The Stovebolt Site Forums The Shop Area The HiPo Shop 49/50 3600 SBC Conversion

I used flat top pistons with valve relief's on one side only, I had a set of Chevy heads with the same casting number and what I thought were 74 cc chambers, when I cc'd the heads one was 74 cc, the other was 76 cc, I had the shop mill the 76 to match the 74, my calculations say I'm at 9.5 :1 I called Comp Cams and told them what my application was and they recommended the cam. I built it for my Vette but now am keeping it stock so I'll just keep the engine for whatever comes along.

I need to cc my chambers because 74 would be a lot different than 64. My calculations with a 64cc head show a static compression ratio of 9.3 with 18cc dished pistons, if I go with 7cc flat top pistons the ratio jumps to 10.4.

Tuts 59, thanks for the idea of measuring the cab location before I remove it. I may still want to put the cab back on before I lock the engine location down but it will provide another degree of certainty.

A question for you hi-po guru's know of any ways to increase compression ratio on 235/261 ?? Pistons would be a fortune,head shave not much,turbo system expensive,anybody know of a way ??

To be sure of the chamber size it would be a good idea to cc them, you never know what was done to them in the past. The casting number will get you close to what they were when manufactured. I think you're close with the numbers you stated with the dished pistons.

[quote=fixite7]A question for you hi-po guru's know of any ways to increase compression ratio on 235/261 ?/[quote]

Deck the block for zero piston clearance, bore the engine 60 over, use an 848 head, and maybe shave a little off the head. Then use a copper shim head gasket .030" thick. Do a VERY careful check on piston to intake valve clearance and flycut the piston tops if necessary to get a minimum clearance of .060". You can get the CR up to maybe 9.25:1 that way.

What makes you think that increasing the compression will help the performance? Compression ratio increases need to compensate for radical camshaft profiles, to get the running compression pressure back to where it once was with a stock camshaft. Raising compression without a corresponding change in camshaft profile just makes the engine prone to pre-ignition and detonation, unless you plan to run premium gas all the time.
Jerry

WICruiser Sorry I missed your mount question,got so I would mount a plte of steel on the tranny just let it slide on the cross member till other stuff was determined. Then make up the rear mount. Never used the front toad stool mounts,felt like it would be top heavy and maybe want to chatter in a pull.

While I am waiting for the weather to warm up to allow cab work to continue I am contemplating engine/transmission mounting again (getting ahead of myself as usual).

I plan to obtain the SBC mount installation kit and locate the engine mounts as suggested to provide cab/firewall clearance for the distributor, etc.

I am still a little fuzzy about the original rear mount (engine/bell housing area) given that I plan to keep the original leaf spring front end. As I understand the original cross member provides frame stability for the rear spring mount. However, I bellieve everything I have seen/read indicates the mount needs to be cut or removed in favor of a transmission mount cross member (new) located further back on the frame.

My original plan was to remove the rivets to allow removal of the original rear cross member, position the engine and use that to determine the transmission cross member/mount location. I don't know if I would try to modify the original cross member to provide the transmissin mount or purchase one of the aftermaket alternatives. My concern is that by doing this I will influence the frame stiffness where the rear mounting point for the front springs.

I am sure I am not the first to go down this path and would appreciate feedback from others that have gone before me.

I have done what you are attempting on a '49 and a '53 3100. What I did was cut the bellhousing crossmember off with a 6" cutoff wheel in two places, removing the center section allowing for clearance for removal of the automatic transmission from below.
I then welded plate steel flanges to the stub ends of the brackets (still riveted to the frame) so that I could reattach the center section of the crossmember 2 inches lower.
I then welded plate steel flanges to each end of the center section so that I could bolt it to the plate steel flanges on the stub ends of the bracket on the frame.
I drilled two holes through the plate steel flanges to accept 1/2" bolts. This will allow you to easily remove the center section to service the transmission or remove it.

I think the idea of making a removable section is a good one. But what does a mealy know?

Thanks for the insight.

I am planning on using the NV3500 manual transmission but the bell housing is integrated to the transmission so in some ways not terribly different than an automatic.

52Carl, if I understand your setup correctly the modified cross member is not attached to the engine/transmission but retained to provide the frame stiffness that would otherwise be lost. I am assuming that there is a new transmission support cross member farther back but given that it is only providing transmission support it doesn't need to be as robust for frame reinforcement.

Sounds like I need to stop getting ahead of myself (again) and when I get to the point of putting in engine mounts I can better evaluate the clearance issues associated with the original bell housing cross member.

I'm late to the game but figured I'd chime in, as I did 25 years ago most of what it looks like you're in the middle of. I put a 350 in my '53 3600, keeping everything else stock (including 4 speed SM420 trans). As I'm sure you've learned, the steering box will need to move about 2" out to clear any kind of conventional exhaust manifolds on a SBC. Also you'll need to cut out part of the firewall to clear the distributor (and also the rear of the rocker arm cover, IIRC). My 350 gave me plenty of power and was fund to drive, but I never was able to get it to cool properly, and so I overheated it regularly and ended up with a pretty massive engine failure (one of the valves snapped off and was actually embedded in the piston).

