Engine and Transmission Tech

So I'm about ready to pull the trigger on big valves for a pair of 3.9L heads I'm building up. I'm really liking the 1979-88 Buick 231 V6 stock valve sizes of 1.710 & 1.500 even though they're slightly longer than the stock rover valves. I think I've got the geometry worked out with Harland Sharp roller rockers and shorter pushrods.

My worry is that whether or not the new seats for the Buick V6 valves are going to "match up" with the existing rover seat insert counterbore. The buick seats are both 0.216" deep, and if the rover counterbore is deeper than that then I guess I'm out of luck. Does anyone out there have the dimensions on the seat inserts for the Rover 3.9/4.2 head? I've looked, but I can't find them anywhere on the web.

Cliff,

I have measured some scale drawings from Des Hamills book "How to Power Tune Rover V8 Engines" and the standard Rover seat inserts appear to be .312" deep and .1875 wide at the base.

May I ask what capacity engine we are talking about and it's intended use. the largest size valves used in Rover heads are normally 1.7" Inlet and 1.5" Ex. so your inlet is only 10 thou. over and exhaust is the same size.


Clearly seats to suit the rover Ultra big valve are available in the UK so should not pose a problem but the heads will require the seat area machining to take the larger seats.

Real Steel in the UK offer seats for their new Merlin heads for 1.73" In. and 1.45" which might work but you would have to check,alternatively ask TA Performance what they could offer.

The valves I used in my 4.35L Rover engine with buick 300 alloy heads are 1.63" In. and 1.4" exhaust for which the standard seats Rover or Buick 300 can be machined, and if your engine is for road use those sizes should be fine unless you are going to 4.8 or 5.0L + capacity.

Kevin.



Flow as you are no doubt aware isn't just down to valve size, port shape and again not necessarily size are whats important for good flow charaterstics and should be matched to the intended use and rev range of the specific engine.

Thanks Kevin. I've got Hamill's book as well, but I didn't think about looking at the head cross sections. Your calculated .312 depth number is very close the only number I could find anywhere, which is the 0.3265 depth Unleaded/LPG exhaust seat insert from RealSteel. Speaking of which I've got a quote from them for their 1.630/1.400 valves and bulleted guides - it was very reasonable except for the packaging, shipping & insurance which I guess is fair, but was $60 GBP - a third of the total cost! I go back and forth between thinking those valves will do fine, and wanting something larger.

The Buick V6 valves I was looking at were from TA Performance (also available from Manley for more $$), so I may send them a note asking about the seats and Rover heads. D&D may be of some help as well.

My engine is very similar to yours I believe. 3.9L block, 4.2L crank, SBC 6.0" small journal rods, and Forged Keith Black KB-834 pistons. The block will need to be decked to get the deck clearance down to 0.001-0.002, which will give me 4.3L, around 0.047 quench and 10.9:1 CR. The car is a TR4 which will see some street time, and a fair amount of track time. Although I also have plans for a 4.9L motor with a reground 4.6L crank (3.375" stroke, 2.1" rod journals), 5.7" SBC rods, Buick 300 heads, and forged KB-831's.

My head porter is my son, who is an avid quarter miler (1999 Trans Am) and has experience (and good results) mostly with LS1 heads. He's an avid fan of David Vizard having mostly memorized his "How to Build and Modify Chevrolet Small-Block V-8 Cylinder Heads".

I'll post up any additional info I get from D&D and/or TA Performance.

Cliff,

Yes very similar engine spec except you stumped up for the forged pistons and I've got the cheap Hypereutectic ones.

I calculated with the 3.736" bore the capacity is 4350cc I had to use as near to a flat top piston as I could get as I am using Buick 300 heads with the larger chambers.

What cam are you going to use?

Be interested as to what D&D and TA Performance have to say.

Kevin.

Quote:

Although I also have plans for a 4.9L motor with a reground 4.6L crank (3.375" stroke, 2.1" rod journals), 5.7" SBC rods, Buick 300 heads, and forged KB-831's.

How does this work? Do you use the Chevy 2.1" rod journals with oversize bearings? You need to go 145 thou, right? 3.23 to 3.375.

