5.7L Non-Vortec to Vortec conversion

[Scott Danforth]

Link in my sig, first post has links to the cam I chosen

268 degrees of duration is the biggest cam you can use with wet exhaust.

Before I spent any money, I would use a dial indicator and determine what you have. Your cam is probably fine

However, with vortec heads most cams hotter than stock will require different seals and valveguides to be machined for clearance.

 

[Panoguy]

@Scott Danforth - Your thread is an interesting (but a bit over my head!) read - thanks for the link share!

It looks to me like the Comp Cam CL12-232-3 would be a good fit for me - what do you think? I'm hoping I can get specs from Mabbco... sucking water into my engine wouldn't be ideal! They did specify the Camshaft was ground for marine use, & I haven't sucked any water into my cylinders yet - so your guess is probably right - & so my current camshaft is probably OK, duration-wise.

Lift-wise, I have a digital caliper that measures in 0.0010 increments, I'm hoping I can somehow use that to measure lifter travel (with the head-off), instead of buying another tool. As much as I like buying tools, I'm running out of cash!

Strangely-enough, my Sea Ray, with it's current bad compression in 3 cylinders & non-Vortec heads, nevertheless tops-out at around 48MPH (GPS) - it's a crazy-fun ride, & I'm looking forward to seeing what the Vortex heads & optimal cylinder compression in all 8 cyls will add. Idle now tends to suck because of my current compression issues, however!

I found the rest of your thread (regarding exhaust) very interesting also, as this is something that concerns my build. My "Y" pipe has less diameter than the one I initially wanted to use, the bolt holes in my gimbal housing didn't mate. So I had to get a round "Y" pipe of somewhat less diameter instead of the square one I got from the pulled engine. I'm sure I'm choking my exhaust somewhat. I still have the square "Y" pipe - so maybe I'll buy the proper gimbal housing some day. (I wish I took the gimbal off of the boat that I got the engine from!)

 

[Scott Danforth]

@Scott Danforth -

Lift-wise, I have a digital caliper that measures in 0.0010 increments, I'm hoping I can somehow use that to measure lifter travel (with the head-off), instead of buying another tool. As much as I like buying tools, I'm running out of cash!

no way to measure a cam shaft with a caliper while in the motor and be accurate.

 

[Tail_Gunner]

Watching this thread is interesting, if your going to install a flat tappet you need your ducks in a row.
More than probably a lot more would be in order, a compete setup, one with springs,keepers cam ect ect.
Spring pressure not to exceed 100 lbs.
New flat tappet cams fail at alarming rates, spring pressure&modern oils are very hard flat tappets
Comp cams has a few issues in this area, know your break in procedure well, the first 20 minutes are critical

 

[Scott Danforth]

Watching this thread is interesting, if your going to install a flat tappet you need your ducks in a row.
More than probably a lot more would be in order, a compete setup, one with springs,keepers cam ect ect.
Spring pressure not to exceed 100 lbs.
New flat tappet cams fail at alarming rates, spring pressure&modern oils are very hard flat tappets
Comp cams has a few issues in this area, know your break in procedure well, the first 20 minutes are critical

and a high zinc additive.

 

[76SeaRay]

Couple of notes on Vortec heads. Make sure they are checked for cracks. If you go to higher lifts and stronger valve springs, make sure you change the press in rocker studs to the threaded studs. Most shops will pull the pressed studs, bore and thread the heads for reasonable price when they do the head work. If you change to a roller cam, make sure you get the correct roller lifters since the earlier blocks are not machined for "dog bones" to keep the roller rockers from spinning, you need the lifters that have the bar across the intake/exhaust pairs. The 1996 and later blocks are machined for dog bones.

I scratch built my 5.7L from a 1996 block. I went with the Comp Cams Xtreme Marine roller cam, roller lifters, stronger valve springs, and roller tip rockers. I was able to use stock length push rods. If you go with roller tip rockers, you will need to add guide plates to make sure the push rod stays under the roller tip.

 

[Lou C]

about flat tappet cams, the only recent vehicle we have that has one, is our
98 Jeep Grand Cherokee with the inline 6. It has 180,000 miles on it now and no problems with the lifters, I've used Valvoline Max Life about the last 100,000 miles, not sure if that helped.

 

[Panoguy]

As it turns-out, my Mabbco short block was improperly assembled - the #2 piston wristpin wasn't fully pressed-in (or was perhaps pressed too far?). The result was 2 huge gouges (from either side of the wristpin) in the cylinder wall.

Other problems with this block: hairline block cracks between #2-4 & #4-6 cylinders - this to me spelled the end of this block. Pistons were .60 oversized, so the block has been re-bored to the max. (I believe) anyways.

Yeah - I wouldn't buy another Mabbco rebuild!

I had a local engine rebuilder (Champlain Valley Engine Rebuilders) build-up a 5.7L Vortec that runs like a champ.

Lesson learned - it's sometimes best to spend a bit more, but buy locally instead. CVER did a really great job for me.

 

[Lou C]

thanks for the info, you just confirmed what I've been thinking of when I have to repower, go local.
Between mistakes and shipping costs, it makes more sense. I can rent a U-Haul to pick up an engine for way less than what shipping costs.

 

[Lou C]

Valvoline ZR-1 has a very high level of zinc, in a 20/50 weight it should be great for a flat tappet engine.

 

[Scott06]

As it turns-out, my Mabbco short block was improperly assembled - the #2 piston wristpin wasn't fully pressed-in (or was perhaps pressed too far?). The result was 2 huge gouges (from either side of the wristpin) in the cylinder wall.

Other problems with this block: hairline block cracks between #2-4 & #4-6 cylinders - this to me spelled the end of this block. Pistons were .60 oversized, so the block has been re-bored to the max. (I believe) anyways.

Yeah - I wouldn't buy another Mabbco rebuild!

I had a local engine rebuilder (Champlain Valley Engine Rebuilders) build-up a 5.7L Vortec that runs like a champ.

Lesson learned - it's sometimes best to spend a bit more, but buy locally instead. CVER did a really great job for me.

Its great if you have a local machine shop who can do a quality rebuild. Stories like yours is whyi bought a new base engine vs rebuilt. Of course this was in 2015 when the difference between new and reman was just under $1k.

i assume you have a noticeable increase in power with the vortec?

 

[Lou C]

Unfortunately new base engines have really gone up in price.

 

[Scott06]

Unfortunately new base engines have really gone up in price.

Yes was a no brainer back then. I think a 5.0 or 5.7 was about $3200-$3400 plus freight no core charge. Reman was like $2200-2400. Maybe off a couple hundred on each but no matter who folks got the reman from it was 50/50. i think the same package i got from Mich Motorz now is about $2 k more.
years agomy dad and i rebuilt the 1.8 l 4 cyl in his jetta. The issue they had was with big end of rod getting out of round leading to low oil pressure. Had rods resized and block hot tanked.block and crank were prefect because of religious 3 k oil changes. Get the rods back and assemble engine but cannot turn engine , take it back apart and big ends of rods were resized at slight angle to crank journals…. One edge of upper bearing and opposite edge of lower is hitting crank. Got another machine shop to redo the work…

locally to me in pa not many machine shops. Im on a year waiting list for the 389 in my GTO From a well known pontiac guy. He used to put prices on his website stock rebuilds of your core started at $6 k.…