3.4 DOHC Torque Plate

[series8217]

Just a note for anyone building up a 3.4 DOHC. BHJ (www.bhjinc.com) made a torque plate (honing plate) for the motor using my head dimensions and head gasket as a template. It is not listed in their catalog but you should be able to call them and order it. It's expensive and your machine shop may not want to buy one just to do your block, so if you're in central or northern California, you can get your block honed at Rossi's Engine and Drivetrain in Gilroy, since Paul Rossi has the first plate they built for my motor. The phone number is 408 8425950. Tell him Steven sent you.

My block was bored without the plate and then honed round to final bore size using the plate, so we were able to see how much the block distorts with the heads torqued on. The cylinder walls were definitely pulled out of shape as we could see by the initial hone pattern where it initially missed the areas pulled wide by the distortion of the block. I highly recommend honing with the torque plate to get the best possible ring seal.

[SappySE107]

RE: 3.4 DOHC Torque Plate

It should be good for the 3400 as well then. Do you know how much it was?

[smilinguy99]

Re: 3.4 DOHC Torque Plate

It's expensive

In 1980 I bit the bullet and bought a BHJ torque plate for a Chevette engine. It was $150 in 1980 dollars. I still have it if anyone is interested. Like you said, all I did was send them the gasket. But I also had to supply the height of the machined bolt faces from the deck face of the cylinder head. The plate has shallow counter bores on top of the plate where tubular spacers fit to simulate the height of the head under the bolts. This permits you to use the same length and type of bolt you intend to use for the final assembly.

sg99

P.S. Sorry for slightly off-topic post.

[Lyle's GTP]

RE: Re: 3.4 DOHC Torque Plate

I'm working on one. I got all the dimensions and the steel plate. Just have to send it to a machine shop.

Lyle

[series8217]

The 3400 has a different head thickness as far as I know, so I dont know that it will work.

Lyle, I dont think steel isn't going to cut it. Thats going to have different distortion properties than aluminum. The block and head both distort.

I don't recall the price because my machinist didnt charge me for the plate. I think it was at least $400 though.

[series8217]

Re: 3.4 DOHC Torque Plate

It's expensive

In 1980 I bit the bullet and bought a BHJ torque plate for a Chevette engine. It was $150 in 1980 dollars. I still have it if anyone is interested. Like you said, all I did was send them the gasket. But I also had to supply the height of the machined bolt faces from the deck face of the cylinder head. The plate has shallow counter bores on top of the plate where tubular spacers fit to simulate the height of the head under the bolts. This permits you to use the same length and type of bolt you intend to use for the final assembly.

sg99

P.S. Sorry for slightly off-topic post.

I wouldn't say its off-topic, that certainly is some good info. The torque plate we got from BHJ is the same way. Its a great piece. I noticed in GM's Super Duty 4 buildup guide they specify a BHJ torque plate also. They're a big name in the industry.

[Lyle's GTP]

Lyle, I dont think steel isn't going to cut it. Thats going to have different distortion properties than aluminum. The block and head both distort.

Well, I think it's better that nothing. There is no way you are going to mimic the destortion properties of an LQ1 head. What would you think you would use, aluminum?

I've been around a machine shop long enough to see several 450HP N/A 350's go out the door. They were built with aluminum heads. They were machined with a Cast Iron torque plate. But I don't work near a foundry so I don't have anybody to pour me a slab of Cast Iron. So, for all intents and purposes I guess steel will have to do.

Actually, one of our builders decided to bolt the heads on without installing the pistons and turned the block upside down and measured the bores again. Suprisingly, very close to the torque plate readings. WAY better than without using the torque plate.

But, I guess if you wanted to nit-pick you could build some sort of oil pan, timing cover and Bell-housing torque plate. That way you would cover all torqued items that may have an effect on the end result of the honing. We talked about such a thing but their was no way all of that would fit into our CK-10. So, you do what you can.

Lyle

[series8217]

Lyle, I dont think steel isn't going to cut it. Thats going to have different distortion properties than aluminum. The block and head both distort.

Well, I think it's better that nothing. There is no way you are going to mimic the destortion properties of an LQ1 head. What would you think you would use, aluminum?

I've been around a machine shop long enough to see several 450HP N/A 350's go out the door. They were built with aluminum heads. They were machined with a Cast Iron torque plate. But I don't work near a foundry so I don't have anybody to pour me a slab of Cast Iron. So, for all intents and purposes I guess steel will have to do.

Actually, one of our builders decided to bolt the heads on without installing the pistons and turned the block upside down and measured the bores again. Suprisingly, very close to the torque plate readings. WAY better than without using the torque plate.

But, I guess if you wanted to nit-pick you could build some sort of oil pan, timing cover and Bell-housing torque plate. That way you would cover all torqued items that may have an effect on the end result of the honing. We talked about such a thing but their was no way all of that would fit into our CK-10. So, you do what you can.

Lyle

Thats understandable. Just keep in mind the 3.4 block is not as sturdy as a 4-bolt main 350. Those things are built tough. You are right though, the difference between the aluminum plate and the iron plate probably isn't enough to worry about, especially if you're just making your own plate.

[v6h.o.]

I already have a 3.4L Torque plate made up. Also have an Ecotec torque plate too,

[Lyle's GTP]

Thats understandable. Just keep in mind the 3.4 block is not as sturdy as a 4-bolt main 350. Those things are built tough. You are right though, the difference between the aluminum plate and the iron plate probably isn't enough to worry about, especially if you're just making your own plate.

LOL I never was comparing an LQ1 to a 4-bolt 350. I was Just stating the fact that we used a cast torque plate, even when aluminum heads were used.

Lyle

[tejohnson]

Good info!

Anyone have a 3400 torque/honing plate? Care to rent? lol

Looking over BHJ's prices, this would be a lil setback...

http://www.bhjinc.com/1products/2-right-toc.htm

[farmerz24]

maybe if you talk to v6ho nicely he will rent it to you....

[napatiger]

My machinist (extra $50) said he line honed it, is that similair?

I think he had to set something up to make sure it was 60degrees.

Just looked at the invoice, it was 'Line Hone the Mains' extra $100.

Whatever that means.

[series8217]

My machinist (extra $50) said he line honed it, is that similair?

I think he had to set something up to make sure it was 60degrees.

Just looked at the invoice, it was 'Line Hone the Mains' extra $100.

Whatever that means.

You don't need a torque plate to line hone the mains on the 3.4. There is not much distortion in the bores for the heads being bolted on.. certainly none in the mains.
Aluminum block motors will often need torque plates to do the line hone, as there is significant distortion when the heads are bolted on.