Well, after I took a 2000 mile road trip from Houston to Bowling Green Ky for a Corvette event, the subject kept coming up about what is streetable and what isn't. Now of course mine might be a little out there as far as valvetrain and 2000 mile trips go, but it did make it and nothing died. I pulled intake and lifters out to check recently and everything is OK. I did feel one roller's needles felt a "little" rough or at least it seemed, but I'm paranoid about this stuff.

So while talking to some buddies we kicked around the old issue about how much performance would be lost on something as radical as this engine if I dropped it back to a flat tappet. I mean if ANY engine will respond to a big roller cam, this one is it. Naturally aspirated, big ports, intake and carb with no power adders.

Just for reference, this is a 540" with ported Brodix 2Xtras, Edelbrock Super Victor, 1050 Dominator, 11.06 compression etc. It runs on 93 octane on the street, dyno and track just fine. It's in a 3600 lb '67 convertible 'Vette with a G-Force 5 speed and 3.07 gears in a custom built Dana 60 IRS rear axle setup. Just a nice little street cruiser.

So the decision was made to slip in a solid flat tappet for several reasons. One was, that it's early in the summer and good race weather isn't going to be here in TX for awhile to get that elusive 9.99 ET I want to get. Lots of cruising to do between now and good weather and it's possible I could lose a lifter or cam before it cools off. Plus there was a free flat tappet laying on a buddys shelf!

This particular cam is one of my old favorites in a radical 427 setup or a 454+ motor. It doesn't look super radical on paper, but it has always turned in great results for me in the past. So I figured what the heck...let's try it.

It's a Crane 266/276@.050 on 110 LSA with .600/.620 lift. Way low on lift for what my race ported heads need, but hey it was free! I pulled out my Engle solid roller with 272/278@.050 on 110 LSA with .731/.731 lift. The Engle is not really a wild cam and is easy in parts (obviously!). I stuck the flat tappet in on a 105 I/C. I checked the .050 and .200 duration numbers to make sure all was well. As usual, Crane makes good stuff. Just for reference, the .200 duration on the intake lobe was 170* vs 185* on the roller.

I changed valvesprings which was one of the trickier things to come up with. It took lots of digging to find a set that would fit my titanium retainers, clear my valve seals, fit my spring locators and have correct pressure open and closed. I installed cam with only outer springs and ran it for break in. Then I installed inner springs and dampeners. PITA, but the only way to break in a cam like this.

Initial impressions are it lost some of the cool radical sound of the roller, but it still sounds pretty tough. Idles at similar speeds (1100 rpm or so..but I keep just about everything idling about there on this hot rod stuff). It will idle lower, I just like it there. Driveability is of course better with less duration and overlap. It lugs down low a little better, but it was OK before really. Not quite as "choppy" while driving around, so maybe all the guys won't complain about riding around behind me and sucking up raw gas fumes like they did on the trip to BG.

I've put maybe 150 miles on it so far. I made a few hard runs with it the other day to see how it pulled and it would easily go into the 7000+ rpm range still.

So today I took it out to play with the G-tech on some back roads. I've had great luck with the G-tech coming very close on ET. I've actually used it at the track and compared it to the ET slips and it always comes up within .02-.03. That's about one quarter of a tenth..pretty close for something you plug in the cigarette lighter! The MPH reads high by design since it reads the actual end of a 1/4 mile instead of the average in the 66' traps like the track does. For example, if you turn around 105 mph at the track, you are probably actually going 109-111 mph at the actual finish line.

I made two runs in pure street trim. Capped headers, BFG plain 'ole street radials, air pressure correct in front tires, sway bars in place, air filter on, no carb spacer etc etc. No tricks at all. I was on a black top road after a bunch of rain in the area, so you can imagine traction was not good and I did lots of feathering to get it moving. I shifted around 6500 rpm and just let it pull.

First run was an 11.42@137+mph. Figuring something must have goofed up, I tried it again. This time it was 11.31@139.8 mph! To say I was impressed is an understatement!

So I have confidence that with practice there might even be a 10.99 run in pure drive around street trim. I can only imagine what slicks, removal of sway bar, setting up drag shocks, pumping up front tires, installing carb spacer, uncapping headers might bring??? Not that 9.99 ET..but for sure deep in the 10's still!

It's only been to the track a couple of times and of course being a convertible without a cage, you don't get many passes. The last time out I had some ignition rev limiter issues that kept it under 6500 rpm (peaked on dyno @ 7400 rpm), 2" headers, a trans that was incredibly hard to shift at high rpm (read that granny shifting!) and 7 year old slicks that caused it to only pull a 10.61@133 with open headers and a carb spacer in place. It now has that fantastic G-force with much better ratios to boot, 2 1/8" headers and ignition issues resolved.

I'll get back to everyone with more results as I play with it some. But at this point, the smaller weenie cam is holding it's own well. I believe the race ported heads and intake are allowing it to perform well, even if it is relatively small for this size engine.

Anyone else have any back to back impressions of something like this?

JIM

i am glad you are doing some testing! very interesting reading, unforutnately your tests are very different, and will be hard if not impossible to compare the 2 cams together. obvioulsy the best way would of been to take it to the track time it, then swap cams with more of a fair comparison of cam then track it again, but it doesn't always work out that way. Thanks for posting your progress!! we need more real world results like this! graemlins/beers.gif

Jim , a great test. Due to durability AND MONEY, I stuck with a solid flat tappet, although Crane indicated ( as did Tommy at UD), that I was giving up 50 hp above 5500 rpms. Glad to hear that performance is close.

