big block conversion ???????????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tbear99 · 06-12-2009, 08:04 PM

This question is how i found this site.I have an 88 blazer love the blazer but while i was otr driver the body roted from sitting.I bought a military 85 blazer with bad motor and basically a parts truck with a good body and frame interior already stripped out which is actually better for me being i want to use my interior and wiring harness from 88.The plan is lift body off and and basically build from frame up.well my little 350 while pushing decent ponies I was thinking of putting a big block in it.I can get a 91 454 SS pickup with about 140k for about 600 in spring.I was thinking i could leave tbi unit to help with fuel economy.What are some of the problems i might run into with the 454?? my dream would be to have a 427 or 396 but thinking i won't find one of them reasonable enough for me to afford.

babyJay · 06-12-2009, 08:11 PM

Subscribing to this thread, sounds like a cool plan. As long as you keep the 88 harness with the tbi, ecu, sensors, etc transferred to the bbc you should be good. Someone will undoubtedly correct me if Im wrong tho.

72 CustomCamper · 06-12-2009, 11:49 PM

The 454 is only 20 more horses than the 350 stock for stock. The torque though 85 more lbft than the 350...

Chuck

tbear99 · 06-13-2009, 11:38 AM

baby jay thanx i was thinking same thing as keeping the wiring harness would work 72 i wasn't totally sure how much of a gain the bb would be.by the way here is a couple current pics of the 88

babyJay · 06-13-2009, 10:30 PM

Well, get it in there already!

tbear99 · 06-14-2009, 04:12 PM

spring time is when i get the 454 that pic is my donor vehicle i'm taking everything from this to the military.Right now trying to learn and make sure everything will work as i think or find out if people have had problems doing similar project

tvblazer78 · 06-14-2009, 08:26 PM

Not to bad for a parts truck. Keep us posted on this one!

tbear99 · 06-14-2009, 10:33 PM

i've had this truck since my bro died in 96 sorta hard to stop this one but when all converted the the military 85 it will live again at least in my head

tvblazer78 · 06-15-2009, 08:17 AM

Quote:

Originally Posted by tbear99

i've had this truck since my bro died in 96 sorta hard to stop this one but when all converted the the military 85 it will live again at least in my head

Sorry about that, but happy that you are doing something with it and just not letting it rot..

rigon4 · 06-17-2009, 06:40 AM

tbear99 did you have this for sale on craigslist a couple months ago? and were in upstate NY you from??

tbear99 · 06-17-2009, 05:47 PM

nope never been for sale their is one that looks about identical but in really nice shape in rush.Don't know if he is selling it.that was a texas truck i believe 6 inch lift.I'm half way between rochester and syracuse right on the lake ontario

rigon4 · 06-17-2009, 06:38 PM

there was a person sell a blazer and a body of a military one.

Fair Haven?

tbear99 · 06-17-2009, 07:33 PM

nope never seen that one

rigon4 · 06-18-2009, 09:32 AM

the person put it back up the other day not the same by far!!

http://syracuse.craigslist.org/cto/1226994190.html

rigon4 · 06-18-2009, 09:41 AM

and for your swap i think the 454ss trucks are only 220 hp?? so if you got some work done to your small block you mite be going backwards

72 CustomCamper · 06-18-2009, 03:41 PM

230 hp @ 3600 rpm's 385 lbft torque @ 1600 rpm's...

Chuck

79blazer · 06-19-2009, 03:42 AM

The 454 TBI flows 650 CFM.

There is a carburetor sizing formula out there, that is a rough guide to getting the right carb air flow CFM (cubic feet per min) but It works okay for TBI.

CFM = (RPM times CID) / 3456

3600 X 454 / 3456 = 473 CFM

Though the TBI is rated 650 CFM, the motor is likely running 75% volumetric efficiency with a restrictive intake cam and exaust... 650/0.75 = 487.5 Which explains why the power peaks at 3600, because that's where the airflow peaks. This low end power is excellent for tow/hauling.

The rest of the motor (camshaft and heads,) is designed to accomidate this, so if you use a bigger TBI, not much will happen. Until you get into cams and heads. Plus the more modifications you do, the more you need to do custom chip tuning.

Basically I'd find a cheaper 454, or cheaper small block.

tbear99 · 06-19-2009, 05:54 PM

thank you guys for the technical info.Now i'm wondering wether to find an older big block or just put money in my motor/I like the ideal of the torque of the bb

rigon4 · 06-20-2009, 12:11 PM

sb to bb its crazy were the power is i have had couple built sb but the truck i have now has a off road 502 in it the 450 hp one and its so fun

06-12-2009, 08:04 PM	#1
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	big block conversion ???????????? This question is how i found this site.I have an 88 blazer love the blazer but while i was otr driver the body roted from sitting.I bought a military 85 blazer with bad motor and basically a parts truck with a good body and frame interior already stripped out which is actually better for me being i want to use my interior and wiring harness from 88.The plan is lift body off and and basically build from frame up.well my little 350 while pushing decent ponies I was thinking of putting a big block in it.I can get a 91 454 SS pickup with about 140k for about 600 in spring.I was thinking i could leave tbi unit to help with fuel economy.What are some of the problems i might run into with the 454?? my dream would be to have a 427 or 396 but thinking i won't find one of them reasonable enough for me to afford.

