[NeighborsComplaint]

If it wasn’t factory built, I’d say compression rings installed upside down on the low compression side.

[srmmmm]

Originally Posted by NeighborsComplaint

If it wasn’t factory built, I’d say compression rings installed upside down on the low compression side.

Or one bank of cylinders didn't get their finish hone.

[ericwoo]

Originally Posted by chiphead

Having one side consistently at 150 and the other side at 190 is not cylinder sealing, usually. Its always possible something went through one side of a motor or the drunk uncle built one side, but that's a weird one-off.

I still say confirm the leakdown then pull the heads.

Originally Posted by Green Elephant

Hey ericwoo, not to pile on with too much information, but if it was me, this would be my plan of attack. Pull the engine, remove heads, have someone cc the chambers, check deck height as suggested below, check compressed head gasket thickness and p/n. Somewhere in there I think you’ll find the culprit for the bank to bank compression disparity.

Originally Posted by Formulas

They also smoke like a forest fire, no mention of smoke being an issue yet.

pressurizing cylinders with shop air with a novice ear and inaccurate tester means relatively nothing, air will escape you will hear it in a healthy engine, .. what matters is an accurate percentage reading then if that is to high you then care if its valves or rings by the audible

Originally Posted by steve25

Once again as I and many others have posted a few times, its high time to pull that head!

Busted rings and broken ring grooves in the Pistons will leave scratchs and even grooves on the cylinder walls

Originally Posted by Green Elephant

I think I saw Jay S mention something about an improperly milled deck height. I’ve seen this before, machine shops do make mistakes. Unless you checked it on assembly, I would check the deck height on both sides when/if you pull the heads. Even if the block wasn’t milled by the machine shop, I would check it anyhow. It’s very easy to do with the heads off and will verify if there is a problem.

Originally Posted by chiphead

Do not pass go, do not waste time on a leakdown, pull both heads and CC the chambers. A leakdown may help confirm condition of bottom end, but I don't think it's the root cause of what's going on here. It would appear that one head got milled and one didn't. Where did these heads come from?

Hey all, I finally got around to pulling the heads. Sure enough you are all right, they did not mill one side!

At first removal, I did a rough measurement with the calipers on one side of the heads. The driver's side head measured a whole 0.1" taller than the passenger side.

Then I CC'd them. Sure enough the driver's side head measured about 80 cc and the passenger measured about 60 cc. What a nightmare trusting others work- this has created a lot more work for me.

Hopefully, others will learn from my mistake by checking machine shops work.

What really bothers me is they advertise their base model D-port heads as being 65 cc. We paid them extra to mill it down further (which one side did get) but I am surprised the other side was significantly higher than 65 cc . Wtf!

Also, the cylinder walls looks very good and smooth, so I am hoping some of the air seeping out is normal. I will start by hiring a machine shop to mill down the driver side to 60 cc also and try running it.

Thank you all! While I am here, should I increase my valve size to 2.11/1.77 ? My current valves put on by Kaufmann are around 2.0/1.66 for my stock 350.

[Squidward]

Glad you found it!

IMO, I don't think you would see a benefit going big valve. I say this as someone using 2.11/177 valved #12's on a 350. My choice was largely due to availability: They had the right CC's for desired compression, they were ported/upgraded, they were priced acceptably, ready to bolt on, and they were local.

Big valves also will limit your cam lift. 2.11/1.77 are a lot of valve area inside a small bore circle. My setup hit an exhaust lift limit of around .510 lift.

Attached is a view from the crank side of a 72 350 wearing a set of #12's...

[Benziii]

What are the odds that 4 out of 8 cylinders have ring problems if its a wring issue.

[steve25]

Something still does not sound right / good here!

To take a 67 and up open chamber head down 20 CCs ( from 80 to 60 CCs ) requires a mill of .120" or a 1/8 of a inch!!

I personally have never milled a head more then .090", nor have I ever seen one milled more then .090"

I think I see head gasket or head cracking problems in your future I fear.

[Jay S]

You need to call KRE and have them make that head right, which will require a different head. Appears that one head had the wrong CNC (85 cc) chamber program when it was machined. They probably did milled it and brought it down to 80cc.

[steve25]

Disregard my post 86 please , I thought you had iron heads.

[HWYSTR455]

Doesn't the 350 block have bore chamfers? That might be a concern when going to a larger valve.



.

[VCho455]

Having talked with Kauffman several times before ordering my heads. There isn't anything to be gained by going to larger valves in a 350 bore size on a NA engine.

