Big block mk5 build question - Team Camaro Tech
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post #1 of 7 (permalink) Old May 21st, 18, 04:37 PM Thread Starter
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Steve
 
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Big block mk5 build question

Friend at work has an early 90ís chevy truck with a mk 5 in it. The truck is kind of a hauler and appears to be in great shape despite real high milage. He want to redo the motor with even better bottom end. From what he says aftermarket parts must be a bear for this generation. He says the original heads are junk, the tpi is junk, but the rest of the motor is a fairly decent base. He wants to add up to date injection. He thinks he found heads ( afr i think) and a cam that will work but not an intake system. I know some of you guys speak bbc. Is this motor as much of a mutt as he thinks or is there a combo out there for him. For him a build is a better option than springing for the latest duramax.
Thanks

67RSSS......owned since 69. A basket case for most of it.
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post #2 of 7 (permalink) Old May 21st, 18, 06:17 PM
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I would call edelbrock and tell them what you have, and what you want. They speak your language.

X-77 keith
1969 x-77 Z/28 orange/ white stripes, named by my daughter "Clementine ", M-22 close ratio, 4:10 12 bolt, CE 302. Hugger orange with white stripes. White standard interior. Restoration complete May 2018
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post #3 of 7 (permalink) Old May 21st, 18, 07:50 PM Thread Starter
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Re: Big block mk5 build question

Hey Keith,
Thats what i told him too. He said the Edelbrock tech told him they couldnt do it. Surprised me. I guess i need to learn enough big block to be dangerous. I dont think ive spent much more than a day with them in 50 years.

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post #4 of 7 (permalink) Old May 21st, 18, 11:13 PM
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Wow. I have built quite a few, but they have all been engines from the 70' s and 80' s. I'm surprised to hear edelbrock say that. Sorry .

X-77 keith
1969 x-77 Z/28 orange/ white stripes, named by my daughter "Clementine ", M-22 close ratio, 4:10 12 bolt, CE 302. Hugger orange with white stripes. White standard interior. Restoration complete May 2018
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post #5 of 7 (permalink) Old May 22nd, 18, 05:13 AM
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Dave
 
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Re: Big block mk5 build question

A Gen V BBC bottom end is bullet proof. They all have a four bolt main bottom end with a one piece rear main seal; and there is no provision for a mechanical fuel pump (how you tell a Gen VI from a Gen V in the bone yard). Your friend wants new higher compression pistons (thirty over), rings and bearings and the bottom end is done.

If you are going with EFI then you will need to buy not only another manifold and MAP controlled port injectors, but an aftermarket CPU to control it. Edelbrock sells a system for the big block using a Victor Jr. intake manifold (a single plane), or a carb replacement self contained TBI. He could also buy the Arizona Speed equipment EFI that uses a tunnel ram manifold with a speed density equipped single throttle plate (similar to the old Gen three Camaro EFI TPI on steroids.

The TBI on the motor now is sitting on top of a low rise Rochester QuadraJet with an EGR valve in it. He could take the TBI off and use a Quadrajet to replace it. But only if he doesn't live in a state with emissions inspection.
Or you can replace the cast iron factory intake with a Edelbrock RPM Air Gap manifold and a 750 Holley carb. This still requires a new small cap HEI distributor; as the one it now is computer controlled (It also has a 5,200 RPM Rev limiter built into it, so it will never go any higher than that). This is because the heads he has now are flow limited to 450 horse in stock form and are done by 4,800 RPM.

Duration in your cam choice is determined by where you want to make power. If you want to spin the motor to 7,200 RPM then the distributor and heads say it won't happen. A lot of valve overlap (long duration cam) also says you are going to have a lot of problems with EFI. A carb is much more forgiving of a big cam choice. If he has to have EFI then you are limited to a short duration cam (under 220 degrees at fifty) ground on a 114 degree LSA with as much valve lift that you can get. This is known as an RV grind.

An RV grind might just be what he is looking for as he may be towing a house behind him as he travels the world. I don't know what he wants his motor to do.

Finally I agree AFR heads are a good choice just keep in mind the cubic inch limits they mention on their web site should be heeded as an intake port that is huge will kill any mid throttle performance. Oval ports are recommended for all BBC under 500 cubes. Rectangular ports work not as well as enlarged oval port intakes as the corners are dead to air flow. Brodix uses huge 440cc oval intakes on their biggest asymmetrical head.

https://www.carid.com/brodix/sr-20-s...der-heads.html

Like I said I don't know what he wants to do with his motor. It could be the "Peanut Port" heads with pocket relief and short side radius work, adjustable valve rocker arm studs, and bigger valves might be the correct path. They will support nearly 600 horse when reworked.

Big Dave
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post #6 of 7 (permalink) Old May 23rd, 18, 03:42 PM Thread Starter
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Re: Big block mk5 build question

Dave, he is towing a house behind him, its that kind of setup. Power in the bottom and mid range. An rv cam might be perfect. He really doesnt want a carb and is stumbling over the manifold injection combination.

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post #7 of 7 (permalink) Old May 26th, 18, 11:48 AM
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Re: Big block mk5 build question

Quote:
Originally Posted by Larger Dave View Post
A Gen V BBC bottom end is bullet proof. They all have a four bolt main bottom end with a one piece rear main seal; and there is no provision for a mechanical fuel pump (how you tell a Gen VI from a Gen V in the bone yard).
Big Dave
Gen 6 didn't have the mechanical fuel pump boss either unless it was OTC or a later model.
I wouldn't touch a gen 5. I just finished my gen 6 454. The difference between the two is is that nothing easily interchanges with the gen 5 like it does with a gen 6. Parts are much easier to source with the gen 6.

'69 SS396 X66 L34 08D (8/22/1969) M21 BS
460ci Gen VI 9.75:1
241/249 @ .050" .625/.625 110 LSA

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