what is largest cam for 340 with factory 10.5 flattops????????

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duster360

duster360

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What is the largest cam you have put in a 340 that still had the stock forged 10.5:1 pistons? I know these engines have close tolerances when it comes to camshafts. I have heard the limit on lift is low .500" and I know duration will also effect clearances. At the moment I dont have the tools too check what max lift could be, reason I am asking.
 
usually have to check the guide height also when getting into a cam with over 475 lift
 
I have had 2 cams in this engine over the years. Both were Crane cams. Specs are actual lift and duration.
1. Duration: 278* 290*
Lift: .467" .494"
2. Duration: 284* 284*
Lift: .480" .480"
I am currently running the 284* cam. I am wanting to put the comp cams 292* with .501" lift in it.
 
mopar performance cams. 509 hydralic set lifters at zero lash. If you put in preload they will hit. 557 solid flat tappit. These cams were installed with standard deck height no head cutting but a pass to clean them. More duration makes more power on the average street car then more lift. You'll still have a real choppy idle and you won't have to get a high stall converter because the motor creates more torque on the bottom.. If its a 4spd. car Go for the lift and scream the sucka, I did and still do. I start my chainsaw up now and then over the winter just to hear it. I was thinking of putting race fuel in it for the smell. Steve
 
You really have to check it for yourself because machining tolerances were all over the board. I have had heads that wouldn't allow more than .450 lift and others that will allow slightly over .500 lift. That's the lift at the valve taking into consideration the lift loss from the poor geometry and less than 1.5 ratio rocker arms inherent with small blocks meaning you will never get a full .484 lift at the valve with a .484 lift cam. It's usually on the order of .020-.025" less than the cam is rated.

I have to disagree with the comment that more duration = more power and low end torque and more lift = more RPM. It's just the opposite. Duration affects the rpm range in which the engine operates so the more duration the less low end torque as a general rule.
 
.509 drops in fine, never had preoal issues.ime
The .528 is way better/durable cam though, broader range,better idle and around 10''-12'' of manifold vac -roughly- it was the modern max wedge grind 2800-6900 and will actually take you into the 7200 range if you install it straight up 112 or 110*
I run mine 107* installed with the 4spd/3.73 gears, good cam

Also the .509 kills the cyl pressure, the .528 with only around 60* o lap doesnt hurt it as bad. gotta remember the ''10.5'' is usually 9.8 or 9.5 comp with the loose fac tolereances.

Always check for guide retainer interference, but about .520 lift is what I have found to be max without cutting down guides... that is with a solid lashed .028/.032 lol

measure it, JMO
 
The Comp Magnum 292H is nothing like the MP 292/.509. It's a much milder cam and it will work fine in the 340. I don't think you'll have any real issues becasue the duration is fairly short for the lift, and the lift is actually about .489 at the retainer. If the engine has never been apart, it should be fine, but I'd pull a head to make sure...
 
I built this engine about 20 yearas ago. Before that it had sat in my parents garage since the mid 70's. It is standard from top to bottom. Even the rings I put in it were perfect circle brand, dated 1969.
 
I guess the biggest reason for the cam swap is I want a little more chop at idle. Just looking fo a little meaner sound and if it improves performance a little that would be a plus.
 
with TRW L2316F pistons, I ran a MP 590 cam. Valve to Piston Clearance was checked...

Dont remember since it was about 25 yrs ago.....
 
I'm running a Comp 225 cam 284/Dur and 507/lift with TRW 2316's and a .039 head gasket. No problems hitting. My block was crocked so the machine shop took .020 off the deck to straighten it up and the pistons are .035 out of the hole. Using X heads
 
The trw 2316 are stock replacement right? I wonder if the valve reliefs are cut the same depth?
 
460 470 lift with 302 duration it will be real choppy and will idle fine in gear. 474, 274 mopar cam same idle but less power and detonates. Both these cames will fit without a spring change so you won,t have to pull the heads, I have done these for guys that were looking for the same as you are a choppy sound. One just left today with a 300 duration. The guy loved it. Idled in gear nice and the duration takes some cylinder pressure away on the bottom. so pump gas will work. With the lower octain you will not feel the pressure loss. and you can add some timing.
 
Usually when somebody asks what is the biggest cam they can put in , they are looking for the sound of horses in gallop the easiest and cheapest way they can get it . Motor builders know you need the package to make max power. This guy just wants the sound of the cam first . with a little more power second. There are alot looking for just that for cruisers. To idle them into the drive-in
 
I'm running a Crower 290/298 with lift of .507"/.522", grind number 290HDP, using TRW pistons, clearance was checked and no problems were found. Been running it for 7 or 8 years.
 
I've ran a 528 / 284 mp 112 cl solid
and a comp 525 / 305 106 cl hyd
dont remember how much room i had, been awhile
I had speed pro forged replacements 69 model 340
its always best to check
 
528/ 528 284 mp shaft fel pro head gaskets heads cut 90 thousands intake side cut 30 cyc pressure 190 static compression now if i could only get it hook up :)
 
The Comp Thumpr cam will give you exactly what you're lookin for and actually run like it sounds.
 
Yeah ,I really enjoy the .528 Solid in my 340 4 speed 3:90,1 gear for about 4 years now . I don t baby it either my neighbors will verify the 20 30 foot sure-grip marks!!!
 
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