction hardened exhaust seats. You'd probably be better off milling the heads .020 on the block side and .019 on the intake side. You can go to .040 and .038 if you need to. "Some light porting to match the gaskets. Maybe a little bowl work" will get you where you want to be. I don't think you need the 2.02 intakes, but it costs very little at this point to add them. Your cam is already 268 duration on the intake side and more on the exhaust side. "73" 340 intakes and carbs are hard to beat on the street. Headers make a noticable difference if you are willing to put up with the hassles.
 
Especially with the larger bore on the 340's (no valve shrouding) it makes sense to go with the 2.02/1.60" valves. You need to have the hardened seats installed and ground anyway, it's not that much more to go to 2.02/1.60 valves, and the 340 will definitely benefit from it. Although it shouldn't matter with the hardened seats, going to a larger valve can also help the machinist set up more accurate valve stem heights if some of the old valves have sunk in the head by getting out into "new" metal.

I had my 308's opened up to 2.02/1.60 and ported, they now flow over 260 cfm at .500" of lift. Shooting for 450 hp with my 340. Now, just the valves won't get you that far, but it'll definitely improve the flow, and the heads on these engines basically control how much power you'll have on the top end.

Also, 10.5:1 stock pistons are unlikely to give you that much compression. If you really want to get that compression, be sure to check your head chamber volume, especially if you have some bowl work done. Most of the heads were larger than the 65cc's that was specified, and I doubt many of the "10.5:1" engines really made that much compression, more like 10:1. Also, be careful if you're going to shave the heads any to boost that compression. The high compression 340 pistons are above the deck of the block by .018", so if you start shaving the heads or decking the block you're going to want to measure your valve to piston clearance.
 
Unless you plan on running the engine at 5500 and over a good bit, you will never see the benefits from the bigger valves.
 
StrokerScamp said:
Unless you plan on running the engine at 5500 and over a good bit, you will never see the benefits from the bigger valves.
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This! the bigger valves are only beneficial if you are turning the rpm's up. For a street driver, bigger valves can cost you bottom end torque.
 
DusterKrazy said:
This! the bigger valves are only beneficial if you are turning the rpm's up. For a street driver, bigger valves can cost you bottom end torque.
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Its all about nailing the throttle boys go for the big valves,you wont regret it when you mash the gas.But if it is just a slow driver they are wright those valves are not going to help down low.
 
fourspeed said:
It's a 340, man. Put the big valves in and wind it up!! ;-)
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Right on !!..on the pistons choose wisely some of those replacement ones are HEAVY especially trw's...less recipricating weight the faster you'll turn that bad boy...
 
Use them. It helps place the seat out away from the worn areas without having to sink the smaller ones and it wont hurt anything. I do it all the time. Cam choice is much more important than 2.02 valves. You really can't go wrong putting them in if you need to buy valves anyway.
 
stroked 340 said:
Right on !!..on the pistons choose wisely some of those replacement ones are HEAVY especially trw's...less recipricating weight the faster you'll turn that bad boy...
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True story, I can give you a box with 8 TRW pistons for a 318, and 8 of my Ross stroker 318 pistons, and you could tell me which ones are the TRW's ten out of ten times.

However, ping, detonate, drop a valve, suck up a carb nut, dump rocks down the carb, and the TRW's wont fail.........
 
I would use KB243 hypereutic pistons....alot lighter...good price..should give you a real compression of 9.5 to 1.
since we are spending your money ...I work use the chevy .100 longer intake and exhaust valve..11/32 stems...can get a full set for the price of mopar 2.02 ...

but will need new guides and spring retainers...machine shop should be able to put bronze liners in the stock guides to get down to 11/32
 
Thanks for all the comments. i do want to wind this motor every so often... That is why I bought a 340... I was looking at the KB243's.. They look affordable and bump my compression up some from the stock 8.5s... Not looking for a full on race motor. Something that takes pump gas that I can have fun with. I may take it to the strip every so often. I want to beat my buddy's 94 vette... he can run mid to high 13s.. Tomorrow I am going to call a guy near my work that does machine work and has his own flow bench. Supposed to be good at hot rodding engines... I'll see what he says.. But I think I want the 2.02 for sure. I will ask him about using chevy valves. I know they are way cheaper... Will keep things updated..
 
On the KB hyper pistons....make sure the top ring gap is set correctly...since the ring land is higher on the piston it needs to be wider to be a wider gap...follow the instructions in the box..
 
mikedevore said:
1968-71 had the 2.02 intake valve. They were redlined @ 5500rpm. although 6500 wasn't that far away. I would install the 2.02's
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i have a add for a 69 340 swinger that reads 6000 rpm for less then $3000 and they had to warranty the engines. i agree put the 2.02s in. if your doing a good valve job your probly going to need new valves in it anyway. put them in. JMO
 
put them in 2.02 and have machinist plunge cut into the bowl, then do a light blending, if you already have the stock pistons and the bores are fine i would use them with the thick .039 gaskets and the decks cleaned your CR would probably be somewhere around 9.8. Remember the 70 340's were 10.5cr and the 71 10.3cr fwiw...
 
If your going to replace your valves and your not doing the work yourself it might be about the same cost (or a little cheaper) to run the Edelbrock RPM Alum heads on it. However if you choose to just go to bigger valves I suggest Ferrea Stainless Steel, Single Groove Valves (I have these in my X Heads).
 
zig said:
Thanks for all the comments. i do want to wind this motor every so often... That is why I bought a 340... I was looking at the KB243's.. They look affordable and bump my compression up some from the stock 8.5s... Not looking for a full on race motor. Something that takes pump gas that I can have fun with. I may take it to the strip every so often. I want to beat my buddy's 94 vette... he can run mid to high 13s.. Tomorrow I am going to call a guy near my work that does machine work and has his own flow bench. Supposed to be good at hot rodding engines... I'll see what he says.. But I think I want the 2.02 for sure. I will ask him about using chevy valves. I know they are way cheaper... Will keep things updated..
Click to expand...

Then by all means, if you're gonna see the strip or want to wrap the motor up every now and then, the 2.02s will show some benefit. I would be sure to run a good header though to help balance out low speed velocity as well. It will be a great runner.
 
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