I'm trying to build a 427 SBC in the coming months. I have a virgin 2-bolt block 400 block that I'm going to stroke. I'm looking at the following rotating kit-- http://www.theengineshop.com/sbkits3.shtml

I'm planning on just using ARP studs on the mains, and not splaying it. I really don't have the cash for that. I wanted to know if I needed to partially fill the block (to the bottom of freeze plugs) for clearancing. I was thinking this would make sure I don't hit the water jackets. This should keep the block really strong, and I think I will still be able to cool the motor off, as long as I don't fill too much.

What do you guys think of this so far? I'm hoping to order the rotating kit in the next couple of weeks (waiting on graduation money).

I plan on using my existing heads, but I might pockt port them first. I will also be using a big solid roller cam. The bottom end shold be up for 7,000RPM shifts right?

Any input is appreciated.
Jay

 

How much horsepower do you plan to make? :D I don't think you will need to spin that high of rpm. Even with a studded two bolt, I wouldn't go over 6500 rpm.

Before you spend any money on machining your block you should have the cylinder walls sonic checked to see how much iron you have (considering that you will need a 0.030" overbore). I would also have the block cleaned using the oven and shot peen method which also stress relieves the block as well as making it look like new. Then have it crack checked.

There are a few things that you should do prior to having the block machined. Port the oil passages in the rear main cap (get rid of sharp corners, chamfer oil ports, etc.), where the oil enters the block, and the filter mounting passages. Use a carbide burr on a high speed die grinder.

Fill the block to the bottom of the front side frost plugs (by the motor mounts). Before you start, install and torque the main bearing caps.It is fairly difficult to fill the block evenly. Use a slightly runny mixture and tap the block to help the fill settle. Start at the lifter side holes by the distributor and work your way to the front. make yourself a depth gauge so that you know when the fill is high enough. When you are finished filling one side, install and torque a head on. This, and torqing the mains, will re-create the stresses normally seen in the block, and is worth a few horsepower. Let dry over night and do the other side.

There are three large cooling holes on the lifter side of the deck (each side)that should be tapped for maximum deck strength. Use a 3/4 npt tap and use a solid pipe plug to thread into the hole. When your deck is machined flat ("decked"),use your head gasket for a template and drill the required cooling holes into the pipe plug (3/16" drill).

Use your die grinder to enlarge the oil drain back holes at the back of the block to get rid of the casting flash, etc. You can also smooth the valley walls where the oil drains out of the heads.

Since you are going solid roller, you may consider oil restrictors to meter the supply to the valvetrain. You may also want to plug the round valley holes that allow oil to splash on the cam (1/4" npt plugs).

Make sure you drill steam holes in your heads. You don't need a whole lot of cam to make big hp. I made the hp and torque in my sig with a mild hydraulic roller (222in and 230 exhaust @0.050"). Nothing worse than a over cammed engine on the street (IMO). I use a Edelbrock Victor water pump to keep it cool.

Good luck!! :cool: :cheers:

 

As 74vetteman asked, what is your power goal?

You mention 7000rpm shift point, if that was the optimum shift point , then you would need a relatively large cam and heads. My NA SBC 427 made a peak of 650hp at 6800 rpm, so my optimum shift point would probably be in the low 7000's. To get that from a 427, I used a 256/264 mech roller cam and my 18* heads have 255cc intake ports. My adivice for building these big strokers it to think of them in terms of small big blocks, because that's basically what they are, only you're handicapped by cylinder heads. Even with 18* heads that flow 355 cfm, I feel my engine was held back by cylidner head flow.

As you guys have already mentioned, filling th eblock to just below the freeze plugs is as good idea. It won't hurt your cooling since there's quite a difference in cylinder and block temperature at the bottom of the bore versus the top and combustion chamber.

A 17 year old with a 600hp SBC 427 Vette...I can only imagine the possibilities ;).

 

I would love to reach close to 600hp, but I don't think it's going to be possible with my heads. I just don't have the cash to get them fully ported. I plan on running a cam with lift up in the mid-to high .600's. It will definately be a custom grind.

People always say cams this big aren't streetable, but I run about .540 lift (1.6 rockers) in a 350 with only a cheap 3000 stall. My car will idle at 850RPM in neutral. I am hoping to get an ATI 8 inch treemaster stall.

I think it will be a high 10 or low 11 second street car.

All of your help is definately appreciated.
Jay

PS--Monty, do you still have your headers, I can get adapter plates to use the on my heads. I would of emailed you, but I'm at school right now.
Thanks,
Jay

 

What heads do you have? Do you have flow bench numbers for them? A 300cfm head has the potential to make 600hp.

