C1 (1960) 245 or 270 build decision - HELP

[Donald H.]

My 1960 is a CU code engine (see photo of pad), but it looks like sometime in its past life it was converted to 245 HP. I verified on a thread yesterday that I have 245 carbs. I spoke to Robbie Kunz (Bob's son) yesterday and he said they could convert the 245 carbs to 270 without much additional cost over their normal rebuild price. I.e. the air valve weight change out, etc.

I took the intake off this morning and took out a lifter (see pictures). I am new to this, but given the hole in the side of the lifter, I assume this is a hydraulic lifter?

Is there any good reason that I should not purchase a correct cam, lifters, etc. and convert this back to a 270HP solid lifter engine?

Thanks,
Don

[Joe R.]

Re: C1 (1960) 245 or 270 build decision - HELP

Don,

If it were me I would convert back to 270 hp. Maybe even do a little head massaging for a bit more power. I'm not very familiar with C1s, is there anything else different between 245 and 270 hp? Heads? Intake? Block?

Joe

[Donald H.]

Re: C1 (1960) 245 or 270 build decision - HELP

Don,

If it were me I would convert back to 270 hp. Maybe even do a little head massaging for a bit more power. I'm not very familiar with C1s, is there anything else different between 245 and 270 hp? Heads? Intake? Block?

Joe

I am included to restore it to what it is supposed to be. Just puzzling to me why someone in the past went to the expense to change out the carbs, cam and lifters. Maybe just didn't want to mess with the solid lifters.

This is my first restoration, so I don't know much. But as far as I have found out from the experts on this forum and other reading. The only differences between the 245hp and 270hp is cam/lifters, and minor differences in the carbs. The carbs are all the same castings but some internal differences, i.e. different fuel nozzles in the primary venturi, and externally have different air valve weight lever. But these are apparently reasonable to replate.

[Donald H.]

Re: C1 (1960) 245 or 270 build decision - HELP

Anyone else with suggestion? I still wonder why this conversion was made in the past.

Thanks
Don

[Doug F.]

Re: C1 (1960) 245 or 270 build decision - HELP

I would think it was probably a case where the 270 HP carbs were separated from the engine at some time and when someone found a set of dual carbs, they were the 245 HP versions.

Someone may correct me, but I was under the impression that the 270 carb jetting was overly rich in daily driving and that 245 HP jeting was all that the engine needed.
Doug

[Joe L.]

Re: C1 (1960) 245 or 270 build decision - HELP

My 1960 is a CU code engine (see photo of pad), but it looks like sometime in its past life it was converted to 245 HP. I verified on a thread yesterday that I have 245 carbs. I spoke to Robbie Kunz (Bob's son) yesterday and he said they could convert the 245 carbs to 270 without much additional cost over their normal rebuild price. I.e. the air valve weight change out, etc.

I took the intake off this morning and took out a lifter (see pictures). I am new to this, but given the hole in the side of the lifter, I assume this is a hydraulic lifter?

Is there any good reason that I should not purchase a correct cam, lifters, etc. and convert this back to a 270HP solid lifter engine?

Thanks,
Don

Don------


What information such as casting numbers or stampings do you have from the installed camshaft?

I'm not 100% sure these are not mechanical (solid) lifters. They could be piddle valve type mechanical lifters. It's easy to determine. Can you force down the pushrod seat with a screwdriver or similar tool? If not, they are mechanical lifters; if you can push it down, they are hydraulics. Keep in mind that mechanical lifters are rarely of 1 piece construction. They have a removable seat which is held in place by a snap ring retainer. They also have a hole in the side of the lifter body. Without such a hole, there would be no oil to the valvetrain.

[Donald H.]

Re: C1 (1960) 245 or 270 build decision - HELP

Don------


What information such as casting numbers or stampings do you have from the installed camshaft?

I'm not 100% sure these are not mechanical (solid) lifters. They could be piddle valve type mechanical lifters. It's easy to determine. Can you force down the pushrod seat with a screwdriver or similar tool? If not, they are mechanical lifters; if you can push it down, they are hydraulics. Keep in mind that mechanical lifters are rarely of 1 piece construction. They have a removable seat which is held in place by a snap ring retainer. They also have a hole in the side of the lifter body. Without such a hole, there would be no oil to the valvetrain.

