Replacement engine revisited.

[10drum]

Ok, a little over a year ago I started a thread about rebuild or replace. I think my best option is to replace my 307 with a new GM 350.

Most of you may think I'm nuts, but I'd like to keep my 2bbl carb, intake, and the rams horn exhaust manifold(s). I want to keep the same original look under the hood. I know that there were a lot of 350/2bbl C10's from 69 on, but I don't know how the stock 2bbl will will match up with a new engine.

[MARKDTN]

No issues with putting a 2-bbl intake on a 350. The only issue might be if you buy a later 350 with center-bolt valve covers then 2 bolts on each side are at a different angle.

[nac46]

Originally Posted by 10drum

Ok, a little over a year ago I started a thread about rebuild or replace. I think my best option is to replace my 307 with a new GM 350.

Most of you may think I'm nuts, but I'd like to keep my 2bbl carb, intake, and the rams horn exhaust manifold(s). I want to keep the same original look under the hood. I know that there were a lot of 350/2bbl C10's from 69 on, but I don't know how the stock 2bbl will will match up with a new engine.

Hello. I am in the same boat. 68 c10 307 manual choke 2bbl roch carb p/s, p/b, fact a/c 3pd on column. thinking about a 350/300 hp from jasper. where did you get yours? thank you.

[10drum]

I'm still running the 307. i use about a quart every 500 to 800 miles.

[In The Ten Ring]

Originally Posted by 10drum

I'm still running the 307. i use about a quart every 500 to 800 miles.

Would switching to synthetic oil help with that?

Even a 2 barrelled carb is twice the carb I'll be running!

I intend to use my original 250 and if/when that goes, try and find a 292.

[10drum]

Originally Posted by In The Ten Ring

Would switching to synthetic oil help with that?

Even a 2 barrelled carb is twice the carb I'll be running!

I intend to use my original 250 and if/when that goes, try and find a 292.

Using synthetic might send this old engine into shock. I'm going to run it as is, then decide. Jasper does have a good warranty, and as this thread indicates, they are sometimes hit and miss. The new crate engines would be good, but I'm like you, I'd like to keep the original carb set up. My engine still has the riser on the carb, the exhaust manifold shroud for the automatic choke, and it all works great. So, if I can incorporate all that into a new engine, that's what I'll do.

[hugger6933]

I don't think your nuts for wanting what you want. That is why they make chocolate and vanilla ice cream. It makes perfect sense to me that you might want the 2 bbl setup while if it were mew I couldn't throw it away fast enough, but each truck is representative of the owner and we are all different. that is what makes us and our trucks great.

[derotoreut]

Running the 307 in my 70 K10, but when the time comes I going LSx. Solid platform and fuel injection. Can pick them up for reasonable price now. I got a take-out 5.3 for $1,000.

[garyd1961]

I was in the same boat as you with my 1970 C10. I really liked the old 307 but when time came to replace it I ended up going with an L31-R GM crate engine. It's a vortec engine and I doubt you will find a two barrel intake for it but for the money it is hard to beat. For around $2000 you get a brand new 350 engine with 9.4 to 1 compression, 4 bolt mains, hydraulic roller can, vortec heads, and heavy duty valves. It even comes with timing chain and cover, balancer,oil pan, and valve covers installed.
You will need a vortec intake and electric fuel pump. The fuel pump nearly stopped me from buying one but most all cars on the road today have an electric fuel pump.
I wanted to keep the original look also but this is pretty close being the last version of the original 350 motor and with a lot more HP than the old 307.
I like mine, it runs smooth and has a lot of torque but not over powered. It really makes my old truck fun to drive.
I know this isn't what you were looking for but at least it gives you another option.
Here's mine it doesn't exactly look factory but I think it does have the old school look.

[TwoFiftyShifter]

It will match up great with a Goodwrench 350 in the 260hp and 290hp versions.

[garyd1961]

Originally Posted by TwoFiftyShifter

It will match up great with a Goodwrench 350 in the 260hp and 290hp versions.

Don't know about the 260 but the 290 hp engine sucks. It's a low compression engine with big cam that makes 290 hp at the extreme top rpm range but has nothing at the low rpm range.

[TwoFiftyShifter]

Originally Posted by garyd1961

Don't know about the 260 but the 290 hp engine sucks. It's a low compression engine with big cam that makes 290 hp at the extreme top rpm range but has nothing at the low rpm range.

I have heard that on the net, however it must have as much low end as an old 307 right? I haven't owned one but I think the perception of that motor is a little off.

