Please educate me on 396/402 big blocks....might be building one soon - Chevelle Tech

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post #1 of 71 (permalink) Old Jan 5th, 05, 12:33 AM Thread Starter
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A neighbor down the street has several 396/402 big blocks sitting in his garage, all needing a rebuild. There is one I picked out which he says he's had checked for cracks and none were found, and he has offered to help me build it and install it in my car.

I know nothing about big blocks other than they're torque monsters so I have several questions to ask.

1. I'd like to push 450 hp/500 tq (or close) at the flywheel. What all will be required to achieve this gain if I stay naturally aspirated w/o nitrous?

2. I've heard 396/402's like oval port heads and not square port heads. Is this so? If so what casting and piston should I use to get a 10.0:1 compression ratio? Or should I go higher on the c.r.?

3. I'd like the power range to run between 2000 and 6500 rpm. Are there any cam kits to run in this range for my desired compression? I'm going to go with a hydraulic cam. I want it to have a hot lope to it while idling.

4. I see Speed Pro makes an engine rebuild kit for the 396. Does anyone make a kit for the 402? Anyone have any experience with this kit? Good? Bad?

5. What size intake/exaust valves should I run with for my desired output?

6. If a .030 396 is a 402, then what is a .030 402?

7. Are the '70 blocks considered 396 or 402? (I know in '71 they were calling them 402)

Sorry this is long but I don't know my big blocks that well. I'll probably be asking more questions when the time comes around.

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #2 of 71 (permalink) Old Jan 5th, 05, 1:29 AM
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1. 450 hp is pretty easy to get. for myself it has taken 10.5 to 1 comp, 233/239 @ .050 cam, stock '390 closed chambered heads...ported (runners cleaned up of casting flash,3 angle valve job,2.19/1.88 valves ,chambers cleaned up and some light unshrouding of valves)rpm intake,3310-2 holley.

2. yes oval ports are the way to go,kb1600 pistons with closed chammbered heads get you over 10 to 1

3.the delta regrind cam that i got has 233/239 @ .050 with 111 lobe seperation w/1.72 rockers .548/.551 lift very nice rumpy idle, hard puller to 6500 rpms.....power really comes on about 2800 rpms.

4. never bought a "kit" just buy what i need from other sources, i found to be cheaper this way.

5. upgrades to 2.19/1.88 valves from competition products..take outs....have done myself good with proper bowl work and 3 angle valve job.

6. 408

7. just depends on the bore size is all.....some 1970 was the 402 if not all.....

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post #3 of 71 (permalink) Old Jan 6th, 05, 2:21 AM Thread Starter
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Wow....so what would it take to make 500 hp from a 402? Cuz that's what I'd really like if at all possible.

This guy I know has a set of 290 casting heads. But I think he's going to give me a set to have some 2.19 valves put in as the ones he has already have I think 2.06's or something like that. I'm not sure what casting heads I'll get. Are there any other castings to look for in terms of performance?

I think I am going to run a Performer RPM intake with a 750 Holley and a high flow fuel pump.

Would it be better to run a dual profile cam with a big block? What are your thoughts of running a cam with a 2500-6500 rpm range?

Dennis I take it the engine you're referring to is the 414 in your Camaro? How did you get it to 414 cubes?

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #4 of 71 (permalink) Old Jan 6th, 05, 2:44 AM
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Hey JYD,

If it were me, and the block was cheap, I'd bore it to 4.25" and make it a std. bore 427. I did that in the past with a 396 and it worked very well. I believe all 396/402 blocks can bore to 4.25". Hopefully others here can verify this.....or say no way. I had no problems with mine! It was a 2 bolt main eng BTW.
I had a 427 in my first drag car, a 68SS Chevelle. I used the L72 pistons with '990 open chamber heads and a Crower street roller. Small by todays standards. Anyway, with a Victor Jr. and a 800DP Holley, it went mid tens. At 3400lbs and 4.88's etc.
To me, 427's just run dang hard. They have a decent rod to stroke ratio to boot.
Oval heads would also be fine, just get the right ones, and folks here can guide you for sure.

