Dave McDufford

I have the same basic question in a post of a couple of days ago that was not answered. So let me ask it in a slightly different way.

If the LT-1 profile (timing, acceleration & lift) is so good can this profile be used in a cam ground to be used with other than flat bottomed solid lifters? Can a flat bottomed hydraulic lifter or roller hydraulic lifter handle the acceleration created by the profile? Can the modern or original hydraulic lifters handle the 6,500 rpm red line of the solid lifter engines? Also can the LT-1 profile be obtained or ground for a solid roller lifter?

I am rebuilding a 65 convertible with an original 350 hp engine. My wife (she wants to do it) is going to begin tearing the engine down today for the its rebuild. I debating how I want to rebuild the engine – stock L-79, L-79 profile with hydraulic rollers, LT-1 stock, LT-1 profile with solid roller lifters or flat/roller hydraulic lifters. The carburetor, intake and exhaust (2 ½”) will be stock L-79. I plan to port match the heads (2.02/1.60 values) and mildly pocket port them per Duke’s suggestion.

I am torn between the “proper” original rebuild (L-79 hydraulic) to increase/maintain the value of what will be a very good (and expensive) restoration of a mildly bubba’ed car and the fact that it is my car that I plan to keep and I love the sound of a solid lifter LT-1.

While I hate to admit it :banghead:, the reason I am considering using a hydraulic lifter with the LT-1 cam is flight judging and the value added to the car for TF.

If it can be done, which cam company would do the best job (Crane, etc)?

Comments anyone?

Dave
:cheers:


[Modified by Dave McDufford, 7:14 AM 11/15/2003]

427Hotrod

Well after reading your post....my first question still is "Why?"

The LT-1 cam is a nice little street cam. It pulls hard and still idles around great. Of course you can easily outpower it with other designs, but it was designed as a good all around deal and it does well. For what you are doing, it sounds like a good choice.

By design, a solid lifter cam has long "clearance" ramps built into it on the opening and closing sides to gradually take up the slack in valve lash so that valve tips etc don't get pounded. They actually don't start moving the valve until that lash is taken up (which I know you know), but that is a key difference. If you install hyd lifters on a solid flat tappet cam, you essentially will make the cam seem "bigger" because you are opening the valves sooner and closing them later due to the fact that instead of taking up lash, the valve immediately starts to move. That's why when comparing hyd to solid cams, you have to allow for the clearance ramps. It often takes a solid cam with 6-10* larger @ .050 numbers to equal a hyd cam. In other words a solid cam with 240* will run real similar to a hyd with 230-235* or so. The actual valve movements will be close. Doesn't mean the hyd is a better cam, it's all in how you have to measure them. Just have to know what you are comparing.

The advantage of a roller whether solid or hyd. is that you can design the lobe to be much more aggressive as far as opening and closing rates. This allows you to maintain the same actual opeing and closing points, yet move the valve much faster which means it will be open further for every point in the cycle than a similar flat tappet. It allows you to get valves open further/quicker. So to design a roller with the lobes of any flat tappet cam would defeat the purpose. It would just be the same cam with a roller lifter. In real life if you get to the nitty gritty, it would be a little worse, because a roller lifter actually moves the valves slightly less in the first few degrees of rotation than a flat tappet due to design of the roller. But it quickly catches up and surpasses all the others as it goes further up the lobe.

There are many folks who claim 6500 rpm with a hyd flat tappet. It can be done with the right lightweight valvetrain components and springs. Many DO rev up there, but I can guarantee you most are floating the valves. The solid still beats all of them by being able to rev just about as high as you want to.

One of my pet issues is that many folks try awful hard to make a hyd cam act like a solid. They will buy high bleed down lifters and "0" lash them to try and get them to not pump up and float the valves. Why? When you do that you have effectively defeated the two things a hyd can do better than a solid. Keep things quiet and be maintenance free. It will be noisy and you will constantly work your butt off trying to maintain "0" lash. In fact it will be worse than a solid, because the hyd cam DOES NOT have that nice clearance ramp built into the lobe and you are pounding the valvetrain.

