305 versus 283 Parts Interchange Tech Info
01-10-2003, 11:27 AM
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305 versus 283 Parts Interchange Tech Info
Every so often, I receive a tech request e-mail that has general interest to people here on the Forum. I thought I'd post up a question I just received from Forum member Todd Collins, along with some info I put together on the subject:
Lars,
First of all I want to thank you for putting out the how to set valve lash - it was very helpful. I was wanting to ask you some questions if you dont mind?
I'm building a small block 283 and I was wondering if the 305 parts will work on the 283? Like the flywheel,oilpan,harmonic balance,cam,timing gearsand chain. If you could help me with these concerns I will forever be grateful and thanks again for the valve lash adjustment procedure. Todd
Todd -
There are a few things to watch out for and to keep in mind when swapping parts between a 305 and a 283. All of the parts will physically bolt up and fit, but you need to be aware of the following:
The 283 is an internally-balanced engine (neutral-balanced). Some late 305s were partially externally balanced, using a neutral-balanced harmonic balancer and a counter-weighted flexplate/flywheel (just like post-'85 350s). The late 305 flexplates with the counterweight are identified by a big moon-shaped piece of metal welded to the flexplate. This cannot, under any circumstances, be used on a 283.
The 283 engines had the starter bolted to the bellhousing. The 305 has the starter bolted to the block. To get the starter to interface correctly with the ring gear, the 283 uses a 168-tooth ring gear. The 305 has a 153-tooth ring gear. If you're going to use a 305 ring gear on the 283, you may end up having to do significant rework to the starter mounting system. I've never tried doing this, and I don't think I'd recommend it...
My recommendation on the flexplate/flywheel: Just buy the right one for the 283 and forget the 305. You can get a brand new 283 flexplate for about $35 (flywheels are a bit more).
The harmonic balancer will interchange. However, keep in mind that in the era of the 305, GM was moving the timing mark around a bit: they moved it up underneath the waterpump, then they slid it down the opposite side from the early engines, etc. If you use the 305 balancer, you will need to accurately verify top dead center and re-mark the balancer so it lines up correctly with your timing pointer. I would not trust the timing marks to be correctly aligned when using the 305 balancer on your 283. But you can use it successfully provided you re-establish TDC.
All other external components will bolt up. You can even use 305 heads on your 283, if you have the small-chamber 305 heads. The 283 had 57cc combustion chambers, and some 305s had 58cc chambers. These 58cc heads will work fine on a 283, but avoid the larger-chambered 305 heads as they will not produce adequate compression on the 283. The waterpumps will interchange, but the 283 uses a short-nosed pump, whereas the 305 has the long-nose. But the components will bolt up and interchange. The intake, oil pan, timing gears, cam, etc. will all interchange.
Good luck with the buildup!
Lars,
First of all I want to thank you for putting out the how to set valve lash - it was very helpful. I was wanting to ask you some questions if you dont mind?
I'm building a small block 283 and I was wondering if the 305 parts will work on the 283? Like the flywheel,oilpan,harmonic balance,cam,timing gearsand chain. If you could help me with these concerns I will forever be grateful and thanks again for the valve lash adjustment procedure. Todd
Todd -
There are a few things to watch out for and to keep in mind when swapping parts between a 305 and a 283. All of the parts will physically bolt up and fit, but you need to be aware of the following:
The 283 is an internally-balanced engine (neutral-balanced). Some late 305s were partially externally balanced, using a neutral-balanced harmonic balancer and a counter-weighted flexplate/flywheel (just like post-'85 350s). The late 305 flexplates with the counterweight are identified by a big moon-shaped piece of metal welded to the flexplate. This cannot, under any circumstances, be used on a 283.
The 283 engines had the starter bolted to the bellhousing. The 305 has the starter bolted to the block. To get the starter to interface correctly with the ring gear, the 283 uses a 168-tooth ring gear. The 305 has a 153-tooth ring gear. If you're going to use a 305 ring gear on the 283, you may end up having to do significant rework to the starter mounting system. I've never tried doing this, and I don't think I'd recommend it...
My recommendation on the flexplate/flywheel: Just buy the right one for the 283 and forget the 305. You can get a brand new 283 flexplate for about $35 (flywheels are a bit more).
The harmonic balancer will interchange. However, keep in mind that in the era of the 305, GM was moving the timing mark around a bit: they moved it up underneath the waterpump, then they slid it down the opposite side from the early engines, etc. If you use the 305 balancer, you will need to accurately verify top dead center and re-mark the balancer so it lines up correctly with your timing pointer. I would not trust the timing marks to be correctly aligned when using the 305 balancer on your 283. But you can use it successfully provided you re-establish TDC.
All other external components will bolt up. You can even use 305 heads on your 283, if you have the small-chamber 305 heads. The 283 had 57cc combustion chambers, and some 305s had 58cc chambers. These 58cc heads will work fine on a 283, but avoid the larger-chambered 305 heads as they will not produce adequate compression on the 283. The waterpumps will interchange, but the 283 uses a short-nosed pump, whereas the 305 has the long-nose. But the components will bolt up and interchange. The intake, oil pan, timing gears, cam, etc. will all interchange.
Good luck with the buildup!
