Hi,
Let me start by stating that this is my first post, I have been using the forum for about 2yrs now but never needed to post anything, until now.

I am about to start rebuilding the original block from my 68 427-390hp and am after some comments on my planned build. Being the original block I have chosen to pay a professional builder to do the work as I didn't want to miss anything and have the thing go bang at a later date!
Here is the plan: I am aiming of an original looking engine as originality is my thing. But I am aiming to get a little more from the motor while not going so far that it cannot be turned back to original. I am planning on different rods/pistons etc to ensure durability
Block: 2 bolt std bore with 2 thou ridge in the bores, planning on minimal overboring depending on the cylinder alignment.
Heads - iron 215's that have been modified - therefore planning to port and rebuilt to the best they can be, and some machining due to cam choice
Cam - Comp 290HR retro fit kit
Manifold - torker II - engine must fit under original hood!
Carb - current is a holley 750DP but may change
I guess the big issue I see is that I am aiming for a true 500hp, the cam plans this a 6000rpm and I currently have a 2 bolt block that I don't want to cut up. Can high quality studs be used to support this HP and rpm? Am I better to go a cam that peaks around 5500 to get the 500hp? Or is it mandatory for me to install 4bolt mains?

 

What trans do you have? Is the engine matching number? Just because there is a .002 ridge, don't count on it cleaning up anywhere near there. Hope it cleans up at .030. What is your budget? You can get outstanding parts, but they are proud of them, so get your wallet ready. I'd stay away from Chinese parts as long as you can aford it. The better the bottom end parts the stronger it will be. The better the heads the faster it will be, for the most part. Compression is power, so if you go with aluminum heads you can go a point higher with your compression and paint them as to look correct for your Vette. If the valve set up gets wild, get spacers for the original covers. For a street driver I like a torque motor more than a horsepower motor.
Why I asked about your trans, is if you are auto, you will probably get into a stall converter. You may not like it so much for a street driver. Four speed no issue. Oliver or Crower rods, JE pistons and a Crower crank or a couple others are good. but there is a few thousand dollars there in a BBC.
It's almost like a restoration, you can keep stepping up in quality for each part. Just remember all the parts are only as good as the weakest link. Oliver rods and JE pistons on an Eagle crank makes all those parts as good as the crank.
Your builder can check for size and surface, but the metallurgy in the parts form over seas IMHO are suspect.

 

500hp and 5000rpm's? Factory 2-bolt block, cast crank, factory rods (with aftermarket bolts) should all be fine at that level, no special parts needed.
Make sure you get good machine work particularly the rotating assy balance.

 

Welcome.

I'll let others guess if your component combination will product 500 HP.

I rebuilt a '68 396/325, 10.25:1, oval port heads, junkyard engine back in '69. .030" overbore to produce 402 cubes. OEM specs throughout. I added an L88 (#3925535) solid lifter cam, Edelbrock C396 aluminum intake and a Holley 3 barrel 950cfm carb. Bill Thomas headers into Corvair turbo mufflers. Backed by an M20 Muncie.

I used to shift at 7200 rpms. Never had a problem with that engine's 2 bolt mains holding things together even when it over-revved when the OEM diaphragm clutch pedal stuck to the floor.

It produced a little over 400 HP on a Clayton chassis dyno on Sunoco 260 fuel.

But the cylinder block wasn't anything special...literally a dime a dozen in auto wrecking yards in the late 60's. I don't think I would risk building such an engine if I REALLY wanted to keep a numbers matching block from grenading.

 

To fill in some information that I left out: Cars got an M21 and 3:55 posi. I am planning on getting pistons and heads to match up to a true 10.5:1 compression ratio. Here is Australia we have 98 RON fuel readily available, there are many people with iron heads running this compression or higher.
I agree with the boring of the block, but I am hoping everything can be made good with a 0.030 over bore. I plan on using the stock forged crank, again, as long as it will clean up without too much work. And definately will not touch anything from china in the build - I want this engine to be solid for many years!
As for budget.....well parts over here are not so easy to get cheap, even with the current exchange, I'm don't want to go cheap on anything but also don't plan on throwing money at parts that are over engineered for this engines use.
Thanks for the info, good to see I am being realistic, keep the comments coming!

 

L88plus is spot on. Often folks skip the balance as it is money spent you can't see. It is one of the most important part of your build. Invest in a good mic. Check everything you get from the machine shop. I like to mic stuff infront of customers, so they feel good with the machining. Or at least plastigage the clearences. You'll feel better knowing you are on the money. If you get good parts they will be balanced to each other, but the assembly will need to be balanced. It must be expensive there, as I'm sending a small block there in a few weeks.

 

I wouldn't worry about the two bolt. There have been plenty strong engines built on the two bolt format. I like them better then the vertical four bolt anyway. The splayed four bolt with billet caps are the strongest I believe.
Like was said, if it's number matching store it and pick up a core block and build it. Just to protect your car value. I don't know how available they are near you, but they are around still here.

 

A REAL cheap 'upgrade' would to stuff a 454 crankshaft into it. You would need a balancer and flywheel as well. I would suggest picking up a different block if you're gonna thrash it. A good 2 bolt block can be had for two bens. Of course you could put in a 4.25" crank for 489 CID. If you're doing the whole thing anyway, a decent scat stroker crank isn't much more.

