I would like some opinions on a few options for a big block build.

I have a '66 427 block, forged crank, a set of 858 rect. port heads, L72 intake manifold and carb.

I have a TKO 600 overdrive transmission with a 3:70 rear end, and side pipes.

I need to get connecting rods and pistons, and a cam.

My goal is to have a pump gas friendly engine that I could have some fun with and still get decent gas mileage. I'd like more torque down low and less of a high rpm screamer. Travelling cross country in fifth gear is about 2K RPM

I was thinking about ditching the crank and installing a 4.25" stroker crank, installing 10:1 compression pistons and using my heads/intake/carb with a milder street hydraulic roller cam.

My thoughts are that with more displacement I wouldn't need to rev as high to make the rectangular port heads work for me.

any thoughts or suggestions?

and thanks
Gerry

 

I wouldn't recommend going the additional cubic inches route. Since you already have a 3.70 rear end, you would end up burning more gas than you need to for the additional torque you want down low. A 427 can provide ample torque for what you want. If anything, think about switching out to a 3.36 rear end to get your cruising RPM down below 2K. Gas ain't getting any cheaper in the future!

If I read your post correctly, you have a set of rectangular port, closed chamber heads and matching aluminum intake manifold off an L-72 engine. I would recommend using Keith Black hypereutetic pistons w/a small dome to drop your compression ratio down to around 8.9:1 for use with pump gas. Definitely contact the piston manufacturer to regarding any technical details in fitting these pistons.

I personally would recommend using this hydraulic tappet cam. However, you did say that you prefer a hydraulic roller tappet cam. Crane's gone so I would talk with Competition Cams about your project to see what they recommend.

Good luck with the rebuild!

 

Thanks for the reply,
I have a 5 speed overdrive, That 2K cruising rpm I mentioned is at about 80 MPH on the interstate. Normal cruising off the interstate is at a much lower speed and RPM. Besides that, I just went from a 3.36 to the 3.70 when I changed the transmission, and I sure don't feel like getting under there and pulling the differential out again!

I agree that a 427 will probably have plenty of torque, but I've read that the bigger cubes will make the car more "driveable" and since I need to buy rods and pistons anyway it might be worth it to buy a stroker kit. On the other hand I do have the 427 crank so I could just save some money and go that way. I just don't want to be disappointed later that I didn't go bigger.

You are recommending 9:1 cr? I thought 10:1 was considered safe with pump premium. I'll have to think about that one. In the meantime, I've been searching through the archives reading all I can find!


Thanks,
Gerry

 

I agree with you that changing out the read end pumpkin isn't all that much fun! Still, I'd keep the 3.36 pumpkin available just in case future economics (i.e., gas prices head towards the $4.50+ mark) dictate more fuel economy. Sounds like the 5-speed and 3.70 rear end are working out well together so far.

I recommended the 9:1 target compression ratio because I see more and more clean air additives in gasoline and less octane as cap & trade advocates legislate in Washington DC. Right now most high performance carbureted engines can run 10:1 compression ratios using 91/93 octane gas; but what happens if these fuels aren't available in five years or cost as much as racing gas? I see E85 and EFI as the wave of the future performance engines right now as does the American LeMans series.

You're correct that more cubic inches means more torque across the engine's bandwidth. I just can't justify the extra inches and torque w/o looking at the extra fuel costs coming down the pike.

Just my thoughts behind my recommendations. Have fun with your project Gerry. It's one sweet ride!

 

If you're willing to add the stroker crank, then it's a no brainer. Go for the cubes for sure. I LOVE 427's....but a 489-496 is REALLY fun and will rev as high as you want. 6500-7000+ rpm with a 496 is no problem.

If that is all *numbers* stuff....then it's obviously worth big bucks. So building it into a 427 makes sense.

The closed chamber rectangular ports will work on the 496...but won't make the big crazy HP. The added cubes will surely help the manners of the big heads though at lower RPM. Cam selection will make biggest impact. The L-72 intake is a good one and will do OK if RPM and HP isn't real high. I know of a 9.0 compression 540 with aluminum heads that picked up 30 RWHP just by swapping that intake to a Holley Strip Dominator....and he was a 5500 RPM type combo.

