I am going to do this no matter how many folks think I shouldn't. I'm going to do a little unshrouding of the intake side of the chamber and don't want to lose the CR. The heads are going on a 3400 block. So If I mill .060 off the 2.8 head, how much do I mill the intake flange?

Thanks for your help!

Woody

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woodys 427

There is a geometry chart online that concerns this, but I'm betting you won't need to bother with the intake flange. Milling the heads makes them sit lower, but also allows the intake to sit lower as well. Test fit the intake before you do anything to it, and simply pay attention to ports lining up correctly. Blueing ink should come in handy.

Be certain check your piston to valve clearance with some modeling clay. 60 thou is quite a bit.

One of the 2.8 engines I built as a 3.2 stroker needed a compression bump, so I had a total of 0.025" milled off the block and heads. As a result, the lower intake didn't fit right. I had to have the intake milled as well... both where it meets the heads AND where it meets the block.

So if you mill 0.060" off the heads, you'll need to mill a bunch off the lower intake as well.

Don't remember the "formula , but each .010 you cut gains 1/4 point in compression boost. so, .060 gets you 1.5 , 9.0-1 to 10.5-1 , hope you like Premium gas. yea, check your piston to valve with clay. high lift cam may create problems.

I don't like to assume, but I seemed to, anyway. If the block deck height is changed as well, it's more likely to alter intake fitment. Just the heads, though, can be different. I do agree here that 60 thousandths is an awful lot.

quote Originally posted by Blacktree: One of the 2.8 engines I built as a 3.2 stroker needed a compression bump, so I had a total of 0.025" milled off the block and heads. As a result, the lower intake didn't fit right. I had to have the intake milled as well... both where it meets the heads AND where it meets the block. So if you mill 0.060" off the heads, you'll need to mill a bunch off the lower intake as well.

I'm using 3.4 pistons in the 3400 block. The 2.8 had flat top pistons - the 3.4 have an .080 dish. The cam has .468 lift - not radical. More importantly to valve clearance is the 112 LSA. and the 217 duration. I will be taking some material off the combustion chamber to unshroud the intake valve. I'll cc the heads while I'm working on the chambers. I like to use set up valve springs and rotate the engine to max. valve lift. I set up a dial indicator - 0 it - and push down on the valve until I hit something. If clearance is too tight I'll make a cutter out of an old valve and put a notch in the piston. One of the problems with milling is the flat space between the intake and block where we put the RTV gets too tight. The blosk usually requires a little milling to open up a gap for silicon. I would rather keep the manifold non motor specific and do the milling on the block and heads. One thing I can't get away from is the intake bolt holes will most likely need to be slotted.

Thanks, Woody

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woodys 427

Have you considered head gasket thickness to help achieve your desired CR? I'm interested to know if you're going thick or thin. When I built my SBC, I had a hard time finding a gasket ideal for the build I wanted to achieve pump gas safety as well as valve clearance reassurance. Cometic was as close as I could find and was still thicker than I wanted.

I think the Camaro gasket is .040" and the 3400 gasket is .080". I always use the Camaro gasket... I also think there are some after market ones...

Personally, I would consider shaving the pistons to be flat and using a 5.8" rod and the thicker gasket...

The stock iron heads support .540" inches of lift with flat pistons... You shouldn't really have any clearance issues. I'm running .480" lift on DOHC pistons and those are domed with the thinner 3.4 gasket.

[This message has been edited by lou_dias (edited 03-17-2016).]

quote Originally posted by lou_dias: I think the Camaro gasket is .040" and the 3400 gasket is .080". I always use the Camaro gasket... I also think there are some after market ones... Personally, I would consider shaving the pistons to be flat and using a 5.8" rod and the thicker gasket... The stock iron heads support .540" inches of lift with flat pistons... You shouldn't really have any clearance issues. I'm running .480" lift on DOHC pistons and those are domed with the thinner 3.4 gasket.

Not a good idea with stock "cast" pistons

I made some drawings and scaled them up 20 times actual size for measurement accuracy. I came up with .845 X amount of cut. I'm taking a .060 cut and "0" decking the block. For example sake a total of .070 total taken off the head and block. The intake side of the head would get .059 taken off. The block flat spot is 1.14 X the amount taken off head and block. That would be 1.14 X .070 = .080 off the flat spot of the block. The intake should fit without further adjustments.
I think the cut to make the piston top flat and use a longer rod is innovative but I think the ring land would get pretty close to the top of the piston. I don't know how the weight of the rods compare either. I think we all to often we parrot what we hear, I know I do. It is refreshing to get a totally different approach.

