Don Terrill’s Speed-Talk

FC-Pilot wrote: ↑Sat Aug 31, 2019 2:32 am Here is the backstory. So a friend of mine races in a class of circle boat that is limited to basic small block chevy’s. He is struggling to even run mid pack, but has decades of experience in circle boat racing and has a good boat. He bought a brand new engine from a local race engine builder and at best it will only turn 6100 rpm’s where his competitors are spinning 7400 with the same prop, gear and hull design. I have set up a couple boats for the class but have never built an engine for it. Being that I have never build an engine for a lift rule class or with limited intake (this one is not near as bad as what some of you dirt and asphalt guys deal with) I don’t know if he has an issue somewhere else or if it is in the engine. The basic long block was built to the spec rules but there is question regarding cam specs. What do you guys think? Is it in the ball park or way out to lunch for what he is trying to do? I am including the engine rules so you guys can see what we are working with. The other issue is he is on the east coast and I am on the west coast otherwise I could help work this stuff out with him.

55.3 Engine
55.3.1 General Notes
55.3.1.1 No titanium engine parts are allowed.
55.3.2 Block Assembly. Any GM cast iron small block or Ford cast iron Windsor small block engine block designed for general automotive
or truck use may be used. Aftermarket blocks may also be used.
55.3.3 Bore and Stroke.. Maximum Bore x Stroke is 4.065” x 3.500”
55.3.4 Crankshaft. Any aftermarket crankshaft may be used.
55.3.5 Pistons.
55.3.5.1 Only flat top pistons with valve relief(s) are permitted.
55.3.5.2 Any aftermarket pistons may be used..
55.3.6 Connecting Rods. Any aftermarket steel connecting rods may be used.
55.3.7 Cylinder Heads.
55.3.7.1 Only stock GM or Ford cylinder heads with in-line valves may be used. 55.3.7.2 No porting, polishing, or grinding is permitted in ports or combustion chambers. 55.3.7.3 Heads shall have a maximum intake runner volume of 170 cc
55.3.7.4 A maximum compression ratio of 9.5:1 only.
55.3.8 Camshaft and Valve Train 55.3.8.1 Camshafts.
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55.3.8.1.1 Only flat tappet camshaft and lifters may be used.
55.3.8.1.2 Either hydraulic or mechanical lifters with a maximum diameter of 0.843” for GM or 0.876” for Ford may be used. 55.3.8.1.3 Maximum lift, measured at the valve, shall not exceed 0.450” (lift is to be inspected @zero lash).
55.3.8.2 Timing Chain. Use of any chain set or gear drive of dual idler design only is permitted. 55.3.8.3 Valves.
55.3.8.3.1 All steel or stainless steel valves with a minimum valve stem diameter of 11/32” with a minimum 0.340/0.341 stem diameter. Aftermarket performance valves and steel or aluminum retainers allowed.
55.3.8.3.2 Maximum diameter of intake valve is 1.945” for GM .GM 305 heads and Ford heads 1.845”. 55.3.8.3.3 Maximum diameter of exhaust valve is 1.505” for GM and 1.545” for Ford.
55.3.8.4 Valve Springs. Valve springs shall have a maximum diameter of 1.260” for GM and 1.445” for Ford with an allowable toler- ance of ±0.040”.
55.3.8.5 Rocker Arms.
55.3.8.5.1 Roller type rocker arms with a maximum ratio of 1.52 for GM or 1.60 for Ford may be used.(Lift at cam x 1.5 for
GM or 1.60 for Fords helps determine legal rocker ratios) may be used. 55.3.8.5.2 Studs and/or guide plates with 5/16” pushrods may be used.
55.3.8.6 Adjusting Nut. Any adjusting nut, posi loc, strut girdle may be used. No shaft type rocker assy 55.3.9 Intake System
55.3.9.1 Intake Manifold.
55.3.9.1.1 Any production style as cast/as produced iron or aluminum intake manifold may be used 55.3.9.1.2 Sheetmetal or tunnel ram style intake manifolds are expressly prohibited.
55.3.9.2 Other Intake System
55.3.9.2.1
55.3.9.2.2
55.3.9.2.3 55.3.10 Fuel System
A carburetor spacer is required; it shall have a minimum thickness of 0.500” (including gaskets) and a maximum thickness of 2.25” (including gaskets. The spacer may be wedge shaped, if desired, providing it fits within the above envelope. A restrictor plate, if required, shall be in addition to this thickness.
The intake manifold may be matched or blended to the carburetor spacer. Use of any intake scoop, velocity stack, and/or air cleaner is permitted.
55.3.10.1 Carburetor
55.3.10.1.1 Carburetor is to be a Holley manufactured # 4776 (all series). The center section/main body must remain stock and as furnished by Holley. The choke mechanism and related components may be removed. The air horn can be milled off. No HP center section/main body allowed. Only the following dimensions are to be inspected/measured: Primary/Secondary venturi @ 1.265/1.3275 maximum. Throttle plate bore @ 1.5675 maximum. All other modi- fications permitted.
55.3.10.1.2 Maximum venturi diameters: Primary/Secondary = 1.265”/1.3275”
55.3.10.1.3 Maximum throttle plate bore is 1.5675” 55.3.10.2 Fuel and Fuel System
55.3.10.2.1 Any pump gas may be used, including E85. See Rule 40.18.12
55.3.10.2.2 Any fuel pump is permitted 55.3.11 Ignition.
55.3.11.1 Ignition system may be either points-type system or HEI system
55.3.11.2 Electronic ignition systems are not permitted. Pertronix distributor points conversions may be used. 55.3.11.3 Any plug wires may be used.
55.3.11.4 Firing order is to be 18436572 for GM and 13726548 for Ford
55.3.12 Exhaust. Any log type manifold, individual pipes “zoomies” or standard 4 into 1 header may be used. The collector must be a standard straight style with no choke/merge type collectors allowed. Each pipe must have no more than one step/diameter change in its length, no multi step tubes allowed. Tri-Y and 180 type headers are prohibited.
55.3.13 Lubrication System.
55.3.13.1 A wet sump system with the oil pump mounted in the stock location is required. 55.3.13.2 Any oil pan is permitted
55.3.13.3 Accusump systems are permitted
55.3.14 Other Specifications
55.3.14.1 Any gasket set may be used.
55.3.14.2 Vacuum pumps are not allowed.
55.3.14.3 Use of a heavy duty/SFI flexplate or aluminum flywheel is recommended.'

