Sorry for the long Post.
I am back. If anyone remembers I rebuilt my 1978 351m in a 1982 F150 step side with a lot of performance stuff. Aussie heads,headers, performer 400, edelbrock1406, Msd 6a, Msd dist (Mechanical advance) Crane 272h cam, headers,hv oil pump ,C6 trans with 3 50 rear. Check list on my Gallery. The eng ran great after, tuning carb and shangin stop and spring on dist. I had 2 problems and I put the hole thing on hold for a while.

1. I could not stop the engine from pinging. Timing was set to all you guys recommendations. Still would ping or would not restart after warmup.

2 The old oil pressure problem. none at Idle, and knock at idle verfied with mechanical guage.

I messed up when I put the eng together. I did not plastic guage it!!! the eng is out now. I have not pulled the pan yet. The orginal crank was cut .10,new bearings etc. This is what I am going to check.
Crank/rod bearing condition
Verify bearing size
Plastic guage
Condition of oil pump and pickup tube.

I will replace.
I have a brand new crank
I will get new bearing and Oil pump
Put back together and Plastic guage.

I need some advise here. I used new stock pistons with rebuilt Aussie heads. Did I mess this up also. while its apart what do you guys reccomend. This is a daily driver.

 

There is another thread here on compression and aussie heads. Generally they give too high of a compression ratio for pump gas. Check with your machinist and calculate the compression ratio for your engine. You can find the formula in the back of a Ford performance catalog. There are some online calculators but I don't trust them.

Let us know what you find out.

Check all of your oil passages to make sure they are drilled correctly and do not have any obstructions in them. The cleveland series oil passages seem to be marginal on size. Somebody at Ford goofed on their calculations.

 

I've found the online compression calculator to be accurate as long as the correct numbers are used. They are not all the same, read the directions carefully. Some calculators say to use a negative number for a piston dish volume and others say to use a positive. If the wrong number is used, the compression will be way off.

Unless you rebuilt your engine with a 400 crank and pistons, the compression shouldn't be that high. A stock 351M is a better candidate for closed chamber AU 302C heads than a stock 400. There is less volume to compress and deck clearance is much better at .016" so ther may be some quench benefits from the closed chamber design.

If I go strictly by the book measurements and (guessing) the C302 chambers at 62cc, your compression should be around 9.25:1. If cam and ignition timing are set correctly it should run fine on 91 or less octane.

Read Building tips for information about quench.
http://www.speedomotive.com/Building%20Tips.htm

The problem is there's too many assumptions about the numbers. I've see anywhere from 56 to 66cc listed for the 302C head volume. All the other engine parts can be plus or minus a small amount but it can add up.

The first thing I would check is the accuracy of the stock timing marks. The outside ring on the balancer is rubber mounted and can slip, throwing your timing marks off. If they check out OK, then you need to dig a little deeper for the problem.

What timing numbers did you use?

 

Ok. I understand the CR. My question is, Can I use the Stock style pistons, is my 272h cam, and my 1406 carb a good match?
Or did I mess this up? Since the eng is out and will be apart, This might be a good time to fix my mistake. Or should I just leave it alone and fix the oil problem. Thanks Art

 

The 272H cam is a mite large but since you have it installed you will have to live with it. It will just suck a little more gas.

The 1406 is good.

Your distributor needs to have BOTH vacuum and mechanical advance to work on a daily driver. The plain mech advance distributor is for racing with a wide open throttle, therefore no vac advance is needed.

Brian- I have seen some of the calculators that did not take into account the top piston land dimensions etc. You are correct about the +/- dimensions, they are not all the same. I just use the old manual formula so there are no questions and no errors.

 

If by top piston land dimensions, you mean the area above the top ring between the piston and cylinder, most calculators don't bother with it. It usually works out to about 1cc. It can be added to the chamber volume on a calculator that doesn't have it in the formula but it won't change the ratio significantly, less than 1/10th of a point.

Your stock 351M pistons will have a round dish to lower compression. A "D" shape reverse dome is better for a closed chamber but your compression shouldn't be that high anyway. Unless the block or heads have been milled a substantial amount, compression shouldn't be an issue. If it pings with 91+ octane fuel, I would check timing first.

 

OK I messed that one up. I can change the cam. I am planning on pulling it anyway to check the cam bearings. What cam should I use?