Just put the solid in it and be done with it if you want to ever really rev it and make the power it is designed to do. If you want low maintenance ( I mean how many miles are you going to put on a Top Flight car?) install a hyd cam that was designed to be one. If you want to keep it quiet for TF judging, just set valves at .002-.004 or something for the judging. Then reset them before you really drive it.

The 350 HP cam is pretty decent, but there are better ones that will sound similar yet run better these days.

You just have to decide what you really want. Setting valves is no big deal, but if you really don't intend to use the rpm range it offers, just put in a good hyd and be done with it. Hold on...did I just say that? I NEVER recommend hydraulics!

Man..I must be getting weak!


JIM

JohnZ

Custom-ground cam profiles can get pretty expensive, as can roller cam installations (about $800 by the time you're done), and neither approach will have the reliability of an OEM system. If I was in your shoes, I'd see two avenues with no downside: 1) Go with the stock L-79 rebuild, or use the LT-1 cam and kit and call the car an L-76 (327/365hp) - there is no external difference (for Flight judging) between a 1965 L-79 and an L-76 except for the number on the band around the base of the distributor, the tach redline, and the engine suffix, and the wrong suffix is only 25 points.

Your call, but I'd go with the stock L-79 rebuild - they run like stink, and are stone-reliable. :thumbs:

TheOman

Hey Jim !

How is it going down there in Houston?

I think a lot of this "getting a hydraulic to perform like a solid" as you stated comes from indecision. A lot of people don't want to putz with solid lifters, they want the higher RPM potential and they want that "hot cam" sound. The LT1 and 30 30 have part of that criteria list locked down but here come those darn solids.

There are thousands of cam profiles out there but it is a daunting task to select one. I hate doing it myself and I hate reading enfless testimonials to "I bought this or that from A or B or whatever manufacturer and it is ....da da da da. It is all subjective unless there is a dyno in the mix to prove or disprove haw a guys particular combo really works.

So what happens at cam slelection time...well the best of both worlds seems like it would be a solid profile with hydraulics...whoops not exactly the best of both worlds as you clearly state. Trouble is a lot of folks follow that logic best of both thought pattern. Seems to me the difficulties of selecting from all the stuff the cam makers can supply (let alone custom grinds if that floats your boat) drives people to the simpler solution. I want A and B but not C or D feature and well you see where I am going.

I am 4 square with John Z on the L79 cam. Sure it is an old design and no doubt ya can get more grunt with something else from Comp or Crane or whoever. That said in terms of driveability and durabiltiy and cost the GM cam is hard to beat. I had a new L79 in 67 and the engine was great, just great. ran around town, out on a date or to the mall to get a new pair of shoes whatever. It was also great for a blast down the highway or thru the gears. Then there was the dependability....set the lifters once observe some sanity as far as shift points and just keep driving it. It was terrific. Bet I rolled 75K miles on that combo w/o any issues and without more than a couple of quick lifter adjustments.

Ironcross

Why dont you use the GM 151 cam, it`s probably the best hydraulic cam GM produced. It was used in the 350 hp 327`s completely interchangable in the 350`s. You will never obtain the performance of the LT1 cam because its a solid lifter cam with the ability to rev past 7000, where as hydraulic cams of any grind cannot go that high because of the lifters. :cheers:

K2

I read these posts with interest as a couple of years ago I was going through the same choice thing. I came to the conclusion that in all likelyhood at my stage in life, reliability and ease of maintenance was more important to me than a few more horsepower or rpm that I would probably never use to full potential anyway. This brings me to my question to your guys.

How many of you would seriously race your Vettes in competition where that last hp or rpm would ever make a difference?

My thought is that most guys with older vettes do far more bench racing then real racing and those that do race for real race for the experience and fun of it more than to absolutely win. Also very few drivers have the ability to use that last hp and rmp to advantage. In most cases at that level of competition the limiting factor is the wheel nut. I chose the hydraulic route and although I race occasionally in autocross and track events, the old technology of the chassis and my own ability limit performance way before I run out of engine power or RPM. :steering:

So do You do more Real racing or Bench racing??

66427-450

That is exactly the point.

