TheSamba.com :: View topic - Cam Break-In and After

Sat Nov 08, 2025 9:17 pm

Engine specs:
2276, 82x94
Web-Cam 86c, Thorsten Piper tool steel lifters, 10.3:1 cr
CB Wedge Ports, 44x37.5
48 IDA's, 3rd prog hole drilled
1.75" merged exhaust

I broke the cam in on my engine stand. All seemed to go well. Did two 10-minute runs above 2k rpm spread about 8 hours apart. No oil leaks visible yet.
At the end of the second run I backed the throttle down to idle and set mixture and made sure the carbs were sync'd. Let it cool a bit so that I could touch it and did a comp check. Here are the numbers:
1. - 120
2. - 130
3. & 4. - 140
:-k
I don't like the look of that. The rings are new, all Grant cast iron rings, and the pistons were thoroughly cleaned and balanced, and cylinders honed. Could it just be that the rings need to seat in more? Another weird thing, I bought straight cut cam gears, and they are the quietest straight cuts I've ever heard. In fact, I don't hear them at all. I did not assemble the engine, but a very reputable engine builder in my area did.

Sat Nov 08, 2025 10:01 pm

I run the CB 1399 straight cuts in 2 engines and about to put a set in a third. They are very quiet.

No way those rings are set yet. Stab it in the car a drive it.

Crazy to me that no one runs heat exchangers.

Sat Nov 08, 2025 10:33 pm

richparker wrote: I run the CB 1399 straight cuts in 2 engines and about to put a set in a third. They are very quiet.

No way those rings are set yet. Stab it in the car a drive it.

Crazy to me that no one runs heat exchangers.
No heat exchangers because the exhaust is too big. No one makes heater boxes for a 1 3/4" exhaust, and if they did, $$$$$! I have an old Berg 1 5/8" heater box system, and I used to run it. This engine needs a bigger exit.

Sun Nov 09, 2025 1:00 am

What kind of straight cuts did you use?

You broke in the cam, but have not taken it out and put a load on it and seated the rings. Put it in your car and find a hill and ride it up hard then put in in second and let the tranny slow it down coming back and down. Do it a handful of times to get it hot and set the rings.

CSP makes 1 3/4 heat exchangers https://www2.cip1.com/c31-255-100-045l/

Sun Nov 09, 2025 7:34 am

Beautiful engine! That thing is a Hoss! Love the color of the shroud too. Like the hammertone.

X2 on what the other guys said, you only broke the cam in. Gotta put a load on it to seat the rings.

Cheers.

Sun Nov 09, 2025 7:50 am

croSSeduP wrote: richparker wrote: I run the CB 1399 straight cuts in 2 engines and about to put a set in a third. They are very quiet.

No way those rings are set yet. Stab it in the car a drive it.

Crazy to me that no one runs heat exchangers.
No heat exchangers because the exhaust is too big. No one makes heater boxes for a 1 3/4" exhaust, and if they did, $$$$$! I have an old Berg 1 5/8" heater box system, and I used to run it. This engine needs a bigger exit.
https://www.csp-shop.com/en/exhaust-heating/heat-exchangers-csp-255-100-038l-22333a.html
But does not work with a regular Phoenix header

Sun Nov 09, 2025 7:56 am

Gary Berg IDA.... nice :thumbsup:

Sun Nov 09, 2025 8:32 am

what kind of reputable engine builder doesn't break in the engine they just built?

Sun Nov 09, 2025 8:41 am

BFB wrote: what kind of reputable engine builder doesn't break in the engine they just built?
One that doesn't have a run stand?

Am I correct?

Sun Nov 09, 2025 9:09 am

Glenn wrote: BFB wrote: what kind of reputable engine builder doesn't break in the engine they just built?
One that doesn't have a run stand?

Am I correct?

I know a very reputable local vw engine guy that just retired and had been building these things since ... shit I dont know, 70's I think? he didn't have a run stand , would just fire them up on the floor.