The 496 will definitely make more power at lower RPM and will enable you to enjoy the O/D a lot easier with the big heads. I'd go ahead and build it...but if you could bring yourself to swap heads and maybe intake you can add tremendous power. If you are sticking with exhaust manifolds..we have another issue.

So here's the overall deal....a 427 with manifolds is already choked up , but the rect heads and L-72 intake will allow it to breathe OK. If you add the cubes, the breathing restrictions get more severe and show up earlier in RPM. If you are going to use a hyd roller cam, then you won't be spinning the 427 too high to allow it to get close to the RPM range those heads want..so in that case a 496 is a better choice. With a solid cam, a high revving (6500-7000 rpm) 427 can walk away from a low revving choked up 496. But if we limit the 427 to the same RPM, obviously the 496 will kill it and drive better too.

I'm not a fan of hypereutectic pistons by any stretch. Go for forged ones from the 4032 material and they will fit tight and not have any issues. You can get into the 10+ compression range even on iron heads.

I get 12 MPG with my 540", huge solid roller cam and a Dominator, 3.07's and no O/D. I have a buddy that got 18.9mpg with a milder 540 using 3.08's and a TKO. Another gets 19+mpg with a 454, 3.08's and a TKO using EFI.

Even if you drove 5000 miles per year, the difference in 12 mpg and 17 mpg is only about $600 or so at $3 per gallon. You can easily get a 496 into the 17-20 mpg range with correct cam and tuning.

JIM

 

Wow, you've almost the exact same setup as my buddy. His is a NOM L36 car with a tko 600 and 3.55's. Go for the 489/496 and don't look back. We used a hyd roller cam w/236 deg intake & .625" lift and it revs quite nicely to 6200 RPM. I'm guessing it's making just north of 600 hp and he just LOVES the thing. But now it's in the paint booth for the winter. 10:1 cr won't be any problem with a combo like this.

One thing to think about with the side pipes if they are OEM. They are cool, but super restrictive. My friend has them, but is going to put "Y's" in and run a second set of pipes underneath the car so the thing can actually breathe.

Other than that, what Jim said. (except he seems to like lots more cam than what I'm used to using.)

Details on the 'milder 540' please? Having followed your "bruiser" threads, this would be of interest. I had a GM 502 basically fall into my lap. It's gonna be a 540 one day soon so details man, details!

 

You have to feed these engines!

Ok...I'm a little more hardcore than some...but I hate to see someone spend a lot of money and then get spanked by someone with a lot less motor. Even if it's just for bragging rights day at the chassis dyno!

The original build of the *mild* 540 was done by a buddy. He read all the magazines and *built for TQ*. He used flat top pistons, Edelbrock rectangular port heads, L-72 intake, 236* HR cam with 114 LSA and about .580" lift, a vacuum sec 850 BG Demon carb (he read you should always run vacuum carbs on the street) and 1-7/8" headers. Also used mandrel bent 2.5" pipes to *build TQ*.

It ran OK and was literally his daily driver in a C-3. I first met him through this site and he described how well it hooked up and didn't have big traction issues. I knew mine headed for the ditch when I stomped it so I was curious what he had working so well. The more we talked, the more I suspected it just didn't make the power I expected. I went to visit him and took a homebuilt 850 DP carb I had. When we went for a ride...I learned the truth..I was right! We put the 850 DP on it and it immediately picked up tons of power and began to drift in 3rd gear whereas before it only barely spun tires on the 1-2 shift. After that little test he was ruined and he began a quest to improve it.

The first dyno tests with the 850 DP made about 410 RWHP..about like a stock Viper. It peaked HP at about 4900RPM and was diving fast at 5500. No telling what it was making with the old POS BG carb. He next installed a Holley Strip Dominator single plane intake to replace the L-72 intake (you just HAVE to run dual planes on the street don't you??!). It picked up 30 RWHP instantly! He then pulled the heads and had them ported very nicely and also milled to get compression up to a little over 10.0. This along with a 240* cam (still on a 114 LSA- no I didn't pick it!) and got him about 35RWHP and finally able to make power past 5500 without falling off like a rock. Later he installed a 1000HP Holley and it made 17 more RWHP AND got the 18.9mpg!! At this point he said his driveability was the best it had ever been despite having a much more *radical* combo.