Lift really doesn't ahve much to do with whether a cam is "streetable" or not, it's more a matter of duration and overlap. If it were possible to run .700" lift with a 220 duration lobe, it would be totally streetable, idle well, and pull decent vacuum. The only problem would be the valve springs necessary to accomodate that lift would also typically be very stiff. Lift should be matched more to the flow characteristics of the cylinder head.

I don't have my NA headers in my possession, but I can possibly get them back. I gave/sold them back to the guy who built them for me and he was going to sell them to another customer of his. As far as I know, the guy never really got his project going, so he may not be using the headers afterall. I'll find out for you.

Jay, just keep in mind that what was appropriate for your 350 engine is going to be restrictive or too small for a 427. Don't be afraid to run a cam with 240+ degrees of duration at .050". I went through several cams on the dyno, and each time I swapped in a larger cam, I picked up horspower and torque all the way across the rpm range. The largest cam I tried actuall made more low rpm torque than the smaller one. We never did get to the point where we were sacrificing low/mid-range torque for high rpm power. As I mentioned earlier, I ended up sticking with a 256/264 duration cam, but I feel like I could have gone to 260/268 or so before I saw a loss of low end torque. Of course every application is different, and is dependent on many things such as static compression ratio and cylinder head flow, but it's still an indicator of how the extra cubic inches require more cam and head.

 

I'm planning on using the heads that are on my 350 now. They are Dart Pro 215cc 64cc chambers with 2.05/1.60 valves. The runners have been polished, but no real porting. They should flow about 265 @ 0.50in lift.

I'm not scared of a little duration either. I currently have 240/246 duration, and it isn't bad at all.

Please keep me informed on those headers Monty.
Jay

 

I'd guess you're probably looking at around 500hp @ 5500rpm and 540 tq @ 4500rpm, with those heads, a 240/246 cam and 10.5 compression ratio, along with headers and your current carb and intake.

 

You don't think the 427 could hold more duration? I was also thinking of switching intakes, and definately a bigger carb. I would love to get more horsepower, but I know it takes better heads. I'll have to try and get some work done to my current heads. Now, where to find the $$$................
Jay

 

A 427 could definitely use more duration, I was just offering you a guess on what I thought it would make based on the components you listed in your profile and the cylinder eheads you have. However, I would n't get too wild with the cam without working the heads first. In my opinion, always start with the cylinder heads, as the saying goes "cylinder heads make power." A set of good heads with a small cam will make more power and offer better drivability than a set of mediocre heads with a killer cam.

 

Ok, I understand now.

What intake should use? I know my intake is pretty decent, but is it good enough?

I wanted to thank you Monty for all of your help so far, I've followed your engine build-up from the beginning. It's always real nice to see a guy with a killer motor THAT ACTUALLY DOES IT HIMSELF!

Jay

 

Jeeze. That's a lot of motor for a street car.
I agree that the heads will hold you back. What I might suggest if you really want mid-600 hp numbers is to stick a roller cam in it with a strong midrange, fuel inject it, and then put a blower on it. Probably a good intercooled centrifugal supercharger, or maybe a screw-type supercharger.
Then you will definitely have a streetable engine that'll make the serious power numbers for dragrace time at the strip.

If you go monster huge on the cam and build the engine for a shift point of 7000 rpm, think about the massive amount of stall you'll need to be able to launch at or close to your torque peak. I have run a 3800 stall on a big block Firebird for a few years now and that's about as large as I'd want on the street. If you end up needing a 4500 or 5000 stall, you can kiss streetability goodbye. Especially with an enormous cam. Partial throttle would be hell in that thing.
Anyway, that's just my opinion.

If you do keep it naturally aspirated and 500 to 550 hp and tq is not enough, then another option is to get a nitrous system. That'll get you the power numbers you're after too, despite small block Chevy head flow limitations. That way, you can "put away" that last 150 hp until you need it at the track, and when you have race gas in the tank, and at all other times, you have a very torquey, very streetable engine.

But I agree that you just will not need 7000 rpm on such a torquey street motor. Besides that, I wouldn't spin those kind of rpm's on a two-bolt main. Especially not without the very best and longest forged H-beam connecting rods and forged crank and 4-bolt splayed mains.
You'll find like I did, that building up a trick 400-based stroker is far more expensive than an equally powerful big block that will always breathe better.

My suggestion is to lower your operating rpm band a bit, and get that extra power with nitrous or a blower maybe. And if carbed, the Edelbrock Performer RPM Air Gap is about the best intake I've ever seen.

IMHO...

 

The kit includes top of the line Eagle H-beams and forged crank. It should be good for whatever I throw at it within reason.

What do you think about the rings being so high? I know it would be able to hold a little Nitrous, but how much is the question. I am not building this motor for Nitrous, but I might (big might) use it later.