Also I guess I have a new mech advance distributor to get rid of only 150 miles on it. I have a MSD 6A with the MSD Mech advanced . I believe MSD makes the VAC Version. Does anyone know if there is a conversion kit? Gosh MSD said it would work.

I am assuming that I am ok with the stock Pistons and should leave them in.

 

Lots of things will "work"...

 

OK the reason it's pinging is that with the aussie heads and the 351m pistons there to much squish area ...
What you should do seeing our rebuilding it anyway is get a 400 crank and D dish pistons and the it will work better with the aussie heads...

 

OK . HELP! I have had multi responces. On other replys it was ok to use the stock pistons and my mechanical advance was the problem. I have spent a lot of $$ on this eng so far. The eng sits out now. I need to know what my problem is. Please somone read my orginal post and give me some needed help.

ENG (150 miles) Truck
1979 351m, 1982 F150 stepside
30 overbore C6 converted from 3 speed SROD
Crane 272h cam 3.50 9 inch rear (change from 2.47)
Crane Roller rockers tires 265/15
Performance 400 with 1406
Msd 6a
Msd Mech adv dist
Headers
Stock pistons
Aussie heads
stock crank and rods

Problem: Low oil pressure and knock at idle. I messed this up on rebuild some how. I need to check this

Problem: Eng pings. If I adjust timing away from TDC ping will go away somewhat, but eng will not turn over, starter drag (new starter) cools down, will start. Move timing closer to TDC pings all the time. Dist recurved to give 30 degree advance.

Do it need to chuck pistons and dist?

 

Well if it comes down to selling that dizzy , I'll buy it .....let me know how much ....

OK how much deck clearance do you have with the 351m pistons .
In order for the aussie heads to work right you should be as close to zero deck as possible.....
Then if you polish the combustion chamber and remove all sharp edges this will help in it not pinging .... if you don't fix it now you'll just wreak the motor ...Pinging is bad ....

As for the low oil pressure are you sure you have all the oil plugs in the block .. some times the oil plugs that are behind the timing gear are forgotten ... Bad mistake ..... Otherwise you should have good pressure even with a Stock Pump......And you don't need a HV pump either and Stock one will work just fine ...

I once had a bad set of Lifter in one of my motors , they where for a Windsor and it would let oil be pumped to the top of the motor all the time . The little oil hole never came out of the oil groove.. It would pump the valve covers full in minutes of just idling and never had really good oil pressure from the get go..
Installed a different set of lifter that would shut the oil off when the valves where in the closed position and I gained 40 Psi in oil pressure..
Rule of thumb... 10 Psi for every 1000 Rpm's your motor is turning.
sitting at idle only need 7 Psi.. turning 3500 Rpm's need 35 psi to keep things well lubed ...


I would recheck all your tolerances ....Plastic gage everything ...
make sure everything is right .. and replace all the bearings if needed ..

What are the chances that you have Std. Bearing on a .10 under crank..??????
That would raise hell with everything....

 

Shazam,
Thanks for the responce. I don't know how much clearance I have. I just ordered stock 351m Pistons to fit the overbore and had the Aussie heads rebuilt, new guides,new valves, springs keepers etc. My friends machine shop did them. I used the felpro eng set. So I woulds assume that the clearance is what ever stock is. (?) Send me an email about the dist. Thanks Art

 

Reread my edit please .. Email me at
dhoma@new.rr.com

Will set up something for the dizzy .....

 

Shazam


The oil pressure Is driving me crazy. I cut the crank to .10, made sure all plugs were in put it together an had great oil pressure. But I did not Plastic guage it. You maybe right about the bearing size ran the eng about 150 mile. After the 150 miles I cam to a stop light and the guage went to zero, I heard a deep Knock. Increased rpm and knock went away. Oil Pressure went up to about 1/4 scale. I verified later with a new sending unit and new guage and same result. The only way Iwill know for sure what went wrong is to pull the pan and caps,inspect and plastic guage.


Pistons and Cam are the other issue.

Thanks Art

 

Yes your right it's the only way to know for sure what went wrong ...
But I'll put my money on the bearings being Std. on a .10 under crank .. .12 clearance is way to much for the oil to work with it will just run out of the bearings .... make sure you check both the Mains and the Rod bearings ..
As for the pistons I wish I knew how much from the top of the block they are sitting when at TDC.. this would help me some to figure out whats going on with your ping ..
The Cam might be a little big but it shouldn't hurt anything...

But let me know about the bearings .

ShaZam