How much lift can stock hemi heads take?

In short, my cam is too small, want to upgrade. Willing to buy new springs and retainers as well.

I have '70 heads with stock guides and stock-length valves. Can't easily measure retainer to guide clearance unless I take stuff apart. I realize the best you guys can do for me with this question is a quick estimate, and that's fine.

Going to be racing against my brothers, so its a must-win situation...

Disregard the current clearance and get what your advisers say is the best cam for your application because if you are willing to change springs that means you are going to take the heads off anyway. When you do that if you find there isn't enough retainer to guide clearance it will be a tiny charge to have a machine shop cut down the guides for clearance.

No adviser to speak of, I built the dumb thing in the first place, but I don't have any notes on what my clearance was with the current cam.

I don't want to disable the car for multiple weeks during the summer, just looking for a rough estimate to pick a cam in a safe range. If it ends up not being compatible with my current retainers and guides, fine, I'll have some machine work done then.

Looking to do the swap over a weekend's time if possible. Not enough space to leave the car all blown apart.

what are the current cam specs?

If I don't say anything, am I still wrong?

A boat ton of duration then? Doesn't NHRA Stock Elim. have to retain stock lift but modified duration? I would get a cam like that! Not only do they run, REALLY GOOD but they sound evil, wicked, mean and nasty!

I've been told the opposite by people that actually race them. Hemis like a lot of lift.

Anybody got a stock head and a loose valve on hand they'd be willing to grab a quick measurement off of?

73DAD...sorry, the only heads I have on the shelf are MP aluminum.

There is always some amusing remark about what some individual engine type wants, likes, needs, does. Like which engine "needs a lot of air"?
A great deal of it is "I was told".

Amusing remarks...ok. A lot of things should work a certain way in theory, but in reality things are much different.

Identifying your opponents remarks as "theory" isn't as useful as you suppose.
"People who actually race them": only someone who bought it can fully understand exactly how it works? What a ridiculous thing to say. The owners, and even builders of most cars have only the most elementary comprehension of what's happening inside the engine.
Is "Jupiter is larger than Earth" a theory?

I'd explain, but then I'd be talking to myself.

Not quite sure I understand the question. We've been racing Hemis for almost 50 years...still running Nostalgia SS with old school stuff, iron heads, cross ram, etc. 426 inches.

Not quite sure what you mean by how much they can 'take'? To give you an idea, we run iron heads, old TRW 12 to one pistons, and the cams we have used over the years have been a variety of rollers, Crane and Racer Brown, usually around .700 lift and 280-285 degrees duration. That was pretty much SOP during the day, and it hasn't changed much in a combo like ours. The SS/AH cars run over .800 lift, but there is a lot of other differences.

Don't know if this helps you or not, but I thought I'd chip in.

Thanks for the reply Steve, do you recall if the guides were cut down on heads when you were running cams around .700 lift? For my particular combo I'm looking at SFT cams a shade under .650

We're still running cams about that size, and no, we've never cut down the valve guides. You figure, .750 is about 3/4 of an inch, and the installed height of a Hemi spring is roughly 2 inches, and you'll be fine. Now, we have never used valve seals, most don't for racing applications, so have never run into that. If you are concerned, take the spring off, hold the valve and retainer together, and lower into the guide about 3/4 of an inch. You will be fine, I'd almost bet the ranch on it.

Just be sure to check piston to valve clearance, but if the pistons have reliefs in them you'll probably be OK there. In the old days, with stock pistons, .650 was getting pretty close. Check your spring when compressed and make sure you have no coil bind, but, I don't imagine you will have any issues there, either. But, check it anyway.

But, my thought is that everything will clear just fine.

I really appreciate the help, Steve. Resources seem pretty scant for these engines despite their notoriety, or maybe I haven't looked in the right places. Every change is a learning experience.

-Thanks, Dan

Technology has really advanced on them. It seems there are two popular camps, the all out race SS type motors, which are incredibly large $$$ and have developed to the point where the garden type Hemi racers can't relate much, big diameter cams, changed valve angles, etc., or there is the pure stock restorers wanting them totally back the way they were stock. Most of the folks writing about them and providing info are real high end developers, or restorers.

Dinosaurs, like me, who are rank and file racers, still racing OEM type versions of the Hemi, are increasingly hard to find, but we're out there. Nostalgia Super Stock, like we do, still has a lot of geezers like me who live for this stuff, and who have loved these motors for decades and still love them. I guess we're like old Harley guys. But, still hooked on them, pound for pound there is nothing like a Hemi. Still the most potent factory produced engine ever. Cantankerous, fidgety, but when right nothing will run with them. We race several, from 650-700 hp 60s style nostalgia motors like ours to the new technology "nostalgia" motors that pump out over 900 hp.

