[Cliff R]

In recent years we have been getting a LOT of complaints from folks who have build 455 Pontiac (and Oldsmobile) engines using relatively "small" cams on 110 or tighter LSA angles. Also getting a good many complaints from those who built BBC engines as well, although they aren't nearly as effected by this issue having a larger bore and shorter stroke at nearly the same CID, but it still applies to those engines as well.

Most don't go public with their troubles, so I'll put it up here for them.

The 455 is a HUGE engine. Avoid small cams right to start with in them, and for sure stay away from little cams on tight LSA's.

Even 455's with relatively "low" compression still need a lot of seat timing to perform well, as the basic laws of physics doesn't change with these things.

A tiny cam that's completely happy in a 350cid build at 8 to 1 compression is a PISS-POOR choice for a 455 build at any compression ratio.

I've helped about a dozen folks out in the last year or so building 455 street engines in the 9.5 to 1 compression ratio range who chose the Comp XE268 or XR276HR cam for their engine builds. All of them were disappointed in the end results, and a few were forced to removed those cams for a better choice.

Had two folks last month who chose the roller version for their 455's and one of them was a very well established engine shop in PA. They installed the XR276HR cam into a 455 engine with 250cfm #96 heads and it worked very poorly on the dyno. They actually "pinged" the engine and hurt the bearings trying to get it to make acceptable power for the combination of parts.

I got involved as we supplied all the parts to the Q-jet they were using and it was getting the blame for all the troubles.

After a long talk with the owner/engine builder he ordered a custom ground HR cam basically the same as the Old Faithful grind but on a 114LSA. The end result was fantastic.

The first dyno runs with the Comp 276 cam maxed at 428hp/516tq, DONE by 4900rpms.

With the new cam and no other changes it made 514hp/559tq, and made MORE power (torque) at every rpm and idled better than the smaller cam on a tighter LSA!

So much for camming your 455 to make MORE power earlier in the rpm range and not worrying so much about top end power. The wrong cam or cam designed to pull power down in the rpm range simply doesn't accomplish this.

You can have your cake and eat it too with these engines. With the right cam your engine will manage pump fuel without any issues, and make over 500ft lbs torque clear across the loaded rpm range. The second cam had the big 455 producing 519ft lbs at 5000rpms, and still 500ft lbs at 5300rpm's! The first cam only made 441tq at 5000rpms and was pretty much DONE making HP by then anyhow.

A conversation I had a few days ago with a customer who built an Olds 455 with 10 to 1 compression and 224/230/110 cam with short seat timing prompted me to go ahead and put this post up. He's having issues, and the carb we built for him is getting some of the blame. It idles "quirky" (common issue with these engines and small-tight LSA cams), and really isn't making nearly the power him and the engine builder had expected.

I figured as much good information that's out there these days we need to avoid making mistakes when it comes to this topic. I hope a few of the Olds enthusiasts wonder over here and see this.........Cliff