Hello everyone,
I do not post much, not being a specialist of your language, but I need help and so I start with the help of Google translation, hoping not to make too many mistakes.
As stated in my presentation, I am in France, where I bought a beautiful 1971 C3, with a brand new BluePrint engine (manufactured in 2015, and sold as having 3,000 miles).


Last photo of my car.

The engine is a BP35513CT1, 355 cubic inch small block Chevy. It features aluminum heads and hydraulic roller camshaft. It is rated at 390 hp/410 torque.

Last month, I broke two rockers on a cylinder.(One rod went through the rocker arm, and the other rocker came out of its housing)


I contacted BluePrint, who helped me repair my engine by sending me new rocker arms, including rods, for all cylinders, while my engine is no longer in warranty. I thank them again warmly for this mailing. My mechanic has reassembled my engine, and with the help of BluePrint remakes the rocker settings and ignition.

The engine was rebuilt, but during tests, my mechanic found that on two cylinders, the temperature at the exhaust was very very high: 300 ° C / 572 ° F on these cylinders, while the rest of the engine is at 180 ° C / 356 ° F. The temperatures are taken on the collector exhaust (Hooker), at the cylinders. A complete cleaning of the carburettor (Holley 670 cfm) was done, but it did not change anything. It was on one of these cylinders that the rockers broke, and it is thought that it was this excessive temperatuer that caused the breakdown

I am still connected to BluePrint, which is looking for their side.

From next Monday, we start all the tests again (compressions, ignition settings, rockers ...), but we do not know where it can come from.

Have you ever encountered this problem? How did you treat him? If nothing is done, is there a risk of engine failure? The breech is made of aluminum, and therefore risks to distort itself.

The next step, if nothing is found, is to open the engine to see where it can come from, but I would like to avoid that.
Thank you in advance for the help you can give me.
Good weekend to all.
Phil

 

If our compression test indicates anomalies, then I'd be more than ready to pull the heads. It's not that difficult and you probably want to look in there and eyeball what's going on anyway.

 

Excessive cylinder exhaust heat is many times caused by a lean burn condition, possibly a vacuum leak. T

 

This seems like a good theory to me. Look for air leaks in the seals between the intake manifold and the cylinder head.

 

Hello,
Thanks for your advices.
My compressions are good, and the joints have been changed since the intake has been removed to change the rocker rods, but I will still re-check. And even enriching the fuel as much as possible, we have these differences.
Following discussions with BluePrint, I have to check the temperatures while driving, engine at 3000 rpm.
See you soon.
Phil.

 

Wonder if your pushrod length is incorrect, those locknuts are torqued awful far down the threads, could have a binding issue there.
No 2 cyls will have the exact same temp especially if you have a dual plane intake not sure thats your issue.

 

Hello,
Thank you all for your help and support. I finally managed to adjust my engine and no longer have differences in temperature. On the other hand, the mechanic finds that I have a carburetor too big (670 cfm, whereas BluePrint recommends a 600) and that I will have to change it. I'll see that this winter. Today everything seems to work well, and that's the main thing.
Good holidays to all, and see you soon.
Phil.

 

That 670 is just fine for your 383, your mechanic is in your wallet hunting.

 

Good idea but I'm not sure he agrees...

Last picture of my Corvette.

 

C'est une belle Corvette