LG4 to LO3
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: LG4 to LO3
I found the 416 pic linked in this thread. I can't say positively that any of these pics are correct. I seem to recall it being said that 081s are the centerbolt version of 416s. If these pics are correct I don't see the similarity. The pics of the ports don't look all too similar either.
https://www.thirdgen.org/forums/tech...highlight=416s
https://www.thirdgen.org/forums/tech...highlight=416s
Fast355 is the member who I was quoting, when I said 081 is the centerbolt version of the 416.
See this thread, post #7 has a few pics as well, for those that are interested.
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Joined: Mar 2007
Posts: 343
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From: Jackson, Michigan
Car: 83 Trans Am
Engine: LT1 350
Transmission: 5 Speed manual
Axle/Gears: 3.73 10bolt till it breaks
Re: LG4 to LO3
ha Nick, hows it going man.
Just to throw my personal opinion into the mix. I have investigated this type of swap quite a bit due to my own personal situation, and from most of the people I have talked to, the LG4 heads do great on the LO3 block, and flow better in the upper range where most people will be "using" the power when needed. Sorry fella's but when I am looking for power I want it in the upper range. I mean seriously, if I am street racing or drag racing or just mashing it in general, how often am I going to do so under 3,000rpm? Therefore, based on the fact the LO3 head was a low end head, I would go with the LG4 head which offers more room on the high end, especially with a bit of porting. Lets also remember that when discussing ported LG4 heads we must keep in mind that many people that port these heads get carried away trying to increase flow volume and in the process of doing so forget that air velocity also effects the outcome, especially up in the higher rpm range where the cylinders need the ramming effect of the velocity. Volume of flow doesnt mean crap up top unless you got velocity to slam it into the cylinder. Why do you think many late model engines use dual length runners. One offers great flow/low velocity at low rpm and one offers greater velocity at the high end.
So Nick, in my own personal opinion, I think you should go with the L03 block and LG4 heads. Another thing I didnt mention is that if your LG4 block was an early 3rd gen engine then the pistons are dished, so going from the dished piston to the L03 flat top piston will offer some instant gains based on that one difference. I do not remember exact model years that had the dished pistons so you will have to figure that out yourself, perhaps someone else here will know.
And last but not least, aside from performance aspects, the LG4 heads are the earlier perimiter valve cover bolt heads, so they will look WAY better witha nice set of valve covers. I hate center bolt heads for that one reason alone.
Hope to see you around more Nick, since I'm not on FBN anymore, I'll have to catch you here or at mifbody.
Just to throw my personal opinion into the mix. I have investigated this type of swap quite a bit due to my own personal situation, and from most of the people I have talked to, the LG4 heads do great on the LO3 block, and flow better in the upper range where most people will be "using" the power when needed. Sorry fella's but when I am looking for power I want it in the upper range. I mean seriously, if I am street racing or drag racing or just mashing it in general, how often am I going to do so under 3,000rpm? Therefore, based on the fact the LO3 head was a low end head, I would go with the LG4 head which offers more room on the high end, especially with a bit of porting. Lets also remember that when discussing ported LG4 heads we must keep in mind that many people that port these heads get carried away trying to increase flow volume and in the process of doing so forget that air velocity also effects the outcome, especially up in the higher rpm range where the cylinders need the ramming effect of the velocity. Volume of flow doesnt mean crap up top unless you got velocity to slam it into the cylinder. Why do you think many late model engines use dual length runners. One offers great flow/low velocity at low rpm and one offers greater velocity at the high end.
So Nick, in my own personal opinion, I think you should go with the L03 block and LG4 heads. Another thing I didnt mention is that if your LG4 block was an early 3rd gen engine then the pistons are dished, so going from the dished piston to the L03 flat top piston will offer some instant gains based on that one difference. I do not remember exact model years that had the dished pistons so you will have to figure that out yourself, perhaps someone else here will know.
And last but not least, aside from performance aspects, the LG4 heads are the earlier perimiter valve cover bolt heads, so they will look WAY better witha nice set of valve covers. I hate center bolt heads for that one reason alone.
Hope to see you around more Nick, since I'm not on FBN anymore, I'll have to catch you here or at mifbody.
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