305 H.O heads on 350 block
05-29-2004, 08:16 AM
#1
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Location: Ottawa/ontario/Canada
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305 H.O heads on 350 block
I've got two engines here at my place,one is a 305 H.O(L69) and the other is an older 350(nothing special)
The 305 is in the car right now but i bought the 350 to build it up abit and drop it in my car.I was wondering if it is possible,and if it will work to drop the heads from my 305 onto the 350 block.
If it does work what can i expect for a compression ratio?I realise the head gaskets will make a difference,which should i use for that too.
The 305 is in the car right now but i bought the 350 to build it up abit and drop it in my car.I was wondering if it is possible,and if it will work to drop the heads from my 305 onto the 350 block.
If it does work what can i expect for a compression ratio?I realise the head gaskets will make a difference,which should i use for that too.
05-29-2004, 10:01 AM
#2
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Join Date: Dec 1969
Location: Phila., PA
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Depends on your pistons, too. What kind of pistons does it have in it?
If it's got flattops then you compression ratio will be around 10.1:1 with standard FelPro .039" head gaskets.
If it's got stock dished pistons (roughly 12cc dish) then you'll be at about 9.6:1, all else held equal.
The 305 heads have ~58cc chambers on them. Stock 350 heads are usually 64cc or 76cc.
If it's got flattops then you compression ratio will be around 10.1:1 with standard FelPro .039" head gaskets.
If it's got stock dished pistons (roughly 12cc dish) then you'll be at about 9.6:1, all else held equal.
The 305 heads have ~58cc chambers on them. Stock 350 heads are usually 64cc or 76cc.
05-29-2004, 06:21 PM
#4
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Join Date: Apr 2004
Location: Grand Rapids, MI
Posts: 100
With porting and polishing, 305 heads are a pretty decent head and can be made to flow in par with the Vortec heads.
If you do use them, bring them into the shop and have them cut for 1.94/1.6 valves. Might want to consider enlarging the spring pocket as well. Get some carbide cutting bits of varoious shapes and lengths and a die grinder. Have at them. After some solid work, they are pretty good heads.
I have a set of Ported 416's on my 355 right now.
If you do use them, bring them into the shop and have them cut for 1.94/1.6 valves. Might want to consider enlarging the spring pocket as well. Get some carbide cutting bits of varoious shapes and lengths and a die grinder. Have at them. After some solid work, they are pretty good heads.
I have a set of Ported 416's on my 355 right now.
05-29-2004, 06:31 PM
#5
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Location: Ottawa/ontario/Canada
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Thanks for the replies.
Damon-the pistons have a mild dish too them,i might be upgrading to flat tops,if i can find a good priced set next weekend as i'm going to a swap meet.
82355-New heads would be awsome,but i'm only 18 and work at a grocery store so that would really hurt my bank account for driving to college next year.
Stekman-thanks for the tips,i'll probably look into that in time.As said before,i only work at a grocery store so i'm trying to get as much as i can out of what i have available to me without tearing my bank account a new hole.
Damon-the pistons have a mild dish too them,i might be upgrading to flat tops,if i can find a good priced set next weekend as i'm going to a swap meet.
82355-New heads would be awsome,but i'm only 18 and work at a grocery store so that would really hurt my bank account for driving to college next year.
Stekman-thanks for the tips,i'll probably look into that in time.As said before,i only work at a grocery store so i'm trying to get as much as i can out of what i have available to me without tearing my bank account a new hole.
05-29-2004, 09:44 PM
#6
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Join Date: Apr 2004
Location: Grand Rapids, MI
Posts: 100
305 heads came in 3 primary versions.
601 which is much like the 416
theres the 416, which is a later version of the 601
then theres the 187 swirl port heads
finally theres the 083, which is the 305 TPI
All have roughly 58cc chambers and 1.84"/1.5" valves
601 which is much like the 416
theres the 416, which is a later version of the 601
then theres the 187 swirl port heads
finally theres the 083, which is the 305 TPI
All have roughly 58cc chambers and 1.84"/1.5" valves
05-29-2004, 10:10 PM
#7
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Location: 51°N 114°W, 3500' elevation
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good and bad idea.
Although It's nice to use a small chamber head to bump up compression, you lose more than you gain in the swap.
Installing bigger valves to help air flow more is counter productive because of the small chamber. The valves become shrouded in the tiny chambers and air flow is reduced trying to get past the valves. The heads are only designed to flow enough for a 305. Adding 45 more CID and the heads will become a severe restriction to performance. For the amount of work involved in "hogging" them out to flow enough, you'd be better off starting with some 350 heads or some aftermarket ones.
The number one item that creates HP is heads. Since you're going to be moving from a 305 to a 350, don't think you're going to get better performance with the 305 heads on the 350 without spending a lot of money to make them work. 1.94/1.60 is baseline valves for a 350. You're going to want a 2.02 intake to help it breath better.
By the time you "bring them into a shop" to have bigger valves installed, spring pockets enlarged, mild port and polish, possibly have screw-in studs installed, you'll probably have spent more than what you would have if you even bought a set of Dart Sportsman heads that already have all that work done plus they'll have better castings.
Although It's nice to use a small chamber head to bump up compression, you lose more than you gain in the swap.
