[joes455]

I have that cam also with a .015 valve timing,I wonder what the .050 lobe lift valve events would be for setting up the degree wheel

[Steve C.]

I suspect the specs reported for the lobes have changed over the years.
Early Comp catalogs state the intake lobe has 256 degrees at .050 and the exhaust with 267 degrees at .050

Today they are 255 / 266


Also keep in mind it is not uncommon to either round up or down the stated valve lift.
Example, 0.3620 x 1.5 = 0.543
But in the early catalog within the Pontiac section the lift is stated to be 0.540


.

[ponjohn]

Cliff replaced a 276HR with an old faithful in a hyd roller 455. Picked up 50+ hp. I wouldn't use it.

[Steve C.]

And it would of been interesting if Cliff had changed to the 290B-6




.

[Stan Weiss]

Originally Posted by ponjohn

Cliff replaced a 276HR with an old faithful in a hyd roller 455. Picked up 50+ hp. I wouldn't use it.

If I have the right data it was closer to 90 HP.

Stan

[Steve C.]

Regarding the dyno testing of the XR276HR cam and the Old Faithful cam. With the initial testing the engine pinged so hard on the dyno with the XR276HR that it spun the rod bearings and had to be torn down to replace them.
This led to the question if the rod bearings were involved in such a large disparity between the two cams and the results. I'm not so sure the question was resolved.


.

[Jay S]

There was an old magazine series called Pure Poncho (???) that had a 4.25” crank in a 400 with some 250cfm ported 6X heads that made about 490HP@5000 with the XR276. At a later date they did some cam swaps and gained some HP and raised the RPM power band. I don’t recall now the specifics on the later cam swap. I have an XR276. I think it can work decent in bigger cubes if it is install a little retarded or run the compression low. The little XR276 will never come close anywhere in performance to a 290B6, other than having more vacuum.

Tom S had a 455 with stock D ports that I think made around 420 ish HP with the XR276. I think it went up to 440+ with and OF cam in the same engine. IRC…Similar results where in the pure Poncho article.

[performerrpm]

i cant remember py users name here for the life of me but ive periodicaly watched the video of his car ' red 65 gto' at a 4th july burnout contest for like 17-18 years now lol.....i dont know what hp he made but i do recall him telling me he his combo was a 12.1 cr 455 with iron heads. @ the time i thought that was the baddest car on the net....i think there was another user here with a maroon 65 gto/ gear drive who also had the 290b cam....i wanna say he was also doing burnouts by his house and side swiped a trailer and took his quarter panel off.

i thought he chassis dynoed his car but couldnt find the results

[Steve C.]

467 cubic inch combo
6X heads / 9.1 CR
XR276HR cam

491 hp at 5200 rpm


https://www.hotrod.com/how-to/engine...e-stuska-dyno/

The testing Cliff did mentioned here in this thread: 455 CID #96 Heads 250 CFM XR276HR cam / peak power - 428.7 HP @4800 rpm

Edit: Project Pure Poncho Build
https://www.hotrod.com/how-to/hppp-1...467ci-stroker/
https://www.hotrod.com/how-to/hppp-1...e-short-block/


.

[PAUL K]

Originally Posted by Steve C.

467 cubic inch combo
6X heads / 9.1 CR
XR276HR cam

491 hp at 5200 rpm


https://www.hotrod.com/how-to/engine...e-stuska-dyno/

The testing Cliff did mentioned here in this thread: 455 CID #96 Heads 250 CFM XR276HR cam / peak power - 428.7 HP @4800 rpm

.



.

Hmmmm

[Stan Weiss]

Originally Posted by Steve C.

467 cubic inch combo
6X heads / 9.1 CR
XR276HR cam

491 hp at 5200 rpm


https://www.hotrod.com/how-to/engine...e-stuska-dyno/

The testing Cliff did mentioned here in this thread: 455 CID #96 Heads 250 CFM XR276HR cam / peak power - 428.7 HP @4800 rpm

Edit: Project Pure Poncho Build
https://www.hotrod.com/how-to/hppp-1...467ci-stroker/
https://www.hotrod.com/how-to/hppp-1...e-short-block/


.

9.1:1 CR and BSFC numbers in the "3".

Stan

After running some numbers. While I have seen it before a Dyno Correction Factor of just about 1.000 is not very normal.

[Jay S]

The cam swap I was thinking about on that engine was to the next step bigger XR288 (433). But the 6X head got replaced with edelbrock D ports before the cam swap. I finally found the article. Thanks Steve for finding those other articles, it helped find this one.

https://www.hotrod.com/how-to/comp-c...t-pure-poncho/


I tend to think of the XR276 is kind of a gateway cam. The XR276 is a gateway cam to a LS transplant because you should have used a bigger cam in your Pontiac!

[Steve C.]

Paying attention to and using adequate valvespring pressure to control the valves...

I see in the link Jay added there is a chart indicating Comp Cams Springs with the closed pressure at 105

I question if that was a misprint .

Within the 6X build I linked it indicated Comp Beehive springs with 137 lbs seat pressure where used.
Which would have been adequate for the XR288HR cam if used in the Edelbrock heads.


.

[Probird]

I ran the 290B-6 in a 440” with ported 16 heads. Unknown torque converter in my Bird. It went 6.80 in the 1/8th. The engine didn’t last too long as a couple rod bearings spun and broke a rod destroying almost everything inside.It ran good for the 10 passes it made.

[performerrpm]

im planning to use the victor 4500 intake with the 290b, but what i wonder is....how would a 66 tripower feel about this cam? im sure it wont run as good as the victor but could it work in tbe 290 b's power band? and do ok?

[ponjohn]

I don't understand why they're is even an argument with the data Cliff produced.
It was NOT anectdotal.
The combo pinged so hard it pounded the bearings out of the engine.
The rotating assembly was fixed and it no longer pinged and made way more power.

Here is the dyo sheet.

[Stan Weiss]

Originally Posted by ponjohn

I don't understand why they're is even an argument with the data Cliff produced.
It was NOT anectdotal.
The combo pinged so hard it pounded the bearings out of the engine.
The rotating assembly was fixed and it no longer pinged and made way more power.

Here is the dyo sheet.

I am still after all of the times that dyno sheet has been posted trying to figure out what actually it is telling me.

XR276 @ 4800 Fuel 221.3 lbs/hr - 424.2 HP

OF @ 4800 Fuel 222.2 lbs/hr - 485.3 HP

Fuel has the BTUs yet a very big difference in HP

Stan

[Steve C.]

"I don't understand why they're is even an argument with the data Cliff produced."

See post #26

That's how it went, so if the rod bearings were holding it back nearly 90HP then we can blame them for the big power loss, because those were the only other items changed besides the camshaft from one dyno test session to the other.......Cliff

https://forums.maxperformanceinc.com...XR276HR&page=3



.

[Stan Weiss]

This thread also has some back and forth about that dyno / cam test.

https://forums.maxperformanceinc.com...d.php?t=858613

Stan

[mysticmissle]

anyone has a good xr 276 used that they want to sell reasonably, because they upgraded let me know. i need another for a speedmaster build