Information wanted on 265,283 HP ratings

[oldhead]

Yes its that old fool Oldhead living in the past.............I have searched the web and have not found what I want. Any one here know HP rating differences in 265,283 & 327 ?:D The is no fool like a old fool Oldhead

[pamotorman]

try this.

[oldhead]

THANK YOU.But not the answer I am looking for...How did the 1955,265,PP 180 hp get to 210 hp in 1956? How did the 283,283HP get to 290 hp and then in 1961 get to 315 (I think alum heads from a next year 327?) THANKS FOR TRYING Oldhead

[Krooser]

I'm thinking those higher HP numbers came from the marketing dept.

[pamotorman]

I was a drag strip tech inspector back then and most of the changes were in what camshaft and carb they used as that was a easy change for the factories.

[panic]

No aluminum heads.
Many of the high HP rating were 2X4 bbl.

[oldhead]

I am sure alum.heads in 61 FI 315 hp. But they might have been recalled, but what were the replacement heads????Oldhead

[pdq67]

And please remember, the old -097 or Little Duntov solid flat tappet lifter cam was installed in the 340 hp carb'd and 360hp FI/327 engines so it even though was small produced great power.

I had a junked engines -097 with coffee canned lifters in my old junk301 and loved the way it rpmmed.

I think these engines had 1.94"/1.50" valved, -461 heads on them but I also think they had ramshorns on them too?

pdq67

[DaveMcLain]

I am sure alum.heads in 61 FI 315 hp. But they might have been recalled, but what were the replacement heads????Oldhead

The 315 horsepower 283 used the 461 heads and this was their first application. This is also why all of those heads, 461, 462 etc will fit on a 3.875 bore diameter as long as they have the 1.94/1.50 valve combination.

[oldhead]

I am sure alum.heads in 61 FI 315 hp. But they might have been recalled, but what were the replacement heads????Oldhead

The 315 horsepower 283 used the 461 heads and this was their first application. This is also why all of those heads, 461, 462 etc will fit on a 3.875 bore diameter as long as they have the 1.94/1.50 valve combination.

THANKYOU FOR YOU ANSWER, Are you saying the heads 461 & 462 raised the 290 hp FI to 315,no other changes?? How did the 1964 FI 360 hp go to 375 Hp in 1965(Cam?),if so I think the 097 was around 226/226 at .400 what would the new if any cam...I see the increase in cam in 1956 made the increase of 30hp. (180 vs.210_) THANKS YOU ALL Oldhead

[pdq67]

The 365 carb'd and 375FI/327 engines as well as the little later 302 Z-28 engine used the -346 solid lifter cam. I call it the, "Big Duntov"..

It was rated by various different people as a 346/313/290 cam.. Take your pick, but I think it's about the 313 advertised duration cam in the real world, not GM's out to lunch cam spec world. (I think the late Pat Kelley if I have the name right? said 313?)...

It was the cam that was in the, "Mule", engine that gave GM the 370hp/350 engine, but they went with the -178 cam if not mistaken instead due to A/C, P/S, and A/T.

Say -- 313/254, 114/112?, .485 gross lift and needs .030" hot lash for a net lift of .455"s.

I hope I have all this right, it's been years and years...

I would install the old Isky Z-30 cam if I was to use one. 290/254, 108, .485 gross lift and also needs .030" hot lash..

pdq67

[fdicrasto]

One important difference in the 461 heads was the X head. The intake port was much wider at the pushrod pinch area and these heads produced more hp then the 461 no X designation head. Still 1.94 intake valve in both versions. In 1964 that head was cast as 461/64 with 2.02 intake valve and was rated on the F.I. 327 at 375 hp. The rare aluminum heads in 61 were full of problems and never did catch on at that time.

[pdq67]

One important difference in the 461 heads was the X head. The intake port was much wider at the pushrod pinch area and these heads produced more hp then the 461 no X designation head. Still 1.94 intake valve in both versions. In 1964 that head was cast as 461/64 with 2.02 intake valve and was rated on the F.I. 327 at 375 hp. The rare aluminum heads in 61 were full of problems and never did catch on at that time.

Right, guys say the -461x heads stock are at 170 intake port cc's vs about 160 cc's for the -461 heads. Oh, and btw, my virgin chamber and port 2.02"/1.60" valve -461 heads chambers are right at 66 or a skosh bigger. And they have the factory relief cut around the intake valves and have a double quench chamber..

I took them to a Machine Shop in South Bend, IN and told the guy they were true fuelie heads and he just gave me that look. When I picked them up, he admitted that I was right, they are fuelie heads!

pdq67

[oldhead]

Hold on a minute,in 64 the 2.02/1.60 valve went in the X head, but the hp stayed the same. In 65 the 30/30 cam pushed the FI hp up from 360 to 375??? What did I miss............Oldhead

[oldhead]

Hold on a minute,in 64 the 2.02/1.60 valve went in the X head, but the hp stayed the same. In 65 the 30/30 cam pushed the FI hp up from 360 to 375??? What did I miss............Oldhead