WTB - Good running 350 engine

[Dazaa]

As per the title, i've given up trying to get my car to run right, just want a good running 350 to drop in and start driving, any out there?

 

[Chuffer]

What`s wrong with it ? Why will it not run right ? If you cannot fix it have you thought about taking it a specialist that knows small block chevy`s

 

[Dazaa]

Terrible idle, constant misfire and i'm yet to have it actually reliably start everytime. It's got a new msd ignition, holley sniper, new distributor but thinking back it never ran right even when it arrived in the UK. Compression is even but very low across all cylinders at 120-130, I think it's just a tired old engine. looks like a blueprint 375hp crate motor might be happening.

 

[Chuffer]

Is the timing set correctly ? Are the plugs and leads ok ? Did you buy it with new carb and dizzy fitted or did you fit them ? Maybe they are not set up right . I dare say many of us C3 owners have tired engines due to age , I know my engine is a bit tired but it runs well enough now it is set up properly . Where do you live ?

 

[Dazaa]

timing is ok, plugs and leads are new, i fitted the distributor and sniper EFI. Sometimes it will start and run ok albeit slightly lumpy at idle (it apparently has a big cam, could be normal) now it wont start at all....after 2 years of working on this car i'm sick of it lol

Based in stratford east london, happy to pay someone to figure this out

 

[Chuffer]

If you have a wild cam it will be lumpy at idle and a bit` tetchy ` at low speed driving in traffic . If just a fast road spec cam it shouldn`t be too bad . Pity you are down in the East End bruv as I can highly recommend Williams Brothers Racing up here in South Northants . They are very experienced Chevy engine builders and don`t charge like a wounded rhino either .

 

[Roscobbc]

Dazaa - going back to 'basics' - you've installed a Holley Sniper injection system, yes?. Presumably you've got a new high pressure electric fuel pump 'feeding' it? (or perhaps a 'sump' system?) - are you able to re-install the original carb set-up (whatever that was, Hollley or Rochester) and 'theoretically' get the engine running 'old school'?

 

[Chuffer]

Also is the inlet manifold correct for your set up ? Any idea what compression ratio your block / cam should be . I know you said that compression was low across all cylinders .

 

[Forrest Gump]

Hi Dazaa
You could drop in a crate engine, but if you’re swapping over the fuel and ignition systems......I would worry it might run exactly the same. Bad running engines are usually fuel or ignition issues. Are you sure there’s not a big air leak somewhere? Is the Pcv valve plumbed up correctly.
I’ve heard that EFI are very voltage sensitive and will play-up if the battery or alternator are iffy.

 

[Dazaa]

Dazaa - going back to 'basics' - you've installed a Holley Sniper injection system, yes?. Presumably you've got a new high pressure electric fuel pump 'feeding' it? (or perhaps a 'sump' system?) - are you able to re-install the original carb set-up (whatever that was, Hollley or Rochester) and 'theoretically' get the engine running 'old school'?

Yes and yes, it was a kit with the pump, fitted a new feed line and used the old one as a return. The engine never ran right with the old carb, it wouldn't idle below 1200rpm which I assume was something to do with it having sat for 20 years. Since I swapped out the fuel pump and lines ect it would be too difficult to go back to a carb unfortunately as the sniper feeds a bunch of stuff like my electric fan feed and temp gauge

 

[Dazaa]

Also is the inlet manifold correct for your set up ? Any idea what compression ratio your block / cam should be . I know you said that compression was low across all cylinders .

All I know is that it's a 70's truck block with really low compression heads that the previous owner stuck an edelbrock performer intake and a big cam in. No other info, when it runs the idle is really lopey, compression test was 120-130 across all cylinders, when I first removed the valve covers I found 2 rocker arms totally loose and set the valve lash correctly. After that it idled ok but still felt like it had a slight misfire and absolutely no power when I drove it, my k10 pickup will throw me back in the seat under acceleration, this couldn't even break the tires loose at wot

 

[Dazaa]

Hi Dazaa
You could drop in a crate engine, but if you’re swapping over the fuel and ignition systems......I would worry it might run exactly the same. Bad running engines are usually fuel or ignition issues. Are you sure there’s not a big air leak somewhere? Is the Pcv valve plumbed up correctly.
I’ve heard that EFI are very voltage sensitive and will play-up if the battery or alternator are iffy.

I've rewired the entire car, spend the last 6 months trying to get it to run right, got a tuner to work on the sniper map, changed the pcv for a different type, nothing will get it to run right. Honestly felt like just giving up on it! The long term plan was always a high power motor swap anyway.

 

[Chuffer]

All I know is that it's a 70's truck block with really low compression heads that the previous owner stuck an edelbrock performer intake and a big cam in. No other info, when it runs the idle is really lopey, compression test was 120-130 across all cylinders, when I first removed the valve covers I found 2 rocker arms totally loose and set the valve lash correctly. After that it idled ok but still felt like it had a slight misfire and absolutely no power when I drove it, my k10 pickup will throw me back in the seat under acceleration, this couldn't even break the tires loose at wot

I am no expert on these matters but very low compression heads mated with a big cam sounds a bit of a mish mash to me . I am sure someone out there will have an opinion on this . Any idea how low very low compression is ?

 

[Roscobbc]

Even on an engine with 9.5 to 10.5 c/r a poorly selected cam will effectively reduce dynamic c/r significantly. Truck or mid 70's stock engine could have a c/r of 8 or even lower. Cam manufacturers can provide cams that are optimised for vehicles with low c/r's and get reasonable performance. My inclination (depending on your budget) would be to source a 'bare' crate engine and utilise much of the stuff already purchased.........perhaps a 383 stroker would give you the oooph you are missing? - look at Roadcraft's website?

RoadCraft – UK Ltd

 

[Chuffer]

I guessed you would hit the proverbial nail on the head Ross and pretty much sums up my gut feeling . A stock late 70`s small block in a C3 was 8.5 : 1 and an earlier truck motor probably somewhat less .

 

[Adtheman]

Dazza. do be careful with a blueprint engine. ive been looking and researching engines for myself, there are one or 2 horror stories with them, not sure if they are true but a basic search will reveal some not too happy customers.

 

[Dazaa]

Even on an engine with 9.5 to 10.5 c/r a poorly selected cam will effectively reduce dynamic c/r significantly. Truck or mid 70's stock engine could have a c/r of 8 or even lower. Cam manufacturers can provide cams that are optimised for vehicles with low c/r's and get reasonable performance. My inclination (depending on your budget) would be to source a 'bare' crate engine and utilise much of the stuff already purchased.........perhaps a 383 stroker would give you the oooph you are missing? - look at Roadcraft's website?

RoadCraft – UK Ltd

Unfortunately they have nothing in stock for the near future, otherwise i'd have jumped on that. Still, my old motor has decided to start running again, will see how long it lasts.