The Dodge Challenger Message Board

With .513 lift, I will have clearance problems. Not between retainer and seal, but because the distance between the top of the Teflon seal and the first stem groove is only .508 (see pic). I have 4 groove valves currently installed.

I guess 1 groove stem will solve the problem, but as mentioned in my other reply, I'm looking for oversize stem valves: the only true .375 stem I found until now are Comp Cams 5.000 long 4 grooves valves.

I think I'll have to stay under .500 lift or re-cut the cast guide to lower the seal...?

Probably the most cost effective choice will be to cut down the guide a bit. If you get new valves, I would get single lock groove if possible. This along with new retainers should give the required .050 clearance you need. The supplier should be able to inform you of the installed height so you can know this before purchasing their products. The one piece valves I am referring to are stronger than the multi-groove design. ALL aftermarket Hi-Po or Racing valves are single lock groove. I am guessing the valve you are referring to is from the exhaust correct. The factory wanted the valve to twist during running, this helped to distribute heat on the seat during operation. Of course the factory didnt use stainless steel one piece valves. They used conically welded 2 piece plain steel valves,(Hi-Carbon), and hoped for the best! BTW, how old is the valve job? If you need to get a valve job accomplished, now would be the time to install new guides, either cast iron or bronze, whatever the budget allows, then hone them to size with the valves you have now or new stainless steel ones with undercut stems that will flow a bit more, plus the valve will be centered on the seat. You will fix the loose guides, which if allowed to operate that way will oval the seats out in short time and the engine will be way down on power, and you'll have to start over.

CHTA, there have been amny excellent suggestions and advice regarding camshaft selection here, but I need to ask you something. Have you done any research on the possiblity of using a state of the art hydraulic roller? This way you can "have your cake and eat it too"!! http://www.cammotion.com/Portals/fee9d5 ... Binder.pdf check out the hydraulic roller profiles at least 80+ grinds listed. A 280/.500 lift would make a nice flat torque curve, pull very hard to 6000+RPM's no camlobe wipe worries, any motor oil will do, much more area under the curve than a flat tappet, they make a nice Beehive spring for your 340 that will allow a stable valvetrain with less weight and more rev potential, and it's a single spring which may cure your clearance problems as well. This is what I settled on. A few years ago most pro-engine builders shunned hyd. rollers due to their heavy weight and low rev potential, usually around 5200 RPM's before the onset of valve float caused by heavy valve train components. If you are contemplating new guides anyways here's possibly an opportunity for you to attain the next level of performance AND reliability. Nothing beats a wheel on a lobe!

Eddie, I really appreciate your interest in my post. Your answers are very interesting and very "disturbing". Let me re-explain as short as possible my situation (it may help to understand my hesitations):

The car & engine are original six-pak '70 FY4 Challenger T/A. My first Mopar rebuild. Last rebuilt (former owner) 1982. Engine rebuild was now motivated by: carbs tuning difficult, low engine vac (7'' @ idle), oil consumption moderate to high, low compression test, resto cosmetics. Installed cam was MP284/484, lobes intact. According to friends: lo end torque was not bad, pulling hard up to 6400. Target of the engine resto: to have the same performance, but without the disadvantages mentionned above!!! A reliable fresh Hi perf engine, but will probabely "never" race. 2500 miles/year max.

I'm now stuck with 2 problems:
1) a new cam is very hard to choose: don't want to add new problems (clearance, etc...), but I don't want to be disappointed compared to the performance I had until now.

2) Valve guides: sorry to mix with my other post, but I have to answer you. The cast guide-to-stem is just out of tolerance, mainly for exh. valves. Now you have to realize 2 important points: we don't have US V8 machine shops specialist around here, and there is NO WAY I take the risk to ruin my original heads with a "bazooka" machinist (I'm refering to the teflon seal and bronze guide problematic of my other post). The mean stem diameter of my exhaust valves is 0,369. At that point, I thought that the easiest way to solve this problem is to use true 3/8 (0,375) stems, and have a "minimal" centered ream of original guides. I know it's not ideal, but low risk (not a budget problem). And with new seals (old ones were worn), I hope it will be enough. Is it really not a good compromise?

