Man, everytime I think this bird is finished..... ugh.


Had my engine out a few months ago (mechanic pulls it, I don't) to paint, replace rear main seal, coat headers, etc etc etc.

Starting a couple of weeks ago, rattling/tapping noise in the bottom end above 2k RPM.

We all suspect main bearings or wrist pins. Engine comes out next week.


My engine has been looked at, but not thoroughly thoroughly gone through in the year I've owned it. It runs well, sounds good, and moves pretty well - considering its age, its poor dyno results, and the THM400 + 3.08.

Engine, intake manifolds, heads are stock. Headers and mild cam are not.

Anyways. It is coming out.
At one end of the spectrum of consideration is repair & cataloging the parts. The other end of the spectrum is a 461 stroker kit. A different spectrum entirely is a new engine.

If you had to pull your original 400 for major surgery - would you do the minimum repair and throw it back in?
Or would you take that as an opportunity to work it up a bit? What would you change?

I would take it back to the same guy who had to replace the seal. How many miles since he did the work? Sounds as if he may have done something to accelerate this issue.

Did you do anything to precipitate the knocking? a high speed manual downshift? Anything?

A wrist pin is usually noticible under load. What may work is removing plug wires one at a time to see if the symptom ceases on the suspected cylinder.

As far as any upgrades, you have an original engine correct? I wouldn't go hog wild as if you grenade your engine and it's unrepairable, you will lose alot of value. When was the engine rebuilt last? Do you know if you are running stock compression? Cam?

I would start with why it's broke and go from there. A good set of forged pistons with valve reliefs for 72 cc heads and a 9.5 to 1 CR is a good start.

I am quite upset that certain things may not have been investigated when the engine was out.
In my ignorance, I simply requested that my mechanic "investigate all things that should be investigated while the engine is out."
Nothing was cataloged, nothing was measured, no tolerances checked. Just a timing chain and gaskets.
That was probably 800 miles ago.

Engine, intake manifold, heads, transmission = original. Mechanic had said last time that the engine "is clean" so it is probably bored 30 over. Mild cam but don't know what it is.

Definitely starting with "why it's broken" - but not sure how far to push it from there! I am weary of stroking the original engine... But am open to upgrading the quality or performance of moving parts in the engine. Open to getting the heads machined as well.

could be several things causing the noise that may not be related to a bad bearing. Cracked flex plate, broken winage tray etc...

If you do have a rod bearing bad then the choice has been made for you. If its something simple I would just fix and have fun. You will have many thousands in a stroker by the time your done.

You do have to loosen/remove the main caps to replace the seal correct? If the mechanic that did the seal re-torqued the caps incorrectly that may be the culprit.

Would be my guess without seeing it first hand....

What does that end up causing?

Here is a picture of my engine upside down on my eng stand. The rear main cap is still on. The seal is under main and embedded in block under the crank. If I had a bad real seal and the engine had not been rebuilt for many years I would have pulled the engine for a rebuild.

All the mains and crank have to come out to replace the rear crank seal. That means disconnecting all the piston rod caps. Mixup the caps and you get piston rod slap (out of round rods).
BEEN THERE, DONE IT.

I would do a stock rebuild of the existing engine.

Thanks for the detail, Gus

Mechanic gave a listen to the engine and has a thought.

Happens warm or cold above a particular RPM (around 1700 right now)
Sound is not at the ends of the engine
Middle/center deep sound (listened from bottom)

He thinks it is definitely a connecting rod.

Ugh...

If the rod is indeed bad

I think you need a PPR 428 lite stroker kit

http://www.pacificperformanceracing.com/products/cranks-rotating.html

Just my .02

The sound level should change depending on how thick the oil is. Most times it is loudest when the engine is hot (thin oil) and at an idle (lowest pressure).

Even a badly worn bearing can be quiet when the engine is cold - and badly worn in one case was about 0.030" clearance! Three or four thumps at start-up (piston was hitting the head) then quiet again until it was warmed up.

If this is the mechanic that did your seal I'd stay away from him. He is going to drain your dry with little fixes.

Second that!!!!

X 3

Alright. So... I'm still on the fence...

