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Author
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Topic: 351W Heads
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quick50stng
Journeyman Posts: 70
From: Bethlehem,GA. USA
Registered: Sep 2004
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posted 09-16-2004 12:37 PM
   
Hello,
I would line to take a second to introduce myself since I am new here. I am an avid auto enthusiast and recently completed a 5.0 conversion on an 82 Mustang coupe for daily street and occasional weekend warrior at the strip. I used a used 78'302 with stock bottom end 500 lift crane cams,edelbrock RPM, and a rebuilt 600 Holley, vaccum seconday carb. All this is backed up with a 74' c4 trans out to 3:73 ratio 7.5 stock rear end. Endless to say I'm not happy with the combination. The car is lazy below 2000 rpm and I can't sort out the problem. I've come to realize my combination sucks. I have to large a cam and not enough compression (8.2-8.6:1 i'm guessing).
My question is: I recently bought 79' 351W heads rebuilt and ready to bolt on. I think they are standard 184/164. Does anyone know what compression ratio I might be running with the 351W heads? I'm hoping for at least 9.2:1. Any help would be great.------------------
quick50stng
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Dubz
Gearhead Posts: 1888
From: Manitoba Canada
Registered: Oct 2002
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posted 09-16-2004 12:53 PM
as far as i know compression i don't think will be any higher, unless the heads have been milled. You're probably not looking at that large of an increase even if they have been. Compression on the bottom end is probably 8.0-8.2 (as my 74 engine is) and with heads milled .030" you might be looking at 8.4-8.6The 79 351 heads will have the same sized valves as your 78 302 heads. This changed i think in 75? if you were to get older 351W heads they would have the larger 1.84/1.54 valves (compared to 1.78/1.45), which will probably flow a little better. However being that they are rebuilt, you'd probably have to measure them to tell. sorry to be the bearrer of bad news  and welcome to MM [This message has been edited by Dubz (edited 09-16-2004).]
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quick50stng
Journeyman Posts: 70
From: Bethlehem,GA. USA
Registered: Sep 2004
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posted 09-16-2004 01:07 PM
quote:
Originally posted by Dubz:
as far as i know compression i don't think will be any higher, unless the heads have been milled. You're probably not looking at that large of an increase even if they have been. Compression on the bottom end is probably 8.0-8.2 (as my 74 engine is) and with heads milled .030" you might be looking at 8.4-8.6The 79 351 heads will have the same sized valves as your 78 302 heads. This changed i think in 75? if you were to get older 351W heads they would have the larger 1.84/1.54 valves (compared to 1.78/1.45), which will probably flow a little better. However being that they are rebuilt, you'd probably have to measure them to tell. sorry to be the bearrer of bad news and welcome to MM [This message has been edited by Dubz (edited 09-16-2004).]
Thanks for the info. I got the heads cheap $100. So I guess no real harm done. Just don't want to break the bank$$ with my toy. The car loves high rpm range its just disappointing after all that work and I'm not gettin set back in my seat off the line. ------------------
quick50stng
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quick50stng
Journeyman Posts: 70
From: Bethlehem,GA. USA
Registered: Sep 2004
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posted 09-16-2004 01:12 PM
What do you think about having the heads milled and using a thinner race head gasket?
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Dubz
Gearhead Posts: 1888
From: Manitoba Canada
Registered: Oct 2002
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posted 09-16-2004 01:24 PM
that was my plan as well, havn't done it yet, so can't give you advice on it. it probably won't get you to 9.0 but it will get you closer. You may just want to stick with milling, as the cheaper thinner gaskets arn't that great i don't thinkwith having a set off of the car you may be able to do a little port work such as grinding off the smog bump in the exhaust port, and getting then getting them milled, and then your car won't have down time, just time enough to take one set off and put the others on. is there a different converter in the c4 or is it a stock one? that may help/hinder the seat of the pants off the line feeling
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quick50stng
Journeyman Posts: 70
From: Bethlehem,GA. USA
Registered: Sep 2004
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posted 09-16-2004 01:40 PM
Yes, I agree the port work should be somewhat beneficial it can't hurt these wheezy heads. I currently have a B&M holeshot 2200rpm converter. I've also been pondering switching to 600 holley dp w/mech.secondaries. Due to the large cam and low compression. Would this create low vaccum and upset the vac secondaries and not respond properly.
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Dubz
Gearhead Posts: 1888
From: Manitoba Canada
Registered: Oct 2002
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posted 09-16-2004 01:57 PM
if you have a 2200 converter that's the reason it will be sluggish under 2000 i would think.
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Rory McNeil
Gearhead Posts: 1611
From: Surrey, B.C. Canada
Registered: Nov 2000
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posted 09-16-2004 02:08 PM
Yes, the 79 351W heads are identical to your current D8 heads, except that the 351 heads will have larger head bolt holes, as the 351W uses 1/2" head bolts, rather that the 302`s 7/16" bolts. For years I ran a 78 Fairmont with the original 302 rebuilt to stock specs. I started adding parts to it, the headers & 3.55 gears (8.8)helped a lot, however a mild hyd. cam & Edelbrock Performer & Holley 4 barrel did very little, until I swapped the heads. I found a pair of 1969 351W heads at a wrecking yard for $40.00, had them rebuilt stock after I "cleaned up" the exh. port bumps, & bolted em on. By my calculations, my compression increased from 8.4-1 with my 69cc heads, up to 9.3 with the early 351W heads 59cc chambers. It still ran fine on 84 octane gas, plus it picked up 6/10`s of a second in the 1/4 mile, after the cyl. head change. If I was in your situation, & on a budget, thats the route I`d go. ------------------
78 Fairmont 428 4 speed 10.20@130mph
80 Fairmont 302 5 speed 12.8@105mph
85 Mustang NHRA M/Stock 302 5speed. [email protected]
59 Meteor (Canadian Ford) 2 dr sedan 332, auto
74 F350 ramp truck 390 4spd
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Dubz
Gearhead Posts: 1888
From: Manitoba Canada
Registered: Oct 2002
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posted 09-16-2004 02:22 PM
when did the combustion chamber volume change? i didn't know there were 69cc heads
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scottford351
Journeyman Posts: 96
From: reedsville ohio usa
Registered: May 2003
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posted 09-16-2004 05:28 PM
I believe in 77 was the change to 69 cc heads. The pistons have a smaller dish and the head volume got bigger. ------------------
91 LX 398w street/bracket 6.88 1/8 60FT 1.44
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Rory McNeil
Gearhead Posts: 1611
From: Surrey, B.C. Canada
Registered: Nov 2000
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posted 09-17-2004 02:01 AM
On my 78 Fairmonts 302, the 69 cc heads give only 8.4 compression, with a FLAT TOP piston! No dish at all, just the 4 valve reliefs.------------------
78 Fairmont 428 4 speed 10.20@130mph
80 Fairmont 302 5 speed 12.8@105mph
85 Mustang NHRA M/Stock 302 5speed. [email protected]
59 Meteor (Canadian Ford) 2 dr sedan 332, auto
74 F350 ramp truck 390 4spd
IP: Logged |
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