Opinions on daily driver 350 Engine Build

[tmino1983]

I have a 70 Stepside c10 that I just competed the install of new suspension and now looking to upgrade the engine. It’s a late 80s GM Goodwrench Target 350 which I have read is around 8.5 to 1 compression with the 76cc heads. I want to build a low end torque monster that can be driven daily so I am looking for opinions on my plan

Carb- replace 2 barrel with 600cfm edelbrock
Intake- Edelbrock Performer
Heads- Trickflow 175 DHC 60cc which should bump compression up to around 9.75 to 1 right? (like the original look of camel humps)
Cam-Howard’s CL110225-2 with 1.5 rockers (I may bump up to the next size up the 235)

For Rear gears I currently have a 12 bolt with 3.08 which I will upgrade to 3.73 when I replace the Turbo 350 with an overdrive Trans in the near future

[Accelo]

Chevy converted to the one-piece rear main seal around 1986 and center bolt valve covers a year later.
Good start as hopefully your 350 likely has a one piece rear main and roller lifters.
If your choice was the CL110225-12 not the CL110225-1? it has a 208 Intake Duration at 050 inch Lift. I consider that a good cam for your goals. I always pick a cam and then go one below.
This procedure has worked excellent for me over the years.

https://www.summitracing.com/newsand...ion-calculator
Use this link for calculation the compression.
I get some thing closer to 10.5:1.
The aluminum heads will allow a higher compression without detonation.
I am missing details like the piston dish and head gasket thickness so it's just a guess.

The 3:73 are the real game changer. Most tend to underestimate the affects of a lower gear ratio.
Personally I would complete the gear change before anything else.
I can't remember for sure but the gear change may require a carrier change.
If you have to change the carrier do a posi if you can.

[57taskforce]

The sucky part about the later 80’s Gen 2 small block stuff is that in the truck world most didn’t get the roller cam love until 96, and the crate engines seem to be largely hit and miss. The blocks have the lifter tray bosses but not all are drilled and tapped. Not that it’s a huge deal it’s pretty easy to add the roller setup it wasn’t originally equipped, just a little extra work to drill and tap the bosses and some extra parts.

If you’ve got a roller block I would definitely run the roller. Flat tappet cams are pretty risky these days.

[MARKDTN]

'80s crate is likely 2-piece seal, flat tappet cam and 4-bolt mains. I'd dump that and get a later 1-piece core to build-maybe a '96-99 Vortec so you get those heads. Roller cam is the way to go. 2 bolt or 4 bolt makes no difference on a stockish engine. I like EFI but a carb is OK.

Bear in mind that a 700R4 has a very deep 1st gear so 3.08 may be fine for a rear ratio. I have a 700R4 in a car with 3.7 rear gears and first gear is useless. Wish I had left it 3.36. I would definitely try it before you change rear ends. My '83 K20 has 700R4 and 3.42 and it is a very good match IMHO.

[tmino1983]

Originally Posted by MARKDTN

'80s crate is likely 2-piece seal, flat tappet cam and 4-bolt mains. I'd dump that and get a later 1-piece core to build-maybe a '96-99 Vortec so you get those heads. Roller cam is the way to go. 2 bolt or 4 bolt makes no difference on a stockish engine. I like EFI but a carb is OK.

Bear in mind that a 700R4 has a very deep 1st gear so 3.08 may be fine for a rear ratio. I have a 700R4 in a car with 3.7 rear gears and first gear is useless. Wish I had left it 3.36. I would definitely try it before you change rear ends. My '83 K20 has 700R4 and 3.42 and it is a very good match IMHO.

Yeah, my original plan was to pull the engine but did a compression test last weekend and all of the cylinders were good (avg 165) with not more than 10% between the high and low so decided not to go through the work of pulling and just improve the top end for now.

I don't have a 700r4 yet but i do want to upgrade the engine first to see how it drives and see if I even need to do the gear change later

[MikeB]

The GM Targetmaster/Goodwrench engine has a very mild flat tappet cam, around 195/202, 112LSA, .383"/.401" valve lift. Seems like some had .390" intake lift.

Having installed a few of them over the years, I can say they have a smooth idle and make really good torque right out of the box. Dual exhaust or a set of headers with small primaries, along with a 600cfm or smaller 4-bbl will wake up the engine and fatten up the power curve. Been there done that at least 3 times.

Actual compression as measured by magazines (and my math) is around 7.8:1. So your 60cc TF heads would bump compression up to around 9.0:1. You could also use a .028" head gasket for a little more. But I'd use whatever gaskets TF recommends.

I had always looked at an Isky cam at 208/208 on a 108 LSA, but that was with stock heads and 7.8:1 compression. With 9.0:1 you could run a cam with 110 LSA for a less overlap and a wider power band.

Guessing at head gasket thickness and how far "down the hole" the pistons are (varies from .025"-.030"), I'd say going from 75cc to 60cc chambers will get you more like 9.0:1.

[tmino1983]

Originally Posted by MikeB

The GM Targetmaster/Goodwrench engine has a very mild flat tappet cam, around 195/202, 112LSA, .383"/.401" valve lift. Seems like some had .390" intake lift.

Having installed a few of them over the years, I can say they have a smooth idle and make really good torque right out of the box. Dual exhaust or a set of headers with small primaries, along with a 600cfm or smaller 4-bbl will wake up the engine and fatten up the power curve. Been there done that at least 3 times.

Actual compression as measured by magazines (and my math) is around 7.8:1. So your 60cc TF heads would bump compression up to around 9.0:1. But you could also use a .028" head gasket for a little more. But I'd use whatever gaskets TF recommends.