Here are my options... and all of them involve pulling the engine:
(Refresher - engine looks clean as of last pull, probably a .30 over already - rod knock noise now)

1. Find a machine shop which will just do the minimum repair (having trouble finding a shop that says they will just replace a broken part without "going through" for $2500)
2. Have a machine shop do a $2500 "go through" the engine (and do I pay the extra $400 for dyno w/tuning?)
3. Go thru engine & port my #16 heads
4. Go thru engine + do rotating assembly
5. Go thru engine + new heads, new intake.
...any other combo...


Also... how much of a cam have you been able to put in without losing manifold vacuum?
I have power breaks and a mild cam, 16PSI of vacuum at the intake.

I would tear it down and have it completey rebuilt IMO.

Otherwise, this thing is going to nickle and dime you to death to well over $2500 and when you are still having problems, you will be kicking yourself in the [censored].

Why don't you go see Pontiac Dude (Ken Keefer) in Brooksville? He is a great guy and straight up. He won't screw you and his reputation is excellent. One of the best builders of Pontiacs around.

What would I do? Depends on the servicability of whats existing and what you want to do. Unless racing the car, leave the heads/porting alone. A stock rebuild with quality parts (Comp Cams, Ferrea, TRW forged pistons) will do just fine. Maybe get new rods and have the rotating assembly balanced. $2500 is a drop in the bucket for a 400. A complete rebuild will vary greatly depending on what is needed. Costs can add up quickly.

You could always keep your original heads stock and purchase another set of heads that have already had the work done to them. In fact, I know of a good set of heads with a negotiable price.

Got a quote from the machine shop:

$3248.72
- New pistons
- New rod bearings
- New main bearings
- Turn crank
- Valve job
- Magnaflux heads
- Clean heads
- Recondition rods
- Put pistons on rods

----

Dyno would be an extra $400

----

If I decide to port the heads and change valve sizes - $800
Cam - $??
If rods need replacement - $??

----

He could put me into a Chevy 400 for $4500... or a powerful 350 for ...more...


I like the idea of sticking with my original Pontiac 400.

It is just crappy to spend $4k to get rid of a noise...

That's why someone created engagement rings...

What is the breakdown? Heads/Block.

Did they give you a breakdown on pistons/rings brand...etc.

Estimate sounds high. Has this guy rebuilt Pontiacs before? If not, I still recommend Ken in Brooksville. There is a difference between generic engine machinists and Pontiac only machinists.

My friend just got his 400 redone with new Ferrea valves, Scat rods and Diamond Pistons for $3,350 with new guides (not knurled) and a SERDI valve job...Sunnen torque plate bored. New COmp Cams Springs and Cam as well.

2nd that.
Dude builds all kinds of engines, but Pontiac is his 1st love.
Kens Speed & Machine Shop.
Call before proceeding any further!
Phn# 352-796-8800

I had much of the same work done, less turning the crank and new pistons, and I was 1/3 that cost.

I cannot imagine what costs $3200, must be gold plated pistons.

Ken hasn't returned my call...
I mentioned him to a mechanic that owns a few Pontiacs here, and was a customer of Ken's... he was very strong in his negative opinion, unfortunately.

Could be bad blood? Things happen.
Can only say from others experiences.
Many from PY have had engines built.
Only heard once someone had a prob, and he took care of it.

I worked at my friends machine shop for many years. Here are a couple things I can tell you.

People don't want to pay for what they need. Getting an engine built or heads done is not like buying gas at BP for 3.49 a gallon or a vaccuum cleaner for $439. There are MANY variables in an engine rebuild...some are known (cleaning block/magging/Bore/hone, hanging rods) and some are not..main alignment, head milling to true deck. There is a set price for the general services and the unknown are reuse valves, knurl guides, align mains, excessive head milling...etc.

Some people (may I say many) don't understand that a reputable machinist/speed shop can't give you a firm price until the work is finished because of those many variables. Yes, parts cost "X" and machine labor is "X" but there is the variable "X" I always use for "what if's"...So..the "what if's" I typically say 30% over a quoted rough estimate just in case.

You can use name brand parts or you can skimp and use parts that aren't so expensive. The difference between a very good replacement spring and valve (stock replacement Fererea 5000 and Comp Cams springs, nothing fancy) versus a marginal spring and valve is roughly 20-40% in cost difference. Well, this equates to maybe $40 on the valves and $30-40 on the springs. To be honest, I would go with the better stock replacement and do it right once.