There are several, very different, personality types here that enjoy their cars in different ways (with lifestyles that are very different as well, I 'm sure). There is no right or wrong, just different. You always need to make sure you are communicating with a person with "like values", or that at least understands / respects your perspective, before you take their advice. Some of us are hardcore performance types, and some of us are cruiser types....... with perspectives that are drastically different (like a 3.08 geared 300HP auto with all the power assist options, air, and whitewalls; compared to a manual steering solid lifter BB with 4.56's, side exhaust, and F-41).

I'll always be a racer type, I've won, and lost :-(, by 2-3' in the 1/4. So you bet every little bit counts to me, the cruiser guys will just shake their heads, I know........ and same to you my Brother (smile).

:seeya

SWCDuke

I've never quite understood the argument that adjusting valves is a hassle. I have three vehicles (two cars and a bike) that have 16-valve DOHC four cylinder engines with shim over bucket clearance adjustment. Each requires a special tool, and I have accumulated a collection of shims for each over the years to ensure that I have the right one when I need it.

Compared to this, adjusting the valves on a solid lifter Chevy is a piece of cake - no special tools - just a 9/16" socket, and no shims, but you do need a set of feeler gauges. Chevrolet recommends checking them every 12K miles, which could be every few years at the rate most of us accumulate mileage on our vintage Corvettes. Using my procedure and with 90 degree marks on the balancer I can adjust the valves in less time than it take to do a decent wash job, and I can even reuse gaskets a couple of times by gluing them to the valve cover then using silicone spray on the bottom of the gasket and head mounting surface, so they don't stick and tear. The 12K mile interval is also a good time to check the points and plugs and change as necessary. This is what we know as the traditional "tuneup", and it's a chance to spend a nice afternoon doing some relatively simple hands on work that is more interesting than polishing the paint and chrome, which gets old after a while.

For mechanical lifter SHP engines I recommend the LT-1 cam as a replacement for both the Duntov and 30-30. It has better torque bandwidth than either, especially the 30-30, with about the same top end power as the 30-30, which is more than the Duntov.

I also recommend it to "upgrade" medium performence or hydraulic lifter SHP engines to mechanical lifter SHP "character". Mechanical lifter SHP engines are just a little "edgier" and have a character that is tough to give up once you've experienced it. The LT-1 cam gives up little, iff anything, in terms or low end compared to the L-79 cam, but make more mid range and top end power, with at least 500 more usable revs.

The L-79 was probably the best overall high performance engine Chevrolet ever offered, especially when you consider that it only cost a little more than $100 on a midyear, and for most people, the L-79 cam is tough to beat, but if you want to experience that faint ticking of mechanical lifters, and slightly more nervous idle that is part of the mechanical lifter cam experience, go for it.

As far as judging is concerned, if you use my method for adjusting the valves you might get through the ops check without anyone knowing the difference and you might even be able to fool a PV judge, but probably not a good one.

Duke

toddalin

Crane sells the "151" 327/350 hp cam in their vintage line. I have one in my '64.

Cam was installed over 15 years ago. The other day on the dyno, the car put out 293 hp and 293 ft-lb at the wheels, so the cam does have potential. Car makes 200 ft-lb at 2,000 rpm. Power peaks at 5,700 rpm and torques is back down to 200 ft-lb at 6,300 rpm. Valves float at 6,500 rpm.

Ironcross

Just go to my web site and see if rpms make any difference to me. :D I dont bench race. :lol:

Dave McDufford

Thanks to everyone for the great response. 427hotrod your description of the differences of the cams was excellent. I have previously read pieces of what you said but not in one place.

The rebuild will be either the straight L-79 or LT-1 cam, with the appropriate lifter. My mind says L-79, my heart says LT-1. It will probably be an LT-1 - I love the sound. This is my one and only vette, and it has been promised to my son so it will likley stay in the family for a while.

Thanks again.

Dave
:cheers:

Viking427

Can't see starting a new thread on the same subject so...
I've been reading about the benefits of the LT1 cam in 327 - 350 cid SBC's here and on the NCRS board, but what about the old 57-61 solid lifter 283's.
Its my understanding the LT1 cam (engineered for a motor 67 cid larger & 1/2" longer stroke) would be too radical in a 283. Can benefit be found in using this "big" cam over the factory 097 "fuelie" cam ?

