Compression and tbi

[anubisani]

HEY GUYS if I hv a 1988 gmc R3500 with TBI 454 . The ??? is if I keep all things the same but change the heads to these :
3993820....71-84...oval...OPEN...454 Passenger and Trucks, 113cc chamber, 255/114 ports
will the TBI still work with the bump in compression , or will I have to upgrade the chip, fuel pumps , and regulator.
THANKS IN ADVANCE GUYS.

 

[philjafo]

It would probably run ok, but to get the most benefit out of head upgrade yes to all the other upgrades too. The speed density fuel injection system doesn't respond really well to changes and was designed for fuel economy and reliablity, not horse power. It can work but it might be easier to just go with a carb, or a new stand alone fi system like FAST or Holley. They are self learning and will adjust to future upgrades. The factory tbi computer would need to be reprogrammed after any major change.

 

[anubisani]

Thanks

 

[Jims86]

Shouldnt be an issue as long as you keep the stock cam, but even then, its worth a good dyno tune.
The big deal with speed density is the cam profile...you install something that lowers vacuum, and the MAP sensor will read low vac, and the ECM will fatten up the fuel big time.

 

[anubisani]

SO WITH THE LIL BUMP IN COMPRESSION do you think it will affect the vacum

 

[Jims86]

SO WITH THE LIL BUMP IN COMPRESSION do you think it will affect the vacum

Shouldnt....will run better if anything. May need to run a higher grade of fuel though.

 

[Irishman999]

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Re: TBI AND COMPRESSION
Reply #1 - Today at 06:40:49 Alert Board Moderator about this Post! Quote All other factors remaining the same , you will notice no difference in performance with the head swap . Actually it will probably loose a bit of seat of the pants feel with the 820's .

TBI will be fine , fuel pump and regulator is always a good upgrade as all of the TBI engines were anemic at best with the stock pump/regulator .

About the only thing you will notice being different is your wallet being lighter from the $ spent to use the different heads.

Welcome to the site

TOM

 

[Jims86]

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Re: TBI AND COMPRESSION
Reply #1 - Today at 06:40:49 Alert Board Moderator about this Post! Quote All other factors remaining the same , you will notice no difference in performance with the head swap . Actually it will probably loose a bit of seat of the pants feel with the 820's .

TBI will be fine , fuel pump and regulator is always a good upgrade as all of the TBI engines were anemic at best with the stock pump/regulator .

About the only thing you will notice being different is your wallet being lighter from the $ spent to use the different heads.

Welcome to the site

TOM

Hmmm...thats the same thing they say about swapping from TBI heads to vortec...a slight SOTP loss in TQ.

 

[GreaseDog]

Hmmm...thats the same thing they say about swapping from TBI heads to vortec...a slight SOTP loss in TQ.

I call ******** on that one. Come on over and take a ride in my K1500, certainly no torque lost there.

 

[Jims86]

I call ******** on that one. Come on over and take a ride in my K1500, certainly no torque lost there.

Yeah, I have not driven a vortec TBI, so I dunno. I would think the larger ports would be more detrimental than anything else. Compression is definately a good thing, as long as your available fuel/wallet will allow.