Inliners International Forums General Discussion Engines Springs for 235 and 261 Engines

Hi,

I just pulled the Bulldog cam out of my 235 to install a stock 261 cam, with stock lifters and pushrods. my question is may I use the springs, installed with the Bulldog cam, to run with my 261 cam? If someone could share the function of stock 235 springs, stock 261 springs, bulldog cam and how they match up together I'd appreciate the help.

Thanks!

Why you switching from the bulldog to a 261 cam in your 235?

Yes, I just got the stock 261 cam installed in the 235 in my 51 Chevy truck. I got the cam from the 261 I've installed in my 1950 Chevy two-door post sedan. I remember the original 235 in the 53 corvette was stock with a 261 cam so now I'm about to find out what the engine will do, but with two Rochester's instead of three side draft carbs.

Think you misunderstood my question. What was the reason to take out the bulldog ? Was it performing poorly in the 235 ?

my problem with the bulldog cam was I could not get it to run smoothly and at a decent idle rpm. Excellent acceleration, quick response.

I had it running for a time at about 1100 rpms and then most recently at about 1600 to 1800 rpms. I just found out this week that part of the recent problem may have been the rocker arm pivot shaft; (on my 51, two pieces) the front shaft broke into two pieces (now a total of 1 shaft, 1/2 shaft and 1/2 shaft.) When I took it out of the engine it looked brand new, but then I only drive the truck 1500 to 2000 miles a year.

Hope that helps,

Hope that helps.

Ted, I am pretty sure all of the rocker assemblies for these motors are two piece shafts. Does anyone know what the specs for the Bulldog cam are? I just fired up and broke in a new 261 a couple of weeks ago. As i noted in an earlier post, on a different but related thread, I used a schneider cam, 492 lift 280 duration, pretty tight center line, lots of rumpety rump and it idles around 800 or so. I actually think something else was driving the high idle, a vacuum leak, timing issue, something.

Any other info on the cam? like when did you notice the torque curve kick in, what rpm did the curve climb to, was the acceleration much better than stock?

Yes, info appreciated on both the Bulldog and the Schneider cams, especially the .050 lobe events.

The most solid info I have is on the 261 / early Vette cam, which is also a Clevite 229-1293:
Lift Lobe / Valve Gross
.274 .406 intake
.281 .416 exhaust
293-338 duration advertised, these are all over the map depending how they are measured since the ramps are so shallow
189-193 duration at .050" lobe intake / exhaust
110 LSA Lobe Separation Angle with 4 advance or 106 ICL Intake CenterLine

Similar info on Bulldog and Schneider appreciated.

My guess is the triple sidedraft Vette carbs would add about 4% across the board vs the twin Rochesters. Just a guess though based on other dyno comparisons and the Gonkulator.

the 261 cam is not really a performance cam but my understanding is that it had timing and lift events that were slightly, and I mean slightly, more aggressive than a stock 235 cam. As for the schneider cam, that cam was made for me (I actually had two made, the cam cores are starting to become hard to come by). Jerry Cantrell at Schneider makes them up as they are ordered. You call him on the telephone, tell him what you want to do, what kind of equipment is on the car, and he will give you a couple of options, you make your decision, and he grinds it up. A little more expensive than an off the shelf cam but the old story is in fact the old story, you get what you pay for. I will tell you that one of the things i wanted was a lot of rumpety rump at idle. I love that sound. Lots of guys find solace in cutting grass, gardening, golf, me I like tuning up the motor and spending a nice Saturday morning enjoying a cup of coffee while I adjust my valves (they actually don't need adjustment all that often), so Jerry cut the cam with a tighter centerline to allow for some additional overlap to get that sound. But again, it all depends on the weight of the car, the equipment, the use of the car, as to what lift, duration, centerline, and valve timing events make the most sense. Me, I do not completely understand all the intricacies of a cam and decided not to guess, but instead to seek the advice of a professional, not an order taker, and was willing to spend a few dollars more for the expertise and product. I am not criticizing the off the shelf grinds mind you, I just knew I was not going to be able to sort that out on my own and did not want to be disappointed with my purchase. In the end, for me it was money well spent. I got terrific advice (which I accepted graciously), no guessing on my part, no issues with installation or break-in, and a superior product. Just my own approach to camshafts.