Paul

FC-Pilot wrote: ↑Sat Aug 31, 2019 7:32 pm I appreciate getting your thoughts on this guys. I had thought about springs being an issue, but he did not know the spring pressure and did not have a way to check it. It is a flat bottom v-drive class, so yes propeller driven. He said the engine builder recommended 32* of timing with pump gas. I know they were planning on heading back out with race fuel and were going to play with timing. If I remember correctly he has a victor junior for an intake. I do know many others in the class run the same intake so I did not thing about the intake as the restriction. They also tested 5 different props so it is not like they have a mismatched prop either. I will see if he can get a hold of a spring tester and post the results. Thanks again for your thoughts.

Paul

CharlieB53 wrote: ↑Sat Sep 07, 2019 12:29 pm With a lift limit would it make sense to increase cam diameter so as to enable increasing duration in the lobes.

thedynoguy wrote: ↑Mon Sep 09, 2019 6:50 amThat engine needs to go on a dyno to see what the problem is. You can throw parts at it all day long, and waste your time and money chasing the problem. There. Bash away...

thedynoguy wrote: ↑Mon Sep 09, 2019 6:50 am That engine needs to go on a dyno to see what the problem is.

thedynoguy wrote: ↑Mon Sep 09, 2019 6:50 am That engine needs to go on a dyno to see what the problem is.