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Old 05-23-2008, 10:33 PM
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400 Mouse Motor

I have a factory 2 bolt main, 400 Chevy small block with a blown head gasket, this engine is factory too my 1973 Caprice Classic it has 87,586 original miles.
I will be replacing the heads with a set of aftermarket due too the fact that the originals are cast thin.
I want too get the most out of this motor without boring it at all the cylinders are fine but I will have the block magnafluxed,decked and squared and any other machining necessary if you can suggest any other machining it would be appreciated.
Now the heads what should I put on my baby also will a stock 327/350 cam out of a 69 z-28 make my engine perform better another question can I put longer rods in like 5.7 and run it without changing my crank.
I will be changing the distributor as well who makes a reasonable set up for me and last but not least I want too change my cooling system meaning the radiator also install an electric fan.
My suggestion for heads were 305s with steams holes drilled for higher compression using flat top pistons would I be better off another direction?
Would 350 heads be better with the steam holes drilled for more power?
I appreciate everyones advice,by the way I'm no mechanic so I would be needing very specific advice I appreciate everyones patience.
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Old 05-23-2008, 11:54 PM
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Engine Building 101

The 400 is a great motor, hold on to that one.

If you know the motor is good to begin with you really don't have to have all that machining done to the engine. I might have them Bake the block and Jet the engine block (Clean), Magnaflux and then Deck the engine block surfaces .010-.020

Alot of the changes that your talking about require alot of work.

Here is a set of heads and camshaft to use with the engine that will give you good perrformance and really peaky performance and lots of low end torque for burning rubber.

Flat Tappet cam GMPP PN#24502476 110 lobe seperation, I:435, E:460
Fast Burn Heads GMPP PN#12464298 .530 max lift, Dual intake bolt patterns for vortec or older pre-86 engine intakes and dual valve cover bolt patters for both center bolt and perimeter bolt covers.
1.6 Roller Rockers PN#12370839 changes lift to I:.464 E:.490 (Self aligning), (Note: That you'll need rockers covers to clearance the added rockers 1.6)
Valve Covers PN#12497978, Added clearance
Gasket Kit PN#88958694 (head gaskets, oil pan gaskets, crank seal, intake gaskets, valve cover gaskets, outlet and fuel pump gaskets, and distributor gaskets) Note: Other parts will be needed
Intake PN#12496820 (Dual carb patterns, vortec pattern, EGR passage, High flowing, Dual plane(All around performer of the torque and HP curve))

Have a blast, do you homework.
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Old 05-24-2008, 06:30 AM
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moving to engine forum
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Old 05-24-2008, 12:04 PM
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As far as heads go, I'd find a large chamber (72cc-76cc). Depending on how much you want to spend, will make a big difference in what you're going to get. If you're keeping it in your Caprice I would not put too big a runner on. A buddy of mine has a 406 in his '84 caprice with AFR heads etc etc etc, and it runs 10.0x 1/4 mile. Too funny. Anyway, keep your intake runner in the 180-200 with a dual plane intake, an HEI would be fine. The 400 is a forgiving motor in the cam department for what I think you are looking for, and I have done them in big bombers like yours with 218-228 dur / 450-480 lift / 112-114's with very good results. The fast burn heads will work but you will need a rather large dished piston with that 62cc chamber. You can find good, or better heads for less, or little more than the GM units. IMO, if you are having the block machined, it might be a wise choice to get the whole engine-lada, and bore the cylinders too. I can't see that as costing you much and would insure a better overall build. Then, you can get pistons that'll work with a 5.7 rod - if thats where you want to go. Talk to your machinist about this first as your cylinders may be OK. What kind of budget are you working with? I had a '72 Impala with a warmed up 400 and it was a whole lot of fun. I ended up yanking/building that motor for a '79 camaro, what a rush!.
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Old 05-24-2008, 02:08 PM
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I agree on the shortblock recommendation. Do a compression test If you get pretty even compression across the board, keep it as is.

