Engine and Transmission Tech

Chad, I'm there with you, as well. Trying to build a "good" but not "best" engine. Sounds like you'll be ahead of me, so I'd be interested in what you come up with. Did I read that you're going with the 300 heads? I did splurge a bit and bought the TA heads, but my engine is in storage, so it'll be awhile before anything is done.

To clarify, you reduce main sizes to 2.5"? Where do oil holes wind up ? Then you twist for maximum HP at 6k.?

300 crank and later (4.0, 4.6) Rover mains are already compatible, but Rover (4.0, 4.6) big ends are bigger than Buick 300.

Early Rover used smaller mains, but same size big ends as Buick.

There’s a handy chart on this page:
[aluminumv8.com]

As far as targeting a particular rpm, both the Pipemax predictions I’ve done, as well as Jim’s dyno software, seem to show the combination not running out of breath until around 7, provided the flow inputs can be matched by reality. So far none of the choices I’ve made would lead me to think I’ve got to worry about breakage at 7, but I haven’t gone for a valve and spring and lifter and head package that I absolutely know won’t float past 6.5. To guarantee stability at 7, I’d think about spending more on those components. That’s the thought process I’ve used to make my purchase decisions - feel free to nudge me differently if you see a logic failure in there!



Edited 1 time(s). Last edit at 02/26/2024 10:02AM by MGBV8.

On the 340-350/300 stroker crank setup, yes the oiling holes do migrate across the main journal a bit when you cut down the mains. A little judicious work with a die grinder gets you back in the center. Then the mains are ground and polished normally. Don't overlook the seal journal. Honda or Toyota rod journal sizes used with Nascar take-out rods (Carillo, etc) gets you back to a standard size on both rods and mains but be aware, some sizes only have standard size racing shells available, so if you have to replace the bearings on down the road it may become necessary to prep another crank or swap rods. Careful rod selection can avoid this.

Incidentally I have a standard 300 crank available if anyone needs one.

Did you buy the bare heads or complete? If bare have you decided on your valve sizes? TA heads can go up to a 2.02" intake with a 1.6" exhaust valve but that requires you to siamese the seats. Which can be done but it does add another potential failure point. A 1.9" intake with the 1.6" exhaust avoids that problem and makes use of the seats the heads come with. It's about as big as you can go with the seats as supplied. But, that's a big step up from any of the OEM heads. It also eliminates any concern about shrouding. I was lucky enough to find some good used titanium valves I could make work, but had to shorten the stems and cut down the heads of the intakes. In the process getting into the whole keeper/retainer issue including angles and groove designs. But these valve weigh about half as much as stainless. Spring height is another issue you can play with, the TA heads are designed to take a taller spring than the OEM heads. There is a good beehive spring that will give you somewhere around 300-350 lbs on the nose and maybe 150 seated. Those numbers are good for 6500-7000 rpm with a 1/2" lift roller cam. The decreased weight of the beehive springs is an advantage, as is the coil stability at speed but you have to run them close to coil bind to get that last benefit. So your calculations are important.

Also important are the weights of your pistons and rods. A good forged piston should come in under 500 grams, a good rod not much over that. You can drop nearly 100 grams by using a light weight wrist pin. The crank bobweights are lightened as a consequence. All of these things matter and result in a more responsive engine. Should be standard cost for balancing. The later 350 crank should be heavy enough to allow internal balancing without adding mallory slugs which can allow you to use Chevy flywheels and balancers without an offset weight, reducing the cost of those parts. The Chevy flywheel requires one hole to be elongated a bit to match the Buick indexing. Not really sure how much of an advantage this is, as matching Buick parts are available at competitive prices.

TA carries a paired roller rocker set that uses the stud mounting and is an economical choice. Uses guide plates. Be aware that the cheap import chevy roller rockers have a history of bearing failures.

If you are going to the trouble of enabling 7k on the top end it just makes good sense to properly prepare the bottom end as well. The resulting engine's performance in an MGB will be outstanding.

Jim

Jim,

I got my heads bare--they would not sell them as complete as they told me they are backed up by over a year on head work. Having said that, I am definitely going to go with your suggestions and stick with the standard valve seats with the 1.9" INT and 1.6 EXH, which, as you mentioned, is already a big improvement over the stock heads. I will also go with the TA roller rocker set you suggested (as well as the Buick flywheel, which I believe they offer).

Regarding your comments on the Nascar takeout rods, I have a set of Ford rods, which I thought has the standard sizes, but now I'm wondering what you mean by "standard size racing shell"?

Once again, the advice here is invaluable :)

Eric, I don't remember the exact details but I bought two sets of 6.2" nascar take-out rods. One set was Carillo and the other was... Pankel? Not sure, they were bought by Carillo and are better in some ways and not in others. (Had a better split interface) They used two different brands of big end bearings both around 1.9", maybe one was Toyota and the other was Honda bearing shell inserts. As it turned out one was pretty common with a variety of bearings available and the other was a one size racing insert. I do not remember which was which so if you see a set of rods you like that is a thing to check out before buying them.

But my point on the nascar rods is that for around a hundred bucks you can have the best rods available anywhere. Then you take what you saved on the rods and spend it on a good set of custom pistons where you can specify every detail so they match your needs perfectly, and then without spending too much money you have a bulletproof bottom end in a perfectly designed engine. Even if you spend $1200 on the pistons, that's still only half that if you split the budget between the pistons and the rods and $650 for a set of custom forged pistons is quite a nice price. It's a handy way to justify it. And then you get to spec out not just the bore size, pin size, compression height, squish distance, skirt design, dish and CR but also ring package size and type, pin locks, gas porting, oil drainback holes, coatings if desired, and any number of other details you can come up with. Spec out light weight tool steel wrist pins at the same time and drop even more weight.

But do not choose teflon buttons. They are nice but they are heavy and unless the engine will be torn down often there is just no need for them.

Jim

Jim, thanks for the additional details--the approach you've suggested is definitely what I'm going to pursue. Should make for a strong and reliable engine :) Now, if I can get one of the piston companies to return my call. Best, Eric

I bought Wiseco through my local machinist, let him make the calls.

Jim

Makes sense, thanks.