'91 454 - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**clay68c10** · 04-17-2007, 10:02 PM

It probably has the factory oil cooler stuff on it. That would be handy to have. The donor I pulled my tbi off of had it, but the block had some extra ventilation holes in it

WinDancer · 04-17-2007, 11:44 PM

I paid more than that for my 396 WITHOUT the tranny...

**53burb** · 04-18-2007, 12:44 AM

Hopefully it will all work out. I forgot to mention that the tranny is a replacement as well. It still has the GM sticker on it. That was $300 of the $1000. I figure a core 4L80E is worth at least that.

**53burb** · 04-23-2007, 07:09 PM

I picked up the engine/tranny on Saturday. I need to do a compression test & pull the valve covers off & check the numbers on those. Now, I need to start a thread on a basic rebuild or stroker if it needs a rebuild. Thanks for help & advice everybody!!!!!!

**Bob B.** · 04-23-2007, 10:34 PM

Before you buy any heads for this engine, you need to find out if it is a Mark V. All factory '91 to '95 454's were Mark V's, and the coolant holes in the block will not match up with the earlier Mark IV design heads. The '96 to '00 454's are Mark VI's, and they can usually use any big block head. Mark V's do not have a mounting for a mechanical fuel pump, and have a sheet metal timing cover. Mark VI's have a roller cam and an aluminum timing cover.

**53burb** · 04-24-2007, 10:49 AM

I am pretty sure my block had Mark 5 imprinted on the back of it near the crank. I do know it has provisions for a fuel pump & has a regular timing cover. Does this make sense?? I will look again tonight & see if Mark 5 is imprinted on it. Would it say Mark 5 or Mark V?? In fact the 5 looked more like an S.

**53burb** · 04-25-2007, 10:58 AM

I looked at the engine last night. It does NOT have the regular timing chain cover, but it DOES have a cover for the fuel pump. I did not remove the bolts to see if the cover comes off. Here is the number & description from Mortec. 12550313...454.......91-up...4-bolt, Gen.V crate motor, Gen. VI 4.25" bare block, fuel pump boss

**Bob B.** · 04-25-2007, 06:08 PM

Some of the non-production crate motors are that way. If it's a Mark VI block, you are pretty much free to use whatever heads you want. Some guys were calling the Mark VI the 'Mark Fix' because it corrected the head interchange problem!

**53burb** · 04-25-2007, 06:28 PM

so then how do I know exactly which one I have???? BTW, thanks for all your help.....any pics that you would like to see????

04-17-2007, 10:02 PM	#26
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,935	Re: '91 454 It probably has the factory oil cooler stuff on it. That would be handy to have. The donor I pulled my tbi off of had it, but the block had some extra ventilation holes in it __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

04-17-2007, 11:44 PM	#27
WinDancer The Original HotRod KnifeMaker Join Date: Jan 2007 Location: Tenino, Washington Posts: 811	Re: '91 454 I paid more than that for my 396 WITHOUT the tranny... __________________ Dave 69 GMC SWB 2WD 454 Turbo 400

04-18-2007, 12:44 AM	#28
53burb Registered User Join Date: May 2004 Location: Queen Creek, AZ Posts: 1,004	Re: '91 454 Hopefully it will all work out. I forgot to mention that the tranny is a replacement as well. It still has the GM sticker on it. That was $300 of the $1000. I figure a core 4L80E is worth at least that.

04-23-2007, 07:09 PM	#29
53burb Registered User Join Date: May 2004 Location: Queen Creek, AZ Posts: 1,004	Re: '91 454 I picked up the engine/tranny on Saturday. I need to do a compression test & pull the valve covers off & check the numbers on those. Now, I need to start a thread on a basic rebuild or stroker if it needs a rebuild. Thanks for help & advice everybody!!!!!!

04-23-2007, 10:34 PM	#30
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,321	Re: '91 454 Before you buy any heads for this engine, you need to find out if it is a Mark V. All factory '91 to '95 454's were Mark V's, and the coolant holes in the block will not match up with the earlier Mark IV design heads. The '96 to '00 454's are Mark VI's, and they can usually use any big block head. Mark V's do not have a mounting for a mechanical fuel pump, and have a sheet metal timing cover. Mark VI's have a roller cam and an aluminum timing cover. __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

04-24-2007, 10:49 AM	#31
53burb Registered User Join Date: May 2004 Location: Queen Creek, AZ Posts: 1,004	Re: '91 454 I am pretty sure my block had Mark 5 imprinted on the back of it near the crank. I do know it has provisions for a fuel pump & has a regular timing cover. Does this make sense?? I will look again tonight & see if Mark 5 is imprinted on it. Would it say Mark 5 or Mark V?? In fact the 5 looked more like an S.

04-25-2007, 10:58 AM	#32
53burb Registered User Join Date: May 2004 Location: Queen Creek, AZ Posts: 1,004	Re: '91 454 I looked at the engine last night. It does NOT have the regular timing chain cover, but it DOES have a cover for the fuel pump. I did not remove the bolts to see if the cover comes off. Here is the number & description from Mortec. 12550313...454.......91-up...4-bolt, Gen.V crate motor, Gen. VI 4.25" bare block, fuel pump boss

04-25-2007, 06:08 PM	#33
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,321	Re: '91 454 Some of the non-production crate motors are that way. If it's a Mark VI block, you are pretty much free to use whatever heads you want. Some guys were calling the Mark VI the 'Mark Fix' because it corrected the head interchange problem! __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

04-25-2007, 06:28 PM	#34
53burb Registered User Join Date: May 2004 Location: Queen Creek, AZ Posts: 1,004	Re: '91 454 so then how do I know exactly which one I have???? BTW, thanks for all your help.....any pics that you would like to see????

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