Once you disassemble it, it almost has to be overbored. Putting new rings in an old bore is kinda like putting new lifters on a flat tappet camshaft. Over those 80k miles you have altered the shape of the bores. They likely have taper, runout, and are eggshaped by a few thousandths. The rings have worn with them and retained seal... that's their job. Puting new perfect rings in used bores often times makes a very poor seal. Even if you document where the old rings came out and re use them, the chances of getting a good seal are very slim.

Its one of those things where if you're going to the trouble of disassembling it, its $30 to tank it which requires cam bearings for $50. Then an overbore is only $150, new pistons are pretty cheap, new rings aren't bad.... pretty soon you've remanufactured the entire block for $600.

But, like has been said, if its fine - its fine. Use it as-is. There is no benefit to tearing it all apart if nothing is wrong.

Last edited by curtis73; 05-24-2008 at 02:13 PM.
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Old 05-24-2008, 02:34 PM
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Quote:
Originally Posted by Hustles365
will a stock 327/350 cam out of a 69 z-28 make my engine perform better another question can I put longer rods in like 5.7 and run it without changing my crank.
On the cam; chances are slim that it will make more power. The cam in a 69 vehicle was hot technology in 1969. Cams today are insanely more advanced than the technology they had 40 years ago. You also can't use a used cam unless you keep the same lifters in the same holes. Even so, tiny variations in lifter bore location could mean a chewed cam in 20 minutes. For the $200, just get new. Also keep in mind that the big HP numbers in that 69 Z are gross HP numbers. A 350/350 hp engine in 1969 would measure about 265 hp on a dyno using today's SAE standards.

On the rods; its not the crank you have to change, its the pistons if you want longer rods, but rod length has shown to have very little effect unless you're finely tuning this for race.
Quote:
I will be changing the distributor as well who makes a reasonable set up for me
Pertronix makes a flame thrower ignition, or you can replace your points with Pertronix's Ignitor module that converts it to electronic. Any post 74 chevy SB or BB should have an HEI that you can drop in. Whatever you do, you'll find that the voltage going to your points and coil is only about 9v. Its usually a resistor wire. Find the section of wire that is resisted and replace it with new regular wire. They did that to prevent rapid wearing of the points, but with an electronic ignition you need full voltage.

I've also used Mallory distributors and disliked them greatly. The shafts on their billet HEI have so much flex I lost 2* at redline. I know it wasn't the mechanical advance malfunctioning because it was welded closed. Avoid Accel products in general. MSD makes good stuff. I've never used their distributors, but hear good things about them.
Quote:
and last but not least I want too change my cooling system meaning the radiator also install an electric fan.
Do a search here for the keywords "electric fan overheat" and read before you buy. The stock mechanical fan is a beacon of simplicity, works well, and its cheap. Electric fans (if not done properly) will either be too little flow at idle, or too much of a restriction to flow at highway speeds. You run the risk of spending $400 on a system that constantly lets your engine overheat versus keeping the stock system which you know works and its free. The 400 has siamesed bores which already put it at a slightly higher risk of overheating. Don't cripple it any further. Putting your mechanical fan on a good stock thermal clutch uses surprisingly little HP, but works like a charm. Besides, whatever hp you gain using an electric fan, you lose most of it driving the alternator to power those fans. You might argue that Chevy does it with electrics all the time... which is true, but they have multi-million dollar budget to design a successful system that only has to cool stock HP levels. You have $500 and one shot.

Quote:
My suggestion for heads were 305s with steams holes drilled for higher compression using flat top pistons would I be better off another direction?
Would 350 heads be better with the steam holes drilled for more power?
I appreciate everyones advice,by the way I'm no mechanic so I would be needing very specific advice I appreciate everyones patience.
It depends on which 305 heads. Some of them had the same ports as a 350, but it was inadequate for either engine. On a 400, serious porting would be in order for decent power from either head. The best production head that fits your application is the Vortec head. It outflows anything they ever put on any SBC from the factory ever. Avoid heads from TBI vehicles. They flow terribly and take a lot of work to fix.

The vortec head would work nicely on a warmed-over 400 with a very mild cam. They would run out of breath at about 5000 rpm, but that's a heck of a lot more than you get now.

Last edited by curtis73; 05-24-2008 at 02:41 PM.
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