We can anlyze the heck out of this and there's just no way we're ever going to know. Yes, it looks like the ring gap was thoroughly checked and found correct, but I'm not confident root cause was found. Again, I think we've exhausted what we can reasonably take from the facts we have and just need to form our own opinions.

 

Looks like quite a few agree w/me that it was inproper end gap. As for the statement that the gap was 0.026; there's no way the gap was anywhere near that. He states it was checked, but by who - the builder? Conflict of interest here.

I am certain the root cause was ring gap failure. The piston ring became too tight in the bore. The weak point in the piston ring is where the gap is; which then imparts additional stress on the piston at that point. Looking at this piston, it was a brittle fracture with the top of the piston breaking upwards and away from the ring at the time of failure. The fracture plane rotates from 45 degrees or so at the ring gap, to the other side where it terminates at nearly vertical. This indicates the failure initiated at the ring gap. AL will fracture at 45 degree angles from the direction of the principle stress which is what is seen here.

Again, the builder blew it big time.

 

What transmission and ratios you using?

 

As you can tell by the car and tripower I am trying to keep an old school theme. I am running a 4.11 with an Autogear M-22 Rockcrusher. 4.11 x 2.20 first. Not the ideal 10 to 1 first gear ratio but with the power to weight ratio, all lightweight rotating assembly and 12.5 Lb Flywheel it should hook up better, still take off ok from a stop and pull hard in the 1/4 mile. I want to keep the engine in it's powerband and don't need to go 160 MPH. I really debated going with a TKO 600 with the .82 OD and a 3.70 gear and still might. I have a 3.70 rear in the garage and will see how the Autogear works.

 

I was inquiring about having my block machined. A shop told me they need the pistons in order to properly do the boring to 4.030?

Why?
Is this a sign of a good shop or a bad one?

If they are needed then wouldn't you have to do the same with a new GM block meaning it is not ready to go?

 

IMHO, this is a sign of a GOOD shop.

The primary reason for this is that each piston brand and P/N CAN BE a bit different in what they expect for clearances and the easiest way to be sure they don't bore/hone to the wrong spec is to have the pistons in-hand. Generally, your safest bet is to measure->buy parts->machine for the whole assembly.

Yes, you should be able to just bore to 4.030 since the clearance is built into the piston...but there will be some variances in the pistons, and they're just being careful to be sure they're not going to end up with an ugly tolerance stack.

Factory clearances are pretty broad - take a look in your service manual. We can - and should - do better with what we build.

 

Perfect answer. I work for a manufacturing company so I definitely understand how tolerance stack-ups can cause problems. I would agree that this attention to detail is a good clue.
Thanks!

 

I have made some decisions:
It seems that with a 350 you can get close to 400HP and good torque at street rpm's while still at around 9.5 CR.

Heres my 2 stage plan:
Stage-1 (Cake and eat it too)
I have decided to go with a 350 build. I guess .030 over means 355.
I will use the current original block, heads and intake. Have them rebuilt.
Find correct Q-carb and have rebuilt.
New cast crank - good to 500 hp
New Hyper or Hypo pistons (I don't undrstand the difference) -Good to 400HP
Maybe forged rods - if necessary? Need some input.
I think I can buy a complete rebuild kit from Summit with everything I need.
I will probably buy a Richmond 4 speed to give me around 10:1 at the wheels as I don't see any other way to get to 10:1. ($1500)
I know it will only produce low 300hp but I will see if I am happy with this set up next summer. I know many of you would not be but I might be because I just want some satisfaction going through the intersections. Total cost $5000-ish
The big benefit is I will know the correct parts work well with the short block.

Phase-2 (if not satisfied with Phase-1)
Remove and store the heads and intake. Again knowing they work fine for future value.
Buy AFR 180 heads? and probably a Edelbrock intake. Maybe another carb., Demon, Holley, etc.
This will get my HP to 375 to 425. (Thats what many magazine articles say is possible while still getting very good street manners.)
Still buy the Richmond trans.

The main thing is the bottom stays the same either way making it easy and economical to switch.

So the big question: Where's the cam in all this? This is the last big question to be answered. I am wondering if I can use the best cam for the Phase-2, in the Phase-1. Will it idle fine, perform as well as the best choice for Phase-1 and not cause trouble or burn excessive fuel? If so, if I eventually choose to go to phase-2 it will most certainly be easy without having to pull the cam.

So, I need input to all above, especially the cam idea. After that Input we can get into cam selection as I already have some ideas.

Thanks in advance!
Alan

 

I'm for stage 1 if stage 2 does not include the new 4 speed, really
I'm for storing the complete numbers matching engine, buying the
new 4 speed, factory blocks and heads can be bought for not much money,
keep the numbers matching stuff in a corner of the garage for later resale.
As far as heads if you go aftermarket the brodix IK180 will flow way more
air then what your HP goals are for $1050.00 the AFR180s will cost you
$1400.00/$1500.00

 

I will have the Richmond 4 speed in both phases. I'll have to check out Brodix.
So Little Mouse you say don't put any money into the numbers matching parts. Just keep them and do whatever makes sense some day down the road. For now build up an engine from new parts. That way I don't have to spend money on machine shops, it can go to good parts.

