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Re: Major engine problem
Jim Sears #1237741 Wed Oct 04 2017 02:54 PM
Joined: Jan 2015
Posts: 1,038
Shop Shark
Originally Posted by Jim Sears
Grigg, good thought on the distributor. In this case that cylinder is always dead and each time it was checked, the spark was good.
It will be easy enough to check the intake chamber in the head when I get the manifold off on the way to removing the head.

Jerry, I know you think carburetors should go through life like hermits, alone. But many years of working on imported cars, of which 80% had a minimum of 2 carbs, says that if you size them correctly, they work very well.

Yes they work well when designed that way from the factory by engineers
that have all kinds of test equipment to verify they have a system that works.

I knew two brothers. They were going to be drag racing legends. In their
quest for speed they would read the hot rod and racing magazines and
install parts in their quest for more speed. With every change their
engine sounded and idle more like a real racing engine.

With every added part to their engine their car went slower.
The only thing they did that gave them more speed was the
first thing that they did. That was changing the rear end ratio.

Last edited by 32vld; Wed Oct 04 2017 02:59 PM.
Re: Major engine problem
Jim Sears #1237889 Thu Oct 05 2017 02:39 PM
Joined: Jan 2013
Posts: 1,426
Shop Shark
OK, so there is certainly something strange going on with #5 cyl. so it's pretty certain that the head will have to come off.
All other speculation will be put on hold until I do a compression test with my equipment and put a vacuum gauge on it.

As predicted, the client is taking this opportunity to talk about replacing the engine.
He really likes the truck, loves driving it, but his one lament has always been " I'd drive it more if it only had more power".
So before we do anything to this engine, he wants a list of options , degree of difficulty and cost, of different engines.
It goes against the grain a bit because I do restorations. However, I'll comply.
I only see 2 options - late model 261 or early small block (283, 302, 327).
All of those should bolt up to the 700R4 with little problem and both will need new front engine mounts. I have an old 283 in the back of the shop so that could be built up as any of those 3 sizes.
261 would have to be bought remanufactured.
Guess I will have to shift that discussion to the modified forum to find people who have done it and what the clearance and installation problems are.

Re: Major engine problem
Jim Sears #1237892 Thu Oct 05 2017 03:03 PM
Joined: May 2005
Posts: 9,147
261 is the logical choice and still resemble original.
A GMC 302 can also fit with some radiator adjustments. The front mount crossmember is different between GMC and Chevy, so could swap it, or modify/adapt.

Have you checked lift on the cam?
I'd check everything that's easy to check before pulling the head, might not be any trouble under the head.

1951 GMC 250 in the Project Journals []
1948 Chevrolet 6400 [] - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
1952 Chevrolet 3800 pickup []
---All pictures []---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-
Re: Major engine problem
Jim Sears #1237925 Thu Oct 05 2017 07:13 PM
Joined: Jan 2013
Posts: 1,426
Shop Shark
I plan to do a complete diagnoses when I see the truck, but the client has to have it trucked down to me first.
That won't happen before I report on the replacement options.
You know how it is, he has to decide what he wants to do (and pay for) and I have to deal with schedules on space and time. A big bolt takes the entire center bay in the shop. Can't store it outside so it is truly the elephant in the room. It effects all of the work in the rest of the shop.

Re: Major engine problem
Jim Sears #1237953 Thu Oct 05 2017 10:44 PM
Joined: Mar 2010
Posts: 9,524
Master Gabster
How did the 235 perform with the 700R4 right after the installation, in your opinion?
Even though the extra gears, which are fairly close together, will help get a little more out of the 235, there is probably a measurable loss of power due to the nature of a stock automatic transmission. Did you notice anything like this when you test drove it?
Was the buyer happy with the performance prior to the sudden failure?
The reason for all of these questions is because if there wasn't much in the way of added performance from the addition of this combination of dual carbs and 700R4, then I wouldn't expect much more from a 261 with this setup. So if your buyer wants more power which he can feel, then you will need to go with a V8. If you up-sell power steering, air conditioning, with a serpentine belt setup, you might be able to charge him enough to come out ahead with the engine plant change.

Re: Major engine problem
Jim Sears #1237958 Fri Oct 06 2017 12:16 AM
Joined: Jan 2013
Posts: 1,426
Shop Shark
I actually think that the 700R4 was an asset to the old splash 235.
The obvious advantage of standing starts with a load. The shifts were adjusted to really match the engine load, and the great asset of the 0.7 OD which allowed the truck to run on the highway without reving it's heart out.
I did choose to not connect the torque convertor lockup so the engine had a little relief when pulling hard. (like when the OD would shift in a little early under no load driving.
I feel there was a power increase by letting it breathe better. Maybe 10% or so (originally 94 hp adding another 9 was a lot)). Enough so that the A/C compressor or the 90 amp alt charging the big accessory battery after using the electric powered lift to raise a loaded bed, didn't make it feel it was dragging an anchor.
He really loved the transmission. He often said it seemed like the engine was working hard, or just needed more power.

I had the same feeling about the 261, I think it would be just an incremental change. It would be an easier install, but I don't think it will make him happy.
I think a small block putting out a solid 250 hp is the answer. Pretty easy to get out of a 283, even easier from the same block punched to 302.
Wish I could find a good way to put power steering onto a 2 ton.

Re: Major engine problem
Jim Sears #1238015 Fri Oct 06 2017 12:32 PM
Joined: Jan 2014
Posts: 1,375
Shop Shark
I have no first hand experience with a 261. But would sure think that 150ish HP vs the current 100ish HP would be a noticeable difference.

Then again, he's running all those accessories.....

I just like it when these trucks retain a 6 cyl.

Re: Major engine problem
Jim Sears #1238017 Fri Oct 06 2017 12:36 PM
Joined: Mar 2005
Posts: 1,721
Shop Shark
I think the difference between the 235 and 261 would be very noticeable. I replaced my 235 with a 261 and the difference was night and day. The 261 came out of a 1960 Viking series 60 school bus. That bus had no problems even loaded rolling down the road at the speed limit at the time. And would pull hills like crazy. I put it in my little 58 half ton pkup and could haul anything I wanted and had plenty of power.

Re: Major engine problem
Jim Sears #1238033 Fri Oct 06 2017 02:43 PM
Joined: Sep 2001
Posts: 30,933
Ditto to what Roy posted.

My 1960 261 (150 hp) is very noticeably different/stronger that the 1954 (high-pressure) 235 (135 hp) it replaced.

The 1948 (low-pressure) 235 was rated even lower (90-93 hp).

Tim []
1954 3106 Carryall Suburban [] - part of the family for 49 years
1954 3104 5-window pickup w/Hydra-Matic [] - part of the family for 15 years
- If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem.
- The 216 and early 235 engines are not "splash oilers" - this is a splash oiler. []
Re: Major engine problem
Jim Sears #1238037 Fri Oct 06 2017 03:12 PM
Joined: Feb 2001
Posts: 6,903
Master Gabster
Well, Jerry, I have dual Rochester b carb on my 1954 up until the issue I asked you about I have had no problems with the setup. My fuel mileage is off by 5 mpg average at highway speeds. I have not had it checked by my mechanic, he has been busy with the end of the year car shows. BTW the truck has 32000 miles since the engine overhaul. Jim, I hope you figure it out.

Ron, The Computer Greek
I love therefore I am.

1960 MGA Roadster Sold 7/18/2017
1954 3100 Chevy truck in the Gallery
2017 Buick Encore
Pix on Photobucket
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