SWCDuke

Based on lots of research I've done with DD2000 and Engine Analyser and analysis of detailed lift-crank angle diagrams, I recommend the LT-1 cam for ALL mechanical lifter rebuilds including 283s. The LT-1 cam has about the same effective overlap as the Duntov cam, but less than the 30-30. On the inlet side, duration and centerline is very similar to the Duntov cam, but it has more peak lift and seats the valve more gently.

The exhaust side has considerably more effective duration than the Duntov and most of this extra duration comes from opening the exhaust valve earlier, which makes for a much earlier centerline and compensates somewhat for the SB's relatively restrictive exhaust port. It also seats the exhaust valve much more gently than the Duntov cam.

A given cam will feel more "radical" in a short than long stroke engine, so the LT-1 cam will feel somewhat radical in a 283, just as the Duntov cam feels pretty radical in a 283, but it will provide more top end and peak power with only a slight loss of low end torque, and given that most mechanical lifter 283s are geared pretty short, the slight loss of low end will not be too noticeable. If anything the low end might feel more soggy because of the noticeably stronger power from 4500 to 6500.

Duke

JohnZ

I stopped racing actively about 20 years ago - my old '61-'62 AA/FD has been resurrected and runs regularly in the Nostalgia Drags at Pomona and Bakersfield (I ran it last at Fontana in '62), so I do more bench racing (going down "memory lane" :D ) than real racing these days, although I do stuff lilke this every now and then just to keep the old reflexes in shape - the most fun you can have with your shoes on :yesnod:


:steering:

427Hotrod

You're right on the money. Everyone has different perspectives and expectations.

You can easily run 12's with a 327/350 cam, and that's a fun little car! There may be only a few tenths difference between some of these cams at the track, but don't underestimate what that means. A tenth can easily be a car length and a few tenths can look pretty impressive to the guy chasing you. Even if it's just banging a few gears on a backroad against your buddy on the way home from the carshow. It's much more fun to be in front!

The 350 HP cam and the Crane variants (check them out-often they aren't exact coppies and typically have tighter LSA's and slightly differnt duration to make them run better, and I'm OK with that!) are great "put it in and forget it" type deals. But c'mon...don't you LIKE playing with your car? I enjoy piddling around with it as long as something isn't broken!

I'm with Duke on valve setting. It's really highly overrated as a complex deal. It takes hardly any time on a Vette and I actually enjoy it. It's fun to do all the little things he suggested as a "tune-up" and see/feel the difference in how it runs. It makes it all new again!

So back to the same deal..to me..considering the few miles that most folks really put on these things, I feel that allows us to go a little further to the performance side of the equation. Since you don't put a gazzilion miles on it, it's no big deal to have it slightly more radical. And when we're talking radical in this case, we're only discussing something that GM engineered to pass all the driveability, performance, reliability and maintenance and warranty stds of the day. Hardly extreme stuff.

I really enjoy seeing an old Vette being used by it's owner whether it's drag racing, corner burning or whatever. I just cringe during bench racing sessions when folks can quote you all the performance numbers of their car but admit to never actually opening the throttle and shifting at over 6000 rpm once! Then when they hear someone else quote what they really actually ran, they look down their noses because they read somewhere where something else ran a better time. I say to them..they need to go out and do it themselves before they speak.

Not saying everyone has to go race their cars by any means, but you really ought to try it. It's a lot of fun and another way to have a good time with your car besides polishing it all the time. You can clean it up after the event! I can't explain how neat it is when I'm at the track to have folks come up and say " I can't belive you're racing this car" or "When are you going to run again?..I don't want to miss it"....or just "Neat car". It's really fun to have something different out there. Folks figure all of our cars are museum pieces.

And you're right, picking cams is one of the toughest decisions of all, because it more than just about anything else, sets the character of the engine. But custom cams are actually very easy to get at low cost. You can call any of the cam co's and put together just about any lobe combination you want for minimal cost. When dealing with roller cams, it's almost a foregone conclusion they expect you to do it and the cost is the same. If you get past the normal counter folks at cam co's and find you one of the "real" guys to talk to, you can get a wealth of info and help. I know several folks on the Forum have "their guy" at different vendors and can get much better service. I've used this at Mcleod (thanks Steve B and Mark L. for giving me names), Flatlander (thanks Nick), Strange, S&K speed etc etc. I've been using Engle cams for the last few years for no other reason than I can call out there and get Mark Engle on the phone and he has been willing to go the extra mile everytime to help.

