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| | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2004 Posts: 2,027 Likes: 51 veteran | OP veteran Joined: Apr 2004 Posts: 2,027 Likes: 51 | I'm in Ireland, anything I buy for it I have to import and heads are heavy and thus cost big money to import. For this motor it's not worth it for me.
My choice is between 624 heads and 882 heads, and the consensus is that 882s are not as bad as 624s.
Thanks guys.
79 chevy G30 cobra camper conversion. | | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2007 Posts: 249 Likes: 59 G Van Man | G Van Man Joined: Apr 2007 Posts: 249 Likes: 59 | I'm in Ireland, anything I buy for it I have to import and heads are heavy and thus cost big money to import. For this motor it's not worth it for me.
My choice is between 624 heads and 882 heads, and the consensus is that 882s are not as bad as 624s.
Thanks guys. I saw you mention 462 heads in your first post. 624s and 882s are all in all roughly the same. Both are large chamber, poor flowing and crack prone lightweight castings. I would magnaflux either. Hopefully one of the other is useable.
1983 G20 Conversion Van, 350 TPI, Reed Hydraulic Roller cam, Ported 906 Vortec, Edelbrock 3817 TPI-Vortec Base, Doug Thorley Tri-Ys, Dual 2 1/2" exhaust, Speed Density 7730 ECM tuned by ME, 700r4 by ME, Stock 1,600 rpm converter, Rebuilt Stock 10 bolt with posi by ME, 3.08 gears, 358 RWHP @ 5,200, 384 RWTQ @ 3,400, 14.66 @ 95.43 w 2.28s 60'
| | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2004 Posts: 2,027 Likes: 51 veteran | OP veteran Joined: Apr 2004 Posts: 2,027 Likes: 51 | Yeah sorry my, mistake they are 624's the full code is 462624 hence the mix up.
Just found the 882 heads are cracked so have to re-assess my options.
79 chevy G30 cobra camper conversion. | | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2007 Posts: 249 Likes: 59 G Van Man | G Van Man Joined: Apr 2007 Posts: 249 Likes: 59 | Compared to the cost of machine work and parts on a crack prone casting it might still be worth investigating what importing new heads would run. I have the same casting as these AFR Enforcers that have been ported on my 383. It runs phenominally well in my heavy Express van. Being aluminun they are much lighter than iron heads. The small 64cc chambers would up your compression as well to help your power and economy on propane.
https://www.speedwaymotors.com/AFR-1001-SBC-195-Enforcer-Heads-Straight-Plug-Assembled,478814.html?sku=1631001&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQjworiXBhDJARIsAMuzAuwOEpJYeHBgGgPETAS4inPQh64yshyJXizW5IxWqJDODa0SInJihXIaAgdLEALw_wcB
Last edited by 1983G20Van; August 06th 2022 1:42 pm.
1983 G20 Conversion Van, 350 TPI, Reed Hydraulic Roller cam, Ported 906 Vortec, Edelbrock 3817 TPI-Vortec Base, Doug Thorley Tri-Ys, Dual 2 1/2" exhaust, Speed Density 7730 ECM tuned by ME, 700r4 by ME, Stock 1,600 rpm converter, Rebuilt Stock 10 bolt with posi by ME, 3.08 gears, 358 RWHP @ 5,200, 384 RWTQ @ 3,400, 14.66 @ 95.43 w 2.28s 60'
| | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2004 Posts: 2,027 Likes: 51 veteran | OP veteran Joined: Apr 2004 Posts: 2,027 Likes: 51 | I've gone with these for my rebuild.... Next decision is cam and lifters and pushrods. Summit Racing SUM-162112 Summit Racing™ 64cc Aluminum Cylinder Heads for Small Chevy https://www.summitracing.com/parts/sum-162112 COMP Cams 1804-16 COMP Cams Ultra Pro Magnum XD Roller Rocker Arms https://www.summitracing.com/parts/cca-1804-16
79 chevy G30 cobra camper conversion. | | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Jan 2014 Posts: 2,290 Likes: 137 veteran | veteran Joined: Jan 2014 Posts: 2,290 Likes: 137 | | | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2004 Posts: 2,027 Likes: 51 veteran | OP veteran Joined: Apr 2004 Posts: 2,027 Likes: 51 | Am I correct in thinking 'RV' cams - designed for low rpm torque, advise against use in engines with high compression because of the increased risk of detonation?