Thanks, Woody

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woodys 427

Have you talked to a machine shop or an engine builder? They should be able to assist if they do the milling.

quote Originally posted by jaskispyder: Have you talked to a machine shop or an engine builder? They should be able to assist if they do the milling.

Assist... YES

However, expect some dis-interest out of them. Not much call for a modified 2.8. If they don't know it just tell them it's basically a SBC with 2 cylinders cut off. Then they might be interested in the challenge.

You might also try finding a shop that has an interest in building 4.3's. There are some fans of the 4.3 and shops that build them. If a shop is building 4.3's then they don't mind building V-6's and those are the shops that would have interest in building a 2.8. Shops that do V-6's will know the little tricks that make them work. If you don't find a shop that knows the little tricks, you might as well just deal with your local NAPA machine shop and hope for the best.

The machinist I use did all the machining on my Dart 427 that's in my 87GT. When I file fit the rings, I took the first ring and checked to see how close the other cylinders were. The same feeler gauge fit exactly the same in all the cylinders. My point being this shop builds all kinds of racing engines and they are good. When I asked the machinist about the flange milling he said he would take a clean up cut and them we could cut the manifold to fit. This isn't a logical solution. They don't do this on their V8's. When I was checking formulas I found that even the 90 degree V8's are all different formulas but they are available. There are none to be found for the 60 degree engines. I took the simple approach. The block is 60 degrees, the intake 90 degrees and worked off a common centerline. The machinist was pretty interested in my project because it's the first performance 3400 they have done. He told me the factory doesn't recommend head or block milling because of the intake bolt misalignment. He showed ma around the shop. I saw everything from 355 sbc's to mountain motors. At any rate I'm going to drop off the formulas at the shop tomorrow. If I am wrong I'll only need a couple of 2.8 heads and intake and start over again.
Woody

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woodys 427

Took my International 345 ('73) heads to a machine shop. The guy knew exactly how to mill these and gave me specific (Intl engine) tips if I have the engine rebuilt. We talked about milling the intake, etc. All depends on the shop.

quote Originally posted by Thunderstruck GT: Assist... YES However, expect some dis-interest out of them. Not much call for a modified 2.8. If they don't know it just tell them it's basically a SBC with 2 cylinders cut off. Then they might be interested in the challenge. You might also try finding a shop that has an interest in building 4.3's. There are some fans of the 4.3 and shops that build them. If a shop is building 4.3's then they don't mind building V-6's and those are the shops that would have interest in building a 2.8. Shops that do V-6's will know the little tricks that make them work. If you don't find a shop that knows the little tricks, you might as well just deal with your local NAPA machine shop and hope for the best.

quote Originally posted by lou_dias: I think the Camaro gasket is .040" and the 3400 gasket is .080". I always use the Camaro gasket... I also think there are some after market ones...

Just FYI, the 3x00 head gasket is 0.060" thick.

Also, the Cometic MLS head gaskets are available as thin as 0.027" for the 60-degree V6.

[This message has been edited by Blacktree (edited 03-17-2016).]

quote Originally posted by woodyhere: I'm using 3.4 pistons in the 3400 block. The 2.8 had flat top pistons - the 3.4 have an .080 dish.

Most people buy the 3.4 DOHC flat-top pistons w/valve reliefs for this app. (gives around 9.5 CR)
Federal Mogul 3.4 DOHC hypereutectic pistons are part number H684CP
More on pistons: https://www.fiero.nl/forum/A...010824-2-008285.html




From Silv-o-lite catalog PN 3483HC

[This message has been edited by fierosound (edited 03-18-2016).]

Thanks for the gasket info. I have some .040 3.4 Camaro gaskets but until I CC the chambers I won't know which gasket to use. I think it's pretty important to mill the head flange surface, not as much on the 2.8 because we don't have many intake choices. To build an engine that is intake manifold specific doesn't make sense. It would mean any intake manifold chance would send you back to the machine shop. In my case if I screw up the intake with some crappy porting, I just find another stock intake and start again.
The guys at the machine shop really like my 87GT. I have done enough work with them that they are interested in my 85 project too. I really didn't feel any prejudice towards my V6 project. In fact the machinist was pretty darn enthusiastic. Real car guys have a real interest in any car or project. My step son is a tuner. Small motors and lots of HP. He still really enjoys my Fiero projects even though one has a big old V8!
I'm using the roller rockers off the 3400 motor. I found that the 2.8 guide plates are just a little too tight and the rocker arms just touch. I think I'll use the plasma torch and split the guide plates and open them up just a little and then tack them back together. I could just sand the groove but then the push rod would have too much wiggle room.
It is definitely easier to build a 90 degree engine but not nearly as much fun.

Woody

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woodys 427