Oh wow that's a pretty huge jump from the stock sub 200 whp. Do you know what his combo was? I was definitely thinking of bigger valves for the rover since they're pretty small (inlet head: 39.75-40.00mm, exhaust: 34.226-34.480 mm) vs 300 head (Inlet: 45.915-46.1645, Exhaust: 34 798- 35.052).
Stock except cam and headers. Edelbrock carb instead of Carter AFB. Both motors are in MGB's. The Stroker has MS multiport EFI. All kinds of info on Mgexperience and BritishV8 boards. Links are in the 300 little guy sticky on this board. I've been messing with Buick 215, 300 and V6 for over 40 years.
You have to cut down the seats and valve guides for anything over .460 lift and Viton seals. + .050 retainers as the Rover heads used shorter valves. The 75-76 Oddfire V6 valves are .060 longer too. I'd make a tracing of the 300 aluminum intake ports and open up the Rover to match.
Ive got a 500 cfm carter avs for my 300, would there be a significant benefit to swapping over to an edelbrock 1403 or similar? I'll read through the two other forums you mentioned as well. Would the oddfire valves you mentioned earlier be longer than the rover ones? I can't find too much info on them nor any for sale, just a set of three on ebay. I'll see what I can do about the small rover ports, not sure how well its going to go for my first time porting.
I have never worked on any of these heads, but the if the valve edge to chamber wall distance on the plug side is less then the amount of valve lift you are running then unshrouding will help the air flow numbers. also a quick flow test on one intake and the another done with the valve in the guide upside down will tell you right away if it’s worth putting time into unshrouding the chamber by comparing the peak cfm difference. the shape of the chamber can have a effect on how much cylinder pressure can be many times. Closed type wedge chambers while they don’t burn clean will be more cylinder pressure tolerant.
I may have to rig up a flow bench in that case to test them out. And by valve edge to chamber wall distance do you mean to measure straight from the valve to the wall on the side the plug is on or intersecting the plug from valve to wall?
The 75-76 Oddfire V6 valves are .060 longer. They use the same 11 degree keepers. They are the biggest you can fit in the stock seats. Valves are at TA. You would need 2 more IN and 2 more EX. V6 Valves | TAPerformance.com
No, You need to lower the spring seats in the head and cut the valve guides down to prevent the retainers from bottoming out on the valve guide boss at over .460 lift. Lowering the spring seat and the longer valves allow a taller spring to work. you need +.050 retainers too. The last half of this video shows the process: Valve guide trimming, cutting for positive valve seal, & cutting deeper spring pocket 620HP 454 BBC - YouTube
That was interesting to watch, I've never seen that type of machining before actually. Do you expect that I'll need a cam with over 0.460 lift? I don't really know where the flow stalls for these heads. I'm definitely going to look into the larger valves but would rather not machine more than is absolutely necessary or highly beneficial.
The issue of spring height can be a challenge if you do not install longer stem valves. If you do then the rocker pedestals need to be spaced upwards to maintain geometry. A drop-in LS valve can work with .550" lift if you cut the pockets about .100" deeper I think, but there are other options. Mainly it's a compromise between lift and the coil bind height. Some of this info is available in the later pages of that thread. Jim
Here’s the basic rule of Thumb for un-shrouding a intake valve. I found flow numbers on the Stan Weiss site for a 300 head and a 4.0 Rover and if the numbers are correct then the 300 head flows better in stock form.
Steve, would you mind sharing a link for those flow numbers? This has become an area of significant interest. Part of the issue is that the 300 head has bigger intake valves but the Rover head has bigger exhaust valves and as we know Buick heads tend to be somewhat restricted on the exhaust side. Also since the Rover heads have the same chamber volume as the TA-Rover heads, using the Rover heads opens up a performance upgrade path that using the 300 heads does not. Jim
I would also suggest that shrouding in a 3.8" bore engine might be more of a concern at the top end of racing development rather than an issue for a street engine and is probably overshadowed by the valve size increase. I'm sure there are numbers to prove or disprove this idea but the smaller LS engines don't seem to have much of an issue with it. Jim.
Here's the site i found with flow numbers for what looks like thousands of heads. They do have the rover and 300 heads listed at the same lift for comparison. http://users.erols.com/srweiss/tablehdc.htm
I've used those tables for inputs on my desktop Dyno pragram. If you look at the ported examples at .500 lift, the 300 is slightly better. I only mentioned unshrouding to enlarge the chamber for lowering compression a bit. Remember the 4.0/4.6 Rover head was designed for a 3.5-3.7 bore and the 300 head was for a 3.75-3.8 bore. The only advantage of the Rover head is availability. The 300 heads were only available for 64. They are softer metal and have corroded over the years. The Rover intake valves are tiny for a 300 and especially a 350. Jim B, LS valves are too big. Chevy V6 valves that Chris used and Ford 2.3 SOHC 4 can work with larger seats.
Actually there are several advantages to the Rover heads. The metallurgy is better as mentioned, so not such an issue with thread pull and mushrooming of the head bolt bosses, the closed chamber design is better and leaves an upgrade path, (in my opinion perhaps the single greatest advantage) and they can be had much more cheaply, with rockers and cast valve covers still often about half what the 300 heads cost bare. Either can be ported and fitted with larger valves. The LS part I mentioned was the spring not the valve and the details are in the above thread. If there's a way to use LS valves I haven't heard of it. The odd thing to me is that the flow numbers do not correlate to the valve sizes used in the 300 and Rover heads. If they did the Rover heads would outflow the 300 heads on the exhaust and they do not. The difference in the numbers is about 10% on the exhaust and 5% on the intake at .500 lift, favoring the 300 in both cases. However, flow benches and their operators can vary greatly on their results and I know of one reputable operator who got better results on the intake side of the Rover than the 300. Not much better, and much depends on the condition of the particular heads also but still, 5% is a significant difference so that should be kept in mind. The usual reason for using the aluminum heads is weight savings and you do give up significant flow capacity to get that 50 lbs or so going from iron heads and intake to aluminum. But in reality if the flow rate is enough of a consideration to accept the weight penalty for another 10% or more of flow capacity with the iron heads it does make you wonder if the TA/Rover heads aren't quite the bargain in spite of the cost considering what you get with them. I've been watching this for some time and it appears to me that the use of the Rover heads is best considered as an inexpensive intermediate step that can lead to greater things. They are noticeably better than the 215 and early Rover heads, maybe as good as but not likely to be better than the 300 heads which have gotten scarce and expensive, and not as good as the iron heads BUT lead to a direct bolt-on replacement with the TA-Rover heads which are at the top of the heap even in terms of all aftermarket heads available for these engines. So if building an engine and cost is a concern (and when is it not?) it makes sense to build for a set of Rover heads with the plan to swap to a set of TA heads later when more cash is available. Can't do that with the 300 heads because the CR won't be right. Jim
I bet the ported versions on both heads used larger valves. You are limited because of spacing to around 1.74 IN and 1.5 EX. Dan Jones used 1.77 Late Buick V6 IN and 1.45 EX valves. Seats are siamesed and valves almost touch. All that Jim B states above is true. I don't know if TA is going to make more Rover heads or not. There are also Wildcat and Real Steel aftermarket heads.
