I bought my truck back in April and to this day it has been a puzzle. Now, when i bought it, I was told it was a 400. Came to find out that the block is a 351m. After a day of research on the web, I found out that it is still possible that I have a 400. I just have to drop the pan and check the markings on the crankshaft. I still have to look at the shape of the transmission pan to be for sure whether or not I have a c4 or c6. I just had my carb rebuilt and an attempt was made to tighten the rocker arms but, they the bolts are tightened and theres still play in the arms. I was told that it would be best to rebuild the heads since I have such a great motor. If they're coming off, I want to make the best of it and get the most performance out of it. Australian 302 flatheads(i believe that's what they're called) would give me a 10:1 compression. This info I found on the internet. Unfortunately, they are hard to come by. Should I just have a machine shop flatten the heads? What are my options? Roller rockers? I'm not very familiar with heads, but I learn quickly. Any info would be greatly appreciated.

TC

 

[font size="1" color="#FF0000"]LAST EDITED ON 06-Sep-01 AT 05:19 PM (EST)[/font][p]first thing to do is pull the #1 spark plug out and take a brass rod in the hole and find top dead center (where the piston is not moving up or down) by turning the crank with a 15/16 socket and a braker bar. Mark the brass rod at a referance point like the top of the spark plug whole. Do the same thing at bottom dead center and mark the rod at the same refrence point. Take the rod out and measure the distance between the two marks on the rod. If it is 4" you have a 400 if it is 3 1/2" you have a 351. I have never heard of the heads you are talking about. The heads on a 351M/400 are the same head that are put on a 351C. Shaving the heads you have causes other problems like needing shorter push rods and higher octane full due to higher compression. roller rockers are great for less friction in the upperend but cost is high 250-300 range. Are you sure you dont have a 351C? If you do have a 351M and you rebuil the whole thing...spend the extra money and make it into a 400. Buy a rebuild crank from Advanced Auto for $175 and buy new pistions for a 400. Have a machine shop change the conecting rods over to the new pistions. Machine work will be the most expensive part of the rebuild. you may look into finding a shop that will sell you a engine already rebuilt. It can be cheeper. If you do it yourself it is cheeper if you buy a full rebuild kit with everything that you need. you will need to know if the block has been bored over usually .010, .030 or .060 and if the crank has been ground under usually .010, .020 or .030

 

oh yes...if you have a 351M/400 you will have a C-6. They don't put C-4's on that engine

 

Yes the Aussie 302C heads are hard to come by. The heads you have on the motor are identical to 351C 2V heads IOW relatively large valves and excellent flow characteristics. You can make them better by gasket matching, pocket porting and polishing. You can improve them still further by having the larger Cleveland 4V valves put in them. You certainly can shave the heads to increase the compression ratio but I'd start by putting new flat top Ohio Piston #1282P pistons in. These will get the C.R. up to 9:1 and if you only take a little off the heads you can get 9.5:1 fairly easily.

 

The heads you want are Australian 351c 2V "Closed Chamber" heads. They run about $350 a set for blank heads that need rebuilding. You can get them from a company in California, I think their called Power Heads. They sell them rebuilt for around $1000. They are in the mustang and fords mags in the back. There are other sources if you ask around. Your best bet is to rebuild what you have. They are an "Open Chanmber" design and work quit well. They are also cleaner burning if the EPA is an issue. You can get a little better flow by adding the 351c 4V exhaust valve. It's a little larger. I would keep my compression at 9.5:1 or below to avoid detonation.

Rocky

 

Uh...no...the 302C Aussie heads are the hot ticket not the 351C heads. The 302Cs have the small (58cc) closed chamber and small ports as opposed to the 351Cs which have a larger (73cc) semi-open chamber.

Powerheads does have a website with Aussie heads.

[link:www.powerheads.com/|Powerheads]

FWIW I have heard some less than stellar reviews of their workmanship & parts quality.

 

The Australian 302 is a destorked 351c. The heads are the same on both engins.

Rocky

 

Well if you look at this page which is put together by a New Zealander I think you might say different:

[link:www.geocities.com/infieldg/v8gallery.html|Geoff Infield's Page]

You can see the difference between the 302C and the 351C head.

 

As I said they use the same head. There are both open and closed chamber heads for BOTH motors. Just because they didn't mention the closed chamber head for the 351c doesn't mean they don't exist. I own a set that I got from a source that buys them when he is in Australia.

 

302Cs are "destroked" 351Cs and they came with the closed chamber/quench heads. The 351Cs came with the larger open chamber heads.

 

I'm already ducking,but here goes."Great motor"? A 351 or 400 M? Before I'd stick $1000 in a set of heads,I'd bite the bullet and spend $2000 for a 460.

 

Well...aren't you special?

 

Well Bill,I did go to special classes in high school and rode to school in a little special bus and Mom always told me I was special so maybe I is. Anyway,have a nice weekend.

 

So have you found out what you have under the hood yet?