Interesting. Thanks man.

It doesn't - meant to type 2.0" journals. But, now that I look at it, I'm not sure where I got the 3.375" stroke. It's a combination I put in my engine recipe spreadsheet some time ago, but I need to go back and look at it again. Looks like I can't get there with the 2.185" rod journals. Looks to me like 3.3225 would be all I could get out of offset grinding.

Dang it. I'm hijacking your thread. Sorry man. I'm not trying to be a math nazi, it's just a super interesting topic to me and I was wondering what the details of your build is. I like the idea of using the Rover crank instead of the Buick 300 for the seal fitment and such.

So I went through some math considering 2" journals. If you didn't need to clean up the rod journals at all you could get as much as an extra 185 thou of stroke. But then it's trying to find the right rod/piston combo to take advantage of it. Ok starting with 3.228 you can get to all the way to 3.415. Cool! That's got to be the way you were getting there.

It's a good idea. I wonder if that is what Tony (hoffbug) was thinking of doing...

Tony/Nick.

The normal finished size for a 4.6 offset ground crank is 86.36mm/3.4" presumably you have to leave a bit of margin from the max 185 thou. to ensure a perfectly round journal although you could possibly find a bit more from an unmachined casting.

With a 5.7" rod that leaves 1.56" for the comp height so one of the Chevy 305 KB Hypereutectic pistons should do the job

This one for 36cc. keads should bring the piston to the top of the bore. alternatively a flat top for 300 heads.

[kb-silvolite.com]

Capacity = approx 4835cc.

Kevin.

Cliff and all. Stg. I Buick V6, 1.77" int/1.5" exh. is max. at std. 1.660" valve centerlines. This leaves the seats pretty "sharp" between them. A lighter valve package would be Ford 4.6L/2 valve motor. Int. is 82 grams at 1.78"dia. w. 7mm. stems. Whatever seats you choose, make sure their hi thermal expansion, ie, hi nickle or bronze, to stay with head growth,(retain interference fit).Radiused exh. seat will work better.Properly done, this set-up should get you over 140 cfm. int. flow such as TA. is claiming on Merlin head. Beehive springs? Good Luck, roverman.

Thanks Art. I hadn't considered the Ford 4.6 2 valve option - I'll definitely take a look at them.

Nick/Kevin - So looking back at my notes on the re-ground 4.6 crank, I find that I first saw the number on D&D's website in an article Dan LaGrou wrote on larger displacement for the Buick 215 and Rover motors. And I also read in Hammill's book that John Eales offers a 3.400" stroke crank that I now assume comes from an offset ground raw casting of a 4.6 crank, as Kevin mentioned.

In any case, I need to quit dreaming up bigger motors and just finish the one I've currently got most of the parts for. If I keep reading Nick's posts on how to put together giant Rovers, I'm never going to get my "mid-size" done! But then again, it doesn't cost anything to dream...

Dude, you are so right on that point. I'm so close to completion. This week I'm at it every morning. All I need to do is fabricate a couple things for the engine and wrap up. Get it done!

Quote:

What cam are you going to use?

Kevin - Forgot to answer your cam question. I like the Isky 282-HL, with its 109 LSA and 0.467" lift. and ICA of 70 ABDC which helps bring down my calculated dynamic CR (8.2 vs 10.9 static). TA Performance has a couple of cams (C110 & TA-284-88H) that I've looked at as well that have 110 LSA with a little more lift and split duration. One of the tools I use to compare cams and engine recipies is engine analyzer software from Performance Trends. Right now it's influencing me to lean toward the Isky 282. Once I've got the engine in the car, then it's off to the dyno and track for the real performance tests. I'd really like to try several different cams and see how things turn out. All it takes is money...

But Nick.... don't you need a girdle for the bottom end? I heard someone was using 1/4" steel plate to make them out of....

Jim

Quote:

Stg. I Buick V6, 1.77" int/1.5" exh. is max. at std. 1.660" valve centerlines.

Art, (or anyone else) do you know the valve centerline for the rover heads?

Same-o same-o. I'm not sure what Des Hamil has say bout it. He clearly states, Olds used "shrink to fit liners like Rover did-LOL. roverman.