These variables transfer to the unknowing buyer/owner who knows little to nothing on how things go in a speed shop. If a person who doesn't do his homework and doesn't know what to expect as far as lead time, completion time, costs etc...will become miffed, aggravated and downright inconsolable. Yes, the relationship between owner and builder is very important...that is why one must understand the workings AND the elements and variables required to build what the owner wants. Communication is the key.

The most irritating thing about people wanting an engine built? Unrealistic, cheap, undecided/changes mind.

People come in with a greasy GTO engine wanting a complete rebuild by the Woodward dream cruise 6 weeks away. Really? There are other people waiting in front of you, plus, the engine has to be torn down, cleaned, inspected, bore measured then pistons ordered. That could take 2-4 weeks before we even ordered one part. Completion time depends on time of year and what is on the books already. The block/heads ready, now crank has to be taken to another shop.

Cheap...Well, most, if not all reputable shops do not and will not use off brand hard parts. Why? Reputation. You may think you did your homework...and know what should cost what...But I will tell you this...No decent machinist will install junk in his motor...in YOUR motor...Thus the price you think you should pay is 40% higher for the correct proven name parts.

Now we get to undecided/changes mind. Once all the parts are ordered...block machined to clearance for "X" piston and ring...and whatever else...People always come in and say I wanna do this to my block, heads etc...I just read, I just heard I just seen this car and the engine rocks. Well, It is not that simple...to change most anything after the process has begun. A basic rebuild is just that. Machine to tolerances and match parts to those tolerances, assemble and go.

I don't know why your friend has an issue with Keefer. I would like to know exactly what happened, when, why, and whatnot. It's a 2 sided story...your friends and Keefer's. Ken Keefer is in business to build Pontiacs...he built a name over a long period...just as Bischop, Butler, Nunzi, Spotts, and Taylor have...I think there is more to this dissatisfaction than what he told you.

You could always send your engine to Bruce Fulper at Rock and Roll Engineering...I heard he makes serious horsepower *snicker*

Off my soapbox.

Thanks for the information

New mechanic.
Wow.

Witnessed disassembly of the engine yesterday.

- Tons of metal in the oil and sticking to various parts
- Oil was metallic silver in color... like some kind of paint or dark mercury.
- Rod bearings trashed (through the 1st layer, through the copper)
- Main bearings trashed
- Cam bearings trashed
- Cam has some etching into it
- Rod has some etching into it
- Found a stamp that says "1978" - guessing it was rebuilt then? 33 years since a rebuild... but...why only 10 years after it was originally built? Sounds too soon.



















Can't figure out the exact cam specs:




Hits a machine shop Monday...

Looks like your on the right track now. Good luck!

Well now you know why it was making noise.

Why only after 10 years was the engine rebuilt? Good question.

More importantly, why did those bearings fail..At some point the engine could have been run a long time without an oil change or detonation could have thrashed the bearings. From the piston top, those are stock 6.7 cc pistons. You need to run a blend of fuel (93 and 110) to prevent the detonation from hammering the rod bearings.

What heads are on the engine?

The original Pontiac 16 heads are on it.

Under my watch, I have heard no pinging.
I always run name brand 93 octane.


It isn't normal for bearings to wear down after 33 to 43 years?

Stock pistons? We suspect the engine is 30 over already, based on the fact that a machine shop must have rebuilt it in 1978...
Are you certain they are stock? Are they compatible with a 30 over (406 CID I think?)?

Is it normal for the pistons to have such a collection of carbon or whatever on the top?

Thanks!

Also... any idea what cam that is?

those pistins are aftremarket cast pistons not factory and your looking at the wrong end of hte cam. your bearings had inadequate cleaence and your pressure was too low

Pistons look like Badgers to me. Cast replacements. Clean off the top of one and look for size stamp(.030)

MY new pistons are TRW and look exactly the same. But there is a big 030 stamped on the face. Can't miss it.

Engine is back and assembled. Going in tomorrow.

They honed the cylinders (which were already 30 over), machined the heads, did valve jobs, installed high power oil pump, new timing gears & chain, turned the crank (20/10), sized the pistons, new bearings, new cam ("one step higher than factory").

In the meantime, I picked up a Monster Transmissions 200-4R (built to 550hp and 500tq), a lock up torque converter (1800 stall), and a 3.73 (had THM400 + 3.08). Sidelining the original transmission in my garage.

Anxious to get back on the road! Very anxious to see/hear/feel the difference!

Wow. How much did they charge to resize those pistons?

Smartass....

Gonna kick some a$$ now! Good luck!