Along about here he started planning a 632" cube motor to replace the 540. He decided to get heads for it and sell the ported Edelbrocks. The heads he picked were AFR 357's which are great heads, but not really suited for a HR cammed 540. They dropped compression back down around 9.0 and picked up only about 10 RWHP...but the RPM range extended out very flat indicating they could use a LOT more cam. He did try a 245* cam with a little over .600 lift but no big changes. STILL just not enough to really make the power. When he was done it was making just over 500 RWHP when the rest of us were making 550-600+ RWHP with mild solid roller combos. Of course now we're all hitting the 700 RWHP range with same basic parts...just feeding them more air.

If you read the articles I just wrote for Corvette Enthusiast you'll see what a good street combo can do. Doug *Snowman* took the mildest combo with a HR cam and a 4150 style carb and small intake to use with his T-56 double O/D trans and 3.73's along with PS, PB and A/C. the sucker drives sweet and will run deep deep 10's@130+ mph easily.

http://editions.amospublishing.com/K...1&pagenum=1&f=

http://editions.amospublishing.com/K...1&pagenum=1&f=


The dyno tests come next month!

JIM

 

Snowman's build and mine will be quite similiar. I've similiar goals of keeping my A/C, PD, PB so I'm looking at 250 and .670 lift or so on my 540 with a hydraulic roller. Wolfplace is setting me up with some 325 AFR's. I currently have a Perf RPM intake since I want to get it all under my L88 hood; but I'm guessing that's gonna cost me some 20 hp on the top. I've a new 4781, but I may get a replacement main body to pick up some additional airflow.

I appreciate your articles. I've probably built some 40 engines or so over the years; but nothing bigger than a 496 until now. It's a bit getting used to the stuff going into these big boys.

Now I have to figure out how to fund a different rear end. Mine is a factory 3.55, but a Tom's is out of my reach for a while. I've emailed Gary about a beefed-up one until then. Here's hoping.

Apologies Mossy - I've kind of hijacked your thread.

 

Well, it looks like I probably can't afford to go with the stroker.---

But just out of curiosity, if one was to order a stroker kit, where would one order it from? Jegs, Summit, Flatlander Racing, CNC Motorsports?
I notice that some of these places advertise 10.2:1 stroker kits. Do they have custom pistons for every head configuration?
I suppose one could call these places and inquire about what each has available.

If one was to be able to afford one of these stroker kits, I'm assuming one would want a forged crank of better quality, say a Callies Dragonslayer, and maybe a set of forged 4032 material Keith Black pistons custom made for 858 heads if they will make them? What would be a good set of rods?

One last question, would one of these companies be willing to talk to you and provide a kit, or does one order these one piece at a time.

Thanks for the replies guys, I really appreciate it.

.
Ben Lurking, no need to apologize.


Gerry

 

From what you said in your initial post, you could get away with using a Scat or Eagle cast steel crank in a streeter 496. Note, however that these are not really high rpm cranks. If you stay below 6500 rpm or so you should be fine. Often times, however, they can cost a bit more to balance and can end up only a couple hundred off of a better 4340 crank because of this additional cost. If you do want a forged 4340 crank, I just picked up an Eagle internal balance 4.25 stroker shipped to my door for $525. PM me if you are interested in this option.

I would recommend a forged piston because with a 4.25 stroke, you get fairly high peak piston speeds. Get a nice quality set of I-Beam rods, 6.385", and and you are on your way. Scat makes a profiled I-beam rod with ARP bolts pre clearanced for stroker assemblies for under $300 - good for 850 hp; really nice rods for the $.

Your heads will hold that motor back; at least compared to more modern designs. If you are determined to use them, you can get a flat top shelf piston and probably end up in the 9.5:1 compression range.

There's a lot of vendors who now are selling internally balanced complete rotating assemblies already balanced. Any one of the ones you mentioned can do it. For overall costs, this may be the best way to go. You could just reuse your harmonic dampner & flywheel with an internally balanced assembly as long as they are in good shape. Wolfplace on the Chevelle board should be on your short list if this is the route you decide to pursue. He's a great guy, knows his stuff and will get you into what you need for at least the same money, and most times less, than anyone