66427-450

I’ve bounced various aspects of my plans for my replacement motor off you guys before, and did a lot of research outside the forum…… After many “plan revisions” I ended up here (see below combo), it looks good to me (effective power/rpm range of each component).

I thought I’d ask for comments one more time before I bolt on the heads/intake and drop it in. The car will be used for high performance street (with a fair amount of Strip and Road Course time as well).


66 coupe 3.70 rear 2.52 first gear

468 cubes
GM alum Rect/Ovals*, pockets cleaned up, chambers worked to 114cc, ports matched**
10.6 static compression
Crane solid 580/600 256 266@ 50 110 LSA, installed straight up
My Original 427/425 intake (1x 1 5/8 plenum notch)
Holley 850 DP (jetted 82f / 84r to start)
My current Headman 1 ¾” side pipe headers (a bit small, I know, but I don’t think it will hurt tremendously….. I’ll be replacing them with 2”-2 1/8” headers later, it’s tough finding good big tube headers for side exh. cars).

* I also have prepared a fresh set of pocket ported, 117cc, 310cc CI Rect port Merlin Grumpy Jenkins heads, (but I now believe the GM Rect/Ovals are better for my gearing/use), the Merlin’s will be For Sale, if I go the Alum head route.

** just blend the top 1 1/4" of the intake port to match the 427 intake

Thanks ! :seeya



[Modified by 66427-450, 8:15 PM 7/12/2003]

69 N.O.X. RATT

That will be a stout combination, may be a little slugish on the bottom end, but should pull like cray on top. You are probably using the intake for hood clearance reasons, if not I would go to an Rpm Air Gap. That is a big cam, not too big for me but some would consider it unstreetabl,e particularly with your poor first gear overall ratio. Depending on your usage I may go to a smaller cam, or advance that one 2-4 degrees.

That would be a great combination with a Richmond 5 or 6 speed. I am running something similarish with a 6 spd and love it.

66427-450

2.52 x 3.70 = 9.32 in first, overall
2.20 x 4.11 = 9.04 in first, overall

i think my 2.52 and 3.70 won't be to bad? (like 4.24's with a close ratio m-21)
if i go to 3.90's i'd be at 9.83 overall, that's an option as well

i do have the rear end apart right now......

69 N.O.X. RATT

You are correct it is not that bad. After looking at the mathematics it will be ok.

66427-450

Just an update -

I just talked to local engine builder / racer type...... he said the Merlin Grumpy 310’s would be perfect for me (1/2 way between the Edelbrock ovals @ 290cc, and the Edelbrock Rect’s @ 325cc)… and that they have some of the best low- and mid-lift flow numbers.... and make considerably more torque than some of the other Rect. port heads (good HP street heads for serious engines 427 to 502). Also, a correction, my intake valves are 2.19”, which I understand is better for the little 4.25 bore than the 2.25" or 2.30".... Something to do with bore shrouding?

I told him I had personal experience with a 68’ Z-28, and that I was ok with “it’s” level of soggy, under 3000 RPM, performance..... and he said that my 468/Crane combo wouldn’t be any worse.

The jury is still out, I just may go with the Merlin’s and the 3.90’s for a 9.83 first gear..... and see what happens. lol



[Modified by 66427-450, 1:51 PM 7/13/2003]

427Hotrod

Well you KNOW I like that cam!!! :D

The way I look at your combo, I think gearing and overall use will determine head choice. You are right on the edge of being able to go either way with the Merlins. With 3.70 gears, you'll be right around 6000 rpm at best in the 1/4 which is right on the edge of oval port territory. And just getting great for rectangular ports on a 468.

The ovals will definitely have more bottom end, but I really don't think the rectangulars would be bad in your case. Plus it allows you to use intake without having to modify heads.

I'm voting for the Merlins! They aren't that big!!

I think some 2" headers would be great for you. I tried back to back tests on my old 427 with 1 3/4" to 2" and found nothing!! Track times didn't change at all. 60's were a little slower and top end a little better, but nothing you could feel. Granted you have a few more cubes, but not that much.

