BHP of Full race 1700 X-flow
Discussion
Stan,
Slight correction - it would be 1310cc with the overbore.
The builder who shared those specs built the engine in the winning car you see here:
http://speedcasttv.com/#/races/402
Slight correction - it would be 1310cc with the overbore.
The builder who shared those specs built the engine in the winning car you see here:
http://speedcasttv.com/#/races/402
I think the top US A and B engines are running 14:1 + CR and are very high revving. We are typically running 1000rpm lower for peak torque and bhp which we feel significantly extends the engine life for our specific uses.
We mainly build to FIA specs and we are not allowed alternative from standard rockers or rocker ratios which restricts the cam choice. This is so with the TR4 head work we do. These engines do endurance racing in terms of 3/4hr plus races and the really high CR ones do not seem to last long away from 10 lap shorter circuit stuff. We are also running pump fuel plus a small amount of additive so cannot run the 118 Octane(UK) race fuels. Consequently we are 11.8:1 CR for the 1840cc Bs and 12.5:1 for the A series. When you say stock valves for the A series I feel they will be running the Cooper S MG Metro 1.401" or even larger inlet valves not the OE 1275 Midget 1.33" as we get an easy 10 bhp more from fitting the 1.401 over the 1.33 and adding 10 to the figures you have given would be rather a lot.
Peter
We mainly build to FIA specs and we are not allowed alternative from standard rockers or rocker ratios which restricts the cam choice. This is so with the TR4 head work we do. These engines do endurance racing in terms of 3/4hr plus races and the really high CR ones do not seem to last long away from 10 lap shorter circuit stuff. We are also running pump fuel plus a small amount of additive so cannot run the 118 Octane(UK) race fuels. Consequently we are 11.8:1 CR for the 1840cc Bs and 12.5:1 for the A series. When you say stock valves for the A series I feel they will be running the Cooper S MG Metro 1.401" or even larger inlet valves not the OE 1275 Midget 1.33" as we get an easy 10 bhp more from fitting the 1.401 over the 1.33 and adding 10 to the figures you have given would be rather a lot.
Peter
Peter,
The SCCA races are typically 40 minute races, which is the venue for the FP and GT-Lite engines. Vintage racing in the states is a bit shorter and can tolerate hotter set-ups.
Also, that is with a 1.33" intake valve. GT-Lite allows any length connecting rod and valve sizes - but you can't add material to the port or relocate anything.
The builder shared this as well:
"With the current head flow that I'm seeing, in FP trim, potential for 156hp 8800 rpm
In a maxed out GT-L setup 179hp 9300 rpm.
That is a lot of dollars away"
They're at the point now that they need to develop the valvetrains to get the lift needed to access that airflow as well as be able to survive. Time to get on the Spintron at that point.
But yet, static compression ratios are typically in the 14.5-ish range for the small bore stuff. Around 12-13:1 for the larger bore stuff.
Here is a video from the pole sitting Lotus 1500 (choke restricted):
https://www.youtube.com/watch?v=sDfqTr0i6IQ
Last year, the Runoffs were at Daytona. Joe Huffaker (black car) was trapping at 138mph (same rules as I posted above) in the draft. Video here:
http://www.scca.com/videos/1972540
Here is a friend's TR4 in vintage:\https://www.youtube.com/watch?v=oKsjd_D-bPM
The SCCA races are typically 40 minute races, which is the venue for the FP and GT-Lite engines. Vintage racing in the states is a bit shorter and can tolerate hotter set-ups.
Also, that is with a 1.33" intake valve. GT-Lite allows any length connecting rod and valve sizes - but you can't add material to the port or relocate anything.
The builder shared this as well:
"With the current head flow that I'm seeing, in FP trim, potential for 156hp 8800 rpm
In a maxed out GT-L setup 179hp 9300 rpm.
That is a lot of dollars away"
They're at the point now that they need to develop the valvetrains to get the lift needed to access that airflow as well as be able to survive. Time to get on the Spintron at that point.
But yet, static compression ratios are typically in the 14.5-ish range for the small bore stuff. Around 12-13:1 for the larger bore stuff.
Here is a video from the pole sitting Lotus 1500 (choke restricted):
https://www.youtube.com/watch?v=sDfqTr0i6IQ
Last year, the Runoffs were at Daytona. Joe Huffaker (black car) was trapping at 138mph (same rules as I posted above) in the draft. Video here:
http://www.scca.com/videos/1972540
Here is a friend's TR4 in vintage:\https://www.youtube.com/watch?v=oKsjd_D-bPM
Edited by hoffman900 on Wednesday 24th February 22:00
Edited by hoffman900 on Wednesday 24th February 22:09
So, what was the outcome ?
BHP of full race Crossflow that is, not the fisticuffs over dyno accuracy.
My oppo locally has just completed a build he believes will be 170+ bhp with a (beautiful) knifed crank, race cam and most of the other ‘routine’ work with the advice of a very old school race builder and tuner. Be interesting to see what power it makes on the rollers albeit I doubt they’ve been calibrated since 1972.
BHP of full race Crossflow that is, not the fisticuffs over dyno accuracy.
My oppo locally has just completed a build he believes will be 170+ bhp with a (beautiful) knifed crank, race cam and most of the other ‘routine’ work with the advice of a very old school race builder and tuner. Be interesting to see what power it makes on the rollers albeit I doubt they’ve been calibrated since 1972.
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