If you want to take the time and spend the money, you can cut the heads for new intake valve seat inserts then angle mill the head then install the new seat inserts then do your valve job, that way you can cut off as much as possible and still be able to put the top angle on the valve job.How close to the valve job is OK to mill? Why can you go closer on a SBC than a BBC, or am I mistaken about that?
I know very little about the BBC, but on the SBC, with say, the 292 head, or the equivalent, when you angle mill the head, and lower the valve angle, even slightly, and raise the roof, and even fill in the floor, you end up with a fairly small intake port, but you see big gains in flow numbers from .300 up. So, angle milling the SBC 23 degree not only helps compression, but if filled, and ported properly, increases flow. If you don’t raise the roof, it can actually hurt flow.If you want to take the time and spend the money, you can cut the heads for new intake valve seat inserts then angle mill the head then install the new seat inserts then do your valve job, that way you can cut off as much as possible and still be able to put the top angle on the valve job.
Angle milling and rolling the head over was done to get compression and more than likely hurt port flow. That's the reason RM welded up the intake side of the head deck surface before they angle milled their BBC alum. heads while developing them.
It's as simple as that the small cuin sbc gained more from the compression increase than did the big cuin BBC's than the decrease in port flow hurt them. And add the cost of milling the intake manifold and anything else needed to match the head angle and it makes no sense to angle mill a BBC head for the little gains you may get when you can buy much better standard angle or lower angle heads and manifolds these days.
Yes, most pistons with the 23 degree valve angle cut will clear most moderate cams, only because most shelf pistons have plenty of clearance. When I’d order a custom piston, I’d always tell them the finished valve angle, but you are correct, .125 normally ain’t a deal breaker on most builds.I believe that most shelf pistons for sbc will accept at least a .125 angle mill. I cannot remember the last SBC that I built without that much of a cut.
Yes, but I had no clue really what I was doing with them. I just listened to guys that had experimented on ratios. And I tried running longer rods in all the 23 degree stuff, from 5.75 to 5.85 to 6 inch to 6.125. I really can’t say one worked better then the other, but for some reason in an automatic, single 4 deals, a short rod seemed to be a tad quicker. We ran some 5.485, to 5.550 length stuff in the 2 speed cars we put engines in. Now, on the Dart Buick stuff, a 5.7 or shorter worked great. I know all about the dwell time of rod lengths, but someone else can explain it better. Like I’ve stated several times, I just tried shit to see for myself.so Randy , did you play around with Rod ratio's
Speaking of rods, what did you use for pins? It seems the current trend is smaller OD with thicker walls, but I don't know how far back that trend goes. Also, some people like bronze bushings, and others run steel on steel with practically zero clearance, but not a press fit.so Randy , did you play around with Rod ratio's
I run .875 pins in my engines 2 1/4 inch length.080 wall tool steel rods are bronze bushed. Pistons are real light. About 340 grams. The engine is a high rpm NA combo SBC. Good reliabilitySpeaking of rods, what did you use for pins? It seems the current trend is smaller OD with thicker walls, but I don't know how far back that trend goes. Also, some people like bronze bushings, and others run steel on steel with practically zero clearance, but not a press fit.
I always ran super light pins in my early engines, and still do in my engines in the 500 to 550 hp range. I’ve ran them as lite as 67 grams, and didn’t see a problem. But, I do understand the reasons behind heavier wall stuff they run today in like Pro Stock. And most Comp Eliminator classes. The cylinder pressure in those engines coupled with extreme rpm, dictates the needs they see. And I always ran lightened pistons in the baby engines. As lite as under 400 grams. But I also understand the reasoning behind heavier pistons to keep the pistons from oil canning. Which unseats the rings, as too lite of wrist pins will do the same.Speaking of rods, what did you use for pins? It seems the current trend is smaller OD with thicker walls, but I don't know how far back that trend goes. Also, some people like bronze bushings, and others run steel on steel with practically zero clearance, but not a press fit.
2.04 hp per cubic inch with a single 4 ?Best engine build ever? Let me think. It’s one of 3 I’d say
Engine 2. Maybe the 289” Brodix spec head that put out 592 hp with the heads unported, Stock Block, and a cast hurricane intake, one 750, clutching every gear, and running 6.29 109 and change in the 1/8th mile, at 10.5 #’s per cid, and setting the local track record at the time.
Ya know, it’s been 11 years, but if I remember right, we angle milled the heads only .125, and maybe ended up with 10.8 to one. It was hard to get compression with those heads and small cubes, because we ran a 2.08 valves in the standard location, and the head starts out as 67 cc chambers. And I used a set of pistons I had laying around that were for the bow tie heads. Now, I built a 285” for the next year that had around 11 to one, but I had the pistons custom made to the chamber. Sold that engine after track didn’t open for a song.2.04 hp per cubic inch with a single 4 ?
How much compression?
Ya know, I don’t know exactly. But if my memory serves me, the 461x heads, and those in that era, .125 was a bunch. I know I had a pair of 292’s that I think were milled .175, and I remember the whole exhaust side seemed paper thin. And we ran a 2.04 valve in them. There was a bit more meat in the bow ties, and we milled most of them .175, and they claim you can mill the vortec bow tie heads like .275. Some head guys may have a more in-depth answer to that.How thick (or thin) were the head decks after you milled them? I looked at my 990 big block heads and I don't think the decks would have enough rigidity left if I had 0.125 angle milled off them.