I've got a 454 built fairly well with just over 6000 miles on it. Rings didn't get broke in right and it is smokes bad during acceleration. The temp on #6 and #8 cylinders is about 250-300 degrees cooler than the others. Changed the plugs today and found a lot of blow by oil on the plugs in those two cylinders. It just started missing out bad and pinging recently. Guess I need to go through the motor. It has stock 333781 heads with some port work done to them. How good are these heads? I was told they are a decent performance head.

I've got a 454 built fairly well with just over 6000 miles on it. Rings didn't get broke in right and it is smokes bad during acceleration. The temp on #6 and #8 cylinders is about 250-300 degrees cooler than the others. Changed the plugs today and found a lot of blow by oil on the plugs in those two cylinders. It just started missing out bad and pinging recently. Guess I need to go through the motor. It has stock 333781 heads with some port work done to them. How good are these heads? I was told they are a decent performance head.

With large valves and a bowl blend there capable of supporting 650+ hp. My old 461 combination ran 10.0's to 10.20's at 3500 lbs with 781 heads (13 to 1 compression though).

You can easily make 500-600 hp without spending a small fortune.Remember howerever........They are 25+ year old castings.Thats about the only reason i prefer "new " heads.I once had a real nice set of 840's only to have one crack.That was a finacial disaster.

I had a fair set of those castings, for a pretty strong BBC - but I agree on the 25 year old comment.

781's are the best oval port head gm made. 2.19's/1.88's, and a mild port job is all you need......oh yeah, and some dome pistons to get some compression with the big 125cc chambers.

Thats why i had mine. great flow plus the big chambers. I had big fat domed forged trw's...and was looking to lower the comp ratio a touch, so these were ideal for me.

I built a few 454s in my day and I used 049 or 781 with 2.19 valves and mild pocket porting and Dome pistons and made about 9.3 to 1 Compression they make great power for the money. The last one I built was a 460.4 with 781 heads stock 2.06 Valves mild Crane Cam I think it was a 262/ 272 or something like that I had it in one of my Elcaminos and it ran on regular Unleaded and ran low 13s on 295/60/15 Radials

Imho, a flat-top pistoned 454 P/U motor then use something like -206's that are like 96.7 to 98 CC's to up your low CR!!

My '75 454 P/U motor that became my 496 had a good pair of -781's on it, but I was afraid that I was gonna get hosed locally to bring them up to modern, big valve spec's so I went new Merlin ovals!!

pdq67

all the oval port heads have roughly the same port configuration. the big difference is in the chamber. the open chamber heads have less shrouding of the valves and will flow more air, but I don think it is a big deal on street heads. I am currently using 290# heads which have semi-closed chambers but the same ports s 781's and I have measured 303 cfm@ .650 lift @ 28" of water(2.19 valves and pocket porting by me). plenty of flow for big HP #'s