I also tried 2" headers against some 2 1/4" dyno headers the other day while dynoing the 825 hp 540. Now this sucker peaks at 7400 rpm, and up to 6500 the 2" beat the big ones hands down even on this thing. Now after that it was another story, but it proves you can get a lot done with small headers!

Don't sweat it, they ain't killing you too bad!


JIM

66427-450

Jim -

As always, thanks for the insight !

Several of the guy’s I’ve talked to say, I’ll be way over cammed..... but like we’ve said here before, “one man’s radical is another man’s mild”. I’m going to give the Crane a go, I don’t think I’ll be disappointed with the low-end cam performance. You said you felt it was streetable in your old 427, and with my longer stroke/40 more cubes (and I do have 6.385 H-beams as well), I may even wish I’d went with a touch more cam :-).

About the personal perspective thing; I remember back when I worked at a local Chevy dealership in the late 60’s, the owner of the place described the Z-28/302 as a real dog ! ...... and said the 327/275 4 speed was a much better performance combo. I can see why, when you rode with the old dude he’d floor it from an idle and wind it out to about 3500-4000 and shift, lol....... the Z-28 haden’t even “cleared it’s throat” by then.

It will be a while until I get my ‘66 strip worthy, but when I do, I’ll post my time slips, and give you guys some feedback concerning it’s street manners as well. I’ve got 3.36, 4.11, and 3.90 gears here…… with a set of 3.70’s on the way. I may just start with the 3.90 / Merlin 310 combo and go from there.

Just for the heck of it, I’m going to do some calculation in an attempt to roughly determine the intake runner velocities for the various head options....... like I said, the flow numbers are pretty hi with the 310 Grumpy Merlin’s, and I’ve slicked this pair up pretty good, I may find that the velocities are pretty darn close to the 290cc ovals. And if I understanding it correctly, that (Velocity), is really the issue as far as degraded low rpm performance, not runner CC....... it’s just that runner CC is typically used to describe the head “size”.

Good Luck with that big 540, with all that power and gearing it’ll be an absolute KILLER ! ....... if you can get it to hook, and I'm sure you will :-)
:seeya

Mike


[Modified by 66427-450, 10:05 AM 7/14/2003]

427Hotrod

That cam is easily streetable. It will idle in gear with an auto (with a slightly looser converter). It will pull hard to 6400+ with oval ports on a 427. With much better heads I see no reason to doubt it won't bump up on the 625+ HP range easily in a 454. Now that assumes a little better intake, but I don't think you'll be too far off...600+ for sure.

If you like a 302/290 Z-28, then this is going to be TQ monster. You won't have any issues with driveability.

Depending on tire size, it would really love the 4.11's or maybe down to the 3.90's.

Didn't one of the magazines build a pump gas, hyd roller cammed 454 with those heads last year for one of the shootouts? Seemed like it made 640-660 or so?

I had Merlin oval iron heads that were ported real nice on the 427 and they were amazing. I was very happy with them. They flowed 324 cfm, but I can't remember the port size after porting.

You're going to have a heck of a fun ride....this has low 11's written all over it with even decent traction. Maybe high 10's if you drive it like crazy!


JIM

Chuck Harmon

Your combination, other than the modest compression ratio, is not too far off from my factory L88 setup. The L88 cam has only a slighly longer duration. Regarding the heads, I think the flow is more important than oval vs. rectangular. There seem to be good and bad examples of both. If you don't care that much about bottom end, I don't think you would need to give a second thought about going to rectangular heads if they provide the flow you're looking for. Personally, I think stock spec oval port heads are only important on engines that don't expect to see any real time above 4500rpm.

I am running a ROD 6 speed with 3.08 gears with my car. This is really a great combination. If I lived in a rural area with few stop lights to get stuck at, the L88 cam would not be a problem. Serious cam overlap makes for very sore eyes with all the gas fumes while stuck waiting for lights to change. I am changing to a Crane roller (#138601) with 246/254 degrees of duration.

I love the high rpm personality of the L88 and didn't want to give that up for streetability. the roller cam will give me a bit more upstairs, and much more down low with hopefully fewer fumes at idle. I would expect between 460 and 490 rwhp with your setup.