Does the 65cc head have an "as cast" combustion chamber? The KRE 65cc heads come "as cast" not with a CNC machined combustion chamber like the 74cc and 85cc heads. If it has a machined combustion chamber it didn’t come from KRE as 65cc head it was cut to that size like mine were.

[steve25]

In a wedge chamber like these have you can get 335 cfm out of a 2.11” valve, but not with anything less then a 4.150” bore.

[ericwoo]

Originally Posted by Squidward

Glad you found it!

IMO, I don't think you would see a benefit going big valve. I say this as someone using 2.11/177 valved #12's on a 350. My choice was largely due to availability: They had the right CC's for desired compression, they were ported/upgraded, they were priced acceptably, ready to bolt on, and they were local.

Noted. Do you think I would benefit from porting work? I read conflicting info about 350's if it is worth the work.

Originally Posted by VCho455

Does the 65cc head have an "as cast" combustion chamber? The KRE 65cc heads come "as cast" not with a CNC machined combustion chamber like the 74cc and 85cc heads. If it has a machined combustion chamber it didn’t come from KRE as 65cc head it was cut to that size like mine were.

The 80cc head came with heavily cast raised lettering "KRE 6500" and then very lightly raised cast number on the other side which I think reads "1395R" then a number 6 below it which seems to be printed on with two circles around it.

The 60 cc head also came with heavily cast raised lettering "KRE 6500" and then very lightly raised cast number on the other side which I think reads "04552"

Originally Posted by HWYSTR455

Doesn't the 350 block have bore chamfers? That might be a concern when going to a larger valve.

.

Yes, mine has bore chamfers. I think I read some of the 1968 blocks did and others did not. Not sure what month it changed.

Originally Posted by Jay S

You need to call KRE and have them make that head right, which will require a different head. Appears that one head had the wrong CNC (85 cc) chamber program when it was machined. They probably did milled it and brought it down to 80cc.

Right, so they probably took 5 ccs off both of the base heads like we requested but didn't realize the driver side was 85 instead of 65 cc?

It doesnt make sense that the cast numbers say KRE 6500 though.

Can't I just mill that 80 cc head down to 60cc to match the other? From what I can tell, it looks like the same head except taller.

[VCho455]

Originally Posted by ericwoo

Noted. Do you think I would benefit from porting work? I read conflicting info about 350's if it is worth the work.

The 80cc head came with heavily cast raised lettering "KRE 6500" and then very lightly raised cast number on the other side which I think reads "1395R" then a number 6 below it which seems to be printed on with two circles around it.

The 60 cc head also came with heavily cast raised lettering "KRE 6500" and then very lightly raised cast number on the other side which I think reads "04552".

What is your goal?
How much power do you want or can you afford?
How will you use the car also dictates whether porting would be a good idea. The KRE's are good heads off the shelf.


The KRE 6500 casting number is for the foundry to identify castings so they don't accidentally ship a ford casting to the Pontiac customer. KRE then takes that casting and machines it into their products. I believe that the basic KRE D-ports all have the same casting number unlike what you see from the OE's. I believe KRE stamps their heads for identification. I'd go look but my only set of KRE's are at the porter at present.

Also posting photos of the combustion chambers of both heads may allow the more experienced folks to determine if they started out the same size and one head had .050 thousands plus cut off od it or did they in fact they left KRE as mismatched heads.

Personally I believe that the difference in combustion chamber size was a result of machining at the machine shop. A friendly inquiring call to Kauffman would provide the answer to that question.

Where did you purchase the heads?

[ericwoo]

Originally Posted by VCho455

What is your goal?
How much power do you want or can you afford?
How will you use the car also dictates whether porting would be a good idea. The KRE's are good heads off the shelf.

A friendly inquiring call to Kauffman would provide the answer to that question.

Where did you purchase the heads?

This is good to know.

I am not getting into competitive racing or anything. I would just like something that has around 400 hp but I probably would be satisfied with 375 hp. Kaufmann estimated with these heads and the crower 60916 cam, I would be in that area. At the moment with these mismatched heads, I would guess it produces around 280-300 hp.

I am okay spending a few thousand dollars more on it, but considering we already spent a few grand to improve this engine being not much better than stock, I may just buy a whole new 383 stroker engine (or a 400 if I can find one) I saw online for that cost to get to 375-400 hp.

