2.9 Crank in 2.8, What's the advandtage?

[MikeH]

Seeing that there is info on installing the 2.9 crankshaft in the 2.8. I was wondering what is gained in doing this? And does it make any difference if you have the Mustang II block or the Bronco II/Ranger block?

 

[Jim E]

My guess is due to the difference in the thrust washers between the early and late versions of the 2.8 you would need a later, Ranger/Bronco type block. The thought here is the 2.9 most likly carries the same flanged main with the thrust washer built in as the later 2.8. I could be wrong and the early 2.8 block would work.

Why... well more displacement but also you can bump the compression to the 10 to 1 range with stock pistons, which is a good bit up from the stock 8 something. Custom 10 to 1 pistons for this motor are pretty pricey so I figure it is mostly a cheap or cheaper way to build power.

I would like to try the 4.0 crank in the 2.8 block, now that would be interesting...

 

[Series6]

2.8 Block-stripped

Jim E.

I'm looking at buying a bunch of parts which includes a stripped 2.8 block. My question is should I look for a 2.8 crankshaft or a 2.9 or do we try the 4.0? Looks like I will be shelving the Cobra replica and building another V6 ground up. I need to start thinking about the engine. Any advice?

I also have a clean reubuilt stock 2.8 waiting in the wings.

So many decisions....

 

[V6 JOSE]

Hi Jim,

Either block will work, because the cranks for the early and late, have the same size thrust journal width. The only difference between them, is that the later crank has undercut fillet radiuses to stengthen them, since they were a truck engine.

Another reason for the 2.9 crank in the 2.8, is that it has a longer stroke, which means more torque too. I would love to see a 4.0 crank in the 2.8, but I think it would take the 4.0 rods and custom pistons. Another concern would be if the 2.8 heads would flow enough air to feed a healthy 4.0 on the top end. For something like that I would guess you'd need to use a set of heads from a 1974 Mustang II/Capri, which have no heat risers.

I don't know if I would want to go with 10 to 1 compression in any of these engines, if they are meant for the street, because I tried that a few years back, with less than spectacular results. These engines make more than respectable power with 8.5 t0 1, so something between 9.0/9.5 to 1 should perform really well, without running the risk of having to deal with detonation.

Jose

 

[MikeH]

Jose,

So do you feel going with the 2.9 crank is a good thing or not worth the added expense if only used on the street.

Mike

 

[V6 JOSE]

Jose,

So do you feel going with the 2.9 crank is a good thing or not worth the added expense if only used on the street.

Mike

Hi Mike,

It all depends on what you want. If you plan on just driving it around, then I think it would be a waste, but if you are wanting to get the most out of your engine, then it could be good. Never having tried a stroker 2.8, I can't really opine definitively, but I would think it would enhance performance significantly.

Rob Wiseman is building one of these engines, so when he finally gets it running, we will have a better idea of what the performance of this combination is.

Jose

 

[Series6]

1974 heads

Jose, Jim E,

I'm sure this was covered before but how do you confirm the year of a set of heads? I have a set of heads already may be getting a second set.

 

[fowfam]

http://www.aacncclub.com/FORD_HEAD_CASTING.html#v6fordhead;)75tm. Josh.

 

[Jim E]

The heads you want are 1974.

Just talked to Standard Crankshaft in Charlotte and they will do the snout mod on the 2.9 crank and grind the crank for around $200. I use Standard for all my crank work they are the Delta Camshaft of the crank shaft world.

 

[MikeH]

Do they know the modification to be done, or do you need to supply the measurements?

 

[Jim E]

I talked to Joe in the machine shop at Standard crank and he said you just need to tell them you want the snout of the 2.9 crank machined to match the snout on a 2.8 crank. He would either pull a 2.8 core off the shelf and match them or go off the crank specs or most likly both. He said figures it is around $125 to machine the crank and $75 to turn the crank, plus or minus. My guess is they have a 2.9 crank in stock and could machine it for you and you just pay the machine cost and the core fee, or you could just ship your core. The direct line to Joe at Standard is 704 538 9877, nice guy and I am sure he will answer any question.

 

[MikeH]

Thanks Jim.

Do you know which rods and pistons are used with the 2.9 crank?

 

[Jim E]

Rods are the same on both motors, as I recall, pistons you just want the size you bore to for the 2.8. I think if you do a search on NAPA for 2.8 pistons they list a couple different units with slightly different compression heights so you can tinker with teh compression a little. Also you may want to check ebay for pistons seen 2.8 pistons on there real cheap

 

[MikeH]

Anyone else have experience with the 2.9 crank in the 2.8? Googling around on the web I've found posts on other forums saying the piston skirts would need to be trimmed as they would hit the counter weights of the crank and that the pistons will protrude approx 1.5mm above the deck.