Chuck

Hank

That should be a great engine. You're definitely close.

I just went through this decision process, ended up with Brodix-headed 502 with a hyd roller. In a 3.36, 2.52 first gear car. My advice --

1. The edelbrock air gap will probably fit if you mill the carb pad about 170 thousandths. I did that and it fits a 66 stock BB hood. It's a great manifold. You might be surprised at how much HP is in the manifold (and exhaust) if you get a big big block revving.

2. Then the rectangular port heads will be a good fit, complementary to the manifold and your cam.

3. Personally I'd take it down to a 750 carb. I just swapped 850 demon down to a 750 Holley and the car really woke up -- much crisper esp below 3000 rpm, and still screams to 6800 pretty well. Maybe if your 850 is really dialed in it'll work fine. My carb was problematic though.

4. I think your cam is on the large side. But with high side static compression and an intent to rev it will pull hard. Don't expect a really crisp bottom end though. I went with a smaller cam (236/244 duration at 50, 610/632 lift) and even with the faster (roller) ramps it's only "OK" for pulling from a stop, compared to a torque monster cam the car had previously, the stock 502/502 cam. First car length or two, I either slip the clutch or slip the tires, and I didn't used to notice the hole coming off a stop sign before.

Some of that may look contradictory -- there is no substitute (unfortunately) for trial and error. Though DD2000 is a pretty good substitute, at least in terms of getting in the ballpark regarding interaction of different components.

Have fun with it.

Gerry

66427-450

Jim & Chuck:
I think we’re on the same wave length, thanks for the feedback :thumbs:

Hank:
Thanks for the comment's, good info on the intake/hood fit. Concerning the cam/carb; I understand your perspective, it’s just that some guys are willing to accept the reduced low RPM performance/smoothness in exchange for more juice from 4000-7000…… It’s not a matter of right or wrong, better or worse, just a preference thing.


In response to the guy that sent me the IM asking about my rotating assembly/bottom end:

- 4-bolt GM block, align bored
- ARP main studs
- Hand fit Scat 4340 crank, 4340 H-beam 6.385” rods w/ARP L-19 bolt upgrade
- JE / SRP pistons, floating pins
- CL77 H bearings
- Fluiddamper

(BTW I found the rods/pistons are significantly lighter than the GM L-88
rod/TRW piston combo)

If you’d like more details let me know





[Modified by 66427-450, 2:36 PM 7/15/2003]

Bearcat

Quote:
________________________________________ _________________
Your combination, other than the modest compression ratio, is not too far off from my factory L88 setup. The L88 cam has only a slighly longer duration. Regarding the heads, I think the flow is more important than oval vs. rectangular. There seem to be good and bad examples of both. If you don't care that much about bottom end, I don't think you would need to give a second thought about going to rectangular heads if they provide the flow you're looking for. Personally, I think stock spec oval port heads are only important on engines that don't expect to see any real time above 4500rpm.
I am running a ROD 6 speed with 3.08 gears with my car. This is really a great combination. If I lived in a rural area with few stop lights to get stuck at, the L88 cam would not be a problem. Serious cam overlap makes for very sore eyes with all the gas fumes while stuck waiting for lights to change. I am changing to a Crane roller (#138601) with 246/254 degrees of duration.

I love the high rpm personality of the L88 and didn't want to give that up for streetability. the roller cam will give me a bit more upstairs, and much more down low with hopefully fewer fumes at idle. I would expect between 460 and 490 rwhp with your setup.

Chuck

________________________________________ ________________________
Chuck,
I'm running the exact Crane solid roller cam that you want to go to on your 427. My engine is a 4-bolt 454 block destroked and overbored to 433 cubes. That cam wakes up around 3500 rpm and pulls to over 7000 rpm. It is a very strong mid to high rpm cam, and would have even stronger midrange in a 454. It is combined with a ported iron oval port head design, bowl blended and large valves, to preserve the midrange and still be able to breathe at a little over 7000. You'll love the idle lope and the way the engine spins up. Very rev-happy.