To answer to your reply:
- last valve job 1982: new 4 grooves unknown valves, guides knurling, and top of guides cut for teflon seals. Miles since '82: 30000.
Eddie, when you say "the valve you mentionned is for the exhaust correct", what do you mean ? (do you mean 0.375 is only for exhaust and effective diameter is less for intake in the valve set?)

- I never considered rollers. But I must confess, it is absolutely because of pure ignorance. I was thinking in my application, flat tappets were enough. I should not have read your post...(joking). Is it possible for you (and others!) to add a few more basic info on rollers: what are drawbacks of such a swap: do I have to change only cam & tappets ? what about pushrods, rockers, lift ?

Thanks again. Very grateful.

I understand fully your position now that we have read and explained everything. Now, I must correct one thing, when I mentioned the exhaust valve I thought that the exhaust valve was the valve shown due to Chrysler and other manufacturers use multi-groove locks or keepers on the exhaust side which usually has either 3 or 4 grooves. it's not important. What IS important is that you spend your money wisely, and return the engine back to a great runnign 340 SixPack. NOw, if you dont have access to a good machinist I would try and remove carefully the necessary amount of material for the springs to clear on the guides, have either the guides replaced, or the new valves ordered in the stem diameter you wish. Either way it HAS to fixed right. So choose the best for your engine, if the machinist says it will work with slight mods to the guides then so be it. If he says the guidesmust be removed then thats what I would do, either way it must be fixed or the valve seat will wear out in short order. In the subject of a hydraulic roller valvetrain. With what you want to accomplish, I would get a fast rate of lift flat tappet hydraulic like Dave, fabien, and Jon suggested, save your money for the headwork. I would rather have a set of very nice fixed heads with a flat tappet old school cam, which will make the same power and torque to 4000 or so RPM's then the hyd. roller will exceed that power but how many times are you going to be at that RPM's especially on the street. Plus the hyd. roller is very expensive, shorter pushrods are needed, adjustable rockers to set the pr-load a bit more accurately, and the cam itself. it all adds up to about 750-1000.00 more dollars. The hydraulic roller will keep the valve open longer, with less spring pressure, and ease it back down quickly but not too quickly, it's a very sound design and the OEM have been using it for 30 years,(hydraulic only not solid roller),The lifters are 550.00 alone! So to cap this long winded reply, I just wanted you to explore your options.

I forgot to mention, and I dont mean this to start anything else "running around" in your head. The engine MUST be sealed in the following areas in order to run good for a long time. The Piston ring seal, valve giude seal, Head gasket seal, and intake manifold and exhaust seal. If these areas are weak, any engine performance increase such as bolting on fancy intakes, exhaust, heads, ect will only make the problem worse. An old saying I can 'Hop up a rock into a Rocket! if the engine is healthy in all those areas I mentioned. If not you'll still have a rock! Hope this helps, sort things out.

Things are getting more technical then my little bits of information can assist.

All I can say is, if I had an original 340 T/A motor/heads, I would tend to stay away from hard, permanent, modifications to the castings. (Including stray connecting rods thru the oil pan)

Jon wrote:Things are getting more technical then my little bits of information can assist.

All I can say is, if I had an original 340 T/A motor/heads, I would tend to stay away from hard, permanent, modifications to the castings. (Including stray connecting rods thru the oil pan)

AMEN!

Thanks to all. You seem wise... I'm very concerned about saving my original heads. If to much machine-work was needed, I even thought buying new six-pack compatible 340 heads and let the original hibernate in my garage. Will let you know what I choosed.

Don't know if you see an edelbrock picture in my last post. Don't know where this poltergeist comes from. Original pics where my T/A & engine.

CHTA wrote:Don't know if you see an edelbrock picture in my last post. Don't know where this poltergeist comes from. Original pics where my T/A & engine.

Not sure why that happened either. Click on "edit" on your post and delete the images, then repost the images but change the file name on each image first. See if that helps.