I'll see if I can CC the piston valve reliefs tomorrow. Not sure how accurate I can get them, but I'll try. Head gaskets I have not purchased and was going to let the shop select them. The stock Ford gaskets I removed measure 0.065" on the uncompressed areas, and 0.045" where compressed. Not sure if that is normal, but that's what was in it for stock gaskets.

If I was to drop to a 0.021" compressed thickness, that would be a pretty significant CC reduction itself no?


I haven't CC'd the old D8 heads, but any documentation I could find online and in the 2 SBF books I have say they're 69cc, and I thought the compression ratio was more like 8.3:1 but that may not be correct...maybe with the flat top pistons the CR was more like 8.5?

This is why I've been getting a bit confused as just swapping the heads, from 69cc down to 65cc should only be about a 1/2 point bump in compression?

However, if Matt's calculations include a 0.020"-0.024" decrease in head gasket thickness, then that would be more like an 8cc reduction, which would be more like a full point bump in compression...If I'm pickin' all this up correctly, lol.

Thanks Gents,
This is just like school, except this time around I'm actually interested.

 

As far as I know, when they went to the large chamber heads in 77 or 78, that's when they also went with the flat top pistons, some with just a very slight dish but not much. I had a 75 302 and it had the smaller chambered heads, but had a very deep dish in the pistons.

 

My pistons are flat as a pancake, and I read that the valve reliefs were something like 4.0 - 4.6 CC combined...but I have no idea if that is correct.

 

The D8 Heads are 67- to 70-cc chambers.

I used the CR formula for calculating the CR with the GT 40 heads. And a 0.021: head gasket thickness (I really should have used .027") as copper head gaskets can be had as thin 0.021" but most thin composite ones are 0.027" and are available with a 4.03" bore. Such as Cometic C5511-027

4.01" bore and 0.021" thick copper head gaskets are available from SCE.

If the block gets bored out then this all changes.


If the engine needs re-bored they will deck the block also in a probability and may deck it any way just to in sure it is flat when they re-hone.. If they do deck the block just get em to peel 0.10" from it so you are working with a constant amount for CR calculation.


If the block is decked 0.10" and using the 4.03" bore 0.27" thick head gaskets with 3 CC's for valve reliefs. it would equal a CR of 9.3:1 Use the 4.01" bore and 0.021" thick copper head gaskets will yeild 9.44:1 CR.

Not decking the block would yield 9:1 with 4.03" bore 0.27" thick head gaskets with 3 CC's for valve reliefs. And 9.2:1 with the 4.01" bore and 0.021" thick copper head gaskets.


Reduce the chamber volume down to 60cc's The same as the big valve 351W D0OE heads using the 4.03" bore 0.27" thick head gaskets with 3 CC's for valve reliefs, it would equal a CR of 9.6:1.

You can now see why the old D0OE Windsor heads were highly sought after back in the day. 60CC chambers decent flow numbers for a factory head and bigger valves.

 

OK let assume the worst 5CC's for the pistons and 65 CC's for the chambers

No decking

4.03" bore 0.27" thick head gaskets 8.86:1 CR

4.01" bore and 0.021" thick copper head gaskets 8.999:1 CR


0.010" Block deck

4.03" bore 0.27" thick head gaskets CR 9.08:1

4.01" bore and 0.021" thick copper head gaskets 9.2:1 CR


Heads milled to 60 CC Combustion chamber no block deck

4.03" bore 0.27" thick head gaskets 9.4:1 CR

4.01" bore and 0.021" thick copper head gaskets 9.55:1 CR


Heads milled to 60 CC Combustion chamber block decked 0.010"

4.03" bore 0.27" thick head gaskets 9.64:1 CR

4.01" bore and 0.021" thick copper head gaskets 9.8:1 CR

 

A couple of the shops I talked to said for a 302 they'd deck the block anyway, for what its worth. The shop the engine is going to recommended 9-9.1-ish for compression for what I want to do with the truck, so that's looking like it will be pretty easy to achieve.

This is all great stuff, and I do appreciate your comments.

I just wanted to have it all sorted out in my head before the work was done so I'm educated on the topic when discussing options with the shop. I also had to rationalize where the 9+ compression ratio was going to come from. I'm waiting on one more order of parts, and I have to spend some time cleaning up rusty/dirty bolts and brackets, etc and then I'll be dropping this thing off at the engine shop.

I feel like this will be a nice little engine when its done, and it should work far better than it did before all this.

 

Back in the mid 80's I built a 302 with the 351W heads and drop it in a early Bronco for off road racing.
For sand drags everyone thought it had a SBC till I popped the hood and showed a SBF!
The stock Bronco front axle could not take the power as it broke and it was hardly on the ground.


Also had a SB in a 68 GT Mustang fast back that was a nice match for road racing. A BB would be too heavy up front for corning.
I am a fan of the SB in a sporty car/truck, towing cant beat a BB.
Dave ----

 

Thought I would post up my info here rather than cloggin' up the other guy's distributor thread.

My reman unit has 10L/15L slots. (My original is 13L/18L).

The springs look fairly similar, but the heavy spring in the reman unit looks to to be heavier than in the original, but who knows...I'm just eyeballing them.

The bad news...in case your eyes aren't already drawn there...check out the holes where the vacuum canister mounts....lol. I didn't realize it was loose until I unpackaged it. Bugger! You'll notice on my old one that one of the screws is snapped off flush also, but I can drill it out and re-tap the hole and you'd never know it was touched. Oh well.

 

No Pics came up

 

Yes, sorry...I forgot to paste the IMG link originally but added it a few seconds later. If you hit refresh it should be there.

 

Funny I get nothing..... no link no nothing.

 

I don't know what's up. I can see it, and it's even in the quoted section in your reply. I'll try posting again below see if that works. Not much to see really, just a picture of the 10L/15L reluctor, and the holes that somebody butchered where the vacuum canister mounts. I'll fix it up, no big deal. I'm going to install the Crane kit, but just curious now whether to start with the 15L or swap in the 13L from my old distributor.

 

I can see it.
Matt try closing your browser and reopen it and see what happens.
There times when I open my browser (IE 11) and this site is 1 of 3 that comes up I have issues posting replies. I post them but they don't show up till I refresh that page.
The fix is to close only this site tab and reopen and all is ok.
Dave ----

 

Might have something to do with my post too, since the IMG tag wasn't included originally, but I did edit and add it within 30 seconds.

 

I would be inclined to return that distributor with the wallowed out holes. That body should have been ash canned or repaired thread inserts IMHO.

I was looking at this with a company computer and well it may have not liked the link since they have Fort Knox like security protocols. . It's all showing up now on my personal one.