BUT...I am learning first hand the importance of combination, combination, combination! I have a Muncie close ratio M-21 with the original 3.36 gears in my 1968 Corvette. That's 2.20 x 3.36 = 7.39. In other words, first gear is VERY tall. With a cam that doesn't wake up until 3500 rpm, I have to launch at some pretty high rpms to get into the torque band. And this also makes the combo not so streetable. I can't even use the 1:1 4th until I'm on the highway doing about 75+. It's a beautiful high speed set up, but at the cost of streetability. The best way to describe it is putting the engine of a Cheetah on the legs of a Giraffe.

So I'd exercise caution using this cam with a 3.08 rear end, even with a Richmond 6-speed. To preserve streetability, I know I need to better balance the high rpm, high speed talents of this road racing engine with the rear end gears to better handle the off idle response. In other words, this M-21 Muncie needs a set of 3.70 gears in a bad way. So I chop my theoretical top speed from 175 to 155 or 160, but the whole attitude of the car changes and it accelerates with much more enthusiasm on its way up there.

When racing against a lighter car in an apex, how well you put the torque down to the pavement will be more important than how fast you can go in the back stretch.

So 3.70 gears are probably the solution for me. Maybe a set of 3.36 with your ROD would work best for you?

66427-450

See gear ratios below........ and note;

3.28x3.08=10.10 (not a bad option for launchng :-)
2.20x4.11=9.04
2.52x3.70=9.32

I wanted to keep a 4 speed, so I went with the M-20 (however, there is a somewhat bigger "gap" between gears....compaired to the M-21/22)...... you really need to consider the "width" of your engines torque, or HP, peak.

Gear.........M-20....M-21/22.. ROD
1st ...........2.52.....2.20........3.28
2nd...........1.88.....1.64........2.14
3rd............1.46.....1.27........1.57
4th............1.00.....1.00........1.24
5th..................................... ....1.00
6th..................................... .... .76

:seeya


[Modified by 66427-450, 2:58 PM 7/27/2003]

Chuck Harmon

Bearcat,

Thanks for your feedback, but the Crane cam is actually a big step down in duration compared to the cam I'm replacing. Crane said it was as short a duration as would be safe with my 12:1 compression. But I would really love to hear more about the difference between the ZL1 cam you're familiar with and the Crane. How did the two compare?

The Crane roller should be much more low rpm friendly than the much longer duration factory L88 cam. With the ROD and 3.08 gears my overall ratio in 1st is the same as a M-22 close ratio trans and 4.56 gears. Even with the L88 cam I can pull stumps. My only gripe with the L88 cam is the raw gas burning my eyes at idle due to the massive overlap.

The machine shop said they should have my heads done late next week. They are enlarging the vlave spring seats for me.

Chuck


[Modified by Chuck Harmon, 1:42 PM 7/27/2003]

Chuck Harmon

66 427,

Richmond strongly suggested going with the .82 od gears for 6th. They said they are much stronger. BB cars have broken the .76 gears. Otherwise, mine has the same gears you posted and I love every one of them. I love the spread even better than my ZO6.


As I have said many times before, I really believe I have the perfect gear for every need!

Chuck

VetteLS6

I Like it!!!!!!!!! My choice is the Rec heads though...they breathe so much better once the rpm's are higher than 6000 rpm. I run the L88 cam in my car and agree with the issue of EYE WASH in traffic. (note: running 3:70 gears in this LS6 Car with the M-22)
:cheers:

Bearcat

Yeah I guess you're right, the ROD does have a steep enough first gear to make the 3.08's work. Pardon.

The ZL1 cam was peakier and had much less down low than the Crane cam. The Crane has better torque for sure, especially in the midrange. And still revs at least as well as the ZL1. Seems to do best up to 7200 rpm or so. But I'm still experimenting with my tuning.

However, in a garage as you pull in, the Crane will still burn your eyes. I've got the idle mixture at the best balance, and it's better, but still burns the eyes a little. The Crane has a very nice lope to it. You'll love it. Good cam. A friend of mine and I both have had trouble with Crane springs though. His lasted 200 miles, mine about 600 miles. He's replaced his with Isky springs. I'm not sure what's going on with Crane's springs, but I'm hoping it's a fluke.