RWD Crank in Series II/III Block

[CTX-SLPR]

Howdy,

Let me explain why since that's likely the first thing on your mind. I'm building Bonneville Land Speed engines and plan on racing with a 'F' motor that's 123-183cid. That's 3.8in bore and 2.66in stroke. I already have the crank, a 2.66in oddfire Sprint Car castoff and I'm hunting up a block. If I get out of Production I can use any block I want and Series II/III blocks are both prevalent and more than strong enough for the level of power needed to get me into expensive safety requirements.

Look at: http://www.enginebuildermag.com/Article/4142/rebuilding_the_38l_buick_engine.aspx I can't spot a difference that looks significant enough to forbid me from putting my crank in a cast off late block from the U-Pull-It.

Anyone know anything I'm missing?

Thanks,

 

[turbodave231]

You will need to fabricate some way of sealing the RWD crank. All the 3800's ( worth using) use a one piece rear main seal that presses in over the end of the crank.

The early VIN C and L 3800's used a 2 piece Rear main, but i don't believe they had the cross bolted main caps. The VIN K and 1 blocks are the stronger block .

The bellhouse pattern on all 3800's is not standard BOP pattern. You can get 4L60E transmissions with the 3800 pattern. You would need an adapter plate to bolt up a 200-4r or 4L80E trans (and that's what I'd be looking at for land speed racing).

 

[CTX-SLPR]

We'll see on the transmission, TH700R4's should take the power at the levels I'm starting at through the Metric-60 bell doesn't leave as much room for a large converter and that drives the lockup clutch size Adapter plates are available though. I have thought about how to seal the rear main with the change in design. Probably build a holder for a 2 piece seal into the existing rear cover so I don't alter the expensive crank incase I decide to go Production racing and go back to a traditional "RWD" block. With the destroke I also expect there to be no clearance issues with counterweights.

 

[CTX-SLPR]

Ok, being stuck on an airplane for a few hours will get you thinking so here's what I've come up with during my meditation/muses.

1. Rear Main Seal (as previously mentioned)
2. Distributor Mounting, I have to run a distributor or magneto so probably a swap to a late 80's 3.0 or early FWD EFI 3.8 cover to add the mounting provisions
3. Cam, need to see if an oddfire Stage II piece will fit since I'd need both the firing order and a distributor drive setup
4. Deck Height, the Series II/III deck height is 1.0in less than a 109 which means I need shorter pistons and maybe shorter rods than the "RWD" setup I have laying around
5. Transmission, (as mentioned) the blocks have Metric-60 bells that limits converter size and for LSR I'd need as big of a converter lock up clutch as I can get

 

[charlief1]

I hate to shoot you in the foot but it won't work unless you're willing to do some serious machine work. The mounting flange for the flexplate is larger on the RWD crank than the FWD crank. It will take more than an adapter to put the crank in. You'll also need to have a custom flexplate made to work since it's got a smaller diameter flexplate in it as well. You may even need to have the block machined to do this.

 

[CTX-SLPR]

Don't worry about "shooting me in the foot", I've not bought anything for this direction and am trying to catch things like this before I do spend any money. Your response is what I am hoping to discover before I get to the spending of money.

As far as the crank flange, I was expecting to have to machine the rear cover to pass the flange through then rig up an adapter to put a seal onto the rear main seal area on the crank. I'll look into the flexplate issue, since I'm going neutral balance that might make the problem easier to solve but we'll see.

Another thing I found today was that Series II/III heads have huge ~63cc chambers and with the short stroke and a target of 9.0=10.0 compression, that might be hard to get without a domed piston and that greatly negates the cost advantage of the Series II/III block if I have to get custom pistons.

I'll keep thinking about this....

 

[Reggie West]

You should give Ken Duttweiler a call. I will bet you he can give you an answer for this.

He has a thing for land speed racing.

 

[turbodave231]

I saw Ken at Bonneville in 2011. He is working on George Poteet's Speed Demon in this picture. Quite sure he can help you!

 

[CTX-SLPR]

Yeah, I probably should give him a call. I guess I'm just scared the word "budget" doesn't sit well with him. I mean I know this will be expensive but I'm trying to limit how much it will be by limiting expectations.

 

[hiboom]

with all the modding and machining and trying to match up mismatched parts aren't you worried about vibration and the thing coming apart at high speeds just curious.

 

[frank_ster]

the bore spacing is a different in the series 1 and 2. why not use a front wheel drive block 1987 3.8 ?

 

[CTX-SLPR]

with all the modding and machining and trying to match up mismatched parts aren't you worried about vibration and the thing coming apart at high speeds just curious.

The oddfire crank will be doling out the vibrations but it's stronger than an evenfire and I got it for a song compared to what a forged 2.66in stroke even fire unit would cost, especially since I couldn't find one with that short of a stroke. The rotating assembly will be balanced to 7000rpm which is as far as I'm likely to ever take it. Balancer and flexplate will be neutral balance pieces and the crank is already an internal balance Moldex unit. I'm not concerned about the "mismatched" parts vibrating and coming apart with a Series II/III block any more than with a RWD or even a Stage block.

the bore spacing is a different in the series 1 and 2. why not use a front wheel drive block 1987 3.8 ?

I'm not sure what you mean, they are all the same bore spacing. The deck height and the bank offset are different but first I've heard of a difference in the bore spacing. And to answer the why in a more general sense, I want the cross bolted mains and other improvements that came with the Series II/III engines.

From my calculations I won't be able to use the Series II/III heads without some form of positive dome custom pistons to hit my 9.5-9.75:1 compression target. The chambers are just too big at ~63cc's. With off the shelf pistons and rods I can meet the compression target with the older 8445 and HA heads just fine but they are still $$'s for a set. This idea is starting to loose it's charm for cost reasons but is still attractive for availability and strength reasons.

 

[frank_ster]

The oddfire crank will be doling out the vibrations but it's stronger than an evenfire and I got it for a song compared to what a forged 2.66in stroke even fire unit would cost, especially since I couldn't find one with that short of a stroke. The rotating assembly will be balanced to 7000rpm which is as far as I'm likely to ever take it. Balancer and flexplate will be neutral balance pieces and the crank is already an internal balance Moldex unit. I'm not concerned about the "mismatched" parts vibrating and coming apart with a Series II/III block any more than with a RWD or even a Stage block.
I'm not sure what you mean, they are all the same bore spacing. The deck height and the bank offset are different but first I've heard of a difference in the bore spacing. And to answer the why in a more general sense, I want the cross bolted mains and other improvements that came with the Series II/III engines.

From my calculations I won't be able to use the Series II/III heads without some form of positive dome custom pistons to hit my 9.5-9.75:1 compression target. The chambers are just too big at ~63cc's. With off the shelf pistons and rods I can meet the compression target with the older 8445 and HA heads just fine but they are still $$'s for a set. This idea is starting to loose it's charm for cost reasons but is still attractive for availability and strength reasons.

oh yea sorry i meant bank offset is different.