06-12-2009, 08:11 PM	#2
babyJay Arrived on a Pale Horse Join Date: Mar 2007 Location: SnagTown Indiana Posts: 2,524	Re: big block conversion ???????????? Subscribing to this thread, sounds like a cool plan. As long as you keep the 88 harness with the tbi, ecu, sensors, etc transferred to the bbc you should be good. Someone will undoubtedly correct me if Im wrong tho. __________________ Jason 87 V30 350TBI/400 White w/Boss V-plow 89 R3500 CC SRW

06-12-2009, 11:49 PM	#3
72 CustomCamper huh ??? Join Date: Nov 2002 Location: Fredericksburg,Va. Posts: 3,369	Re: big block conversion ???????????? The 454 is only 20 more horses than the 350 stock for stock. The torque though 85 more lbft than the 350... Chuck __________________ 90 Blazer Silverado 350w/ 700R4 and 32" Kelly's "I am a bomb technician. If you see me running try to keep up!"

06-13-2009, 11:38 AM	#4
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	Re: big block conversion ???????????? baby jay thanx i was thinking same thing as keeping the wiring harness would work 72 i wasn't totally sure how much of a gain the bb would be.by the way here is a couple current pics of the 88 Attached Images

06-13-2009, 10:30 PM	#5
babyJay Arrived on a Pale Horse Join Date: Mar 2007 Location: SnagTown Indiana Posts: 2,524	Re: big block conversion ???????????? Well, get it in there already! __________________ Jason 87 V30 350TBI/400 White w/Boss V-plow 89 R3500 CC SRW

06-14-2009, 04:12 PM	#6
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	Re: big block conversion ???????????? spring time is when i get the 454 that pic is my donor vehicle i'm taking everything from this to the military.Right now trying to learn and make sure everything will work as i think or find out if people have had problems doing similar project

06-14-2009, 08:26 PM	#7
tvblazer78 Low & Fast! Join Date: Jan 2007 Location: Knoxville, TN Posts: 3,110	Re: big block conversion ???????????? Not to bad for a parts truck. Keep us posted on this one! __________________ Southeastern Mini Truckin' Nationals April 27 and 28, 2012

06-14-2009, 10:33 PM	#8
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	Re: big block conversion ???????????? i've had this truck since my bro died in 96 sorta hard to stop this one but when all converted the the military 85 it will live again at least in my head

06-17-2009, 06:40 AM	#10
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: big block conversion ???????????? tbear99 did you have this for sale on craigslist a couple months ago? and were in upstate NY you from?? __________________ 1981 K-5 Blazer 2wd 1985 C-10 Short step 1988 C-10 Suburban

06-17-2009, 05:47 PM	#11
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	Re: big block conversion ???????????? nope never been for sale their is one that looks about identical but in really nice shape in rush.Don't know if he is selling it.that was a texas truck i believe 6 inch lift.I'm half way between rochester and syracuse right on the lake ontario

06-17-2009, 06:38 PM	#12
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: big block conversion ???????????? there was a person sell a blazer and a body of a military one. Fair Haven? __________________ 1981 K-5 Blazer 2wd 1985 C-10 Short step 1988 C-10 Suburban

06-17-2009, 07:33 PM	#13
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	Re: big block conversion ???????????? nope never seen that one

06-18-2009, 09:32 AM	#14
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: big block conversion ???????????? the person put it back up the other day not the same by far!! http://syracuse.craigslist.org/cto/1226994190.html __________________ 1981 K-5 Blazer 2wd 1985 C-10 Short step 1988 C-10 Suburban Last edited by rigon4; 06-18-2009 at 09:32 AM.

06-18-2009, 09:41 AM	#15
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: big block conversion ???????????? and for your swap i think the 454ss trucks are only 220 hp?? so if you got some work done to your small block you mite be going backwards __________________ 1981 K-5 Blazer 2wd 1985 C-10 Short step 1988 C-10 Suburban

06-18-2009, 03:41 PM	#16
72 CustomCamper huh ??? Join Date: Nov 2002 Location: Fredericksburg,Va. Posts: 3,369	Re: big block conversion ???????????? 230 hp @ 3600 rpm's 385 lbft torque @ 1600 rpm's... Chuck __________________ 90 Blazer Silverado 350w/ 700R4 and 32" Kelly's "I am a bomb technician. If you see me running try to keep up!"



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06-19-2009, 03:42 AM	#17
79blazer Registered User Join Date: Aug 2006 Location: Mesa, Arizona Posts: 136	Re: big block conversion ???????????? The 454 TBI flows 650 CFM. There is a carburetor sizing formula out there, that is a rough guide to getting the right carb air flow CFM (cubic feet per min) but It works okay for TBI. CFM = (RPM times CID) / 3456 3600 X 454 / 3456 = 473 CFM Though the TBI is rated 650 CFM, the motor is likely running 75% volumetric efficiency with a restrictive intake cam and exaust... 650/0.75 = 487.5 Which explains why the power peaks at 3600, because that's where the airflow peaks. This low end power is excellent for tow/hauling. The rest of the motor (camshaft and heads,) is designed to accomidate this, so if you use a bigger TBI, not much will happen. Until you get into cams and heads. Plus the more modifications you do, the more you need to do custom chip tuning. Basically I'd find a cheaper 454, or cheaper small block. __________________ 79 Blazer Cheyenne, 2wd 305 3.42 stock 85 Caprice, TBI converted, new 350 crate motor, Monte Carlo SS Wheels, Bilstein shocks,

06-19-2009, 05:54 PM	#18
tbear99 Registered User Join Date: May 2009 Location: upstate ny Posts: 24	Re: big block conversion ???????????? thank you guys for the technical info.Now i'm wondering wether to find an older big block or just put money in my motor/I like the ideal of the torque of the bb

06-20-2009, 12:11 PM	#19
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: big block conversion ???????????? sb to bb its crazy were the power is i have had couple built sb but the truck i have now has a off road 502 in it the 450 hp one and its so fun __________________ 1981 K-5 Blazer 2wd 1985 C-10 Short step 1988 C-10 Suburban

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