JIM

63FI

BIG vote for the LT-1 cam. I have had the 151, the 140 off road Z-28 cam, (which you really need a tunnel ram or ram quads to make work,) and the best all around street/performance cam I have used is the LT-1. I have had it in my '63 Fuel car for 15 years and it is great. Good mileage also.

And Jim, the most comments I also get is "how can you drive your car like that?' I can say I use mine and I have fun with it. It's just too much fun keeping your foot in it going into second and going sideways untill you get traction. Goes to 7000 with no problem. The last time I rebuilt this motor was in '75, and it is due. I'm doing it now. As Duke said, it is simple to do the valve adjustments. I do use polly-locks and they never seem to go out of adjustment. I have a 4:11 also! Anyway, you can't go wrong with the LT-1.
In fact I'm going to get a new one for the rebuild. I figure 15 years of my abuse has had to put some wear on it. So, let me know where the best price to get it these days is. My original one came from GM.

K2

Points well taken 66427-450. I must now confess, last year I built the engine I've wanted to build since my youth but kids, house, business, etc always seemed to take priority then. Didn't stop me from racing even though I didn't have the muscle I wanted at the time. This forced me to concentrate on honing my driving skills. I'm a little longer of tooth now and my reactions aren't quite as quick maybe but I sure enjoy the extra ponies and intend to surprise a few at the AC events next summer with the new testosterone under the hood. Now pulling about 420 hp the challenge becomes putting all that power to the pavement in a judicious manner. The tempering of age and reduction in testosterone (mine) now helps to keep the tires from going up in smoke and the lap times down. :steering:
Great picture John Z. Do you have any pics of the 61?


[Modified by K2, 1:05 AM 11/17/2003]

TheOman

I do have a set of solids in my LS6 so I am not without experience with the lifters. I really don't drive the car much anymore matter of fact I think it has been in the garage for about 4 years. The G-damn 66 has eaten up all my money and my time.

I don't mind the solids in that engine but doing the adjustment is, I dunno, a chore. My first car had soild lifters in an SBC and I guess I had my fill them. Number 1 criteria when I got the L-79 mentioned earlier was hydraulic lifters and considering that I was a kid then I guess I was "thinking like an oldie' already. .

A point that might have been missed in my earlier post. I was alluding to the fact that a lot of guys who are pickin a cam are likely picken the only one they will ever buy. They don't have a lot of experience at this stuff and they tend to sitick with the known. proven commodities like the LT-1 or the L-79 or 30/30. They want some of the nostalgia of the "radical" sound and the tick tick of the solds so a solid can is always on the short list. The idea of settin valves sometimes deters them though. Look at some of the posts about how do ya set valves (both hydraulic and solid) it is becoming a lost art, if art is the right word. Heck just the other day I rad a post (on another form) the flavor of wdcih was " How do carb equipped cars run in the cold...I never drove one and now I have a beater that has a carb. What should I ecpect and how do I tune / adjust'?

Lifter adjustment has gone that way for most folks. What with the 200K engines and platinum plugs and titanium this and that...A lot of folks who get these older Vettes have no point of reference for even basic maint of an old engine. I bet that in a lot of cases the cars are older than the owners. Result.....a rather steap learning curve and / or a desire for a little of the old (radical cam) combined with a little of the new (low or no maint) results in how can I get the RPm amd sound and perf of soilds without the aggravation.


[Modified by TheOman, 7:29 AM 11/17/2003]

newbe60

what cam do people reccomend for the hydraulic lifters..it seems the LT-1 is better suited for solid lifters.. or is it just the solid lifters are the way to go for a 327 or 350?

66427-450

Very nice car. I think your story (made our money, got that career BS out of our system, did our family related stuff, now back to having fun!) is very typical of many of us here. And don't give up on the high testosterone related "activities", I'm 51 and I've never enjoyed life more, and by the way, I don't think my testosterone levels have dropped at all ":-).... can still give the kids in the their 20's a run for their money.