4-vettes

Sounds like a plan. Sorry you found that crack. Sometimes it works out this way. Sometimes we win.
At any rate. The 406 with a little rework sounds great!

augiedoggy

Ok so I went to look at the 406 im buying from a friend of my aunt and late uncle.

I bought a cheap borescope camera to check it out for rust since its been wrapped in plastic since 2005 when coming back from assy.

Its a "817" 2 bolt like what I had previously bought..
it had "D" dish pistons on 5.7 rods that give only 9.2:1 compression with 64c head which is lower than Id like. (he built it for a 3/4 truck application)
The engine has 10k since the shortblock was originally built but it was refreshed by the shop with new bearings and rings when the 170 /64cc chamber etek heads were installed and he had the cam card that shows the comp XR270HR-10 roller cam was also installed.
Ironically this is the exact same cam I have in my 355 now and I was going to pull and likely install in the 406 anyway
in has crane 1.5rr on the edelbrock heads.

He told me prior to having the speed shop refresh.build it, That he noticed the engine would be kinda noisy when cold like piston slap which went away when warmed up and he never knew why. He said he believes they are hyper pistons. I guess the new roller cam and heads were the reason it was pulled he said he has the original cam I can have too which tells me at least it wasnt wiped.


My plan in to pull the heads and swap them with the ported 195-200 /64cc chamber heads that I build for my 355 and put the edelbrock heads on the 355. i'll be running an airgap clone manifold i'll port match to the heads for whatever its worth.

I havent had luck finding any thin shim gaskets for the 400 block so I'm considering breaking the engine down and having it decked to bump the compression closer to 9.7-8:1. Is this a good approach? Any disadvantages to doing this?

The engine was stored in a dry garage and theres no rust in the bores or anywhere that I could find.

I will be paying 3 grand and that includes delivery. it comes with some spare parts like a 650 edelbrock carb, a performer intake and polished tuff stuff water pump. also an hei without tach drive I wont be using

And in case anyone wonders the truck he had the engine built for ended up getting wrecked while he was driving it with a 350 swapped in. He held on to the 406 engine with aspirations to install in a later 86 3/4 ton he bought to replace it but he ended up being happy with the engine that was in it and never motivated enough to do the swap. He tells me he got the engine out of a 74 chevelle or malibu (I though 73 was the last year) and he said the ironic part was he bought the car for like 700 bucks because the engine was stuck but after pulling the engine he found it was actually a starter bolt that was preventing the engine from turning over... He kept the engine and sold the car with a 305 installed to fund buying the truck.

augiedoggy

I was also eyeing up this summit cam with the ls firing order which ive read helps with crank bearing wear but not really sure if I would value the torque from the smaller comp cam more than the higher rpm hp ill likely never really utilize on the street.

https://www.summitracing.com/parts/sum-1223
The comp cam I have now will peak hp at 5000rpm (around 430hp potential) and deliver a peak torque just shy of 500lbs at 3500rpm... This is with the lower 9.2:1 compression id like to raise.

The more I think about it I believe the comp may be best for my actual combo with a 2004r trans and 3.55 rear gear for spirited street use.

MichaelCar001

In this situation, I’d start by doing a thorough inspection with the right tools, and maybe even getting advice from a pro. This will help you figure out if you just need to re-ring and hone or if you need a bigger rebuild. This kind of groundwork is key, especially if you're planning to build a reliable, high-performance engine.

augiedoggy

I know its confusing because Ive decided to abandon the short block in the photos I started with due to a cracked block but this engine has been gone through and rebuilt by respected a local speed shop and I do trust the guy whos selling it to me as hes a family friend. I approached him about buying it.
As far a performance I think 425-450hp is a pretty mild goal for a 400 with decent flowing heads and a mild cam but I could be wrong and its why im here.

I will be at least replacing the heads and timing chain cover on the shortblock along with the oil pan so I will be checking the bearings and surfaces then just to see things with my own eyes... dyno software tells me decking the block would give me potentially about 13hp and 12lbs of additional torque not really sure if its worth ripping everything down for that. Or is there other gains? I know the downside is needed premium fuel which ive been living with for the last 12 years already with my 10.1:1 355..

augiedoggy

so Ive been doing some reading and one of the things that can cause the piston slap on a cold engine is excessive piston clearance in the bores... hmm

I did notice the pistons were completely clean when looking with a camera but they could have just been cleaned and not replaced by the speed shop when they went through and rebuilt it. This does concern me a bit as its already 30 over. I guess the dial bore gauge might come in handy afterall.

Bikespace

Have you done a leak down test? Can you fully inspect it before you buy it? That might mean pulling the heads.

augiedoggy

Its on a wooden cart.. no leakdown. it was still sealed up in plastic when we pulled it into the light to look it over. I inspected each cylinder with a borescope camera and they crosshatching and pistons looked new. Other than that no..

I did pull a valve cover and see the gold crane roller rockers which appear new. Theres evidence that it was test run after being build as there was some oil pooled under the valve covers.