Sun Nov 09, 2025 9:28 am

BFB wrote: Glenn wrote: BFB wrote: what kind of reputable engine builder doesn't break in the engine they just built?
One that doesn't have a run stand?

Am I correct?

I know a very reputable local vw engine guy that just retired and had been building these things since ... shit I dont know, 70's I think? he didn't have a run stand , would just fire them up on the floor.
Like this?

Sun Nov 09, 2025 9:31 am

BFB wrote: what kind of reputable engine builder doesn't break in the engine they just built?

maybe the customer wanted to assemble from the long block himself?

there are TONS of skilled builders that can supply just a long block. It's up to the customer to do final assembly and then break it in properly. Not every "reputable builder" sells only turn key engines.

Sun Nov 09, 2025 9:53 am

sled wrote: BFB wrote: what kind of reputable engine builder doesn't break in the engine they just built?

maybe the customer wanted to assemble from the long block himself?

there are TONS of skilled builders that can supply just a long block. It's up to the customer to do final assembly and then break it in properly. Not every "reputable builder" sells only turn key engines.
https://empius.com/products/empi-1914cc-long-block-engine/

Sun Nov 09, 2025 4:21 pm

sled wrote: BFB wrote: what kind of reputable engine builder doesn't break in the engine they just built?

maybe the customer wanted to assemble from the long block himself?

there are TONS of skilled builders that can supply just a long block. It's up to the customer to do final assembly and then break it in properly. Not every "reputable builder" sells only turn key engines.

thats a valid point, but you dont have to sell a turn key engine to fire it up and break it in.
even what little I do as a side gig, I still have a box of parts, intake, carb, exhaust , all thats needed set aside just to fire up and break in an engine. then I take it all off , drain the oil and ship it.

way I see it is this, no its not a hard process to break the engine in and anyone should be able to do it. however, what about the guy you sell a long block to who puts all his own shit on it then goes to break it in and can't get it started or running? what about the guy that sits there fiddling with the carbs and trying to get it to idle instead of getting it to rpm? there's too many possibilities there to for me to leave it on the shoulders of someone else and then them come complaining about issues they have. makes more sense to me to finish the work you started and break the engine in.
aside from not leaving the responsibility on the customers shoulders and the fact that we all make mistakes so firing it up and breaking it in covers your ass, I want to hear what I built run. some may not understand, but to me thats it moment of birth, and I want to be there to welcome it into the world, hear its voice as it comes to life, celebrate its birth though blood & fire, and put my mark on it. yeh, thats right.

Sun Nov 09, 2025 6:19 pm

That compression is awful low for that build.

Did you pull all 4 plugs before testing and was the battery fully charged? Throttle wide open and valves adjusted good?

Sun Nov 09, 2025 11:00 pm

right, but if the rings haven't seated fully (which they won't on just a cam-burn) then compression numbers will not be accurate.

Mon Nov 10, 2025 12:01 am

10.3 CR? more like 8.3 bad ring seat valves are leaking or its just not built to 10.3 you should have like a 54cc head and a .040 deck. That cam will bleed off some pressure but still its LOW.

Mon Nov 10, 2025 4:55 pm

To answer some questions:
I only wanted the assembled long block. I was taking on the responsibility of fitting the tin and intake manifolds, etc., and breaking in the cam. I know what I’m doing. Done this several times. I just didn’t want to assemble the long block.
It is definitely set to 10.3:1. I had the heads cc’d to my spec, and the deck set to make that cr. I’m pretty sure it just needs a load put on it to seat the rings.
I sure hope there isn’t valve or guide leakage! The heads are NEW.
Yes, all 4 plugs out, battery fully charged, throttles opened to about 3/4. I guess I could try and get the throttles opened all the way, but the differences in the numbers is what had me most concerned. 120 low, 140 high? That’s 15% difference.
The cam gears are CB, so that might be why they’re quiet.

Mon Nov 10, 2025 8:09 pm

Put a load on it and check again.

Tue Nov 11, 2025 11:19 am

No reason to crank to check compression until you seat the rings.