My friends spray everything, but I prefer to keep it all motor.
Jay

 

I'm basically building the same motor, I'm looking at about 550-560 HP. I'm gonna use the Dart Pro 230cc's with 2.08 and 1.65's, those valves will also fit in your head for a little bit more flow. I'm going to use the Comp cams 12-443-8 (242-248 .540-.562) with 1.6's for .576-.599 and have them grind it with a small base circle and 112 lobe separation. This should be a very streetable and torquey cam up to about 6500,,not gonna go too much above that with the 400 2 bolt. For an intake I'm using the new demon Mighty Mouse 825 CFM with an air gap RPM intake, American Speed builds some great high HP 400 SBC's with this intake and they said on the dyno up to about 6500 it only gives up 7HP to the Victor Jr. with a lot better torque numbers down below, and since I'm running an auto, I feel the dual plane will give me better streetabilty. So that's my recipe,,basically everything's the same except I'm not filling the block, it's already been decked, line bored, lifter valleys done, bead blasted, baked oil restrictors and everything else you can do to a 400 after sonic testing good. I plan on giving this motor a 200 shot with a plate system. So I'll be watching your build to see how everything goes. I'm about 2 months away from completion of the motor (too many other things on agenda).

 

You two guys, please use 6-inch rods. Even with that, the rod/stroke ratio of the 427 SB won't be too good. But it will help. The high pin location of the pistons if anything will help control piston rock and increase stability. There isn't much room for rings, that's true. But you'll be okay. This won't be a real eager revver, as compared to a 350 for example. So I'm not too sure about building it for a power peak so high that you'll be pushing some dangerous piston speeds to reach it. Even with modern metallurgy, 6500 rpm will be pushing it on those motors. I'd be very concerned about someday having a rod exit the block or getting sideways in the bore.
I know more and more engine builders are less and less concerned about piston speeds and rod/stroke ratios than in the old days. This is no doubt because of some very good metallurgical advances in recent years.

In otherwords, it'll work great and make buttloads of power and torque, but if there's one little flaw or hairline crack, BOOM...no warning.
Maybe I'm a little old fashioned, but that worries me about these monster big blocks.

One thing's for sure though, you'll run with big blocks and handle like small blocks. Just watch those stratospheric rpm's on these giant SBC strokers.

 

One more comment. Call me nuts, but what I plan to do with my 400 SBC that I decided not to stroke is to DESTROKE it. That's right. Forged 350 crank and 6-inch forged H-beam rods. That gives a rod/stroke ratio of 1.724. Very close to the famous rpm-happy 327's. Except 50 more cubic inches at 377. Then cam it with a modern solid roller cam, set it up for low compression with some dished pistons, and twin turbocharge and intercool it.

That'll probably make some similar power numbers that you guys will be at, except by going the opposite way with the stroke and using turbos. It'll be softer on the bottom end, but no worse than your average street 350 with a healthy build up. However, in the midrange, things start getting interesting real quick. You'll hear a pair of turbos whistle as they "come on line" and then BAMMMMM!!!! Just like a freight train ramming you in the back.

I know how I'm going to build it up, just not exactly what I'm going to put it in. I'd love to find a 68-73 Corvette coupe to put it in, because of the great bod and plenty of room for turbos and a huge intercooler. That with a ZF-6 speed or ROD and some nice steep rear end gears, (3.90 would be good), would make that an interesting project.

And I'm sure except for the off-line response, it'll about run with my 427 Corvette, which will probably have the same power numbers.

There's more than one way to skin a cat. (Or a Viper).

 

This is a great thread, since I'm still running numbers to see how I want to build up my rocket block!

Momo, I thought about doing exactly that, destroking, but I'm not convinced that I'd really be taking advantage of the higher RPM potential by doing that.

Out of curiosity, what are the limitations on rod length? Monty's running 6.125's, which is pretty long, but a tall deck looks like it might even handle a BB rod at 6.325, or would that be cutting it too close?

Tony

 

Tony,

Your only limit to rod length is space. If you have a 9.325" deck height, with a 4.00" crank, that means you have 7.325" to fit in your rod, the piston compression height, and a deck distance if any (the distance between the piston top and the plane of the blcoks deck surface).

Deck height = 1/2 (stroke) + rod length + piston compression height + deck distance (if any)

We milled my Dart Iron Eagle/Rocket block deck down to 9.300 to standardize and square it. With a 4.00 stroke and 6.125" rods, I run pistons with a 1.175" compression height with leaves the piston .010" in the hole. With .029" gaskets, that gives me a .039" quench height which is in the optimum range. A longer rod would really pack the rings together, practically eliminating the possibility of N20 or forced induction since the top ring should be at least .300" down. You might be able to run a 6.200" rod, but I think that would be the longest with a 4.00 stroke and the 9.325" deck height. The aluminum Dart/Rocket blocks with a 9.500" deck would certainly allow a longer rod though.