I had always looked at an Isky cam at 208/208 on a 108 LSA, but that was with stock heads and 7.8:1 compression With 9.0:1 you could run a cam with 110 LSA for a less overlap and a wider power band.

Guessing at head gasket thickness and how far "down the hole" the pistons are (varies from .025"-.030"), I'd say going from 75cc to 60cc chambers will get you more like 9.0:1.

Do you mind sharing the magazine arcticles or your math on the 7:8:1? That would be great because I'd like to end up at 9.0:1... isn't 0.1 for every 1cc of chamber reduction?

[MARKDTN]

Originally Posted by tmino1983

Yeah, my original plan was to pull the engine but did a compression test last weekend and all of the cylinders were good (avg 165) with not more than 10% between the high and low so decided not to go through the work of pulling and just improve the top end for now.

I don't have a 700r4 yet but i do want to upgrade the engine first to see how it drives and see if I even need to do the gear change later

There are articles on putting Vortec heads on those shortblocks that boosts power a bit. Another option might be Tuned Port fuel injection (85-92 Corvette and F-body). Gets you nice low end torque. I really like them. I've done several conversions. Put one on a bone stock '84 SWB with a 305 for a guy at work and it is night and day different.

[72SB]

IMHO a 700R4 with 3:08 would be a good combo. I had that setup (4L60E) and 3:08 in a SBC heavy car before I did a T56 swap. At most, do 3:42's with a 700R, especially with a tall tire. As mentioned 1st gear is very low so a 3:08 or 3:42 will be better, IMHO, than 3:73. Especially for Fwy driving.

A "RV" cam makes TQ down low and good for a street truck.

[LS short box]

The other thing to consider with your build is a quality stall converter. I like and use Circle and Yank billet. Maybe 2500-2800 rpm stall?

[BROWN 70]

hi, one magazine that did a big work up was Chevy high performance. they worked with the Goodwrench 350. the articles were called the Goodwrench quest. they were 7.8-8.0 to one stock. they ran a 4bbl headers and got 265hp and 350 ft lbs. not bad for a stockish crate engine. I bought one in 99 for my GMC. its been great. BROWN 70

[MikeB]

Originally Posted by BROWN 70

One magazine that did a big work up was Chevy high performance. they worked with the Goodwrench 350. the articles were called the Goodwrench quest. they were 7.8-8.0 to one stock. they ran a 4bbl headers and got 265hp and 350 ft lbs. not bad for a stockish crate engine. I bought one in 99 for my GMC. its been great. BROWN 70

Thanks for that confirmation. As I recall, there was was also an article in Hot Rod Magazine. It's been many years since those articles, and I doubt I could find any of them. Heck, I could do the math if I remembered the piston dish and valve relief volume, along with head gasket thickness.

The OP here can google "Goodwrench 350 actual compression" and get lots of hits.

[BROWN 70]

the Goodwrench quest is still on the net. good read I think there were 6-7 chapters. I put a 204 214 420 442 cam in mine with headers, hei, flowmasters with three cambers. its not overly loud. BROWN 70

[MikeB]

Originally Posted by BROWN 70

the Goodwrench quest is still on the net. good read I think there were 6-7 chapters. I put a 204 214 420 442 cam in mine with headers, hei, flowmasters with three cambers. its not overly loud. BROWN 70

Funny, I put that same cam in one back around 1990! Also a Holley Economaster 450 cfm 4bbl on a Q-jet manifold. And dual exhausts (a whopping 2") with generic turbo mufflers.

[tmino1983]

Update: put on new manifold, 4bl carb and better dual exhaust and it did really wake the engine up. However, still needs a little more power so looking at new heads (either vortec or trick flow double humps). Do you think it would be worth it to run 1.6 stamped rockers to get a little more lift out of the stock cam? After reading so much about flat tappet cam failures and the cost of going roller….I’m not really wanting to change the cam.

[Lokin4AReason]

what kind of torque conventor are you running ?

[tim_mc]

You didn't mention your ignition setup, so if you're running a stock HEI, swapping the OEM module to a Davis Unified Ignition Dyna-Module will noticeably improve throttle response and acceleration. It woke up my GM 350 crate short block w/Brodix IK180 70cc heads, Comp Cams SK12-408-8 XR258HR roller cam kit, Edelbrock EPS intake & AVS2 carb. I also added DUI's 50K coil upgrade. At $65 MSRP, the module is a relatively low-buck way to squeeze a little more performance without tearing into the top end.

[Willshook]

Since the engine is strong, a head/cam change seems like a good choice.

Don't buy your heads until you have the old ones off and can measure the quench and do a good estimate on the CR...sometimes there are surprises, and you want to see if you can get the quench in the .040 ballpark. 175cc runners are a great choice for a street head...but I don't see the value here in aluminum heads for this mild of a build, especially with a very small cam. I would buy less head...or more cam.

I'd personally recommend a Holley over an Edelbrock every time. The Holley Street Avenger is a great choice - the 670 is a little big, but probably the right choice. Performer is a great intake choice.

Cam choice seems reasonable - I would say that it's pretty mild especially for those heads; I'd definitely at least go with 1.6 rockers (CompCams roller tip at most) But again...seems pretty small for those heads. For what you want to do maybe that cam plus some upgraded Vortecs - probably a better deal overall.

REMEMBER to check all your valvetrain geometry carefully. The biggest screw-ups on these head swaps is getting the quench/CR wrong, and/or failing to check the geometry and ending up bending pushrods or breaking springs.