I'm in contact through email with Kauffman but I probably should call since the email responses are very vague. The problem with this is it was purchased directly through them 20 years ago! When I was young and dumb, I installed the heads and couldnt get it running right so I quickly abandoned the project until I got the motivation to get it on the road for the first time in 2024. Now I am just trying to figure out how to get it to perform like an actual muscle car instead of something to putt around on.

[Squidward]

Originally Posted by ericwoo

Noted. Do you think I would benefit from porting work? I read conflicting info about 350's if it is worth the work.

Out of the box KRE heads will flow better than standard iron heads. My ported iron heads were somewhere over 200 intake (210-220?), and under 200 exhaust. I'd have to dig out my flow sheet for exact numbers. KRE's are much better than that. Stick with the 1.66 exhaust valve.

So... If it were me, with your stated goals, I would run KRE heads without porting, minus the head mismatch. I also like the cam suggestion with the Crower 60916. You will need a little gear, and some stall to compensate for a little off idle squishiness, but I would expect by 2000 rpm it would start to scream.

What fun!

[ericwoo]

Hey folks, I finally got my heads matching in cc's on each side. Boy this project has been quite the hassle between dealing with the head manufacturer and getting it complete. Long story short, I got wronged a second time. Not happy about that.

Any way, the local machine shop ($325) got them matching to around 58-59 cc on each side. After reading Jim Hand's book, I then gasket matched the heads which was quite off. I am still learning what tasks are necessary when bolting on aftermarket parts.

Drove it today and it definitely has more upper end horsepower. However, it is still not streetable at all. The low end torque is surprisingly dismal. Not really fun to drive.

As many of you suggested my 60916 crower cam, Kauffman heads and RPM Performer intake isn't a good fit for the 350 engine. Jim Hands book suggested a much lower flowing heads to perform well on these smaller engines.

My question is, do you think I can still get my set up to perform well on the street by only changing the intake manifold to a regular Performer? Or am I **** out of luck getting these high flowing heads to perform well on my 350?

Since we already spent probably $4-5 grand on engine parts, it would be great to get this to work. But I am afraid most of it went to waste and I may just need to spend another $5 grand to get a 400

[b-man]

Get your car on a chassis dyno and have it tuned by a professional.

You might find quite a bit of power that way.

Maybe your jetting, timing curve and timing settings are way off.

Getting an oxygen sensor installed in the proper location and the gauge that’s part of the package may pay some dividends and will be a tuning aid.

That 350 should be a little monster not a pooch.

[Formulas]

Carb work... IFR. Transition slot .. Needs more fuel i bet.. That's what is in play from idle up to main jet and you have reduced signal..

Takes knowledge but is cheap doing it yourself

[HWYSTR455]

When you deck a block the chamfers get cut down, and w large valve heads it can be a problem. That's kind of where I was going with that. It's more of a problem with higher lift cams than what you have though.

There is nothing wrong with using an RPM intake on a 350, people do it with success all the time.

With larger runner heads it can lose port velocity with smaller displacement engines, but still think because of your lift you should be fine.

And good point some others have made that the power range will move higher with a smaller displacement.

I think you will be fine if you have a good gear, min 3.55s, 3.73s would be better, even 3.90s/4.11s for that matter, but you will lose some highway driving comfort.


.

[Squidward]

Agree that you should have a fun combo.

Your cam is only a couple of degrees more than mine, 221/229 on a 112, vs mine, 219/227 on a 112. My cam is a touch more lift than yours, but not a significant difference. Very similar.

I can't remember what cc's my heads were, but they were worked, and started at factory spec of 72cc. So you have some extra compression I don't have. Score one for you.

I run a knockoff of the performer rpm, the Crosswind, when it was made by Professional Products. I found it fit better than the actual Performer RPM I had, but it is almost identical except for the heat crossover. Call it a wash.

I run a th350 with 2000 stall converter. I also run 3.73 gears. These crutch the relative softness off idle due to cam, but it is not soft in the way you have described. It screams after that. You have more stall, and 3.55's.

Your timing curve is very similar to mine. I like manifold advance, but that only matters at idle.

I'm just trying to make as much apples to apples as I can. I think your combo sounds very cool.

I agree with previous posters, gotta look at fuel or timing. Did the cam get degreed? What kind of idle vacuum do you have?

I see nothing wrong with your timing curve as long as it was set on a balancer that had accurate timing marks. My best guess is cam timing/timing chain, or carb not set up right. And an out of the box Holley 600 should be a very good starting match.

But don't discount the differences in butt dyno's. Your expectations and definitions for streetable might be different than mine. I am totally happy these days with a 14.0 second car.