As here in Ireland minimum octane count is 95 RON will I be OK to run an RV cam with higher compression?
79 chevy G30 cobra camper conversion. | | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2007 Posts: 249 Likes: 59 G Van Man | G Van Man Joined: Apr 2007 Posts: 249 Likes: 59 | Am I correct in thinking 'RV' cams - designed for low rpm torque, advise against use in engines with high compression because of the increased risk of detonation?
As here in Ireland minimum octane count is 95 RON will I be OK to run an RV cam with higher compression? 95 RON is roughly equivalent to 91 octane here in the US. If you still have the stock GM pistons in your 350 those are typically 12cc worth of dish. With a decent head gasket thickness and 64cc chamber that puts you in the 9.2:1 to 9.4:1 static range. I would not consider that higher compression. The factory 350 Vortec engines run iron heads with a 9.4:1 and a 191/196 @ 0.050 cam that is on a tight 111 LSA and advanced to a 106* intake centerline. My aluminum head 383 is 11:1 static with a 0.041" quench. My cam is a 271/284 @ 0.006 and 218/228 @ 0.050 on a 108 LSA and advanced to a 106 ICL. With a 61.5* intake closing angle, 3.75" stroke and 6" rods it calculates to at 8.97:1 dynamic compression ratio. However, it does not stop there. My 383 has Rhoads V-Max lifters in it that reduce the duration of the camshaft by 20* at low rpm. With the lifter adjusted how I run them, measured statically on an engine that is not running, the camshaft has a 51.5* intake closing. That boosts the dynamic compression ratio to 9.57:1. It runs detonation free on 91 octane with 31* total ignition advance at WOT and as much as 42* at cruising speed. My Vortec distributor setup is limited to ~42* total ignition advance by the design of the distributor as additional timing will cause the spark to jump to the previously fired cylinder and create a misfire. For your combination I would start with a HEI curved to give 22* of mechanical advance. Start with the initial set at 4* BTDC. Use the stiffest springs to delay the total advance until 3,600+ RPM. That would give the engine 26* of total timing at 3,600 to start. The vacuum advance canister used on a later 70s and early 80s SBC should provide about 16* of advance at about 12 in/hg vacuum and fall off to no additional advance around 6 in/hg vacuum. Connect it to MANIFOLD vacuum not ported. From there dial in the fueling on the carb. Once the fuel mixture is safe, then you can play with the timing a bit. It might want as much as 34-36* total advance at WOT and upwards of 50* at cruising speeds. Each combination is going to be different. Reading the plugs will be important as you start getting the timing advance dialed in. Too much timing can actually start causing small bits of aluminum from the piston tops to be deposited on the spark plugs from pre-ignition well before you even audibly hear detonation or pinging. In all actuality it will likely end up around 10-12* initial timing and 32-34* total timing at WOT with about 48-50* of cruise timing. You want to run as much initial timing as possible without the engine having tip-in knock or kick back on the starter when it is hot. The higher the initial advance the engine can safely run, the better the throttle response and the more responsive it will be off-idle. I like the stiffer mechanical advance springs for two reasons. First reason is that the mechanical advance will return back to zero advance at low rpm which is important for idle stability. The second reason is that the initial advance can be a bit higher which will help get the engine off its lazy rear at low rpm and build more torque to help flash the torque converter to get you rolling. Mechanical advance coming in too quickly will cause the idle to dance around in RPM as it advances and retards erratically as well as potentially cause detonation off-idle which will force the initial advance to be retarded.
Last edited by 1983G20Van; October 08th 2022 1:02 pm.
1983 G20 Conversion Van, 350 TPI, Reed Hydraulic Roller cam, Ported 906 Vortec, Edelbrock 3817 TPI-Vortec Base, Doug Thorley Tri-Ys, Dual 2 1/2" exhaust, Speed Density 7730 ECM tuned by ME, 700r4 by ME, Stock 1,600 rpm converter, Rebuilt Stock 10 bolt with posi by ME, 3.08 gears, 358 RWHP @ 5,200, 384 RWTQ @ 3,400, 14.66 @ 95.43 w 2.28s 60'
| | | Re: Advice wanted- Building a 350 SBC for a G30 | Joined: Apr 2004 Posts: 2,027 Likes: 51 veteran | OP veteran Joined: Apr 2004 Posts: 2,027 Likes: 51 |
79 chevy G30 cobra camper conversion. | | |
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