[finewayne]

290hp versions is the best

[garyd1961]

Originally Posted by finewayne

290hp versions is the best

Have you ever seen the dyno results on the 290 hp engine, it sucks. The 307 has a lot of low end torque. My L31-R is rated at 255 hp and 330 ft/lbs of torque. With my Holley four barrel and long tube headers I'm running 300+ hp and it makes a lot of low end torque.
You need low end torque to get these trucks up and going.
BTW what kind of gas mileage are you all getting with the 290 hp motors?

[Gromit]

I think markdtn had it right and second his opinion.

Just for kicks, see what you think about this adaptor.. you can use your 2BBL on a 350 crate and just a regular Edelbrock aluminum performer 2101 - it will still look stock and those manifolds are cheap and easy to get.

Here's a link to the one in the attached photo:

http://www.quickfueltechnology.com/c...0-4412-1a.html

I can understand being attached or partial to a particular carb - but a manifold? :-) Naw, I have my own biases so its all good.

Anyway; here is a photo and a link to the adaptor - at $157 it is kind of pricey though - I think I would put the money into a NEW carb..Just because those butterfly valve arm bushings tend to start to leak vacuum and once that starts they are impossible to tune.

As far as the 260 HP vs 290 HP argument - I wholeheartedly agree with the GM crates overall but my two cents is if you have an automatic go with the 260 HP crate; if you have a manual transmission by all means go ahead and get the 290 HP version.

The problem with the 290 HP with an automatic is that the stock stall torque converter locks up before the motor gets into its comfort zone and truck is too heavy for the motor at that low 2200 rpm so you end up lugging the motor.

If you have a manual you can adjust for it by winding it out more but you're locked in with an automatic unless you get a non-stock stall converter.

[garyd1961]

Originally Posted by Gromit

I think markdtn had it right and second his opinion.

Just for kicks, see what you think about this adaptor.. you can use your 2BBL on a 350 crate and just a regular Edelbrock aluminum performer 2101 - it will still look stock and those manifolds are cheap and easy to get.

Here's a link to the one in the attached photo:

http://www.quickfueltechnology.com/c...0-4412-1a.html

I can understand being attached or partial to a particular carb - but a manifold? :-) Naw, I have my own biases so its all good.

Anyway; here is a photo and a link to the adaptor - at $157 it is kind of pricey though - I think I would put the money into a NEW carb..Just because those butterfly valve arm bushings tend to start to leak vacuum and once that starts they are impossible to tune.

As far as the 260 HP vs 290 HP argument - I wholeheartedly agree with the GM crates overall but my two cents is if you have an automatic go with the 260 HP crate; if you have a manual transmission by all means go ahead and get the 290 HP version.

The problem with the 290 HP with an automatic is that the stock stall torque converter locks up before the motor gets into its comfort zone and truck is too heavy for the motor at that low 2200 rpm so you end up lugging the motor.

If you have a manual you can adjust for it by winding it out more but you're locked in with an automatic unless you get a non-stock stall converter.

I agree but would like to add the 290 hp motor has 8:1 compression not 8.5:1 as sometimes advertised and a cam made for an 11:1 compression engine. With this and poor flowing heads it has poor combustion and waste a lot of fuel out the exhaust. To get the 290 hp you have to rev it to 5200 rpm, in the normal driving range it just doesn't perform well.
The L31-R vortec engine has 9.4:1 compression with the best flowing heads Chevrolet ever made. It will make more HP than the 290 engine even though it only has a 214/228 lift cam which means it runs smooth and has a lot of low end power. It's also a hydraulic roller cam and can easily be upgraded to make 400 hp with a cam swap and minor head work.

[TwoFiftyShifter]

Originally Posted by garyd1961

I agree but would like to add the 290 hp motor has 8:1 compression not 8.5:1 as sometimes advertised and a cam made for an 11:1 compression engine. With this and poor flowing heads it has poor combustion and waste a lot of fuel out the exhaust. To get the 290 hp you have to rev it to 5200 rpm, in the normal driving range it just doesn't perform well.
The L31-R vortec engine has 9.4:1 compression with the best flowing heads Chevrolet ever made. It will make more HP than the 290 engine even though it only has a 214/228 lift cam which means it runs smooth and has a lot of low end power. It's also a hydraulic roller cam and can easily be upgraded to make 400 hp with a cam swap and minor head work.

That is the best motor for the money out there. IF you don't mind running an electric fuel pump and a juice clutch.