Engine and Transmission Tech

tips, technology, tools and techniques related to vehicle driveline components

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5567 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Stroker P76?
Posted by: BlownMGB-V8
Date: April 15, 2018 12:19PM

Here's a question. Since the P76 had a taller deck, (slightly shorter than the Buick 300) how feasible would it be to use a 350 Buick crank in the P76 block?

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3434 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Stroker P76?
Posted by: MGBV8
Date: April 16, 2018 09:37AM



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5567 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Stroker P76?
Posted by: BlownMGB-V8
Date: April 16, 2018 11:55AM

Thanks Carl, I'd forgotten those threads. Yes there would be issues but I think they could be worked around.

First off, you wouldn't want to use the 350 rods. They are both too long and too heavy. Something about the length of the 300 rod would let you get out of the ring package with the piston pin. There are plenty of dirt cheap forged nascar rods available these days in that range that are both strong and light, and then it's a matter of choosing the right piston. The less weight the better. Hundreds of grams can be removed from the rod/piston/wrist pin combo. This and a lightened flywheel can make for an engine that will rev very freely. Worth the expense of a custom forged slipper skirt piston here.

And allow me to make a point. If you are racing, the faster the engine will rev the better, with no limitation. On the street things are not the same. A V8 that revs like a motorcycle engine will not make you happy for very long. Unless you have it hooked to an automatic maybe but then what's the point? Starts can be an absolute pain in the butt, and something that demands all your attention. Same with gear changes. There comes a point where you will just want a heavier flywheel. Ask Chris about that after he swapped out his aluminum wheel on his stroker 300/350. Not like it didn't have the torque or the momentum to get the car going. No, it's all about the comfort level when driving. You may think it'll be better but the truth is, it may not be. In reality it's all about finding the right balance point. Very much like choosing the right axle gear set. There is a range that will make you happy. Right in the middle of that range is probably ideal, but go very far off in either direction and you begin wanting something different, to the point that the car has lost it's charm. So your goal is to hit that target. Not work towards one end, because I can assure you it is possible to overdo it if you plan to drive the car regularly.

About the bore. It is not cost effective to re-sleeve the block to a larger bore. Much better to put the money into the heads and that way you do not compromise the reliability. For the cost of a re-sleeve you can just about buy a set of TA Rover heads. Or if you want to go cheap use the 300 heads. Any other choice is largely pointless I think.

What you end up with is a 5 liter engine that weighs in around 350 lbs. Should be very streetable and reliable too. I don't buy into the comments about not being able to rev. It makes about as much sense for me to say that the stock 1800 won't rev because it has a bore of 3.15" and a stroke of 3.5" and we know quite well that engine can hit 7 grand. It's all about how you build it, and the lighter the reciprocating assembly the better it will rev. Hence the nascar rods and custom pistons. And good heads.

As for the intake, single plane intakes for the P76 do exist. Not easy to find and not especially cheap but they definitely are out there.

So for someone who is especially conscious of vehicle weight this does offer a path to a 5 liter car at the absolute weight minimum. (Curtis, are you listening?)

Personally, I find the iron 300 block more attractive. Yeah it does weigh probably somewhere between 50 and 80 lbs more (actual weight of the P76 block is unknown, the difference could be less) but you get the 3.75" bore size and the 350 crank is a drop-in. (Mains are the same size)

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3434 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Stroker P76?
Posted by: MGBV8
Date: April 16, 2018 04:45PM

Then, there is some grumbling about the 4.4 block being known to split down the lifter valley. Not good.


mgb260
Jim Nichols
Sequim,WA
(1894 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Stroker P76?
Posted by: mgb260
Date: April 16, 2018 06:15PM

Plus it is in Australia!


roverman
Art Gertz
Winchester, CA.
(2899 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Stroker P76?
Posted by: roverman
Date: April 16, 2018 07:07PM

IMHO. Much trouble, underwhelming results. Why not off-set grind rod journals on a 4.6 crank ? Cross bolted mains and better breathing 3.7" bore. Better oil pump and siphon tract, plus availability ?


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5567 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Stroker P76?
Posted by: BlownMGB-V8
Date: April 17, 2018 11:04AM

Probably right Art. 1/2" off the mains, or offset grind. Too much money, just drop the 350 crank in the 300 block and go.

Jim



roverman
Art Gertz
Winchester, CA.
(2899 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Stroker P76?
Posted by: roverman
Date: April 17, 2018 04:42PM

3.85" stroke is a lot ! Advantage in a 2,500/less, lb. LBC ?


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5567 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Stroker P76?
Posted by: BlownMGB-V8
Date: April 17, 2018 06:04PM

Well, I can tell you it seems to work right well in my car with the 340, light reciprocating assembly and flywheel. I wouldn't want to take any more weight out than I already have, it already wants to go, and it really has the power when it does. Of course I haven't got the tune sorted yet for high speed, that'll come later. But so far I couldn't ask for more.

Jim


Sorry, only registered users may post in this forum.