403 Build- #5 Heads or #2 Heads
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Joined: Jul 2015
Posts: 2
403 Build- #5 Heads or #2 Heads
Hey Guys!
Im looking into changing the heads on my 403 to get a little performance boost after having issues with the head gaskets. I've found a couple sets of heads on craigslist near me and I was wondering if anyone had any ideas on modifications ill have to do to bolt them on or which set of heads would be better in general (the #5 or #2)? I understand that I need to have the head bolt holes machined to 1/2" to accommodate the bolts. But what other work may need to be done to get ether of these set of heads to work?
Here is the sales write up for both heads.
1965 #2 Heads
1965`Olds Small Block No.2# Heads,Special Factory 3/8" screw-in Rocker Arm Studs(Chevy Style)for a "fully adjustable" Performance"Valve Train"(Allows** "racing style" solid lifter,Zero clearance lashing of a hydraulic Valve Lifter,the pushrod "Pre-load",which allows a Higher engine RPM for maxium HP,- before Valve Float &lifter Pump up)..these are the rare High Compression(9.5:to 1) Combustion Chambers with smaller 60cc squish -with some mild decking for higher engine compression ratio (10:00 -11:00 to 1)giving a very streetable HP performance boost on High Octane Gas -(Stock Head Specs: Intake/Exhaust Valves(1.875"/1.56)" Race Machine Shop recently rebuilt(by "Farmer Automotive Machine&Race Shop",in Webster NY)with fresh "3 angle" Valve Job,Guide Work,Shimmed,Seals,"Cylinder Head" Deck Resurfaced Flat(Heads never used in plastic customer "Dust Bags" never used or installed on engine ready to install )these mid-1960`s HP Olds Heads are very good for early Olds 350-330 engines --OR**with Head Bolt mounting Holes "machine shop" bored slightly oversize to 1/2"head bolts ,they can be successfully mounted &used on a typical late 1970s-80s Olds 307-403 for a big performance pickup boost (these late 70s-80s Olds engines came "stock" with very small valves, low compression head chambers ,a very low Horsepower rated "Smog&Street Bog heads"..) Like New- "Never installed" $395 or Best Offer-
1968-9 #5 Heads
1968`-69 rare(W-31 style) Dr. Oldsmobile (Small Block no.5# Head) for HP - High Compression Heads,(W-31 style) Good Original"as pulled"factory stock virgin 742 # Castings,..NO previous Mods or Port Work the best factory Small Block Olds head for the 2.0"inch Big Valve,high flow ports. HP Modification-$395 or B.O.
I know theres a lot of text here but any help is appreciated !!!
Im looking into changing the heads on my 403 to get a little performance boost after having issues with the head gaskets. I've found a couple sets of heads on craigslist near me and I was wondering if anyone had any ideas on modifications ill have to do to bolt them on or which set of heads would be better in general (the #5 or #2)? I understand that I need to have the head bolt holes machined to 1/2" to accommodate the bolts. But what other work may need to be done to get ether of these set of heads to work?
Here is the sales write up for both heads.
1965 #2 Heads
1965`Olds Small Block No.2# Heads,Special Factory 3/8" screw-in Rocker Arm Studs(Chevy Style)for a "fully adjustable" Performance"Valve Train"(Allows** "racing style" solid lifter,Zero clearance lashing of a hydraulic Valve Lifter,the pushrod "Pre-load",which allows a Higher engine RPM for maxium HP,- before Valve Float &lifter Pump up)..these are the rare High Compression(9.5:to 1) Combustion Chambers with smaller 60cc squish -with some mild decking for higher engine compression ratio (10:00 -11:00 to 1)giving a very streetable HP performance boost on High Octane Gas -(Stock Head Specs: Intake/Exhaust Valves(1.875"/1.56)" Race Machine Shop recently rebuilt(by "Farmer Automotive Machine&Race Shop",in Webster NY)with fresh "3 angle" Valve Job,Guide Work,Shimmed,Seals,"Cylinder Head" Deck Resurfaced Flat(Heads never used in plastic customer "Dust Bags" never used or installed on engine ready to install )these mid-1960`s HP Olds Heads are very good for early Olds 350-330 engines --OR**with Head Bolt mounting Holes "machine shop" bored slightly oversize to 1/2"head bolts ,they can be successfully mounted &used on a typical late 1970s-80s Olds 307-403 for a big performance pickup boost (these late 70s-80s Olds engines came "stock" with very small valves, low compression head chambers ,a very low Horsepower rated "Smog&Street Bog heads"..) Like New- "Never installed" $395 or Best Offer-
1968-9 #5 Heads
1968`-69 rare(W-31 style) Dr. Oldsmobile (Small Block no.5# Head) for HP - High Compression Heads,(W-31 style) Good Original"as pulled"factory stock virgin 742 # Castings,..NO previous Mods or Port Work the best factory Small Block Olds head for the 2.0"inch Big Valve,high flow ports. HP Modification-$395 or B.O.
I know theres a lot of text here but any help is appreciated !!!
Registered User
Joined: Mar 2008
Posts: 1,012
From: Phx, AZ
1st off the #2 heads have a 3/8th-3/8 ths stud, but it is not and adjustable setup from the factory. It actually tightens down onto a shoulder on the stud. Be careful, you may have to clearance or oversize drill the pushrod holes for the number 2 heads because the 330 used a different cam lifter angle. Not doing this may cause pushrod/cylinder head contact (not good). Wish I could have saved the originals from my car (#2 is 1965 only).
Either set needs to have at least a 2 inch intake valve installed for the 403, great engine just needs compression & to breathe. Anything less than a 2" intake valve is like trying to run 5 miles with a rag in your mouth.
Both the #5/#2 heads need 1 of the locator pins in each head drilled to 5/16th" also. The needed pin was drilled a smaller size, locate that one with a 403 head gasket. Can be done by hand drill. Head bolt holes MUST be done on a machine/drill press with good travel.
Measure the valves/ check guides on anything you purchase, be sure what you are getting.
The difference HP wise between #2/#5 is not much, but a bunch over the 403 heads. Just be aware of the couple of details you must address to make either work. I have #5 heads on my 403.
Jim
Either set needs to have at least a 2 inch intake valve installed for the 403, great engine just needs compression & to breathe. Anything less than a 2" intake valve is like trying to run 5 miles with a rag in your mouth.
Both the #5/#2 heads need 1 of the locator pins in each head drilled to 5/16th" also. The needed pin was drilled a smaller size, locate that one with a 403 head gasket. Can be done by hand drill. Head bolt holes MUST be done on a machine/drill press with good travel.
Measure the valves/ check guides on anything you purchase, be sure what you are getting.
The difference HP wise between #2/#5 is not much, but a bunch over the 403 heads. Just be aware of the couple of details you must address to make either work. I have #5 heads on my 403.
Jim
Last edited by Warhead; Jul 3, 2015 at 05:58 PM.
Out of Line, Everytime😉
Joined: Dec 2006
Posts: 10,108
From: Melville, Saskatchewan
Since the number 2 heads have been rebuilt, it is a no brainer. A 2" or even 2.07" intake valve with the bowl opened up and upgrade to 3/8" stud full roller rockers while your at it.
Thread Starter
Registered User
Joined: Jul 2015
Posts: 2
Ok, I have been going through some other posts online where a saw a couple other #5 heads for sale for a little cheaper. Do you guys have any ballpark numbers for how much it would cost to get the intake and exhaust valves to the proper size? As well as maching the head bolt holes and milling the bottom of the heads to clean it up/boost cr.
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