My old friend the late "Bullet" Bob Reed said it best. "There ain't but two kinds of people in this world. Those that have Hemis, and those that want Hemis". It's still that way.

Good resources for the nostalgia Hemi stuff would be the old DC engine manual, or Larry Shephard's HP book "How to Rebuild and Modify Chrysler 426 Hemi engines". You can probably get it on Amazon. He was a Chrysler engineer that was involved in the initial development, and the race teams of the 60s.

Jim, it can still be done. There are a lot of guys racing old school Hemis in NSS, but, if you are starting from scratch it would be hard to match the cost/performance factor of an Indy headed wedge, which is what most guys use. The heads are about as good as the stock, old school Hemi heads. There is still a lot of old school stuff out there, cams, especially that can be had reasonable. Heads are still pretty reasonable, you can get new ones, but the blocks are getting tough. We built a Hemi Dart out of old school stuff we had laying around, basically a 484 inch crate motor, and it runs 9.70s and does a real good job in NSS. We don't have $10K in the whole car. It can certainly be done.

Personally, I think racing one in NHRA Stock/SS is a pipe dream for most. Barton gets 75K for a motor. That's ridiculous. The motors have become so far away from what they were intended to be it's not even funny. Years back, a buddy of mine who works for Chrysler was pushing hard to force them to keep to stock type cross rams, but the big money guys pushed for the sheetmetal intakes, and now, you have to have a 10,500 rpm motor to compete. Most folks who have this 'dream' really have no concept in what it takes to do it. And, you have to have the money to buy EVERYTHING, not just part of it. If you only have 8 of the state of the art stuff when you should have all ten, you are just pissing your money away, will become discouraged and quit soon.

Put your stuff together, run NSS, and have some fun.

If maintenance is an issue I understand that about .630 lift is the current limit for a street cam. Rich Nedbal's book has a great roller cam design in it....Are you wanting flat tappet or roller?

BINGO

Amen, Gary. Some folks read too many magazines.

Here's what we did for the Dart. We had the car for years, it was an old home brew Hemi Dart, and exact copy of a factory car.

We found a damaged 472 crate motor from Mancini. It had dropped a valve during a dyno session, we got it, the crank, 7 rods, 7 pistons, and one good head. Didn't pay much for it.

Tossed the rods and 7 pistons, swapped the good head for a set of Manley rods, cleaned it up to .30 and bought a set of Diamond pistons. We had a set of stock aluminum MP heads around, got a valve job on them. Found an old Crane R280 roller on ebay. Had it cleaned up, balanced out, and put it together. Used the new MP cross ram with the Holley replacement carburetors. A Turbo Action 4200, shifts at 6600. In the Dart it has gone 9.70@136. Consistent, never work on it, will last forever. Now, we've been doing it a long time, but we aren't geniuses. What we did anyone can do.

Everyone thinks they have to have all this morphodite stuff. You don't. Put it together and have some fun!!! I had a pal who was 'collecting' stuff for a SS/BA 65 Plymouth for thirty years. He never quite got around to do it because he had to get the good stuff. We attended his funeral the other day, and he never did do it. Go have some fun.

.650ish is the largest I had run on my old stock iron Hemi heads in my little ole +.030 426" on the street. It was good for a 10:17 in my old combo.

Mopar aluminum Hemi heads now with much more lift than that on my 528".

Well old school is great but the cost of building a 426 is the same as building a 572...so you have options that can take either path. It just comes down to what you want to do......

[quote=Steve1118
Good resources for the nostalgia Hemi stuff would be the old DC engine manual, or Larry Shephard's HP book "How to Rebuild and Modify Chrysler 426 Hemi engines". You can probably get it on Amazon. He was a Chrysler engineer that was involved in the initial development, and the race teams of the 60s. [/quote]

Among the typical concerns when increasing cam size, with a Hemi there is also the concern of valve clipping,(when the intake and Exhaust valve may touch as they pass each other in a cycle). The old DC/Mopar performance books cover most if not all the basics of Hemi building. Some of the methods may be dated but the intent is still valid.

he never did do it
ut he had fun planning every day. The journey as well, not just the destination?
And as we all know, no race car is ever finished, there's always something for next season (or your 1040 refund).

You are right about the valve clipping, but that is an issue for real long duration cams more than lift. And, you are right, the info is dated, and probably not much use to someone with 100K to race SS/AH, but for a ham and egg guy like we are it is as valid now as it was then.