What were the times with the SR, same config, on that Gtech? DId you get a chance to Gtech it after you cleared up ignition issues? HP seems real close, judging by mph, but one is a track reading, and the other is the higher Gtech reading, right?

Oh, " just a nice street cruiser."

:eek:

This wasn't really an A-B test in the purest sense. I've used G-Tech often with it, and it will match ET very closely, but of course MPH is off some I really don't have an exact G-tech reading for it in roller mode with street tires etc. But at the track the MPH routinely showed 136-137 while track clocks showed 132-133. It really is a top end car and is making it's real gains at the other end. Remember those 3.07 gears?

The high MPH can also be attributed to the really slow start and more time to make MPH once it got rolling. I'm sure I gave up some HP, but it wasn't as terrible as I might expect with this much less cam.

I'll get back to everyone with it in "race mode" soon to see how it does. But again that won't be a pure test either, because I'm using larger headers (it REALLY liked them on the dyno) and a much better trans that you can actually shift.

I just thought it was interesting as a preliminary study. More to come!


JIM

Jim,

What clutch do you run in that beast? sorry to get off the cam subject. Thats a ton of power to harness with a gear grabber. Im doing the same with mine and was curious. Does the g-force down shift well and hold on deceleration.

thanks Rich

I'm using a McLeod Street twin dual disc clutch. I used a Centerforce DF up to the 700 hp range with no issues, but it wouldn't hold it in the 800+ hp range. I had it built with an extra 200# static to make sure it held. No problems so far. A race type slipper would be better overall, but there goes that streetabilty issue again. When you get it set to slip a little and then grab perfect, you better hope some Viper doesn't come up to play when RPMs are down! it'll be slip city!

The G-force can be built as a clutchless, semi clutchless or regular. Either way has no synchros, so driving it takes a little getting used to. To downshift you usually have to blip the throttle if you're going pretty fast. If you're just riding around in traffic, it's no big deal, you can downshift with a little practice. Mine is a regular version. The other two will not downshift. You must stop and start over unless you're real lucky. The Semi will downshift ftom 5th to 4th and then to 3rd, but you'll have to stop to get it into 2nd or 1st. But it will upshift 1-2-3 with no clutch under full power. I almost went that way, but I decided not too..it really is a street cruiser. But the regular version is fantastic and the harder you bang it, the better it shifts!

The only difference in the trans is the slider assys. You can retrofit them anyway you want. The cluchless ones are a two piece deal with springs holding it together. It actually engages two gears at once and kicks the other one out as you upshift. G-force says springs doen't last long on street and will require regualr replacement. That means trans disassembly!


JIM

Hey 540 Hotrod, Glad to see you making progress with your car. I used to know a guy down Houston way that ran a four speed '67 Chevelle with 4.33 gears and a 427 B.B. that ran a similar cam to what you're using now ( Crane and he ran 10.33 @ 133 in the 70s. Some people think you have to have a roller but i'm not so sure the're that much of an advantage in a rat motor. If you were to run them over 8000 RPM maybe but not up to 7200 or so. My son's been playing with a little N2O so his chevelle isn't biting to well but did run 9.49 @ 147.67 MPH Saturday night running a blower Mustang. It's going to be tricky giting this thing to E.T. ( Lets see, two stage take out some timing, oops thinking out loud again). Good Luck. Have you got hold of any Vipers yet?

That wasn't a guy with a light yellow '67 was it? Seems like there was a father/son team with near identical appearing cars...just one was faster. But I remember them having 4 speeds and being fast.

I think timing control is the secret to getting something like these stupid HP deals out of the hole. I haven't moved to that level yet, but need to investigate it some.

Sounds like the Chevelle is coming around nicely!

I just get into this stuff because no one else wants to try it. You never know until you do and I get tired of bench racing with just opinions without knowledge/facts to back it up. Much more playing to to before I consider this experiment to provide that, but it's interesting enough so far to keep me exploring it.


Thanks,


JIM
JIM

Jim, any idea when you'll be at the W-M on a Saturday evening? I'd like to meet you out there in the next few weeks. I've got the 67 up and running and want to hit the track (possibly next Friday or Sunday) and get a few Saturday cruises in before the long days of summer are gone.

Glad to hear the motor did'nt do a nose dive with the new cam.

Hi Jim, Yes the '67 was yellow and the guy was a telephone tech. that was originally from around Ft. Smith, Arkansas and eventually transfered back there. I worked with him in Houston in 1973 on a switch reconditioning project. That type of equipment is long gone now and i only saw a picture of the car launching and a timeslip so info. is skimpy at best. He said at the time it only weighed 3300 pounds with no one aboard but I don't think he had any kids old enough to drive.

It might be the same car. Maybe it was two brothers or something. I just remember they looked almost identical but one ran 10's and the other maybe high 11's/lo 12's.

I actually met them in Waco at the old Street Machine Mini Nats. They were there every year back in the early 90's during Memorial Day weekend.

John....I'm staying in Denver this weekend for the 4th and will be back home weekend after that. I will definitely be out with the car....I'm having withdrawal symptoms!

Waiting to see your car!


JIM