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Title says it all, I've built a TPI 305 with stock LT1 cam and TBI heads. I'm sure these heads have different timing requirements than the 081s did, so I'm just looking for suggestions if anyone has done any TBI tuning and knows about what they like timing wise. I may just dump the timing values from a TBI tune in to the stock TPI 5spd .bin and start from there. Thanks guys.
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86 IROC, Superram 383, TKO 600, C4 IRS
89 GTA, L98, A4. T56 swap pending
91 TA LB9/T5 (R.I.P)
Re: 305 TPI with TBI heads, need timing suggestions.
The 081 heads came off of your 86 car? I have an 86 and was wondering what head casting i had.. thnx
__________________ "An engine is like an orchestra. It's made up of wind, brass, percussion, and a whole range of other complimentary sections, all working to make that beautiful music that we call 'performance'..."
271FWHP - 354FWTQ --> (UN-TUNED... Tuning in progress! Will DYNO again soon...)
For mods go here --> http://1986irocz.tripod.com/
14.2 @ 96 on the 1/4 mile...
Re: 305 TPI with TBI heads, need timing suggestions.
081s are the 87 and later center bolt TPI 305 heads. 416 castings are basically the same ports but perimeter style bolt pattern. They were used on LB9, L69, and LG4.
__________________
86 IROC, Superram 383, TKO 600, C4 IRS
89 GTA, L98, A4. T56 swap pending
91 TA LB9/T5 (R.I.P)
Re: 305 TPI with TBI heads, need timing suggestions.
I have centerbolt heads, but i have an 86 iroc... they rebuilt the engine before i bought it.. could it be possible there were some 86 irocs with this head? Or are the heads NOT from my original engine?
__________________ "An engine is like an orchestra. It's made up of wind, brass, percussion, and a whole range of other complimentary sections, all working to make that beautiful music that we call 'performance'..."
271FWHP - 354FWTQ --> (UN-TUNED... Tuning in progress! Will DYNO again soon...)
For mods go here --> http://1986irocz.tripod.com/
14.2 @ 96 on the 1/4 mile...
Re: 305 TPI with TBI heads, need timing suggestions.
center bolts are not original to an 86 engine, but they are no different than the perimeter style 416 heads as far as the ports are concerned. The only difference is the center bolt valve cover bolts and the angle of the middle 2 intake bolts is at a slightly different angle but you can fix that by drilling the intake out slightly.
If the engine has center bolts on it, you may have a later engine all together. Check the numbers on the bellhousing pad behind the driver's side head and run them on mortec.com You may have a later roller cam block as well.
__________________
86 IROC, Superram 383, TKO 600, C4 IRS
89 GTA, L98, A4. T56 swap pending
91 TA LB9/T5 (R.I.P)