 

454 - looks just like a 427, ...ssh !
parts are much more reasonable priced, and you get free cubic inches.
I would keep/bag the orginal motor,
mmmm "Sunco 260"

 

As already mentioned, probably looking at a 0.30" overbore and maybe TRW forged piston's. You're wanting to get this assembly balanced while at it. You may be looking at a little more money than first thought, as probably end up align honing the block, turning the crank 0.10" under and resizing the rods/bearings. I'd re-think using a single plane intake on the street. They do pull strong at high rpm, but mostly dead for street cruising.

 

Cubic inches make low rpm power increases much easier.

 

I would rebuild the 427, keep the character of a short stroke motor, if you want to go bigger and buy a new block, but retain bore stroke ratio you could go 510cu......

 

I stored the L36 lump out of my '68 to keep originality - then had a 489 built-up with new rotating assy., heads, cam, inlet etc etc, develops an easy and genuine 500 + hp - other than usable power band starting at 1200 rpm if performs much like L36 - except that there is 50% more torque & HP. Works well with 4 speed & 3.08 ear end. Cost was less than doing re-building stock 427.

 

As much as I would like to build a big motor with some random core, the blocks are just not cheap over here. If I was going that route I would probably just get a new Dart and build big. But I want to go close to original, and just enjoy driving the car. For me, putting a 4.25 crank in would be taking something away from the car. I really like the fact that I'm driving around something that was made over 40yrs ago and it shames most modern sports cars! I am happy to have a different intake/carb for some performance because I can change it back easily. Same reason I'm using the 215 iron heads.
I know the torker II manifold is not great for bottom end, but what other choices are there other than the hard-to-get LS6 manifold?

 

I really like 427's and was never scared to jump on a 454 with one...but I was also willing to spin it a little to get there. I usually used solid flat tappet cams and as long as you stay out of the crazy categories they will last a long time and run great.

Your close ratio and 3.55's is definitely not the hot setup with a 427. That will make it pretty long geared and weak out of the hole. That might be an advantage with small street tires though.

I'd plan on a .030" overbore and use some TQ plates to make sure things are round. If the block ck's OK on line bore...no need to mess with it. Same on crank...the factory steel ones are pretty tough and hopefully just a quick polish job will take care of it. Factory rods are tough too with some decent bolts installed. I've run 427's in the 7000+ rpm range for years with stock rods and 2 bolt mains (not even studs!). The pistons ARE heavy though...so anything you can do to get lighter pistons will help. That's one advantage of the strokers and long rods. Yes the stroke is longer and piston speed goes up, but the piston gets a LOT lighter and will still stay together just fine.

Find someone who REALLY pays attention to port design and get heads done by them. You can make insane power with iron GM oval ports in the right hands.

While the Torker II isn't perfect, there's not a lot of choices. It will work OK..but again won't be as friendly with your gearing. I'd be looking into a Richmond 5 speed to keep RPM's up all through the gears (underdrive 4th) or one of the O/D's. They won't accelerate quite as hard through the gears since 4th is 1-1...but you will get O/D as well as a LOT better acceleration in 1st and 2nd gear.

JIM

 

Good luck getting 500 out of that, I'd guess more around 460 max. You may look at the Edel. performer 2.0 dual plane, over the torker for some grunt, and it will fit. Full headers of course. If you cut the deck, you will take off the numbers, you know that? Comp cams steel roller rockers fit under stock covers. Too bad you're so far away, I've got a ported set of heads all done up I'm selling. A stud kit on the mains with a windage tray will strengthen the 2-bolt bottom end big time, and give free hp from the tray. have fun....Good on ya mate!


Did a 427-390 last year like this. Make sure there's no scoring behind the cam gear on the block.

 

Once again, 427Hotrod is right on target.

A 427 properly built for a few extra revs can be an awful lot of fun. I'd definitely go with a solid cam (preferably steel core with iron gear). Good 3/8" pushrods, 11/32" valve stems and titanium retainers will help valvetrain weight without breaking the bank. Don't get timid with valve spring rates; follow recommendations given for the cam in question.

You can turn the downside of limited off-the-shelf piston choices for the 427 into a plus by just ordering pistons done to your specs. Suggest dealing directly with someone like JE, who can help you make sure your ducks are in a row before you pull the trigger. As mentioned, you may not need to do everything, but don't cut corners in the machining process. I'd replace and upgrade the rod bolts, and consider main studs cheap insurance in a 2-bolt.

Finally, better gearing will transform your car, and IMCO the Richmond SS 5-speed w/OD (2.89:1 1st) would be hard to beat ahead of the 3.55:1.

My $.02

 

You are rebuilding the original block and you say "originality is my thing". Does your engine have the original stampings on the pad, including the vin derivative? If so, make sure your rebuilder understands the importance of preserving these numbers and not destroying them while decking the block. Then, ask him again, pointing to the numbers with your finger. Explain that losing those numbers will cost real $$$. Please don't be another of the many posters that comes on here moaning about losing original numbers after engine builder assured him they would remain intact.

 

One more vote for preserving the serial #'s. The serial numbers on my original L36 are pretty dim. And there ain't no going back. I guess I thought the machine shop would know...

 

I'd definitely stroke it, you will be much happier. I had a 454 and now finishing off a 533. No one knows how big the engine is except yourself and the bigger engine makes more torque which is more pleasureable on the street.

A long discontinued Holley Street dominator would work better than a Edelbrock Torquer. I had one on my 454 and fitted runner extensions. Found it on ebay and used the slow boat to get it cheaply to OZ. I could even fit a half inch spacer and keep it under a BB hood.

Go for a solid cam and use the lifters with an oil hole. If you can use a windage tray and scraper etc