I'm not sure if this is advanced enough for some of you guys so feel free to relocate this post.

I came upon a name the other day that some of you might know, Pete Aardema. Mr. Aardema has made a living building wild OHC motors out of previously pushrod blocks. Most notably attaching Porsche 928 DOHC heads to a BBC after realizing the bore centers were within .030".

Anyway, on his website you can buy an OHC kit.

http://www.aardemasohc.net/index_files/Page313.htm

Anybody have any experience with these? Any thoughts on advantages/disadvantages.

I know that GM sticks with pushrod engines for its racing motors for many reasons; lower center of gravity, lighter weight, simplicity of proven technology, etc.

Still, Aardema claims 7500rpm on stock valvesprings. I think this has some good application on smaller displacement motors (i.e. the beloved 302).

Your thoughts?

Jeremy

 

I have a 302ci SBC....a cammer mouse motor would be the ****

 

I actually just talked to Pete Aardema on the phone. He's a really cool guy. For what I want to do his kit would cost around $3000. But he also suggested I get some DOHC heads from an infinity/nissan. The bore centers are about .009" off an SBC.

Food for thought,

Jeremy

 

Can you tell us what he will provide for $3k?

 

Look at the link. I think he makes it out to be a little more simple than it really is, i'm not sure. It looks like an adapter to go on top of the heads. You actually send him your heads for fitment. 2 cams, of course. A belt and miscellaneous other pieces. The problems you might run into in the LT1 are your cam driven opti and water pump. The stock cam stays in the motor to run the oil pump, but the faceplate with all of the timing belt pulleys doesn't really look like it's meant for the LT1.

Still, for $3000 it doesn't seem like a bad deal if you just want something different. This guy loves different, he has a mid-engined Model A hotrod.

The only thing is that he didn't really seem like bothers with the OHC SBC anymore. He said he'd build one for someone who wanted it, but he's bored with them now. I'm not sure if that applies to the kits or not.

Hope that helps,

Jeremy

 

I'd be curious to know three things:

1. Are the implied horsepower gains strictly from being able to rev the engine higher, or are there any gains in the form of reduced frictional losses, etc.?

2. If 55mm LSx cams can be used.

3. If the adapters will accomodate shaft rockers.



That Donovan block with the 4-valve Infiniti heads looks downright menacing.

 

Hmmm, wonder if he would tackle a set of Dominion 32V heads...

 

It seemed to me that when it was tested on a dyno it gained something like 35 hp without revving any higher than a pushrod motor.

I'm sure you could fit any cam to this adapter, it just might take some work. The cams he uses are stock cams with every other lobe missing.

I have no idea about shaft rockers, call and ask him.

Jeremy

Edit: Bob, don't go ruining the guy's fun by making him try to get those heads to work on your motor. I think I might try that Nissan DOHC swap though, maybe we can line up if either of us ever finishes our motors.

 

There was a sprint car running out of Auto Speed Supply stables that had a set of hemi,OHC heads on a SBC back about '65/'66. They had a lot of trouble with it too. Don't remember the name of the heads though.

 

That Nissan head swap-- makes my head hurt.

 

You need to see a picture of the intake ports though, I'll post one when I get home tonight.

The runner is a perfectly concentric cylinder, you don't have to port it, just bore it until you get to the bowl and then do some blending. I don't think they will support the kind of airflow needed for 2 per cube, but they should deliver some good low-end torque numbers as well as power up high (hopefully).

I'm still trying to get some answers out of the nissan guys about which heads to use. The VK45 is the predecessor to the VK56 (Titan motor). I would figure the VK56 would be closer to fitting but if they share similar dimensions I like the 45's intake better (more LT1 styled). I think the VH45 is the VVT motor, i'm probably not even going to attempt that.

Thanks for the input guys, keep it coming,
Jeremy

 

That makes my head hurt worse.
I would like to see the pictures. Maybe by them my headache will be gone.

 

http://forums.nicoclub.com/zerothread/179262

About 2/3 down the page the guy who started the thread "defrag010" posted the pictures.

 

Ya might get the flow ya need but ya are probably have to use velocity to do it and sometimes that ain't good.

 

I don't mind not getting 350+cfm flow numbers. To tell you the truth if I build a motor for those heads it will probably make use of light-weight internals not designed for 600+hp.

If you'll notice the size of the combustion chamber though, I'll bet building a high-compression motor would not be a problem at all.

We'll see though, I'm not really crazy about trying to run 8500rpm or higher with a belt driven valvetrain. I also have to find a machinist to modify a block for those head bolts.

Just wondering though, what's wrong with high velocity air coming into the heads? Is it harder to distribute evenly?

Jeremy