Installing bigger valves to help air flow more is counter productive because of the small chamber. The valves become shrouded in the tiny chambers and air flow is reduced trying to get past the valves. The heads are only designed to flow enough for a 305. Adding 45 more CID and the heads will become a severe restriction to performance. For the amount of work involved in "hogging" them out to flow enough, you'd be better off starting with some 350 heads or some aftermarket ones.
The number one item that creates HP is heads. Since you're going to be moving from a 305 to a 350, don't think you're going to get better performance with the 305 heads on the 350 without spending a lot of money to make them work. 1.94/1.60 is baseline valves for a 350. You're going to want a 2.02 intake to help it breath better.
By the time you "bring them into a shop" to have bigger valves installed, spring pockets enlarged, mild port and polish, possibly have screw-in studs installed, you'll probably have spent more than what you would have if you even bought a set of Dart Sportsman heads that already have all that work done plus they'll have better castings.
05-29-2004, 10:34 PM
#8
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Join Date: Jul 2001
Location: Calgary, Alberta, Republic of Western Canada
Posts: 550
Originally posted by Stephen 87 IROC
good and bad idea.
Although It's nice to use a small chamber head to bump up compression, you lose more than you gain in the swap.
Installing bigger valves to help air flow more is counter productive because of the small chamber. The valves become shrouded in the tiny chambers and air flow is reduced trying to get past the valves. The heads are only designed to flow enough for a 305. Adding 45 more CID and the heads will become a severe restriction to performance. For the amount of work involved in "hogging" them out to flow enough, you'd be better off starting with some 350 heads or some aftermarket ones.
The number one item that creates HP is heads. Since you're going to be moving from a 305 to a 350, don't think you're going to get better performance with the 305 heads on the 350 without spending a lot of money to make them work. 1.94/1.60 is baseline valves for a 350. You're going to want a 2.02 intake to help it breath better.
By the time you "bring them into a shop" to have bigger valves installed, spring pockets enlarged, mild port and polish, possibly have screw-in studs installed, you'll probably have spent more than what you would have if you even bought a set of Dart Sportsman heads that already have all that work done plus they'll have better castings.
good and bad idea.
Although It's nice to use a small chamber head to bump up compression, you lose more than you gain in the swap.
Installing bigger valves to help air flow more is counter productive because of the small chamber. The valves become shrouded in the tiny chambers and air flow is reduced trying to get past the valves. The heads are only designed to flow enough for a 305. Adding 45 more CID and the heads will become a severe restriction to performance. For the amount of work involved in "hogging" them out to flow enough, you'd be better off starting with some 350 heads or some aftermarket ones.
The number one item that creates HP is heads. Since you're going to be moving from a 305 to a 350, don't think you're going to get better performance with the 305 heads on the 350 without spending a lot of money to make them work. 1.94/1.60 is baseline valves for a 350. You're going to want a 2.02 intake to help it breath better.
By the time you "bring them into a shop" to have bigger valves installed, spring pockets enlarged, mild port and polish, possibly have screw-in studs installed, you'll probably have spent more than what you would have if you even bought a set of Dart Sportsman heads that already have all that work done plus they'll have better castings.
Lots of us on thirdgen.org have ported and polished these 305 heads and they work extremely well. There is no shrouding because the enlarging of the intake valve ends up unshrounding it. I put a total of $600 Canadian into mine and they work very well, indeed. For $400 US for the guys south of the line they can have heads that have proven to flow like Vortecs.
How can anyone beat that?
Follow the link at the end of my sig.
05-30-2004, 09:53 AM
#10
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Thanks for the link
I'll deffinatly have to use those directions on my heads.Out of pure curiosity,do you think that those steps would have the same effects of my 350 heads?(i'll check the casting # when i have the chance).If it would work,then i'll do the work to them and keep the H.O heads stock most likely.
As for the warning about "shrouding" i believe it was,would a set of ratio'd(ie:1.6:1 roller rockers) rockers not solve this problem?(remeber here people i'm still learning the ways of engine performance and how certain parts react with other parts)
I'll deffinatly have to use those directions on my heads.Out of pure curiosity,do you think that those steps would have the same effects of my 350 heads?(i'll check the casting # when i have the chance).If it would work,then i'll do the work to them and keep the H.O heads stock most likely.
As for the warning about "shrouding" i believe it was,would a set of ratio'd(ie:1.6:1 roller rockers) rockers not solve this problem?(remeber here people i'm still learning the ways of engine performance and how certain parts react with other parts)
05-31-2004, 01:03 AM
#11
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Join Date: Apr 2004
Location: Grand Rapids, MI
Posts: 100
Rocker arm ratio has a direct effect on the amount the valve opens. i.e. if the lifter itself moves .350", the rocker muliples that times 1.5 or 1.6, depending on the ratio and then transfers it to the valve motion. So the total valve lift would be either .525 with 1.5 ratio or .560 with 1.6 ratio arms.
Shrouding has to do with the mount of material (metal) that is around the head of the valve. Deshrouding is removal of this metal to make for a more streamlined air flow when larger valves are used.
Shrouding has to do with the mount of material (metal) that is around the head of the valve. Deshrouding is removal of this metal to make for a more streamlined air flow when larger valves are used.
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