The guy has no reason to lie to me the only way I found out he had it was through a conversation I had with him at my uncles wake when I happen to mention I wanted to build a 400 for my car. at that time he had no idea of the details of what size chamber heads where on it other than them being 170cc edelbrock heads. nor did he know what pistons. So I assumed they were flat tops which would not work with my heads.

I know the heads sell for about a grand each and the new roller cam and lifters arent cheap as they have increased quite a bit since even 2 years ago when I installed them in my 355. I know the speed shop that assembled it is still in business and I would like to believe they wouldnt assemble something out of spec with issues but... I also believe when the guy did put the 10k he did on the engine, that it had the stock low compression heads. Also I believe stock cam.
I know he had steam holes drilled on the etek heads. He told me he had like 6 grand into the engine.... Seems kind of a lot in 2005 but who knows being the shop costs were likely a good chunk of it.

he said he has a "turbo 375" trans that I could have that he had build for towing in the truck with a long tail shaft that I could have for $100 also but I really have no use for it with the overdrive trans im installing. I assume that came out of the same chevelle/malibu..

torinodude59

Do yourself a favor take a look at the blueprint engines 400, 500hp forged rods,pistons and crank and a no go flat roller cam . As you are learning by the time you buy all the parts and pay for all the machining and having it sit for 2 to 4 months at some shop at best you would save maybe a couple thousand. Call summit it is delivered in a couple days and the motor comes with a 3yr 36000 mile warranty.

TommyFox

400 blocks scare me .My last one that was being built at the machine shop cracked as they torqued the last head bolt when I was standing there. Had to find another block and start over.

augiedoggy

See thats the thing.. that blueprint engine is like 7,500 after taxes and shipping which is more than twice the cost of what im looking at. If I had more disposable income and less time id consider it.

I built the engine thats in my car for less than a couple thousand bucks 12 years ago and ive been buying parts in recent years for it with the plan to use those parts on a 400. I only need a shortblock but machining costs alone to repair the block I bought are going to run my more than half of what I can buy this 406 for and ill have an extra roller cam and set of decent heads out of it to put on the 355 which along with my th400 gives me a decent spare drivetrain if I happen to stumble on another project like an old c10 pickup.

Bikespace

I hope it all works out for you, and it sounds like you will buy a pile of parts worth more than you are paying if it doesn't, so hopefully you come out ahead either way.

If you haven't already discovered these, Speedway makes nice rolling engine stands, for both LS/LT and SBC/BBC blocks (Amazon Link). If you can work out a way to bring a battery and starter to the engine location, it might be worth spinning it before you commit to buying. Of course, it might be easier to buy it and then sort it all out.

I pull heads on a proper stand, but the Speedway stands are great for compression/leakdown tests (without wheels) or for moving around a crowded garage (with wheels). Bolt it to a Harbor Freight lift table, and get the best of both worlds, and access to the transmission end.

augiedoggy

Well I took delivery of the 406 Yesterday. I pulled a head yesterday and discovered a few things.

It is assembled with ARP bolts which is good and the block has been decked to .005.
Everything so far looks great except there are Kieth Black 30cc dished pistons from what I can tell which are only 9.2:1 compression even with the decked block. the seller did tell me is was built for 9.2:1 compression but I assumed I could improve on it a bit with shim gaskets or decking
I may swap the pistons and rings.
It also has never been run since its last assembly as there is assy lube everywhere still.

kossuth

A lot of debate out there whether you need them or not. I’m not smart enough to know how necessary they are. My thoughts are if GM went through the machining process to put them in then they are needed. Easy modification to any set of heads though if you opt to do it.

Torqued Off

And what you will get is a large production build of unknown not-brand name components assembled by production type people and the result is an engine that may work well….or not. I’m not fooled by their marketing.

augiedoggy

I will be drilling at least the lower holes (I believe it was the lower holes jebby said were needed) and possibly both. I have to get them off my 355 which is still in the car ive watched a couple you tube videos on this now and it seems simple enough. compared to the risks I took porting the heads.

augiedoggy

Ok so lower holes were drilled in the etec heads.. pulled both heads, oil pan and timing cover. everythings still looking good but I noticed the pistons seemed kinda tight to me in the bores so I measured the cylinders quick with a caliper and got 4.150? the pistons are stamped 030 on the underside and I measured the dish with a syringe (30cc)
isnt a .030 over block supposed to be 4.155? really confused here.

The engine came with some paperwork mainly notes about the cam and the previous cam and mileage for oil changed and such which shows it has 12,600miles since initial rebuild and I can see the bores were lightly rehoned when reassembled during the cam /heads replacement

augiedoggy

Motorvation

4.125 +0.020 overbore + 0.005 piston to wall clearance…..4.150-ish…

Steve O.

augiedoggy

ok so could the 030 stamped in the bottom denote the 30cc pistons? Thats my guess then

I will pull a piston and check the diameter tomorrow to be sure. I spoke with the owner again about it and he said it certainly could be only .020 over because he pulled it from the original yellow 74 malibu himself and he only had it rebuilt once years later.