[steve25]

Why bother shelling out money for a leak down tester?
Your to the point now of having to pull both heads to find out what’s going on at least in my mind.

Even if you did a leak down tester and it pointed to valve leakage, then you’re still yanking that head at that point anyway.

You lower compression on that bank is so even that I can’t see it being due to rings, so that leaves the head as the cause.

[ericwoo]

Originally Posted by steve25

Why bother shelling out money for a leak down tester?
Your to the point now of having to pull both heads to find out what’s going on at least in my mind.

Even if you did a leak down tester and it pointed to valve leakage, then you’re still yanking that head at that point anyway.

You lower compression on that bank is so even that I can’t see it being due to rings, so that leaves the head as the cause.

Good point, but wont the leak down tester show me if its leaking out of the head gasket vs the valves so I know what to fix when removed? I've never used a leak down tester- just looking into stuff I read online.

If it's a valve leak, is that most likely the valve stems that need to be replaced?

[Joe-Touring]

Originally Posted by ericwoo

Good point, but wont the leak down tester show me if its leaking out of the head gasket vs the valves so I know what to fix when removed? I've never used a leak down tester- just looking into stuff I read online.

If it's a valve leak, is that most likely the valve stems that need to be replaced?

Does your compression tester have a quick disconnect on it between the hose and gauge? A lot of the comp tester hoses have what’s essentially an air compressor fitting on the end.

All you’d have to do is screw your comp tester hose into the head, and hook up your air compressor hose to it. Then you can listen to the intake/exhaust manifolds to see if you can hear air rushing out

[johnta1]

The next thing I realized, is the pushrods are indeed a little too short. See the test I did in the attached photos

Do a test with the driver's side head rockers. Back them off 1/2 turn and see what the compression test shows for that side?

[Green Elephant]

Lots of good suggestions by others. In my mind the compression difference from bank to bank is a big red flag. Particularly with all the cylinders being so close to each other on each bank.
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.
Pistons will need to be at absolute TDC to check. Piston tops will also need to be clean (no carbon) and you’ll need to measure at the center of the piston to eliminate any piston rock in the bore. Any good machinist friend should have a depth micrometer, you can also use a caliper but it’s very easy to tilt those at an angle and get an improper reading.
It could be the cylinder head chambers too, as others have suggested. CC’ing the head chamber should tell you that.

[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