 

If your going to use a different crank, heads may as well put the
numbers matching block, heads, trans all to the side.

 

Then what new small block would you recommend?

 

This is from GMPartsDirect, A forum sponser. It can accept a Factory style roller cam and lifters, 4 bolt main, Under $700.




GM PART # 10105123
CATEGORY: All
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $950.00
OUR PRICE: $691.60


DESCRIPTION: 350ci Bare Block
This engine block is used in 1986-99 Gen I heavy-duty applications. It has 4.00" diameter cylinder bores and four-bolt main bearing caps. This block is machined for a one-piece rear crankshaft seal. (Does not include rear seal or adaptor.) These blocks weigh 181lbs. Technical Notes: Cylinder wall thickness is the same as current production engines. The lifter valley is machined for hydraulic roller and flat tappets. Crankshafts with two-piece seals can be installed with adapter P/N 10051118. (Block casting P/N 10243880 or 14093638.)

 

Decisions are good - you've done a great job of sorting through some hard choices.

400HP is a bit of a stretch for a mild 350 without sacrificing some level of driveability IMHO.

Stage 1

• "Hyper" and "Hypo" both refer to hypereutectic pistons.
• If you're buying a new cast crank, the price of a 383 crank is
  exactly the same
• Generally, it's cheaper to buy new rods vs. reconditioning the old ones with new bolts. At this power level, an OEM-level rod with ARP bolts is perfectly acceptable.
• This shouldn't cost $5000

Phase-2
I'd think more around 340-360 HP at the flywheel for this combo. Remember that the magazines typically publish dyno specs with no accessories, an electric fuel pump and dyno headers with open exhaust.

The cam is the single most important buy as you've noted. I would consider a relatively mild flat-tappet cam for Stage 1 and plan for a swap to either a more agressive flat-tappet or hydraulic roller cam for Stage 2.
[/QUOTE]

 

A BRAND NEW factory roller-cam capable block is about $650 from the General.

[EDIT] I just read 63mako's post and that's the one. I almost exclusively use these new blocks now, as cores are such a crap shoot any more. Note that these let you use the factory roller cam setup, which is (relatively) dirt cheap and good to .525 lift at the cam. This is about 1/2 the price of a GEN I retrofit roller cam kit from CompCams or Crane.

 

Starting with a new block would be good, the 10105123 block has the advantage of being made to accept a hydraulic roller and it uses the
one piece rear seal, only disadvantage to it the one piece seal cranks
the ones I have seen are external balance that would cost you some
more money for another flywheel and balancer. this block is a new
version of the old two piece 10066034. I know chevy made a large
journal 327 in 69 because I used a 69 large journal 327 crank to build
a .030 over 331. If a 68 has a large journal block it may be hard to come up with another one to numbers match your car.

 

Thats what u need to ask that shop. The shop does not need your pistons to bore the block - only to hand hone each piston to an individual hole (rare these days). It sounds more like they want u to buy the pistons from them.

If u want to save money and are only looking for 1hp per c.i. then just use your old block and crank. Why do u need a new crank when u can recon your old crank for half the price. BTW a used seasoned block (once machined) is better than a brand new block that will change diminsions once temp cycled.

Why do u need expensive AFR heads with big port and big flow numbers that u won't use? Are u going to run a 0.600" lift cam? More like 0.500" lift is reality. Learn what pocket porting can do for less than $250. Pocket porting and unshrouding the vlvs will get u most of what u want. Big port heads with big flow numbers do little for a mild cam, moderate rpm combo.

Nail your c.r. first and thats <9.5 for iron heads (<10.5 alum). U need to choose/measure your head chamber and pistons for this. Then look for a cam. Shopping for a cam without knowing the c.r. is guessing and u will be dissipointed like many other on the forum. Sorry if the truth hurts but at least u can deside for your self now.

cardo0

 

The truth hurts sometimes, but wrong info and dead ends hurt more. So please don't hold back, as long as it is constructive.

 

One-piece cranks are typically neutral in front and require a weighted flywheel in back. A two-piece seal crank has a flange on the back for weighting, but the one piece must be round to seal so the weight gets pushed to the flywheel/flexplate.

Once we start talking about replacment cranks, we come back to the idea that the best buy is a pre-balanced kit from a single manufacturer...

 

Respectfully disagree with most of Cardo0's points, but 'nuff said I do agree that usage drives the cam, and the cam drives the heads...and we build the engine around these two parts.

As a reference:

Crank machining prices in Seattle:

* Crank clean and mag: $45
* Grinding: $145

= $190. Balancing a complete ***'y goes for about $275.

A two-piece, internal balance cast SCAT crank sells for about $169 on SUMMITRACING.COM.

Bringing a "seasoned" used block up to snuff:

* Thermal block clean and mag: $137
* Pressure test: $60
* Bore and hone: $198
* Align hone: $181 I usually see this as optional if reusing the crank
* Resurface deck: $98

= $675.

I know a lot of shops do prefer a "seasoned' block, but I'm just seeing it harder every day to find decent cores and at $135 apiece to find out they're junk you can end up on the wrong side of the economics pretty quickly. IMHO the risks and costs outweigh any potential benefits.