What would be the goals for the car?

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post #5 of 71 (permalink) Old Jan 6th, 05, 4:16 AM Thread Starter
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Well, I'd like to make this an 11 second car. I already have a 12 bolt rear with a 4.10 posi. I've not had the car weighed but it has factory buckets, power steering and power brakes. I removed the heater/ac and all of the duct work.

I don't know if you'd consider the block cheap or not but he's selling me the heads and the bare block for $500. He's had the block checked for cracks and he's had it cleaned but he didn't have it bored.

Right now I'm trying to get a ball park price on building this thing. I plan on sending the heads in for porting and polishing and possibly fitting some bigger valves. I also plan to have the cylinders bored.

I'm going to keep it naturally aspirated. I'm not sure on what pistons, rods, etc. to use. I'd like the cam to have a pretty good but not too radical of a lope to it...something I can still cruise on the streets with. And I want a stall coverter that winds up to like 3k on light launch....you know, the things that tell the guy in the next lane "he's got something.....don't even try and challenge him."

BTW I did not know a 396 could be bored to a 427...what size overbore is that?

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #6 of 71 (permalink) Old Jan 6th, 05, 7:54 AM
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I got a whole motor,including 781's,power steering pump and brackets,alternator and brackets and HEI for 500.00. All I used was the heads and block,but it was a very good deal.
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post #7 of 71 (permalink) Old Jan 6th, 05, 8:35 AM
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You have to sonic check the blocks and a lot depends on how much corrosion has occured over the years. The bottums of the cylinders start to thin out. Personally, if you need to overbore go to 4.185 on a 402, take it out to about 414CI. If you're really ambitious and will need to get a crank anyway [and don't mind some hand grinding], look into the KB361 stroker piston to put a 4" crank into the 402 block for a 434 (.030 over) or 440 (.060 over).
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post #8 of 71 (permalink) Old Jan 6th, 05, 11:21 AM Thread Starter
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I think he's got some cranks in his garage that have been turned.

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #9 of 71 (permalink) Old Jan 6th, 05, 12:01 PM
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Most 396/402 can not be safely bored out to 427 bore size... Mostly the early blocks (65-66) are used for the 4.25" overbore... But sonic testing is a good idea anyway.

For the price, I'd consider looking for a 454 block. If your not in a hurry, you should be able to find block and heads (needing rebuild) for that $500... The only thing special I see is that these blocks are cleaned and crack checked...

Afterall, you are looking for the most power within your budget... Much easier to do with the bigger engine. Not only more cubic inches to make more power, but the longer stroke will help make more low-end torque to get a car such as a Chevelle moving. And the larger bore (454 or 427) unshrouds the valves a bit more for better flow.

The 396/402 and the 454 should cost about the same to rebuild, and most likely a little cheaper to do the 454 (aside from pistons and rings, most parts will be the same)...

Quote:
I see Speed Pro makes an engine rebuild kit for the 396. Does anyone make a kit for the 402?
You should be able to use the 396 kit for the 402, as long as the bore size is available in the 396 kit (0.030 over 402 ~= 0.060 over 396, etc). The piston choice will likely be somewhat head specific (open chamber or closed chamber).

Quote:
Are the '70 blocks considered 396 or 402? (I know in '71 they were calling them 402)
The 1970 "396" engeines were actually 402s... I don't think they ever called them "402" though... I think the 402 might have come out in late 1969 (model year), but not sure...

The 402 in 1970+ Chevelles and Camaros was still called the "396" as in SS396...

The 402 in 1970+ full-size and Malibus (LS3?) were called "400"s

Did the early 1970's pickups call it a "402" or a "396", or both (I recall seeing "396" emblems on some trucks)...

Once you go RAT, you never go back...
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post #10 of 71 (permalink) Old Jan 6th, 05, 12:26 PM Thread Starter
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1966_L78, this block I'm getting is 1970 block. So I guess that makes it a 402.

