OK, just for the sake of argument let's say that you could bolt up the new TA heads to a 350 and the pushrod geometry was close but acceptable and would run without making contact. What then? Headers are already available, our friend in Australia could be persuaded to make a single plane intake (an open question, would this entice TA to also make an intake?) and that leaves the cam. I do not know what it would take to get a 350 cam made up with a 340 lobe pattern but I know somebody who should know. Maybe it's just the excuse I need to call him. But no guarantees, I have many irons in the fire at the moment and I'll get to it when and if I can. Some of you guys could make that call just as easily and are more likely to actually make use of the information. So don't wait on me to do it. So that's quite a prospect. An abundance of inexpensive short blocks to build a 400lb 350 with exceptionally good heads. I think this one can travel. Jim
All it needs for the cam is to make a roller from steel billet. TA already have half the job done. Another way would be to take a 350 cam and machine off the lobes for the centre 4 cylinders and weld/metal spray some new ones on the 340 index. The end cylinders are the same 340/350. Lots of engines run with crazier pushrod angles than this thing. I'll bet they will clear one way or another, but if it's tight flex might be a problem. I thought TA were making a manifold (post 68 other thread). Something else that needs looking at is whether the new cam lobes will clear the rotating assembly.
no reason why it shouldn't.. the 340 is essentially the same rods and crank as the 350... isn't it?o No:
That's right. TA say to check it when using one of their roller cams in a 350 with 350 heads, now all the centre lobes have swapped places for the 340 heads. It might be possible to check with a regular 350 cam by degreeing each lobe separately
With stock rods it shouldn't be a problem. Cam grinders add lift to a SBB cam by reducing the base circle because even the stock low lift cam is in close proximity to the rods. This applies equally to the 340 and 350 as well as the V6 and all the other SBB engine sizes. The lobe size is also limited by the cam journal diameter. So a higher lift cam is simply ground deeper into the blank. (This explains why pushrod length is so critical in these engines.) What has the potential to cause trouble with a roller cam is the usually wider profile of the lobe. That is where you might run into clearance issues. The different lobe spacing may have some effect but that is doubtful, and the difference in the valve order probably means the clearances need to be checked at different lobe positions, rather than making any difference in the actual clearance. Jim
YellaTerra make 1.9:1 rockers for the Holden/Buick V6's that are popular here Might be a way to keep the base circle reasonable and big fat lobes away from the crank and rods
Makes sense. I mis-stated the facts above though, the shorter stroke engines don't have as much of an issue since they use the same timing set and therefore have more clearance. Jim
I agree...lets get to the bottom of this. Last year I asked a very similar question. I had wanted to use a 350 SBB head on a 300 block and see what kind of screamer I could build. Jim Blackwood answered the question that the lobes of the cam would not line up with the valves. I agree since the valve order is incorrect, but think about this. GM is in the business of mass production, why change the block for a different head design....from the 340 to the 350 I would bet the valve alignment is fine as would the 300 to the 350. There is no reason that they would change the block after changing the head.....why not make the head fit the block to begin with.......after all it's Mass Production. It's all about making money and that does not make sense. So, to really find out....Does anyone know for sure if the 1st gen SBB heads fit a 350 or vice versa......when looking at the head gaskets for the 68 SBB 350, it has the same holes as the 215-300 engines. I do not want anyone to assume (it makes an ass outta you and me), I really want to know if the heads will fit. So if anyone has or is willing to try please let me know cause I have the perfect High RPM Street SBB combo made from off the shelf parts with exception of an intake manifold stuck in my head, like a nail.
your idea of GM not changing blocks n' such wasn't the case though.. common sense didn't seem to be too common case in point: the nailhead Rather than just design a better flowing head (perhaps a more conventional design) for the strong block and oiling system of the 'nail, the buick engineers designed a weaker block with crappy oiling system and some better flowing heads.
Lightningbird, the heads fit but the lifter bores are not all in the same place. Put a 300 cam into a 350 block and see for yourself, then post the results here. I've tried a P76 (Rover) cam in a 350 block, the results are in this thread.
1.9:1 rockers? I haven't done the math, but already I don't like the loads on the lobes and lifter bores. Could this be related to P76 blocks splitting in the lifter valley? Anyone tried a set of "Coates" rotary valve heads yet? rovermanou:
So, if the lobes can't be moved enough, then off-set lifter/push rod cups? Available from various manufacturers.roverman.:Brow:
P76's don't have or need 1.9:1 rockers. They are a LOW RPM ENGINE and will break with big bores and high rpm. Yes, offset pushrod cups will help.