At that point I decided to go back to the stovebolt 6 that the truck was designed for. I ran a bone stock 216 for several years with zero problems. I found a slightly used 1.5 ton truck 235 (splash oiler) for sale near me for $250. The guy said it only had 5,000 miles on it. I put that engine in and have never looked back! A well-running 235 has plenty of power for this truck, and with 235/75 R16 tires and a 4.11 rear end transplant, I can cruise comfortably between 65-70 on the highway.

You are correct about the modified crossmember is just there for support of the leaf spring mount.
I used the original bolt-on crossmember which supports the torque tube for my transmission tail mount. I had to slide it back on the frame 4 inches, but got lucky as the two rear holes in the frame lined up with the two front holes of the crossmember, so I only had to drill two holes in the frame.
I used a transmission mount designed for my auto transmission.

Tyler, I am surprised to hear that you had cooling problems with the SBC.

I am familiar with the steering interference issue, just have not decided exactly how I plan to resolve it.

Several have advised that engine placement is key to allowing the engine to be installed with firewall clearance for the distributor and rocker covers so I remain hopeful that I can navigate those concerns.

Glad to hear that your 235 is working well.

Well it was my own stupid fault. When I got my truck it was missing the sheet metal filler piece between the bottom grille bar and the radiator, so the air flow through the grille was not all forced into the radiator. After I blew up the 350 I discovered this problem, was able to source a take-off bottom grille pan, and have been running cool ever since with my Stovebolt 6s.

Best of luck with your project! Sounds like your truck is going to be a very sweet ride. :-)

The 50 3600 I bought in 99 had a SBC V8 in it already. Farm/home conversion. Steering gear and column moved outboard to clear exhaust, etc. SM-420 behind it with original everything else. Built for grunt work and not speed or sport. It even had a goose neck hitch plate in the bed… Many times I have wished I still had it.

Good luck with your project.

As noted in my project journal I cut out the original cross member to clear the transmission and got my engine and transmission mounts located and installed.

I am still planning to rebuild the original cross member as a bolt in similar to what 52carl indicated although I think my transmission will require the center section to be moved further back and perhaps not as low. I noticed that the driver's side cross member is cracked when it is rivited to the frame so I will need to weld that in the process.

The steering gear/exhaust interference problem can be solved by running a driver's side exhaust manifold for a 1955-57 265 V8. Ebay or your friendly local swap meet usually has a few available. The outlet flange is all the way forward, which eliminates the steering column interference a rams' horn manifold causes. Unless you're planning to run very high RPM most of the time, there won't be enoug exhaust back pressure to notice with a daily driver. RUN- - - -do not walk away from any kind of tubular steel header system. All they do for a street machine is increase the underhood temperature, blow out gaskets, and melt spark plug wires!
Jerry

Thanks Jerry, I have not gotten to the point of deciding about the steering yet (original vs. aftermarket column; manual vs. power) but agree that exhaust restriction will not be a problem. I am not a fan of tubular header systems for all the reason you mention plus flange warpping problems.

I just finished installing a 350 in my 3800. I used a 67-87 chevy truck steering box which mounts on the outside of the frame. It works great, the only thing I may do also is add a front sway bar because sometimes under acceleration you get a little bump steer but other than that it's flawless. I would recommend anyone doing a V8 swap to consider it.

John, do you have any pictures that show your installation? Is the bump steer related to the drag link being at an angle such that as the spring is deflected the spindle pushs/pulls on the steering wheel?

Here is a picture of my Delphi(Saginaw), unknown source and year, installation in my ‘55 GMC 370, your location may not be exactly the same. Important to box the frame where the box attaches with sleeves between to prevent crushing the frame.

Ed

I don't have any pics at the moment but I will try to remember to take a few. The drag link is pretty flat and is not very long, I'm guessing maybe 10" As I said in the previous post the bump steer isn't bad, you notice it during acceleration and when you let out of the throttle.
When you know what it's going to do it's manageable, but I think a sway bar would take care of it. I think the reason for it is the short length of the drag link.

I temporarily installed the cab yesterday and found that the transmission clearance needed to be modified. I cut the opening higher, bent a flange along the endge for stiffness and then formed the area to have a slope that more closely matched the transmission (NV3500) bellhousing angle. I'm not sure how I will address the transmission cover modification to match the revised area but that's down the road.

Distributor clearance (large HEI version) was good as I could wrap my fingers around the cap without interfernece from the firewall.

I check fit the 1991 K2500 passenger side exhaust manifold and it does not clear the frame (discharge area hits the frame). I am considering rams horn center dump exhaust manifolds but need to decide how I am going to address the steering interference potential before I proceed.

Note: This thread turned into a duplicate of WICruiser’s Project Journal so it has been locked.