But then I'm looking at Summits engine kits...they don't specifically say they have one for a 402 but they do have them for a 396 from '65-'70.

Then I find out later the so-called engine kits don't come with connecting rods.

I agree I would like to do a 454 more than a 396 but try finding one of those around here. I was lucky enuff to even find a guy with a 396 already crack checked.

Of course then again the way I see it if I can make this 402 push 450-500 horses and spank every LS1 out there (like I want to do) then at least I can say that it was all from the mighty power of the little big block.

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #11 of 71 (permalink) Old Jan 6th, 05, 12:39 PM
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Dawg,

Got a question for you. What car is this going in? I see you have mostly small blocks now. I have a .030 over 402 that came in my car - so I gave it a freshening up and have been running it. But it didn't need any parts. All we did was cook the block, cleaned up the decks, hone the cylinders, resize the rods with new bolts and put it back together with new rings and bearings. If it was in need of everything, I would not even have considered it.

For the money you are going to get into, I would either search out a 454 and be prepared to spend the cash to make it work in the car - or - strongly consider an alum head 383 motor. The GMPP 383?? (425HP Smallblock) is about the best bang for the buck small block replacement out there. Probably a 150 - 200 lb weight difference over an iron head big block and that equates to a lot of useable power. You can use all the same acces. brackets. Just a thought.
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post #12 of 71 (permalink) Old Jan 6th, 05, 1:23 PM
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I agree I would like to do a 454 more than a 396 but try finding one of those around here. I was lucky enuff to even find a guy with a 396 already crack checked.
Do you need to buy one right now?... Crack checked, how much does that cost? $150 (including initial cleaning)???

Maybe find the machine shop you plan to use and ask them how much for a core 454? Complete engine with crank and rods too... Check wrecking yards too... You should be able to find a core for not much more than $500, maybe less. And you might also get pulleys, flex plate, starter, etc wit hthe core that will work in your car...

$500 for a bare 396 block, needing machining? Does that include the heads? include the crank and rods? I would think that $500 for a 396/402 block/heads/crank and rods would be an okay price (considering they still all need to be rebuilt), but if he wants extra for the heads and extra for the crank, then his price seems to be getting too high (unless its an L78 4-bolt block, etc)...

I'd also consider what GRN69CHV stated, and think about a nice SB crate... Figure in the extra costs of brackets, pulleys, headers, oilpan, water pump, exhaust work...

Quote:
I'd like to push 450 hp/500 tq (or close) at the flywheel.
If you are after power,and starting from scratch, WHY limit yourself to the 396/402, especially if you are NOT getting a great deal?

Once you go RAT, you never go back...
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post #13 of 71 (permalink) Old Jan 6th, 05, 2:04 PM Thread Starter
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This engine is going in my Chevelle.

I had considered a small block but if I wanted to do that I have a pos 350 in the car now. I just have wanted a big block for awhile now and saw this as a first oppritunity to both own one and learn how to build one.

About the engine....all of the internals have been removed. The block and heads were checked for cracks and cleaned....that's it. With the block I get a crank and a set of heads. I could probably get the 290 heads that he has now which have already been fitted with new valves and springs, but he recommended if I want to oversize the valves to take a different set of heads (that have been cleaned and crack checked) and have them worked.

Good luck finding any 454's around here. Boneyards snatch them up and sell them quick for high dollar (if they even get them), and you don't even know if it's any good.

Crack checking....this guy has ties with the local machine shop so he gets good deals. I couldn't do the same unless I became buddy-buddy.

Where did you see a 425 hp 383? The ones I've seen say 340 hp...which that's with specially tuned dyno headers and such....still not impressive IMO. Besides I have to question some of the internals on the GMPP engines. Not to mention just how realistic is it to get 425 from a natually aspirated 383 without killing street manners? I want upwards of 450-500 hp. The only way I'm going to get that out of a small block and still keep it streetable is if I spray it or run a blower. And I really don't want to run either.

Oh, btw I've been informed I can reuse my starter, alternator, power steering.It's the brackets and water pump, etc.that I gotta buy new.

