Engine questions-rebuild time

[lak2004]

Ok so I understand how a gasoline engine works but there are some questions I have.

What is the difference with a flat top piston and dish style? Advantages and uses?

How do you port and polish a head? Something I can do at home with a port and polish kit?

Anyone have any good links to engine rebuilding?

I want to bump up my compression a bit to run propane, how do I go about doing that and what parts will I need?

Thanks for the info guys!

 

[Hogback Fabrication]

What is the difference with a flat top piston and dish style? Advantages and uses?

A dish, flat top, or dome piston is used to influence the size of the combustion chamber and hence influence the compression ratio.

Dish top pistons will yield a lower CR than a flat top piston etc.

How do you port and polish a head? Something I can do at home with a port and polish kit?

Basically you are just smoothing out the casting to allow air to flow through the head more easily. Some people take enough material out to match the ports on the head to the intake and header.

 

[lak2004]

Sweet thanks Chris always quick to answer my noob questions

Ok so now dif between a double roller and true roller timing chain?

I am looking at a rebuild kit from northernautoparts.com , think I could handle it? I dont plan on boring out the block but I can get new pistons and rings and all that good stuff for like $250. Will I need forged connecting rods or is that overkill? I just want this thing to stop leaking oil.

I will be pulling the heads in the next couple of weeks to scope everything out and see whats needed as well.

 

[shaun89]

another way to bump up the compression is to deck the head, if u dont know what it is, its just taking a small amount of metal off the bottom of the heads, so the combustion chamber is smaller, people do this a lot if their heads get warped and blow head gaskets. you would have to bring your heads to a machine shop to do that.

 

[Hogback Fabrication]

But if he's replacing the pistons anyway he might as well get his compression from them.

I don't think forged rods are necessary (I'm running the stock resized 5.7" rods in mine). Hypereutectic pistons may be a good idea.

Keep in mind that higher compression is harder on all of the rotating assembly. What compression ratio are you thinking about? 11:1?

I'm sure 4x4HIGH will see this and be able to tell you what you need.

 

[lak2004]

Well to be honest I have no idea what compression to even shoot for, this is going to be really low budget so I can at least come wheelin a few times with you guys.

What is stock compression? 9:1 or something? Would 11:1 be a good goal?
Can I deck the block a bit and change the pistons to accomplish that?

 

[Russell]

Stock is like 8.5:1 for most of the mid 80s 350s. 9.6:1 is already in premium fuel range, but if you are planning to run propane, I'd shoot for 9.8:1 to 10:1. Make sure you run a distributor that is curved for running on propane as well, they like lots of timing compared to a normal gasoline engine.

Simply running flat tops with a 64cc head would get you up in compression a great deal. If you are serious about taking all of this apart, you'd probably want to pay a visit to your local engine / hotrod shop and have a chat with one of the guys there. They can probably offer you way better advice

 

[UPS]

10:1 is about the most you should go if you are going to run pump gas.

Edit
I read this yesterday and forgot you said you wanted to run on propane.

Mike

 

[travisc454]

what about slapping one of these on there . kill two birds with one stone sick power gain and higher compression (boost). 1,829$ 142 blower

 

[Hogback Fabrication]

Well to be honest I have no idea what compression to even shoot for, this is going to be really low budget so I can at least come wheelin a few times with you guys.

What is stock compression? 9:1 or something? Would 11:1 be a good goal?
Can I deck the block a bit and change the pistons to accomplish that?

Does the motor need a rebuild?

 

[lak2004]

Not too sure yet. I am going to pull the heads soon. My plugs were pretty oil soaked when I checked them the other day.

 

[Hogback Fabrication]

Not too sure yet. I am going to pull the heads soon. My plugs were pretty oil soaked when I checked them the other day.

You can try a compression and/or leakdown test. Its a lot less work and money than pulling the heads.

The oil could be coming from the valve seals.

 

[4X4HIGH]

PM me when you can and i'll go over with you what you need to do.

 

[bradshawtech]

Hey Lak, Dont forget to mention our elevation here in SW Colo. It tends to alter engine build plans and net gains. When people speak of HP and engine spec's they are using sea level data.