With a 4.00" stroke and 6.125" rods, you end up with a 1.53 rod/stroke ratio whcih is identical to a 454 big block, and slightly better than the 1.52 rod/stroke ratio a 5.7" rod 383 has. We spun my SBC 427 up to 7500 rpm on the dyno during testin/tuning without worry. The Crower billet rods are rated to 8500+ rpm, so I never felt unfomfortable, and the engine accerlates very quickly, the guys at Fast Times commented on how "frisky" it was.

There seems to be many differing opinions on whether rod length and rod/stroke ratio is really that importnat. I've read articles and comments from many well-known engine builder snad it seems about half of them recoomend running the longest rod possible, while the other half consider the rod nothing more than just a means of connecting the piston to the crank. I tend to think that you should always strive for the best rod/stroke ratio possible, within reason, and keep it above 1.5. However, I wouldn't sacrifice displacement by running a shorter stroke just to get a better rod/stroke ratio. I just build street engines that don't see 8000+ rpms for extended periods of time. If I were building a road racing engine that would be spun that high for extedned periods of time, I'd defintely destroke it, run longer rods, as well as use small main and rod journal (Honda size) diameter to reduce bearing speed.


[Modified by Monty, 11:03 AM 5/7/2002]

 

Rod length is limited by compression height. That gets pretty tricky. But if you work with your machinist or a knowledgeable parts source rep, you can usually increase rod length by altering the piston design. You can get custom pistons too, but of course, price increases the more exotic you go.

A 6 inch rod can be put in about any small block Chevy and still use off the shelf pistons that are widely available. For over 6 inch lengths, you really need to work with someone who can calculate that and advise you. I've worked with PAW and Speedomotive in the past, as well as a decent machinist. But I find machinists tend to be impatient and less willing to help because you're taking time away from their machine work that they have stacked up. Call Speedomotive at (562)945-2758 and ask them. Tell them you want to get the longest rod possible and still use available pistons without having to go custom, and see what they can do for you.

Keep in mind that the higher the pin location and the smaller the compression height, the higher the resulting compression. You'll have to tell them your desired compression ratio, and the pistons will have an increasingly deep dish to compensate. In otherwords, you couldn't very easily build a stroker AND keep compression low enough to use forced induction. By building a stroker, you're pretty much dedicating yourself to naturally aspirated use.

I thought of destroking because then it's a lot easier to get a killer rod/stroke ratio and longer rods and still be able to easily lower compression with available pistons and heads. Then if I wanted to run it fuel injected and naturally aspirated for awhile, I could use a steel shim head gasket and still have 9.5:1 compression with a 72 cc combustion chamber. Then use a Felpro thick head gasket to drop it to 8.5 later and convert to forced induction. The only complication would be a cam change to run a supercharged or turbocharged cam grind.

A 377 with 9.5:1 compression with an LT1 or Miniram FI set up and full dual exhaust would still be no slouch as a street engine. The only thing I was worried about is, to run the kind of cam duration it would take to make full use of a 377's rpm potential, I'd have trouble passing emissions. So that's why I'd use it on a pre-'74 car.
I'd expect to make around 350 to 400 hp at the rear wheels with a high-revving, solid-roller 377, and probably pick up another 200 hp by twin turbocharging.

 

Momo,

Only 200 more hp from twin turbocharging? Yeah right ;). You'll get used to that real quick and you'll be turning the wick up in no time!

 

Hi Monty! Long time no talk.
We must have been posting simultaneously.

The only comment on the rod/stroke ratio debate that I have is my own personal experience driving a 327 with a 1.73 rod/stroke ratio, and a 350 with a 1.64 rod/stroke ratio. They had a similar build up otherwise.

With the 327, the engine tended to climb in rpm's so much easier and more eagerly. It really was very noticeable. Plus with the shorter stroke, the piston speed is a lot less, and that's a fact. You really can go higher in rpm with identical rods as compared to an engine with a longer stroke, because the piston speed is a lot lower at a given rpm.

The 350 in comparison had much better torque, and still revved okay, but not as well as that 327.

Likewise, a 427 or 396 is going to rev noticeably better than a 454 or 502.
Some engine builders don't believe it, others do. I do because I've built both and compared them on the same car.

So that's part of the rationale for a destroked motor. The other part is the ability to more easily lower compression to used forced induction. As you say, a 4-inch stroke is not going to allow you to run forced induction with such a short compression height. I agree with you.
However, nitrous is another story. You can have high compression and still run nitrous. You have to have good high octane fuel in sufficient quantity and timing backed off to avoid detonation. But people do it all the time at the strip. Some people run a fuel cell and switch the fuel source over when they engage nitrous, which is an excellent idea.

By the way, your engine looks very nice.