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #14 of 71 (permalink) Old Jan 7th, 05, 12:17 PM
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I completely understand the allure of the Big Block...

Just trying to impart some advice based on experience...And trying to prevent you from making a costly mistake... I have built several nice 396s that started as $100-$200 cores (block/heads/crank/rods/etc). While nice, I wish I had looked a little deeper for the 454 to start with, for more power at the same streetability...

A 396 (402) is a good motor and great for a resto, but power potential it is not that great.

The 396/402 can be a powerful engine, but it might not reach your goals of 450-500HP AND good street manners... Plus in a heavy Chevelle, the extra torque of the 454 really helps...

Quote:
Not to mention just how realistic is it to get 425 from a natually aspirated 383 without killing street manners? I want upwards of 450-500 hp. The only way I'm going to get that out of a small block and still keep it streetable is if I spray it or run a blower. And I really don't want to run either.
As realistic as it would be making 425-430 HP from a 396. The power potential of a 396 will NOT be that much greater than a 383 SB... And overall, the 383 might be cheaper...

Quote:
I want upwards of 450-500 hp
From a 396... AND you are worried about street manners, etc... Even more reason to go with the 454...

Even if your initial cash outlay for a 454 (for the core) is more than the 396, you should be able to arrive at that 450-500 HP much easier with the 454 (and cheaper overall too, including the extra for the core), plus have better manners and the potential to get even more power (do you honestly think you will be satisfied with 450-500HP once you actually have it? Of course not, you will want more )

I am not sure what the #290 head specs are, but if they have new valves, valve job and guides and he is including them, I'd take them... The 396s don't really need big huge valves. In fact, the smaller bore actually shrouds the valves as it is. Bigger valves might need block clearancing and probably won't make any more power, especially in a "streetable" engine... And it will be at least several hundred dollars to rebuilt another set...

Have you placed a "wanted" add for a 454 on Team Chevelle? Have you asked the local Machine shops if you can buy a core and how much?

No big deal, but I think the starters are different between BB and SB (staggered bolts versus straight across... You can also use your distributor...

Crack checking, its been a while, but it is very easy and only takes a few minutes on a clean block... The block would need to be pretty clean first, not necessarily hot tanked, but at least a good degreasing by you...

Once you go RAT, you never go back...
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'66 Convertible Sold
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post #15 of 71 (permalink) Old Jan 7th, 05, 12:45 PM Thread Starter
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Originally posted by 1966_L78:As realistic as it would be making 425-430 HP from a 396. The power potential of a 396 will NOT be that much greater than a 383 SB... And overall, the 383 might be cheaper...
So you're saying that it is going to be about as difficult to extract those numbers from a 402 as compared to a 383?

Quote:
Honestly, for the $500 is the guy including heads/crank/rods or is it just a bare block? How much does he want for those pieces? How much is the "high-dollar" 454 core selling for?
Yes this engine does include the crank and heads. I'm not sure about the rods. I will need to ask him. He probably still has them.

I would not know about the "high dollar 454 core". I do not know of anyone off hand that has one. I've looked with no luck. I was even hoping I'd find an old Caprice or a pick up for sale somewhere nearby with one in it that but nope...not to be found. I'm sure they're out there but it wouldn't be locally. No I'm not willing to travel across the country for an engine.

Quote:
Have you placed a "wanted" add on Team Chevelle? Have you asked the local Machine shops if you can buy a core and how much?
Yes I just did, hopefully it will be someone local with a good core and not someone in California with a junk core. If it's not local I'm not interested. I found this out first hand when I first placed an ad on here for a car.I mentioned local sales only. Sure got alot of responses from people many many miles away.

The other thing I am worried about is what if I do shell out however much to buy a core and have it crack checked and then they say "We're sorry to say this but your block is junk." Then wouldn't that put me out of some $$?

I would be suprised if any machine shops around here had any 454's, let alone any big blocks.

Oh yeah,how am I supposed to bring a core home? I don't have an old junk truck to haul the silly thing in. That and how much weight we talkin?

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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