Joe,

Thanks, when I first took out the lifter I did try to push the seat down and could not seem to get it to budge. I will try that again. How easy should it be to push it down? I don't have the engine out or apart yet, so I can't get a look at the cam.

Don

[Richard M.]

Re: C1 (1960) 245 or 270 build decision - HELP

Don, On my '59, I converted my CU/270 to 245 in 1995 after 10 years as solid lifter high lift cam. Here is why.......

1-Engine always ran rich and loaded up all of the time
2-Hot restarts were nearly impossible
3-Valve adjustments were a pain
4-I could never get a good idle adjustment
5-Idle had to be higher than I preferred

When it came time to rebuild I decided to step it back........ Hydraulic lifters and a new slightly aggressive hydraulic cam. I also found a replacement primary carb set up for 245hp. My secondary was a mongrel anyways and only worked on occasion so I left as is.

When I was done, I was much happier. I could get a nice idle and the engine ran perfect for cruising around. I missed the throaghty sound from the Duntov cam/solids though. I preferred cruising versus racing so I felt I did the right thing for myself. And I didn't have to play with the lifter adjustments anymore. I was very happy about that. I was looking for drivability.

Rich

[Edward B.]

Re: C1 (1960) 245 or 270 build decision - HELP

The sounds at idle are enough to justify the 270 version.

[Joe L.]

Re: C1 (1960) 245 or 270 build decision - HELP

Joe,

Thanks, when I first took out the lifter I did try to push the seat down and could not seem to get it to budge. I will try that again. How easy should it be to push it down? I don't have the engine out or apart yet, so I can't get a look at the cam.

Don

Don-----

It takes a good push to depress the plunger of hydraulics, but, if they are hydraulics, you should be able to push it down without monstrous force. You could use a bolt in the lifter seat in a vice if you wish to do the depression test that way.

[Duke W.]

Re: C1 (1960) 245 or 270 build decision - HELP

Anyone else with suggestion? I still wonder why this conversion was made in the past.

Thanks
Don

Don't do anything to the engine until you get the next issue of The Corvette Restorer.

Duke

[Donald H.]

Re: C1 (1960) 245 or 270 build decision - HELP

Don't do anything to the engine until you get the next issue of The Corvette Restorer.

Duke

Duke.

I just gave my carbs to bob kunz here in Carlisle. He is going to look into swapping the middle section from 245 hp version to 270 hp versions. I am torn between just having him restore them or also modify!

If I choose in the future to have the car judged then I assume that I need the correct 270 hp caebs

[Ted S.]

Re: C1 (1960) 245 or 270 build decision - HELP

I'd make sure whether the lifters are solid or hydraulic first. Also check the pistons to see if they're domed. The old Motors manuals I have show that the 270hp and 290hp engines had a higher compression ratio than the 230, 245, and 250 hp engines. Like others have said the carbs may have been replaced.

[Duke W.]

Re: C1 (1960) 245 or 270 build decision - HELP

Duke.

I just gave my carbs to bob kunz here in Carlisle. He is going to look into swapping the middle section from 245 hp version to 270 hp versions. I am torn between just having him restore them or also modify!

If I choose in the future to have the car judged then I assume that I need the correct 270 hp caebs

You will also need the correct cam, too. Tell us how the engine idled. There is a clear and obvious difference between the Duntov cam of the 270 HP engine and the base engine cam in the 245 HP engine.

According to the NCRS Spec Guide all engines except the Duntov cam, FI engine have 9.5:1 compression, and in stock trim they can run on mid-grade or even regular gasoline.

Duke

[Ted S.]

Re: C1 (1960) 245 or 270 build decision - HELP

According to the NCRS Spec Guide all engines except the Duntov cam, FI engine have 9.5:1 compression, and in stock trim they can run on mid-grade or even regular gasoline.

Duke

Well I guess my 1962 Motors manual must have a typo since it clearly states 10.5:1 for both the 270hp and 290hp engines. Seems a little odd since cams and compression ratio usually go hand in hand. Why would GM have run such a low compression ratio given the duration of the Duntov cam?