Setting the stage I have a 68 430 in my 70 vert, engine acquired from a friend decades ago. He stated that the owner of the 68 Electra had the motor rebuilt - which I believe is true since it runs strong, burns no oil, no exhaust by-pass, etc. What I don't know is specifics of the rebuild - bored?, cam?, valve job?, heads milled? block decked?, etc. I have a set of '71 heads that I home ported, had S1 stainless valves, good valve job, new TA springs, hardened seats installed, that I have been sitting on for about 20 years. I was gong to have a short block built, but if I were to do that now I would get TA aluminum heads. So, I was wondering if it would be worthwhile to install the 455 S1 heads on the 430? If I did so, I would probably over indulge and get a TA AL manifold, new cam, lifters, pushrods (?). Any input or comments are welcomed.
The 400 & 430 oiled the rocker arms via oil passages drilled into the block & heads. To use 455 heads, you'll have to convert to pushrod oiling, which means hollow pushrods and a new set of lifters that feature the oiling orifice in the cup (the 400-430 lifters do not have this feature). Other than that it's pretty straightforward, but you have the added expense of new lifters & pushrods. Devon
Thanks Devon. I'm aware of the oiling/lifter/pushrod issues, just wondering if it would gain me anything or if the smaller bore would shroud enough to not make a difference in performance. and along with new lifters comes a new cam, and then a decision on whether to use the aluminum rockers and hybrid pushrods, or go with the 70 up rockers and pushrods (rockers, shafts, and adjustable pushrods sitting on a shelf in garage). Looking for the next project to go with the JW converter and 3.42 rear with Gearvendors...
I did it on my convertible. I put a 112 cam in it, shorty headers and b4b aluminum intake. Very reliable and was spunky.
I remember reading Buick didnt bother with bigger valve heads (Stage 1) on the 400/430 because of the shrouding the smaller bore.
The only way we'll ever know the difference is if someone takes the time to dyno small vs big valve heads on the same 400 or 430 build and shares the results with us. The last time I built my 430 (1980's) I'd done my own homework, and wondered the same about the bore being too small for benefits from my large port 430 heads that I upgraded to Stage 1 valve sizes. I had no dyno $ so I just went with what others had done...not necessarily Buick. I took hints from Big Block Chevy and carved out the top of the cylinder bores in the valve area down to the swept area of the top piston ring. This idea is essentially giving valve relief where the cyl head stops and the cylinder bore begins. Food for thought. Devon
The loss of compression with the later heads will negate any gain. The 430 probably already has low compression to begin with...
Joe, I haven't looked at the advertised head cc's of the stock 68 heads, but I do know the S1 irons that I have average 65 cc, so I doubt they would drop static CR much, and I thought 68's all sported a static CR >10.
My untouched 1970 Stage 1 heads measured 71cc. My 462 with Felpro head gaskets, Speed Pro pistons (.035" in the hole), and 23cc dish, measured to 9.4:1 static.
The factory advertised 10.25:1. The real world number was around 9:1. To make matters worse the stock replacement pistons had a lower deck height and the new head gaskets are twice as thick.. my .030 430 with an untouched deck ended up at 7.9:1 with pistons that were supposed to be 10:1.. this is really common as well. So id be very leary about swapping heads if the chambers are bigger.
I found the sheet with the measured chamber cc's, they varied from 65.5 to 67.5, with NGK UR4 plugs. (Anyone need a lab grade burette?) They were milled enough make them flat, S1 valves, TA springs, and hardened seats, though it was so long ago I don't remember all the details. So it looks like they would increase the CR. It still probably wouldn't be worth the effort, except giving me an excuse to get a new intake manifold, cam, timing set, ...
You shouldn't have any compression ratio loss concerns. I would pull the heads on the 430 and see what it has for pistons and how low they are. Those heads would probably work good.