Yup I show the stock vanilla 235 cam as Clevite 229-1251 or 229-1338 with
168-170 and 108 LSA
Gross valve lift
.311 int .333 exh

So the 261 & Corvette cam had about 21-22 degrees more duration at .050, quite a bump, and a lot more lift. It is about the same "performance" level as the "Nova 6" cam for the 230/155hp and the 292 truck cam.

Good to hear about the Schneider experience, any expertise beyond "Amazon" is getting hard to find.

I don't have any specs on the Bulldog though!

I am not sure that your specs are right for a stock 235. For a stock 235 in a 57 for example, my books tell me its 244 degrees of duration and a valve lift of .4004.

Oops I missed that one.
The 168-170-108 cam was 53 and older PG, 55 and older stick.

For 54 up PG and 56up stick I show Clevite 229-1252 at
244-244 ADVERTISED duration, again those vary all over
185-185 duration at .050 lobe, a more consistent spec
109 LSA
.400 int .400 exh gross lift
So it looks like at the time of the Vette (53-54), the Vette cam was quite a bit bigger than the vanilla 235 cam.

But, the base 235 cam got bigger in a few years anyway, and by the late 50s was near as big as the Blue Flame Vette cam.

Good catch, I am still learning stovebolts!

Here are the specs for the Bulldog cam ground by Delta Cams ...

Bulldog 254/264 dual pattern cam specs

If those specs are correct, The bull dog cam is just not that radical to require a 1100 rpm idle. Something else was driving the problem. Clifford listed his 264h hydraulic cam as 264 degrees duration and .444 lift. His 260m mechanical cam was 260 duration and .428 lift. His old catalogs noted that both cams had very smooth idles. While the bulldog is a dual pattern it is not any more radical then the Clifford cams. So the high idle is a puzzle.

So the Bulldog (thanks RoadRunner- nice 261 pics too!) is quite a bit bigger, 20-some degrees, vs the Vette cam.
At .050" lobe, the durations and Lobe Separattion are then
Early 235
168-170-108
Vette Blue Flame
189-193-110
Later 235
185-185-109
Bulldog
211-220-110

The Clifford cams at .050 spec out to (I'm using their 194-230-250cid specs)
264h
206-206-110
270h
214-214-110
280h
226-226-110
So the Bulldog would be somewhere between a Clifford 270 and a Clifford 280 cam, not race only but a pretty healthy cam for just 235 inches. Still, at 1100rpm it should idle very smooth. But not 600rpm.

I don't think that is quite right. I could be mistaken, but I was under the impression that all of the early the vette motors were power glide motors which would have had the the better cam profile. The 261 cam was just a smidgen better I assume to assist with the three carter yh side drafts which were essentially the carter yf on its side. As for the bull dog, it is not like a 270-280 cam. It is a 260 cam. It is not an aggressive profile at all. And notwithstanding that I have never used the bulldog, looking at the specs I would think a smooth idle, a mild cam in my humble opinion. A health cam for the 235 would be something in the 272, 278 or so and .480 lift range. A mild to mid is the 264 cam. A race only cam, and I have one but decided it was to much for the street, was Clifford's 292 duration and .529 lift.

mdonohue,
Well you might indeed be right, as I noted above I've never built a stovebolt, but I am wary of "advertised" durations of cams in general because they are all over the map - the advertised duration is measured on the shallow part of the ramp so its hard to tell how the engine will make power or even idle from that number alone.

So I tend to go by duration at .050" lobe, where the ramp is steep and it is a more consistent way to gage how a cam will run.

That said, it is true that the IDLE quality depends on the ramps. Long shallow ramps are easy on the valve train but will idle rougher. The Bulldog has a fair bit of duration at .050 (211-220), but given its low advertised duration 254-264, it could have fairly steep ramps so might have a smoother idle - this is kind of what roller cams do.

I hope it helps to exchange info in the thread, it is helping me for sure, to dig into this engine family a little more!

You also need to pay attention to the intake lobe center line...The intake closing has the biggest effect on engine performance...
On the last 261 I built ,455 Buick springs worked out nicely with after marker retainers and went right in at the correct installed height. Of course this depends on the location of the valve seats.You need to measure a mock up of the valve retainer and locks and compare the measurements to what's available. The Buick springs were about 90 lbs on the seat and 220 open..